2014 Microbiological baseline survey of the
Queensland egg production environment
Authors:
Dr. Leigh Cuttell B.Sc. (Hons), Ph.D., Dr. Mitch Groves B.App. Sc. (Hons), Ph.D.
Dr. Andrew Wilson B.Ag.Sc. (Hons), Ph.D.
1
About this document
This document reports a microbiological survey of Queensland egg farms sampled between October
and November 2014. It forms a baseline for the risks of pathogenic microbial inputs, namely
Salmonella, in commercial egg production that will assist in future evaluations of the performance of
the Queensland Egg Food Safety Scheme. The survey reported here replicates a survey conducted
by the New South Wales Food Authority in 2010/2011 and provides useful cross-jurisdictional data.
Any enquiries about this document should be directed to Safe Food Production Queensland on (07)
3253 9800 or email [email protected].
Acknowledgements
Safe Food Production Queensland would like to thank the participating accredited egg businesses for
their cooperation during the 2014 Microbiological survey. Dr. Margaret Sexton (Primary Industries &
Resources South Australia) and Dr. Craig Shadbolt (New South Wales Food Authority) are also
thanked for their comments on the draft report. Laboratory analysis was conducted by Symbio
Alliance, Brisbane and the Microbiological Diagnostics Unit, University of Melbourne, Melbourne.
2014 Microbiological baseline survey of the QLD egg production environment
Page 2 of 31
Contents
Executive Summary ……………......................................................................................
5
1
Background ………….………………………………………………………………………….
8
1.1
Objectives of the baseline survey …….………………………………………………………..
9
2
Methodology …………………………………………………………………………………….. 10
2.1
Proportionate numbers of egg businesses were sampled across all regions ……………..
2.2
Sample type and collection ……………………………………………………………………… 11
2.3
Laboratory methods and analysis ………………………………………………………………. 12
3
Results and Discussion ……………………………………………………………………….. 13
3.1
Salmonella was widespread on Queensland farms ……………………………………..…… 13
3.2
A baseline of Salmonella presence in farm inputs and in the egg-laying environment …… 16
3.3
Observations on Salmonella prevalence by production system, flock size and flock age … 17
3.4
A baseline of Salmonella prevalence on egg farms may inform the effectiveness of future
Salmonella reduction strategies ………………………………………………………………..... 20
3.5
Salmonella Typhimurium and Queensland egg farms………………………………………... 21
3.6
Salmonella Typhimurium phage and MLVA types identified from the current study ………. 23
10
4
Conclusion ………………………………………………………………………………………….. 24
5
References ………………………………………………………………………………………….. 25
Appendix 1 Summary of Salmonella-related food borne outbreaks and food association in
Queensland and Australia in 2010, 2011 and 2012 ………………………………………………….. 27
Appendix 2 Proportion of samples from total Queensland accreditation holders by region …… 28
Appendix 3 Sample numbers …………………………………………………………………………. 29
Appendix 4 Sampling methodology and laboratory methods for Salmonella analysis ………….. 30
2014 Microbiological baseline survey of the QLD egg production environment
Page 3 of 31
Executive summary
Overview
Egg-borne salmonellosis, caused by Salmonella bacteria contamination in raw or undercooked eggs,
is a significant contributor to Australian foodborne illnesses annually. In Queensland (QLD) and
Australia, the regulatory framework for egg safety aims to reduce salmonellosis in the community
through eliminating the supply of cracked and/or visually contaminated eggs that are at higher risk of
microbial contamination. The QLD Egg Food Safety Scheme administered by Safe Food Production
Queensland (SFPQ) as the statutory authority, has been in place since 2005 and the Primary
Production and Processing Standard for Eggs and Egg Products (Standard 4.2.5 of the Australia New
Zealand Food Standards Code) commenced in late 2012. The National Standard is modelled on the
QLD Egg Scheme. Presently, businesses that produce eggs must implement measures to control
food safety hazards, including microbiological pathogens such as Salmonella, and be able to
demonstrate compliance with the Standard. To assist egg businesses, several codes of practice and
guidelines for biosecurity and production and processing of shell eggs describe prevention and control
measures for poultry diseases (including Salmonella). Voluntary egg quality assurance programs,
focused on food safety and quality, are also available.
Understanding the prevalence and serovar diversity of Salmonella on egg farms is an important first
step towards establishing, validating and verifying measures to control the pathogen at the farm level
and underpins the importance of baseline surveys. From December 2010 to November 2011, the New
South Wales Food Authority (NSWFA) conducted a microbiological survey of NSW egg farms to
establish a baseline and assess the future impact of Salmonella risk reduction on the prevalence and
serovar diversity of Salmonella in egg-laying environments. This report provides similar baseline data
of Salmonella on Queensland commercial egg farms that permits comparisons with other jurisdictions.
Strategic objectives
The strategic objectives of the project included:

Collect useful microbiological data for Salmonella in the egg-laying environment for promoting
awareness of the risks of Salmonella transference to eggs through production and assessing
the impacts of the QLD Egg Food Safety Scheme, as well as changes in the industry’s
composition and activities in the future.
2014 Microbiological baseline survey of the QLD egg production environment
Page 4 of 31

Collect industry profile information which contributes insight into the appropriateness of current
industry practices and food safety measures for Salmonella risk reduction in commercial egg
production, and identify any potential areas for improvement.

Provide SFPQ with a snapshot of the QLD egg industry’s microbiological risks by estimating the
prevalence and serovar diversity of Salmonella on egg farms including phage and multi-locus
variable number tandem repeat (MLVA) type profiles of Salmonella Typhimurium. S.
Typhimurium is the most common serovar in human notifications of egg-associated
salmonellosis.
Methods
Selection of egg businesses to be invited to participate in the survey followed the same methodology
as the 2010/2011 NSWFA survey. To ensure state-wide coverage, a proportionate number of farms
were sampled from 10 regional areas. More than 100 environmental (pooled faecal material and
boot/sponge swabs) and 42 farm input (bulk feed and water) samples were collected (total number of
samples 148). The 21 participating farms represented approximately 25% of egg-producing
businesses accredited with SFPQ in August 2014, and more than 75% of the state’s egg production
volume (~2.5 million eggs/day). From each farm, samples were collected from 1, 2 or 4 layer sheds
depending on the farm’s production size. From each shed, two samples were collected, comprising
faecal material and boot swabs for free-range and barn systems, or faecal material and sponge swabs
from caged systems. Bird feed and water was collected from major storage reservoirs to represent
inputs for each farm. The participation of each farm in the survey was voluntary.
All samples were analysed for Salmonella serovars at a NATA-accredited laboratory. The Salmonella
prevalence was calculated for the egg-laying environment samples (pooled faecal material and
boot/sponge swabs) and farm inputs (bulk feed and water). Further data analysis considered
Salmonella prevalence by production system type, flock size and flock age at the shed and farm level.
However, it is important to note that based on the level of sampling undertaken for this survey, any
observed differences are qualitative only as statistically valid conclusions cannot be made.
General findings
The general findings of the survey were as follows:

Salmonella was widespread on Queensland egg farms (57%; 95% C.I. 35 -78%) and the results
were comparable to NSW results from 2010/2011 (45%; 95% C.I. 32-59%) .
2014 Microbiological baseline survey of the QLD egg production environment
Page 5 of 31

S. Typhimurium was found on 3 of 21 surveyed farms (13.5%; 95% C.I. 3.0–35%) compared with
10/49 (20%) of NSW farms. No samples in the QLD survey were positive for S. Enteritidis.

Pooled faecal material or boot/sponge swabs were sensitive samples types for this kind of survey.
No Salmonella was isolated from any feed or water bulk stored samples, possibly indicating these
farm inputs were not major sources of Salmonella transmission to poultry at the time of the survey.

In total, fifteen different Salmonella serovars were isolated from Salmonella-positive egg farms of
which S. Typhimurium was the most common serovar amongst samples (20%; 7/35). This was
followed by S. Infantis and S. Agona (12%; 4/35). In the 2010/2011 NSW survey 17 serovars were
isolated, of which S. Typhimurium was most common, followed by S. Infantis.

Phage and MLVA-typing carried out for seven S. Typhimurium isolates identified three phage
types and five MLVA types.

Measuring the number of Salmonella-positive farms and the proportion of positive samples on
those farms can help to improve awareness around the risk of transference of Salmonella to eggs
through egg production as well as the extent of Salmonella infection on the farm. At the time of
survey, Salmonella was isolated from the egg-laying environment of 12 Queensland commercial
egg farms. For half of the Salmonella-positive farms (at the 50th percentile), at most, the proportion
of positive samples was 56%. For 90% of positive farms (at the 90 th percentile), 100% of samples
were positive. In the future, improvements in the Salmonella reduction strategies on-farm may
decrease the number of positive samples on-farm and decrease the proportion of farms with
positive samples.
Conclusion
The overarching aim of the QLD Egg Food Safety Scheme is to ensure the safety and suitability of
eggs and egg products and subsequently reduce the potential for foodborne illness arising from the
consumption of contaminated eggs. Although this legislative framework, in partnership with the egg
industry, has historically delivered a good record of egg safety in QLD, further reducing this risk means
continual monitoring of the effectiveness of the through-chain food safety system. This is important in
order to respond to ever-changing patterns of consumption and foodborne disease. This survey
accords with this philosophy by providing a platform of knowledge to further promote awareness of
the risks of Salmonella contamination on eggs and the importance of implementing and monitoring
best-practice controls that reduce the opportunity for this pathogen to proceed through the egg supply
chain. The findings in this survey highlight the need to maintain effective food safety controls as
Salmonella was widely detected on surveyed QLD commercial egg farms. These findings were not
2014 Microbiological baseline survey of the QLD egg production environment
Page 6 of 31
unexpected, given the universal nature of Salmonella in the environment. Achieving Salmonella
reductions at the farm-level is one of the ways to contribute to minimising the risk of Salmonella
contamination on eggs and, as a result, to a further reduction in egg-associated foodborne illnesses.
Collecting information about Salmonella prevalence in the egg-laying environment provides a baseline
for assessing the effectiveness and appropriateness of Salmonella risk reduction strategies as well as
monitoring future impacts of industry changes in composition and activity on microbial risks. In
particular, the baseline can allow SFPQ to work better with industry to promote awareness of the food
safety risks around egg production, ensure provisions are in place to control and reduce food safety
risks and measure industry commitment to make changes or implement best practices to achieve a
safe and suitable product. In recognition of consumer-driven changes to the Australian egg industry
from predominantly caged systems to cage-free systems, the baseline can be used to assess how
changes in the composition and activities of the industry impact the microbiological profile of QLD egg
farms in the future.
2014 Microbiological baseline survey of the QLD egg production environment
Page 7 of 31
1
Background
Salmonella is a bacterium that is widely distributed in wild and domestic animals and in humans can
cause food poisoning or salmonellosis. In 2010, OzFoodNet reported that Salmonella was the most
common disease agent in foodborne illness outbreaks in Australia, and raw or undercooked eggs
were implicated in a large proportion of these (OzFoodNet 2010). The economic cost of salmonellosis
to the Australian economy has been estimated at $44 million per year (Food Standards Australia New
Zealand 2011). Salmonella Typhimurium (STm) has mainly been responsible for human cases of
salmonellosis in Australia (OzFoodNet 2010, OzFoodNet 2011, OzFoodNet 2012) (Appendix 1).
Although non-STm serovars are not considered to pose the same public health risk as STm, all
Salmonella serovars should be considered potentially harmful to human health. It is important to note
the Australian poultry industry is considered free from virulent strains of Salmonella Enteriditis (SE), a
foodborne pathogen that has major economic and social impacts in other regions of the world.
Previous research has shown that a relatively high proportion of Australian egg farms are positive for
Salmonella (Scott 2014). S. Infantis is thought to be the most common Salmonella serovar among
Australian layer flocks and is also common amongst layers elsewhere in the world (Cox 2002,
Chousalkar 2012). The New South Wales Food Authority’s (NSWFA) microbiological survey of egg
farms in 2010/2011 found 45% of farms were Salmonella-positive (NSWFA 2013). S. Typhimurium
was the predominant serovar (20%), followed by S. Infantis (NSWFA 2013).
Most egg-related salmonellosis is assumed to arise from a combination of surface contamination on
cracked or visually contaminated eggs and cross-contamination or undercooking of eggs. Poor control
during processing (i.e. incorrect egg washing, storage conditions) may also contribute to
contamination or the potential for Salmonella growth. Salmonella does not often cause disease in
poultry, however its presence in the bird’s intestinal tract means eggs and meat can be contaminated
with bacterial cells shed in the faeces. Cracks and abnormalities in egg shells (including thin shells)
can allow Salmonella to penetrate inside the egg. Washing eggs can compound this risk, particularly
when washing parameters (e.g. load of organic matter in wash liquid, temperature differences between
eggs and wash water) are poorly controlled and can allow ingress of the pathogen through intact, but
porous, shells. Best on-farm biosecurity practices, the removal of dirty and cracked eggs and good
control of food safety hazards along the egg production and supply chain are the most effective
measures to reduce the Salmonella risk from consumption of eggs by egg businesses.
The Queensland (QLD) Egg Food Safety Scheme and the National Standard has the key aim of
reducing salmonellosis in the community through reducing the supply of cracked and/or dirty eggs.
Presently, guidance on the prevention and control of Salmonella at the farm-level relies on codes of
2014 Microbiological baseline survey of the QLD egg production environment
Page 8 of 31
practice, national guidelines, quality assurance programs and industry best practice strategies to
achieve a pathogen-free egg product. This is different from the international scene where prescriptive
legislative control and costly interventions have been introduced to prevent and control Salmonella in
layer hens. For example, in the European Union (EU), strict control programs include the compulsory
slaughter of SE and STm-positive flocks if eggs are to be used as table eggs, the feeding of
supplements that impede the survival of Salmonella and, importantly, flock vaccination (European
Commission 2003). In United States regulation, prevention and control of Salmonella in eggs focusses
mainly on SE and includes the Food and Drug Administration’s (FDA) Egg Safety Rule. The FDA’s
Egg Safety Rule requires extensive environmental sampling throughout production, with eggs from
positive flocks to be diverted for lower-earning pasteurization before human consumption. Voluntary
egg quality assurance programs, such as the United Egg Producers 5 star program, also specifically
advise SE vaccine types and prevention tools, and these programs carry marketing advantages over
eggs produced from non-UEP accredited flocks.
In order to avoid additional compliance measures in Australia for Salmonella prevention and control,
it is important that the QLD and Australian egg industries be proactive in recognizing and managing
the through-chain food safety risks in commercial egg production. Knowledge of Salmonella on egg
farms is an important first step to establishing and verifying effective best practice guidelines for the
prevention and control of this pathogen and underpins the importance of baseline surveys.
1.1 Objectives of the baseline survey
From October to November 2014, Safe Food Production Queensland (SFPQ) undertook a baseline
microbiological survey of egg-producing businesses in QLD. The baseline survey intended to:

Collect industry profile information which contributes insight into the appropriateness of current
industry practices and food safety measures for Salmonella risk reduction in commercial egg
production, and identify any potential areas of concern.

Provide SFPQ with a snapshot of the QLD egg industry’s microbiological risks by estimating the
prevalence and serovar diversity of Salmonella on egg farms including phage and multi-locus
variable number tandem repeat (MLVA) type profiles of Salmonella Typhimurium. S.
Typhimurium is the predominant serovar in human notifications of egg-associated salmonellosis.

Collect useful microbiological data for Salmonella in the egg-laying environment for promoting
awareness of the risks of Salmonella transference to eggs through the production chain and
2014 Microbiological baseline survey of the QLD egg production environment
Page 9 of 31
assessing the impacts of the QLD Egg Food Safety Scheme, as well as changes in the industry’s
composition and activities, in the future.
2
Methodology
The QLD Egg Food Safety Scheme covers businesses producing, grading or processing eggs and
egg products for sale. As of 30 August 2014, there were approximately 89 egg businesses accredited
by SFPQ. These included 71 egg producers (any business that produces eggs for supply) and 18 egg
processors (producers that also handle the eggs of other businesses).
In addition to gathering industry profile information (e.g. egg production system, flock size, flock age),
SFPQ officers collected samples for microbiological testing from ~25% (21/89) of accredited QLD egg
businesses. More than 140 environmental (faecal material and boot/sponge swabs) and farm input
(bulk feed and water supply) samples were collected.
2.1 Proportionate numbers of egg businesses were sampled across all regions
To obtain the list of farm participants, the total number of SFPQ-accredited egg businesses and the
geographic region they were located in, was extracted from the SFPQ accreditation database. The
number of regions (with accredited egg businesses) was 12, with the majority (35%) of egg-producing
businesses located in the Darling Downs-South West region and the remaining regions ranging from
1-10% of the total number of QLD farms. A sampling plan was employed where proportionate numbers
of egg farms for 10 of the 12 regions were selected for sampling (Appendix 2).
SFPQ officers collected samples from 21 farms representing 23.5% of the total number of egg
businesses accredited in Queensland and just over 75% of Queensland’s egg production (~2.5 million
eggs/day). Of the 21 farms, 72% (15/21) were egg producers and 28% (6/21) were processors.
Participation in the survey was voluntary. Farms were randomly selected in the most part, but selection
processes were also influenced by audit/assessment schedules, logistical reasons and biosecurity
considerations. SFPQ provided all participating farms with a written analysis of their survey results.
2014 Microbiological baseline survey of the QLD egg production environment
Page 10 of 31
2.2 Sample type and collection
Eggs were excluded from the survey as the number of egg samples required to generate statistically
significant results was outside the economic scope of the study. Sampling for Salmonella using
environmental methods was regarded as the most cost-effective and practical approach. In regards
to food safety, sampling for Salmonella using environmental samples does not directly link the
presence of Salmonella on-farm to the public health risk from eggs, but does give some insight into
the microbiological risks of cross-contamination of eggs through the supply chain.
Environmental factors such as humidity and temperature, as well as management practices such as
bird density, production system and quality and additives in stock feed can influence the Salmonella
status of a flock or shed. As such, the sampling for the survey was conducted within a 2 month period
(October and November 2014) to reduce any temporal effects on Salmonella prevalence. Generally,
weather conditions during the survey period were hot and dry with below-average rainfall for the
months of October and November. Caged, free-range and barn housing systems were included in the
study to assess any variability between these different production systems. Of the 21 farms included
in the study, 9 (43%) used a caged system, 10 (47.5%) used a free-range system (of which 4 were
free-range organic) and 2 (9.5%) used a barn system. In farms with mixed production types, the
production type that comprised the majority of the farm’s commercial activities was sampled.
Sample type and number
The most sensitive sample types for Salmonella isolation from the egg-laying environment were
determined to be pooled faecal material samples and swabs of the floor or manure belts or pits based
on the 2010/2011 NSWFA baseline survey. Therefore, for barn and free-range systems, faecal
material samples and boot swabs were collected from laying sheds. For caged systems, faecal
material samples, as well as sponge swabs of belts, cages or floors, were collected. Stock feed and
water samples (collected from bulk reservoirs) were also included in the sampling as they have the
potential to be vehicles for Salmonella into the farm environment if contaminated (Jones 2011).
The number of each sample type required was determined using Salmonella prevalence data from
the 2010/2011 NSWFA baseline survey (Appendix 3). The number of samples collected aimed to
provide at least 90% confidence of the study estimate being within 5% of the true prevalence assuming
the true Salmonella prevalence was ≤ 17% in faecal material, ≤ 26% in boot or cage swabs and ≤ 10%
in bulk feed or water. It was determined 57 pooled faecal samples, 63 boot/sponge swabs and 47
feed/water samples were required. In total, 148 samples were collected from 21 farms including 53
2014 Microbiological baseline survey of the QLD egg production environment
Page 11 of 31
boot/sponge swabs (84% of required), 53 pooled faecal material samples (93% of required) and 42
farm input samples (89% of required).
For each farm, the number of sheds to be sampled was based on the farm’s production size. An egg
farm was classified as ‘small’ if it housed less than 20 000 birds and a maximum of two sheds were
sampled. Farms with greater than 20 000 birds had a maximum of 4 sheds sampled. Feed samples
were taken from silos attached to one of the sampled sheds, or from retention samples when feed
inside silos could not be accessed. Water samples were taken from water storage reservoirs.
Sample collection
An initial phone questionnaire to participating egg producers/processors was conducted to acquire
preliminary industry profile details such as farm production system (cage, barn, free-range, organic
free-range), flock size, number of sheds, number of birds per shed and flock age (multi-age or singleage). On farm, SFPQ officers used standardized sample collection methods in order to control the
effects of sampling on accuracy (Appendix 4). If a farm was due a regulatory audit, samples were
collected at the same time in order to minimize the time and disruption of sampling and audit to the
business owner. All samples were transported to the laboratory under temperature control within 2-24
hours and all samples, except faeces, were analysed within 24 hours of receipt in the laboratory.
Faecal material was frozen for 24 hours prior to analysis to eliminate live insects and their eggs/larvae.
2.3 Laboratory methods and analysis
In the laboratory, all samples were analysed qualitatively for Salmonella using the Salmonella
Australian Standard 5013.10-2009 method (Appendix 4). For each Salmonella-positive sample, one
isolate was recovered and subjected to serotyping. Isolates identified as STm were also phage and
MLVA typed. Phage and MLVA typing are tools that can be used to refine the details about the degree
of relatedness of different Salmonella strains within a serotype. The decision to select one isolate per
sample was based on the 2010/2011 NSWFA study which reported less than 8% (n=5/65) of
Salmonella-positive samples yielded more than one serovar (when testing two isolates per
Salmonella-positive sample). Therefore the likelihood of a sample yielding more than one serovar
when testing two isolates was considered low.
Salmonella prevalence was determined for the egg-laying environment and farm input samples. The
results distinguish between Salmonella serovars and STm. Consistent with the 2010/2011 NSWFA
survey, a farm was classified as ‘positive’ if any sample from that farm was positive for Salmonella.
2014 Microbiological baseline survey of the QLD egg production environment
Page 12 of 31
Further, a shed was classified as ‘positive’ if either the faecal material or boot/sponge swab was
Salmonella-positive. Farms, sheds and inputs were classified as ‘negative’ if all relevant samples were
negative, however due to the limited number of samples collected, negative results do not guarantee
the absence of Salmonella on the farm. Furthermore, variability in factors that influence the rate of
Salmonella shedding in infected birds may also lead to false negative results. Further analysis of the
data was conducted for Salmonella prevalence in a number of sub-categories including farm
production system, flock size, flock age and region.
3
Results and discussion
The aims of the survey included estimating the baseline prevalence of Salmonella and collecting a
profile of Salmonella serovars of commercial egg farms in QLD. For studies of this nature it is not
unusual for multiple risk factors including farm production system, flock size, flock age, geographic
location, stressors and type of feed and source of water to have an effect on Salmonella prevalence.
As stated in the 2010/2011 NSWFA study, the small sample numbers collected for some of the risk
categories, and issues with dependencies between risk factors, make it impossible to draw accurate
conclusions regarding the effect of one factor over another on the prevalence of Salmonella. Only
simple analyses have been undertaken here.
3.1 Salmonella was widespread on Queensland egg farms
Figure 1 illustrates the prevalence of Salmonella on 21 egg farms, 53 sheds and 45 single-age flocks
examined in the survey. Salmonella was detected in 12 of the 21 QLD egg farms with an estimated
prevalence of 57% (95% CI 37-76%). STm was detected on 14% of farms and no farm was positive
for SE. At the shed level, Salmonella was detected in 23/53 (44%) of sheds sampled which was similar
to the proportion of positive sheds reported by the 2010/2011 NSWFA survey (56/113; 49.5%). When
flocks were examined on the basis of being single- or multi-aged, the prevalence of Salmonella was
again comparable with 42% (19/45) in single-aged flocks and 37.5% (3/8) in multi-aged flocks (data
not shown).
Overall, the survey findings provide insight into the prevalence of Salmonella on QLD commercial egg
farms. The results were comparable to the 2010/2011 NSWFA survey which found 45% (95% CI 3259%) of NSW egg farms positive for Salmonella and 20% of farms positive for STm. The QLD STm
prevalence was lower than the NSWFA survey data as well as the NSW/VIC SE Monitoring and
2014 Microbiological baseline survey of the QLD egg production environment
Page 13 of 31
Accreditation Program1 conducted in 2006-2007 that reported 10/22 (45%) of farms STm-positive
(NSWFA 2013). The findings here support previous assumptions about a relatively high carriage rate
of Salmonella in Australian layer flocks (Cox 2002, Scott 2014). As agreement between the carriage
rate of Salmonella in layer hens and the incidence of egg-related human illness has been suggested,
achieving Salmonella reductions at the farm-level should contribute to reductions of Salmonella loads
on eggs and ultimately, a reduction in the risk of salmonellosis from consuming eggs (FAO/WHO
2002, Wales 2007). It is vital to recognize however that a through-chain approach to reducing
Salmonella risk, including steps of the supply chain beyond the farm gate, is required.
The proportion of Salmonella-infected single-age flocks versus multi-age flocks was similar in this
study even through farms operating single-aged flocks have greater opportunities for Salmonella
reduction. Sheds that can operate on an all-in/all-out basis (considered industry best practice) have
the opportunity for improved cleaning and sanitation between flocks, whereas multi-aged flocks are
more often economical but can perpetuate Salmonella infections by allowing pathogens to spread
from older layers to replacement birds (AECL 2003). In Australia, there has been an increasing trend
in commercial egg farms to move from multi-aged flocks to single-aged flocks, and the greater
numbers of single-aged flocks examined in this study reflected this trend in Queensland. The similar
Salmonella prevalence in multi-age versus single-age flocks reported here however does not reflect
a substantial reduction in Salmonella infection between the two systems and is most likely because
single-aged farms, in the main, do not operate sheds as biosecure units. Vehicles for Salmonella
transference such as personnel, equipment and rodents are often moved between sheds and may be
vehicles for infection.
1
The NSW Department of Primary Industries operates a joint NSW/Victoria Salmonella Enteritidis
accreditation program, which covers about 70% of the layer chickens in these states
2014 Microbiological baseline survey of the QLD egg production environment
Page 14 of 31
Queensland 2014
120%
Not detected
100%
proportion (%)
14%
Other Salmonella spp
S. Typhimurium
8%
7%
36%
36%
57%
58%
Sheds (n=53)
Single Age Flocks (n=45)
80%
60%
43%
40%
20%
43%
0%
Farms (n=21)
New South Wales - 2010/2011
120%
Not detected
Other Salmonella spp
S. Typhimurium
100%
10%
20%
23%
proportion (%)
80%
21%
25%
60%
27%
40%
69%
55%
50%
20%
0%
Farms (n=49)
Sheds (n=113)
Single Age Flocks (n=67)
Figure 1. Comparison of Salmonella prevalence of on egg farms, sheds and single-aged
flocks in Queensland, 2014 and New South Wales egg farms in 2010/2011.
2014 Microbiological baseline survey of the QLD egg production environment
Page 15 of 31
3.2 A baseline of Salmonella prevalence in farm inputs and in the egg-laying
environment
Figure 2 presents Salmonella prevalence for the farm inputs (stock feed and drinking water) and the
egg-laying environmental samples for the farms surveyed. Note that in the QLD survey, feed and
water at the point of consumption were not sampled as in the 2010/2011 NSWFA survey.
Queensland - 2014
120%
Not detected
Other Salmonella spp
100%
6%
80%
proportion (%)
S. Typhimurium
8%
21%
32%
60%
100%
100%
40%
72%
62%
20%
0%
Stock feed (bulk
stored) (n=21)
Drinking water
source (n=21)
Boot/sponge swab
(n=53)
Faecal material
(n=53)
New South Wales - 2010/2011
Not detected
Other Salmonella spp
S. Typhimurium
proportion of samples (%)
120%
100%
1%
11%
4%
2%
16%
80%
6%
8%
29%
21%
65%
72%
60%
40%
89%
100%
83%
93%
20%
0%
Stock feed
Drinking Stock feed (at Hen drinking Boot/sponge
(bulk stored) water source
point of
water (n=46) swab (n=99)
(n=27)
(n=20)
consumption)
(n=101)
Faecal
material
(n=90)
Figure 2. Comparison of Salmonella prevalence in egg-laying environmental and farm
input samples in Queensland, 2014 and New South Wales, 2010/2011
2014 Microbiological baseline survey of the QLD egg production environment
Page 16 of 31
There were no Salmonella detections in bulk feed or water samples
Overall, the results showed that the samples of stock feed and bird drinking water were not
contaminated with Salmonella in any of the surveyed QLD egg farms compared to a low level of
Salmonella feed detections in NSW egg farms in 2010/2011 (11%; 3/27). These results were not
unexpected given that 20/21 (95%) of farms used town supplied or bore water which are relatively low
risk water supplies for microbiological contamination (compared to surface water), and 14/21 (66%)
farms purchased feed from an accredited supplier. Feed mills that operate under quality assurance
programs may have more effective control mechanisms and biosecurity of feed production that
eliminate or reduce Salmonella in stock feed. Although self-produced feed is thought to have a higher
risk of Salmonella contamination because of greater contamination opportunities by wildlife/pests than
at commercial feed mills (Davies 2010), there were no Salmonella detections in 7 self-produced feed
samples examined in this survey.
The type and manufacturing process of poultry feed can have some effect on the presence and
concentration of Salmonella contaminants. Overseas studies have reported lower levels of Salmonella
contamination in pellets2 compared to dry mash3 due to the use of heat in pellet manufacture which
decreases most microbial contaminants (Jones 1991). Despite this, the majority of QLD egg farms
surveyed supplied dry mash to birds with the exception of one free-range farm that supplied dry pellets
and two cage-based farms that supplied crumble4.
Faecal material and boot/sponge swabs are sensitive sample types for Salmonella in sheds
In the egg-laying environment, Salmonella was detected in 38% (20/53) of boot/sponge swabs which
was a greater prevalence of this sample type to the 2010/2011 NSWFA survey (27%; 27/99).
Salmonella prevalence in pooled faecal material was 29% (15/53) and higher than that reported in the
NSWFA study (17%; 15/90). Both sample types demonstrated they were sufficiently sensitive to detect
Salmonella in the egg-laying environment.
3.3 Observations on Salmonella prevalence by production system, flock size
and flock age
Salmonella prevalence was considered in a number of sub-categories including production system,
flock size, the number of birds per shed as well as flock age. It is important to re-iterate that based on
2
Pellets are a form of feed that are compacted and extruded by mixing steam with mash feed.
Dry mash is a form of a complete feed that is finely ground and mixed so that birds cannot easily separate
out ingredients.
4
Crumble is a complete feed source derived from pellets that have been broken into small fragments
3
2014 Microbiological baseline survey of the QLD egg production environment
Page 17 of 31
this level of sampling and arbitrary cut-offs, statistically valid conclusions cannot be made when
assigning cause to any observed differences.
Production system
Table 1 presents the results of Salmonella infection in different QLD egg farm production types. Of
the 21 QLD egg farms included in the survey, 9 (43%) used a cage-based system of which one was
single-tiered, two were 2- or 3-tiered and 6 farms were multi-tiered (6- to 8-tiered). Two (9.5%) farms
used a barn system and 10 (47.5%) were free-range, of which 4 farms were free-range organic.
Salmonella was detected across all types of production systems. Salmonella prevalence was highest
in cage-based systems (89%; 8/9) within which multi-tiered sheds had the highest number of
Salmonella detections. The free-range Salmonella prevalence in the QLD survey was lower than that
reported for the 2010/2011 NSWFA survey (40%; 12/30).
Table 1. Salmonella infection in different Queensland egg farm production systems
Production system
Number of farms
% Salmonella Positive
47.5% (10/21)
30% (3/10)
Barn
9.5% (2/21)
50% (1/2)
Cage
43% (9/21)
89% (8/9)
Free-range
Due to a lack of research, it is unclear whether, or how, different egg production systems impact onfarm Salmonella carriage rates. The impact of layer production systems on egg safety and quality is
of increasing interest to food safety and public health authorities however, given consumer-driven
changes for the sale of cage-free produced eggs in Australia, particularly through the largest
supermarket chains. Changes from caged systems to non-caged productions systems have been
suggested to affect the safety and quality of eggs through microbiological or chemical contamination,
but these effects have not yet been fully investigated (Holt et al. 2011).
Salmonella prevalence has previously been reported at greater levels in conventional caged systems
compared to cage-free (birds housed on floors) in countries such as Germany, the United Kingdom,
Wales, France and Belgium (Snow and O’Connor 2007, Holt 2011). The findings here support those
reports, where the tiered, caged production systems had a higher carriage rate of Salmonella than
free-range or barn systems. In contrast, other studies have detected a lower incidence of Salmonella
in caged than cage-free systems suggesting there are likely to be confounding factors influencing the
2014 Microbiological baseline survey of the QLD egg production environment
Page 18 of 31
incidence and prevalence of Salmonella in different production systems. These factors need to be
further investigated as a matter of priority.
Flock size and bird density
Table 2 presents the Salmonella infection results in varying farm flock sizes and bird numbers per
shed. The total farm flock sizes on surveyed QLD egg farms ranged from 200 to 1 million birds. Farms
were categorized as ‘small’ if they carried less than 15 000 birds, ‘medium’ if they carried less than 50
000 birds and ‘large’ if they carried more than 50 000 birds. A higher prevalence of Salmonella was
found on ‘large’ (5/7; 71%) farms compared to ‘medium’ (3/6; 50%) and ‘small’ farms (4/8; 50%). At
the shed level, bird numbers per layer shed ranged from 200 birds/shed to 72 000 birds/shed. There
was an increasing trend of Salmonella infection as the number of birds housed per shed increased
(Table 2).
Table 2. Salmonella infection results in farm flocks by size and the number of birds housed in each
layer shed.
Category
Category cut-offs
Number of farms
% Salmonella
or sheds
Positive
Farm Flock Size
Small
≤ 15 000
38% (8/21)
50% (4/8)
Medium
≤ 50 000
29% (6/21)
50% (3/6)
Large
> 50 000
33% (7/21)
71% (5/7)
Low density
< 10 000
45% (24/53)
21% (5/24)
Medium density
11 000 – 40 000
34% (18/53)
39% (7/18)
High density
≥ 41 000 – 72 000
21% (11/53)
82% (9/11)
Birds/Layer shed
Flock size and/or bird number per shed has been shown to be an important factor affecting the
prevalence of Salmonella where larger flocks are reported to have greater carriage rates of Salmonella
than smaller flocks. Possible explanations for this increase may be that higher densities of birds lead
to concomitant increases in Salmonella-contaminated dust, dander and faeces. Analysing the relative
role of flock size and the number of birds per shed in exacerbating Salmonella problems can be
confounded by the fact that high densities of birds and large flock sizes are usually reflective of
conventional caged production systems.
2014 Microbiological baseline survey of the QLD egg production environment
Page 19 of 31
Flock Age
The age of the flocks examined in the survey ranged from 18 to 104 weeks. In total there were 45/53
(85%) sheds that housed single-aged flocks for which an observation about Salmonella prevalence
could be made. Salmonella prevalence was determined for four flock age categories corresponding
to a point in the production cycle including 18 – 35 weeks (9/45; 20%); 36 – 52 weeks (11/45; 25%);
53 – 64 weeks (12/45; 26%); and 65 - > 100 weeks (13/45; 29%). Salmonella was detected in flocks
of all ages, and the proportion of infected flocks was comparable for all age categories at 45%, 46%,
50% and 39% respectively.
For layers, flock age and its relevance to a point in the egg production cycle may affect Salmonella
carriage and prevalence within the flock, however the specifics and extent of the role of flock age has
not been fully investigated. In this survey, there was no clear difference in Salmonella prevalence
between age groups however different stressors within the production cycle, such as bird placement,
initiation of lay, induced moulting (where applied) and/or greater age have been reported to increase
bird susceptibility to Salmonella infection or the rate of bacterial shedding in infected flocks.
3.4 A baseline of Salmonella prevalence on egg farms may inform the
effectiveness of future Salmonella reduction strategies
The number of farms with positive Salmonella samples (‘positive farms’) and the proportion of positive
samples on those farms raises awareness of the risks of transference of Salmonella to eggs through
production and the extent of Salmonella infection on an individual farm. This measure can be used to
monitor the impact of Salmonella reduction strategies utilized on-farm in the future. In this survey, the
proportion of positive samples (boot/sponge and faecal material samples) within each farm provides
a general indication of the overall effectiveness of the on-farm Salmonella reduction practices,
although biological factors such as intermittent shedding of Salmonella can confound this measure.
Selected percentile rankings for Salmonella-positive farms were calculated as in the 2010/2011
NSWFA survey and Table 3 presents a comparison of the NSW and QLD data. For half of the
Salmonella-positive farms (at the 50 th percentile), at most, the proportion of Salmonella-positive
samples in the Queensland survey was 56%. At the 90th percentile, 100% of the QLD samples were
Salmonella-positive. It should be noted that for each farm the number of samples varied in accordance
with the size of the farm and number of sheds. For farms with greater than 20 000 birds, a maximum
of four sheds were sampled, meaning up to 8 samples were analysed, compared to 2-4 samples for
smaller farms.
2014 Microbiological baseline survey of the QLD egg production environment
Page 20 of 31
Table 3. Comparison of egg farms in the 2014 Queensland survey and 2010/2011 New South Wales
survey ranked by proportion of Salmonella-positive samples
% of Positive Samples
2014 Queensland survey
2010/2011 NSW surveya
Median
56%
27%
90th percentile
100%
60%
95th percentile
-
66%
99th percentile
-
93%
Percentile ranking
a
NSWFA, 2013
3.5 Salmonella Typhimurium and Queensland egg farms
Figure 3 provides a profile of Salmonella serovars isolated from samples collected in the survey.
Thirty-five isolates were serotyped from single isolates collected from 35 positive samples. In total,
fifteen serovars were isolated with STm as the most common serovar (20%; 7/35), followed by S.
Agona and S. Infantis (both 12%; 4/35). In the 2010/2011 NSWFA survey, the most common serovar
was also STm (30%), followed by S. Infantis (19%) and S. Senftenberg (14%) (NSWFA 2013). Even
though the total flock size heavily influenced the number of sheds on the farm, and therefore the
number of samples tested per farm, STm was also the most common serovar when the results were
examined at the farm-level (3/21 farms; 14%). The next most common serovars were S. Infantis, S.
Zanzibar and S. Alachua infecting 2/21 (9.5%) farms each.
2014 Microbiological baseline survey of the QLD egg production environment
Page 21 of 31
20%
15%
20%
10%
12% 12%
9%
6%
6%
6%
6%
6%
5%
6%
3%
3%
3%
3%
0%
proportion of isolates
25%
Queensland - 2014
NSW - 2010/2011
proportion of isolates
35%
30%
30%
25%
20%
15%
10%
5%
19%
14%
8%
5%
4%
4%
3%
2%
2%
2%
2%
2%
2%
2%
1%
1%
0%
Figure 3. Comparison of Salmonella serovar profiles from positive samples collected from
egg farms in Queensland, 2014 and NSW, 2010/2011
The number and proportions of different Salmonella serovars present in an egg-laying environment
appears to be dynamic and the predominance of a serovar may change over time. The NSWFA
reported apparent changes in the Salmonella serovar profile in egg farms over the past 15 years using
data from the joint NSW/VIC S. Enteritidis Monitoring and Accreditation Program and the recent
2010/2011 survey. There is limited data available on the prevalence and diversity of Salmonella
serotypes in layers and egg production environments in QLD. Table 4 summarises and compares
data from the few studies that have been performed in QLD and NSW.
2014 Microbiological baseline survey of the QLD egg production environment
Page 22 of 31
Table 4. Comparison of Salmonella serovar profiles over time in Queensland and New South Wales
layer hens
Queensland
Year
Location
1991a
SE QLD
1993-1995b
SE QLD
2014
QLD
Predominant serovars
1. S. Orion
2. S. Infantis
1. S. Singapore
2. S. Cerro
1. S. Typhimurium
2. S. Infantis
NSW
Year
Location
1996 – 2000c
NSW/VIC
2001-2003 c
NSW/VIC
2004 - 2005 c
NSW/VIC
2010/2011d
NSW
Predominant serovars
1. S. Sofia
2. S. Agona
1. S. Agona
2. S. Infantis
1. S. Mbandaka
2. S. Typhimurium
1. S. Typhimurium
2. S. Infantis
a
(Cox unpublished)
(Cox 2002)
c
(Arzey 2008)
d
(NSWFA 2013)
b
3.6 Salmonella Typhimurium phage and MLVA types isolated from the current
study
Phage and MLVA typing was carried out for seven STm isolates. Three phage types and five MLVA
types were identified from both swab and pooled faecal material samples from 3 commercial egg
farms. None of the phage or MLVA types identified in this study were common to QLD STm outbreaks
published in OzFoodNet reports from 2011-2013 but note that data for individual notified human cases
were not obtained.
In Australia, a national MLVA typing network has been established since 2006 where notifications of
human salmonellosis caused by STm – the serovar most often linked to human illness – are further
characterized by phage and MLVA typing. These tools can allow identification of linkages between
human cases involved in foodborne outbreaks or in some cases, to complement traceback of
Salmonella isolates to the source for incident response or surveillance. Phage typing is the traditional
strain typing method used in Australia although MLVA has been investigated as an alternative due to
its superior speed of analysis and ability to differentiate closely related strains. When applied at the
farm or production level, MLVA has shown good discrimination by identifying identical profiles among
isolates obtained at different points of a pork food supply chain (Prendergast 2011). A level of technical
2014 Microbiological baseline survey of the QLD egg production environment
Page 23 of 31
expertise is required to interpret both phage and MLVA type results and make robust conclusions
about the sources or relatedness of disease outbreaks. For these reasons, it is often recommended
that phage and MLVA typing are used in conjunction with eachother and precautions taken when
conclusions are made. Table 3 presents the phage and MLVA types from STm isolates identified in
this study.
Table 5. S. Typhimurium phage and multi-locus variable number tandem repeat (MLVA) types from
isolates on egg farms in the 2014 Queensland egg farm survey.
Egg Farms (2014)
Isolate
Phage type
MLVA
1
135
03-17-09-12-525*
2
135
03-17-09-12-526*
3
U307
03-12-06-13-525
4
135a
03-12-12-10-525
5
135a
03-14-12-10-525
6
135
03-17-09-11-525
7
135
03-17-09-11-525
* indicates these isolates are considered the same
4
Conclusion
The overarching aim of the QLD Egg Food Safety Scheme is to ensure the safety and suitability of
eggs and egg products and subsequently reduce the potential for foodborne illness arising from the
consumption of eggs. This survey has delivered a platform of knowledge required to further promote
awareness of the risks of Salmonella contamination on eggs through production and the importance
of implementing and monitoring controls that minimize it’s transference through the egg supply chain.
The findings in this survey highlight the need to maintain effective food safety controls as more than
half of the surveyed QLD commercial egg farms were positive for Salmonella. Although findings from
environmental samples (from which the data was obtained) do not directly link the presence of
Salmonella on-farm to contamination of graded, whole eggs, the data does give insight into the
increased risks of contamination of eggs as they move through the processing system. Achieving
Salmonella reductions at the farm-level should lead to a reduced risk of Salmonella contamination on
eggs and ultimately contribute to a further reduction in egg-associated foodborne illnesses.
Collecting information about Salmonella prevalence in the egg-laying environment provides a baseline
for assessing the impacts of Salmonella risk reduction strategies as well as for monitoring the future
2014 Microbiological baseline survey of the QLD egg production environment
Page 24 of 31
impacts of industry changes in composition and activity on microbial risks. In particular, the baseline
can allow SFPQ to work better with industry to promote awareness of the food safety risks around egg
production, ensure provisions are in place to control and reduce food safety risks and measure
industry commitment to make changes or implement best practices to achieve a safe and suitable
product. In recognition of consumer-driven changes to the Australian egg industry from predominantly
caged systems to cage-free systems, the baseline can also be used to assess how changes in the
composition and activities of the industry impact the microbiological profile of QLD egg farms in the
future.
5
References
AECL (2003). Code of Practice for Biosecurity in the Commercial Egg industry Version 1, June 2003,
Australian Egg Corporation Limited.
Arzey, G. G. (2008). Persistence of Salmonella on layer farms and implications to foodborne risks and
risk interventions. . Paper published in the Proceedings of the WPSA, Brisbane.
Chousalkar, K. K., & Roberts, J. R. (2012). "Recovery of Salmonella from eggshell wash, eggshell
crush and egg internal contents of unwashed commercial shell eggs in Australia." Poultry Science
91(7): 1739-1741.
Cox, J. (unpublished). Cited in Cox 2002.
Cox, J., Woolcock, J. & Sartor, A., (2002). The significance of Salmonella, particularly S. Infantis, to
the Australian egg industry, A report of the Rural Industries and Develoment Corporation.
Davies, R. H. W., A.D., (2010). "Investigations into Salmonella contamination in poultry feedmills in
the United Kingdom." Jounral of Applied Microbiology 109: 1430-1440.
European Commission (2003). Regulation (EC) No 2160/2003 of the European parliament and of the
council of 17 November 2003 on the control of Salmonella and other specified food-borne zoonotic
agents. E. Commission.
FAO/WHO (2002). Risk assessments of Salmonella in Eggs and Broiler Chickens - 2, Food and
Agriculture Organisation of the United Nations and World Health Organisation.
Food Standards Australia New Zealand (2011). Explanatory Statement, Proposal P301: Primary
Production & Processing Standard for Eggs & Egg Products. F2011L00860. F. S. A. N. Zealand.
Holt, P. S., Davies, R.H., Dewulf, J., Gast, R.K., Huwe, J.K., jones, D.R., Waltman, D., Willian, K.R.
(2011). "The impact of different housing systems on egg safety and quality." Poultry Science 90: 251262.
Jones, F., Axtell, R., Rives, D., Scheideler, S., Tarver, F., Walker, R. et al, (1991). "A survey of
Salmonella contamination in modern broiler production." Journal of Food Protection 54: 502-507.
Jones, F. T. (2011). "A review of practical Salmonella control measures in animal feed. ." Journal of
Applied Poultry Research 20: 102-113.
NSWFA (2013). Baseline evaluation of the NSW Egg Food Safety Scheme – microbiological survey
of egg farms in NSW. , New South Wales Food Authority.
OzFoodNet (2010). Monitoring the incidence and causes of diseases potentially transmitted by food
in Australia: Annual report of the OzFoodNet network. O. W. Group.
OzFoodNet (2010). OzFoodNet Quarterly Reports.
OzFoodNet (2011). "OzFoodNet Quarterly Reports."
2014 Microbiological baseline survey of the QLD egg production environment
Page 25 of 31
OzFoodNet (2012). "OzFoodNet Quarterly Reports."
Prendergast, D. M., O'Grady, D.O., Fanning, S., Cormican, M., Delappe, N., Egan, J., Mannion, C.,
Fanning, J., Gutierrez, M., (2011). "Application of multiple locus variable number of tandem repeat
analysis (MLVA), phage typing and antimicrobial susceptibility testing to subtype Salmonella enterica
serovar Typhimurium isolated from pig farms , pork slaughterhouses and meat producing plants in
Ireland." Food Microbiology 28(5): 1087-1094.
Scott, P. (2014). Strategy for Salmonella prevention on egg laying farms. PIX. Gold Coast, Australia.
Snow, L. C., Davies, R. H., Christiansen, K. H., Carrique-Mas, J. J., Wales, A. D., and J. L. O’Connor,
Cook, A. J. C., Evans, S. J., (2007). "Survey of the prevalence of Salmonella species on commercial
laying farms in the United Kingdom." Veterinary Record 161: 471-476.
Wales, A., Breslin, M., Carter, B., Sayers, R. Davies, R., (2007). "A longitudinal study of environmental
Salmonella contamination in caged and free-range layer flocks." Avian Pathology 36(3): 187-197.
2014 Microbiological baseline survey of the QLD egg production environment
Page 26 of 31
Appendix 1. Summary of Salmonella-related food borne outbreaks and food
association in Queensland and Australia in 2010, 2011 and 2012
Queensland
Nationally
No. of
outbreaks
Year
Salmonella serovar
(% of
National
Foodassociation
Salmonella serovar
No. of
outbreaks
Food-association
STm)
2010
S. Typhimurium
7 (14%)
Unknown (4)
S. Typhimurium
52
Eggs (3)
Eggs (22)
Unknown (20)
Pork (5)
Rice (2)
Nut mix (1)
Raw chicken (1)
Salad (1)
S. Singapore
1
Eggs (1)
S. Infantis
1
Raw chicken (1)
S. Saintpaul
1
Unknown (1)
S. Virchow
1
Unknown (1)
Eggs (31)
2011
S. Typhimurium
2 (0.04%)
Eggs (1)
S. Typhimurium
50
Unknown (15)
Chicken pate (1)
Unknown (1)
Chicken/lamb (1)
Pork (1)
Duck parfait (1)
S. Birkenhead
1
Unknown (1)
S. Singapore
2
Chicken (2)
S. Saintpaul
1
Eggs (1)
S. Infantis
1
Duck parfait (1)
S. subsp 1 ser 4,5,12:i:-
1
Pork (1)
S. Typhimurium
58
Eggs (28)
2012
S. Typhimurium
10 (17%)
Unknown (5)
Eggs (4)
Unknown (23)
Chicken (3)
Vitamin meal (1)
Sushi (1)
Sushi (1)
Raw almonds (1)
S. Infantis
1
Prawn roll (1)
S. Give
1
Pasta salad (1)
S. subsp 1 ser 4,5,12:-:1,2
1
Unknown (1)
S. Muenchen
1
Ham (1)
S. Wangata
1
Unknown (1)
S. Infantis
1
Prawn rolls (1)
S. Anatum
1
Salad (1)
S. subsp 1 ser 4,5,12:-:1,2
1
Unknown (1)
S. subsp 1 ser 4,5,12:i:-
1
Eggs (1)
S. Newport
1
Kebab (1)
S. Singapore
1
Unknown (1)
2014 Microbiological baseline survey of the QLD egg production environment
Page 27 of 31
Appendix 2. Proportion of samples taken from total Queensland accreditation
holders by region
To obtain the list of farm participants, the total number of SFPQ-accredited egg businesses and the
region they were located in, was extracted from the SFPQ accreditation database. The number of
regions (with accredited egg businesses) was 12, with the majority (35%) of egg-producing businesses
located in the Darling Downs-South West region and the remaining regions ranging from 1-10% of the
total number of QLD businesses. A sampling plan was employed where proportionate numbers of egg
businesses for 10 of the 12 regions were selected for sampling.
Region
# Farms
Target %of
total facilities
(n=89)
Proposed # of
facilities*
Actual
Brisbane (Inner Ring)
1
1%
0
0
Brisbane (Outer Ring)
North BSD Balance
6
1
7%
1%
2
0
2
0
South East BSD Balance
5
5%
1
2
West Moreton
9
10%
2
1
Darling Downs-South West
31
35%
9
9
Far North
6
7%
2
1
Gold Coast
5
5%
1
1
Mackay-Fitzroy-Central West
5
5%
1
1
Northern-North West
7
8%
2
1
Sunshine Coast
4
4%
1
1
Wide Bay-Burnett
9
10%
2
2
Total
89
100
23
21
*25% of facilities = 23 facilities
2014 Microbiological baseline survey of the QLD egg production environment
Page 28 of 31
Appendix 3. Sample numbers
The number of samples required for each sample category were determined from Salmonella
prevalence data in the 2010/2011 NSWFA baseline survey. Based on the normal approximation of the
binomial distribution, the number of samples collected aimed to provide at least 90% confidence of the
study estimate being within 5% of the true prevalence assuming the true Salmonella prevalence was ≤
17% in faecal matter, ≤ 26% in boot or cage swabs and ≤ 10% in bulk feed or water. It was determined
57 pooled faecal samples, 63 boot/cage swabs and 47 feed/water samples were required.
Type and number of farms and samples collected and analysed for Salmonella in the survey
Sample Type
Number of samples
Farms
Egg producers
15
Egg processors
6
Total
21
Production systems
Cage
9
Free-range
10
Barn
2
Total
21
Sheds
53
Egg-laying environment
Pooled faecal samples
53 (93% of required)
Boot/sponge swabs
53 (84% of required)
Farm inputs
Feed (bulk stored)
21
Hen drinking water (at source)
21
Bore
12
Town, reticulated
8
Dam
2a
Rainwater
1b
Total
a
b
42
(89% of required)
farm uses bore and dam
farm using bore predominantly and rainwater when available
2014 Microbiological baseline survey of the QLD egg production environment
Page 29 of 31
Appendix 4. Sampling methodology and laboratory methods for Salmonella
analysis
Sample
Bulk stored feed
Water source – primary
source used for hen
drinking water
Sampling methodology
Australian
Standard Method
Approximately 500 g of sample was collected
per farm from a hopper, silo or retention
AS 5013.10-2009
sample.
Approximately 500 mL was collected from the
farm’s main storage tank or tap connected to
a shed
AS 5013.10-2009
For barn/free-range systems: One pair of boot
swabs (spun-bonded polypropylene boot
overshoes) was used per shed. Boot swab
sampling involved pre-moistening the swabs
with buffered peptone water before placing on
feet and taking at least 100 paces within the
bird access area.
Boot/sponge swab
AS 5013.10-2009
For caged systems: Sponges were premoistened with buffered peptone water before
swabbing on ends of manure belts of multiple
tiers and cage lines. For caged systems
without manure belts, swabs were taken of
floors or the bottoms of cages.
For barn/free-range systems: Approximately
200 g or 60 pinches of moist faecal material
was collected from the floor or nesting boxes
of the laying shed.
Faecal materiala
a
For caged systems: Approximately 200 g or 60
pinches of moist faecal material was collected AS 5013.10-2009
from the ends of manure belts of multiple tiers
and cage lines. For cage systems with a pit
manure collection system, moist faecal
material was collected along the cages of
multiple lines.
faecal material samples were frozen for 24 hours before testing
2014 Microbiological baseline survey of the QLD egg production environment
Page 30 of 31
Document acceptance and authorization
Name
Name/Signature
Date
Project Manager
Andrew Wilson
02 02 2015
Project Leader
Leigh Cuttell
02 02 2015
Chief Executive Officer
Barbara Wilson
File #
File Name
2014 Microbiological baseline survey of the
Queensland egg production environment
Release Date:
Review Date: not required
Version
Date
Modified by
Details
Modified
1.0
21/01/2015
Leigh Cuttell
Document created
2.0
02/02/2015
Leigh Cuttell
Comments from reviewers incorporated
2014 Microbiological baseline survey of the QLD egg production environment
Page 31 of 31