Short Communications
Short Communications
Sequence type 398
meticillin-resistant
Staphylococcus aureus
infection and colonisation
in dogs
A. Floras, K. Lawn, D. Slavic, G. R. Golding,
M. R. Mulvey, J. S. Weese
A RESPIRATORY disease outbreak was identified in a litter of
American boxer dogs at a breeding kennel in Ontario, Canada. Three
of the puppies died aged three weeks. Virus isolation was negative
but Bordetella bronchiseptica and meticillin-resistant Staphylococcus aureus
(MRSA) were isolated from nasal and oropharyngeal samples. The
MRSA isolate was spa-type t034, negative for Panton-Valentine leukocidin genes, non-typable by SmaI pulsed-field gel electrophoresis,
and sequence type (ST) 398. This clone of MRSA is usually associated with livestock. Typing of the staphylococcal chromosomal
cassette determined it to be SCCmecV(nt). The role of MRSA in the
death of the puppies was unclear. Because ST398 MRSA has been
rarely reported in dogs, and because of the increasing evidence of the
importance of ST398 as a zoonotic pathogen, an investigation was
undertaken.
The kennel consisted of 12 breeding animals (10 females and two
males), four adult pet dogs and two pet cats. At the time of initial
investigation, two litters of puppies were present, including the litter
containing the puppies that died. Two other bitches were pregnant
and due to deliver within the next two weeks. Because of the potential
for direct transmission of MRSA between certain animals as well as
direct transmission from human beings to animals or indirect transmission to animals, all animals were considered potentially exposed
and were tested. Nasal and rectal swabs were collected from all animals (12 breeding dogs, four pet dogs, two pet cats and 12 puppies) 21
days after the deaths of the puppies. MRSA was isolated from 12 of
30 (40 per cent) animals (Table 1): two of 12 (17 per cent) breeding animals (both periparturient bitches), three of four (75 per cent) surviving
six-week old puppies from the affected litter, six of eight (75 per cent)
three-week old puppies from the other litter, and a pet dog housed
in the same pen as the first bitch. The other three dogs and two pet
cats were negative for MRSA. Household infection control practices
were in place, particularly hand hygiene. Contact between colonised
(MRSA-positive) dogs and other dogs and people was restricted. It was
Veterinary Record (2010) 166, 826-827
A. Floras, DVM,
D. Slavic, DVM, MSc, PhD,
J. S. Weese, DVM, DVSc, DipACVIM,
University of Guelph, Guelph, Ontario,
N1G 2W1, Canada
K. Lawn, DVM,
Paris Veterinary Clinic, Paris, Ontario,
N3L 2N9, Canada
doi: 10.1136/vr.b4870
G. R. Golding, PhD,
M. R. Mulvey, PhD, ARMCCM,
National Microbiology Laboratory,
Winnipeg, Manitoba, R3E 3R2, Canada
Correspondence to Dr Weese, e-mail:
[email protected]
Provenance: not commissioned;
externally peer reviewed
826 | Veterinary Record | June 26, 2010
TABLE 1: Number (%) of nasal and rectal samples from dogs in a
breeding kennel positive for meticillin-resistant Staphylococcus
aureus
Number (%) of samples positive
Sampling period Number of positive dogs Nasal only Nasal and rectal Rectal only
Day 0
Day 14
12
12
5 (42)
10 (83)
6 (50)
2 (17)
1 (8)
0
reported that one of the two people in the household worked on a pig
farm. Because of the strong association between ST398 colonisation
of human beings and contact with livestock, and the high rates of
ST398 colonisation among pig farmers (Van Loo and others 2007),
colonised people were considered a possible source of infection for
the dogs.
Testing was repeated 14 days later. Nasal and rectal samples were
collected from 28 originally tested dogs (cats were not retested) and
one new dog. Further, two bitches had whelped, and puppies from
the two new litters (one of eight puppies and one of five) were also
tested, giving a total of 42 dogs tested. In the interim, one of the colonised bitches had developed MRSA gangrenous mastitis and two of its
puppies had developed severe MRSA pyoderma. MRSA was isolated
from 12 of the 42 (29 per cent) dogs: eight of 25 (32 per cent) puppies
and four of 17 (24 per cent) adults. One of 12 (8.3 per cent) puppies
from the initial two litters, five of eight (63 per cent) puppies from one
new litter and two of five (40 per cent) puppies from the other new
litter were MRSA-positive. The only dog that was positive on both
occasions was the bitch that had developed MRSA mastitis, which is
consistent with evidence that MRSA colonisation in dogs tends to be
transient (Lefebvre and others 2009, Loeffler and others 2010). Nasal
swabs were also collected from both people in the household and were
negative. Attempts to obtain subsequent rounds of samples from the
animals were unsuccessful because the owners were not interested in
continued sampling.
Overall, spa-type t034 MRSA was isolated from nasal or rectal
swabs on one or more occasions from 23 of 44 (52 per cent) animals;
23 of 42 (55 per cent) dogs (not including the dead puppies) were positive and both cats were negative.
ST398 MRSA is an emerging problem in livestock and human
beings in some regions (van Rijen and others 2008, 2009, Wulf and
Voss 2008). It is present widely in pigs internationally (Huijsdens
and others 2006, de Neeling and others 2007, Dewaele and others 2008, Khanna and others 2008, Smith and others 2009) and is
an increasing cause of community-associated MRSA infection and
colonisation in people in some European countries (Lewis and others 2008, van Rijen and others 2008). Currently, ST398 MRSA is
rare in human beings in North America (Golding and others 2009)
but it can commonly be found in pigs (Khanna and others 2008,
Smith and others 2009).
There is only one previous report of clinical ST398 MRSA infection in the dog, a single case from Germany of pyoderma caused by
ST398, spa-type t034 (Witte and others 2007). Colonisation of the
dog owned by a pig veterinarian with ST398 MRSA has also been
reported (Nienhoff and others 2009). Identification of multiple cases
of ST398 MRSA in dogs, with apparent transmission between dogs,
was therefore remarkable.
It is tempting, and perhaps not unreasonable, to speculate that
the owner who worked on the pig farm was the source of MRSA.
Confirmation of this is impossible because of the retrospective nature
of the investigation and inability to test pigs on the farm. Lack of
identification of human colonisation with only a single round of sampling taken well after the start of the outbreak should certainly not be
taken as an indication that human beings were not a potential source
of MRSA, nor that transmission of MRSA from the colonised dogs to
human beings did not occur.
Short Communications
It is unclear whether this outbreak truly represents a rare phenomenon or whether ST398 MRSA may be an emerging problem
in companion animals. Given the widespread presence of this clone
in livestock and the increasing frequency with which it is detected in
human beings in some regions, exposure to dogs is likely to increase.
Ongoing surveillance of pet populations is required to better understand the epidemiology of ST398 MRSA in pets and to determine the
risks to pets and human beings.
References
DE NEELING, A., VAN DEN BROEK, M., SPALBURG, E., VAN SANTENVERHEUVEL, M., DAM-DEISZ, W., BOSHUIZEN, H., VAN DE GIESSEN, A.,
VAN DUIJKEREN, E. & HUIJSDENS, X. (2007) High prevalence of methicillin resistant Staphylococcus aureus in pigs. Veterinary Microbiology 122, 366-372
DEWAELE, I., DE MAN, I., STAEL, A., DELPUTTE, P., BUTAYE, P., VLAEMYNCK,
G., HERMAN, L., HEYNDRICKX, M. & RASSCHAERT, G. (2008) Methicillinresistant Staphylococcus aureus (MRSA) in Belgian pig farms. In American Society for
Microbiology Conference on Antimicrobial Resistance in Zoonotic Bacteria and
Foodborne Pathogens. Copenhagen, June 15 to 18, 2008. p 23
GOLDING, G. R., LEVETT, P. N., MCDONALD, R. R., WYLIE, J. & MULVEY, M.
R. (2009) Molecular characterization of the first clinical infections of ‘livestock associated’ ST398 methicllin-resistant Staphylococcus aureus in Canada. In American Society
for Microbiology-European Society of Clinical Microbiology and Infectious Diseases
Conference on Methicillin-Resistant Staphylococci in Animals. London, September
22 to 25, 2009. p 44
HUIJSDENS, X., VAN DIJKE, B., SPALBURG, E., VAN SANTEN-VERHEUVEL,
M., HECK, M., PLUISTER, G., VOSS, A., WANNET, W. & DE NEELING, A.
(2006) Community-acquired MRSA and pig-farming. Annals of Clinical Microbiology and
Antimicrobials 5, 26
KHANNA, T., FRIENDSHIP, R., DEWEY, C. & WEESE, J. S. (2008) Methicillin resistant Staphylococcus aureus colonization in pigs and pig farmers. Veterinary Microbiology 128,
298-303
LEFEBVRE, S. L., REID-SMITH, R. J., WALTNER-TOEWS, D. & WEESE, J. S.
(2009) Incidence of acquisition of methicillin-resistant Staphylococcus aureus, Clostridium
difficile, and other health-care-associated pathogens by dogs that participate in animal-assisted interventions. Journal of the American Veterinary Medical Association 234,
1404-1417
LEWIS, H. C., MØLBAK, K., REESE, C., AARESTRUP, F. M., SELCHAU,
M., SØRUM, M. & SKOV, R. L. (2008) Pigs as source of methicillin-resistant
Staphylococcus aureus CC398 infections in humans, Denmark. Emerging Infectious
Diseases 14, 1383-1389
LOEFFLER, A., PFEIFFER, D. U., LINDSAY, J. A., SOARES-MAGALHAES, R. &
LLOYD, D. H. (2010) Lack of transmission of methicillin-resistant Staphylococcus aureus
(MRSA) between apparently healthy dogs in a rescue kennel. Veterinary Microbiology
141, 178-181
NIENHOFF, U., KADLEC, K., CHABERNY, I. F., VERSPOHL, J., GERLACH, G. F.,
SCHWARZ, S., SIMON, D. & NOLTE, I. (2009) Transmission of methicillin-resistant Staphylococcus aureus strains between humans and dogs: two case reports. Journal of
Antimicrobial Chemotherapy 64, 660-662
SMITH, T. C., MALE, M. J., HARPER, A. L., KROEGER, J. S., TINKLER, G. P.,
MORITZ, E. D., CAPUANO, A. W., HERWALDT, L. A. & DIEKEMA, D. J. (2009)
Methicillin-resistant Staphylococcus aureus (MRSA) strain ST398 is present in midwestern US swine and swine workers. PloS ONE 4, e4258
VAN LOO, I., HUIJSDENS, X., TIEMERSMA, E., DE NEELING, A., VAN DE
SANDE-BRUINSMA, N., BEAUJEAN, D., VOSS, A. & KLUYTMANS, J. (2007)
Emergence of methicillin-resistant Staphylococcus aureus of animal origin in humans.
Emerging Infectious Diseases 13, 1834-1839
VAN RIJEN, M. M., BOSCH, T., HECK, M. E. & KLUYTMANS, J. A. (2009)
Meticillin-resistant Staphylococcus aureus epidemiology and transmission in a Dutch
hospital. Journal of Hospital Infection 72, 299-306
VAN RIJEN, M. M., VAN KEULEN, P. H. & KLUYTMANS, J. A. (2008) Increase in a
Dutch hospital of methicillin-resistant Staphylococcus aureus related to animal farming.
Clinical Infectious Diseases 46, 261-263
WITTE, W., STROMMENGER, B., STANEK, C. & CUNY, C. (2007) Methicillinresistant Staphylococcus aureus ST398 in humans and animals, Central Europe. Emerging
Infectious Diseases 13, 255-258
WULF, M. & VOSS, A. (2008) MRSA in livestock animals-an epidemic waiting to
happen? Clinical Microbiology and Infection 14, 519-521
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