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1
Indian Journal of Medical Microbiology, (2012) 30(2): 212-4
Brief Communication
Detection of bacterial growth in blood components using oxygen consumption as a
surrogate marker in a tertiary oncology setup
PD Chavan, *VG Bhat, S Ojha, RS Kelkar, SB Rajadhyaksha, AN Marathe
Abstract
Microbiological contamination of blood and blood products is a well-recognised transfusion risk. This study was
performed in the blood bank of our oncology centre, with an objective to detect bacterial contamination in our blood
products using oxygen consumption as a surrogate marker [Pall Enhanced Bacterial Detection System (eBDS)].
Results revealed that the percentages of failed units were 1.16% for random donor platelets (RDP), 0.81% for
single donor platelets (SDP) and 2.94% for packed red blood cells (PRBCs), of which one RDP and one SDP grew
coagulase-negative staphylococcus, while one PRBC culture grew Gram-positive bacilli.
Key words: Bacterial contamination, eBDS, platelets, red cells
Introduction
Microbiological contamination of blood and blood
products is a well-recognised transfusion risk contributing
to the morbidity and mortality associated with blood
transfusions.[1] The risk of transmission of bacterially
contaminated blood components is manifold higher than the
combined risk of common transmissible viruses.[2]
While interventions in the form of improved technology,
refrigeration/freezing of blood products, improved
phlebotomy practices, etc. have generally reduced the
incidence of bacterial contamination in blood components,[3]
however, it still remains an important concern, with an
overall prevalence ranging from 0.04 to 2.0%.[4] It is
particularly relevant in platelets because of the possibility
of even small numbers of bacteria multiplying to clinically
significant levels during the storage period of 5 days at
room temperatures of 20–24°C.[5] The infectious risk from
transfused platelets has been estimated to range from 1 of
2000–3000 whole-blood derived, random donor platelets
*Corresponding author (email: <[email protected]>)
Laboratory Manager (PDC), Composite Lab, ACTREC,
Department of Microbiology (VGB, RSK), Transfusion Medicine
(SO, SBR), Blood Bank Officer (ANM), ACTREC, Tata Memorial
Centre, Kharghar, Navi Mumbai - 410 210, India
Received: 10-01-2012
Accepted: 04-03-2012
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PMID:
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DOI:
10.4103/0255-0857.96695
(RDP), and apheresis-derived, single donor platelets
(SDP).[6,7] Significant clinical events have been estimated to
occur in approximately 1 in 25,000 for platelet transfusions
and 1 in 250,000 for red blood cell (RBC) transfusions,[8] and
this may be an underestimation. Mortality rates associated
with bacterial contamination of platelets have ranged from
1 in 17,000 for RDP to 1 in 61,000 for SDPs.[9] Bacterial
contamination may be introduced into blood products through
skin flora during collection, or during manipulations while
processing, or occasionally may be present in donor blood.[5]
Bacteria implicated in infections associated with platelet and
red cell transfusion include coagulase-negative staphylococci,
Staphylococcus aureus, Streptococcus spp., Bacillus spp. and
propionibacteria among Gram-positive bacteria, and Serratia
spp., Yersinia enteocolitica, Acinetobacter spp., Pseudomonas
spp. and members of the Enterobacteriaceae group.[1]
This study was performed in the blood bank of
our oncology centre with a haematopoietic stem cell
transplant unit. The objective of this study was to detect
bacterial contamination in our blood products – RDPs,
SDPs and packed red blood cells (PRBCs) – using
oxygen consumption as a surrogate marker. This in turn
would enable us to reduce the incidence of transfusion
transmitted infections in a setting such as ours with
immunocompromised transplant patients.
Materials and Methods
RDPs, SDPs and PRBCs meant for transfusion in
haematopoietic stem cell transplant patients were collected
between October 2008 and July 2010 at the Department
of Transfusion Medicine and tested by the Pall Enhanced
Bacterial Detection System (eBDS). The system uses an
oxygen analyser to measure the percentage of oxygen in the
headspace gas of the sample pouch. If bacteria are present in
the blood component sample, then their metabolic activity
and proliferation during incubation results in a measurable
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April-June 2012
Chavan, et al.: Detection of bacterial growth in blood components
decrease in the oxygen content of the sample and the air within
the sample pouch. The system recommends use of apheresis
and whole-blood derived platelets and leucocyte-reduced
red cell components for testing. Briefly, the method was as
follows: The representative sample was collected and filled
up to the mark on the testing pouch using sterile connecting
device (SCD) and sealed. The sample pouch was placed on
the platelet agitator horizontally at 35°C in the incubator for
30 h. The percent O2 in the headspace of the sample pouch
on oxygen analyser was measured after 30 h. Results were
interpreted by the system as PASS or FAIL based on the level
of oxygen consumption after 30 h of incubation at 35°C.
All failed units were then tested for bacterial culture on
Bactec 9050 system (BD diagnostics, Franklin Lakes NJ,
USA). All failed platelet and PRBC units were quarantined.
Confirmed culture positives were discarded and culture
negatives taken back on stock.
Results
A total of 258 RDPs, 246 SDPs and 272 PRBCs were
tested by using eBDS (M/S PALL Life Sciences – Pall
Medical, Portsmouth, England). The results are displayed in
Table 1.
Percentages of failed units were 1.16% for RDPs, 0.81%
for SDPs and 2.94% for PRBCs. Of the three RDPs which
failed eBDS, two failed to show any growth on bacterial
culture and one RDP (0.38%) grew coagulase-negative
Staphylococcus.
Similarly, of the two SDPs which failed eBDS, one SDP
(0.4%) had shown contamination with coagulase-negative
Staphylococcus and the other one showed no growth. Only
one PRBC (0.36%) out of eight PRBCs sent for culture
showed contamination with Gram-positive bacilli, which
was not identified, and the other units did not grow bacteria.
Discussion
definitive marker indicative for bacterial contamination
would be isolation of the microorganism by bacterial culture,
systems like the eBDS could be useful where facilities for
culture may not be present, and also because the system is
small, compact and portable. In addition, the test procedure
is cheaper and does not require a high level of technical
expertise as compared to microbiological testing. We found
higher rates of positivity in the eBDS systems as compared
to the other studies. One study by Blajchman et al.[3] found a
contamination rate of 0.07% for RDP and 0.23% for SDPs,
whereas another study by Barrett et al.[12] found contamination
rates of 0.03% for SDPs and 0.003% for PRBCs. So, there
was some disparity with respect to platelets and a wider
disparity with respect to PRBCs in our study [Table 1]. This
could be attributed to the fact that our RDPs and PRBCs
are not leucodepleted at source as compared to universally
leucodepleted products used in other studies.[13] Unlike RDPs
and PRBCs, all SDPs are leucodepleted at source and thus
are less prone to false-positive results. In the Indian setting,
probably due to cost restraints, universal leucodepletion at
source is not a general practice and could be the major reason
for false positivity. The organisms isolated in our study, viz.
coagulase-negative staphylococci and Gram-positive bacilli,
were similar to the spectrum of organisms isolated in other
studies.[1]
Conclusion
The eBDS system may be used as a screening method
for detection of bacterial contamination in SDPs and RDPs;
however, it is associated with false positivity. Further
studies with a larger sample size are warranted to assess
the usefulness of the eBDS system to detect bacterial
contamination in blood components.
References
1.
2.
Various methods have been used for the detection of
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Gram stain, pH testing, automated blood culture systems
like Bactec, BacTAlert and the VersaTrek systems and the
Pall eBDS systems amongst others[10,11] While the most
Table 1: No. of blood components tested with failed
units and units positive for bacterial growth
Blood
No of
No of failed
No. of units
component
units
units by
showing growth in
tested
eBDS
bacterial cultures
RDP
258
03
01
SDP
246
02
01
PRBCs
272
08
01
RDP: Random donor platelets, SDP: Single donor platelets,
PRBCs: Packed red blood cells, eBDS: Pall Enhanced Bacterial
Detection System
213
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How to cite this article: Chavan PD, Bhat VG, Ojha S, Kelkar RS,
Rajadhyaksha SB, Marathe AN. Detection of bacterial growth in blood
components using oxygen consumption as a surrogate marker in a
tertiary oncology setup. Indian J Med Microbiol 2012;30:212-4.
Source of Support: Nil, Conflict of Interest: None declared.
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