Bacterial Contamination of Platelet Pools -- Ohio, 1991

From June 27 through July 30, 1991, four episodes of bacterial contamination of platelet pools occurred in an Ohio hospital and were reported by the hospital through the Food and Drug Administration (FDA) to CDC. This report summarizes the results of the epidemiologic investigation of these episodes.

Three of the four patients who received the platelet pools were hospitalized for malignancies and developed chills and rigors within 1-40 minutes after initiation of the transfusion; one of the three developed hypotension. After two of these episodes, the hospital began pretransfusion Gram staining and culturing of all platelets but did not delay platelet transfusion awaiting Gram stain or culture results. This increased surveillance detected a fourth contaminated platelet pool, but it had already been transfused to a hemodialysis patient with idiopathic thrombocytopenia associated with myelodysplasia; this patient developed asymptomatic bacteremia.

The FDA and CDC initiated an investigation to attempt to detect the source of and risk factors for contamination of these platelet pools. A contaminated platelet pool was defined as a platelet pool with a positive bacterial culture confirmed by either a positive Gram stain of the pool, a positive culture in an individual platelet unit that was part of the platelet pool, or a positive culture from blood obtained from the transfusion recipient from June 27 through July 31. The four contaminated platelet pools, each derived from five individual platelet units, were positive by Gram stain and culture for Bacillus cereus (two platelet pools) and Staphylococcus epidermidis and Pseudomonas aeruginosa (one platelet pool each); colony counts ranged from 10 superscript 6 to 10 superscript 8 colony-forming units (CFU) per mL in the platelet pools, and from 10 to 10 superscript 10 CFU/mL among 11 of the 20 individual platelet units constituting the pools.

On average, the individual platelet units constituting the contaminated platelet pools were pooled 2.5 hours (range: 15 minutes-3.2 hours) before transfusion. Investigators examined data on the four contaminated platelet pools for associations with the phlebotomists, bloodmobile sites or dates, component separation technicians, pooling technician, pooling date and time, and platelet age. However, no units from any two pools shared any of these factors.

From June 27 through July 30, the rate of bacterial contamination of platelet pools at the hospital (four (0.4%) of 1063 platelet pools transfused) was significantly greater than for the previous 21 months (one (0.01%) of 7350 platelet pools transfused, p=0.001). During the 21 months before June 27, 1991 (when the hospital instituted more stringent guidelines for detection and reporting of platelet-transfusion reactions), the nursing staff at the hospital increasingly reported platelet-transfusion reactions to the hospital blood bank (99% of which resulted in culturing of the involved platelet pool). The rate of reported reactions, by month, increased from 2.3 per 1000 platelet pools transfused during September 1989 to 72.4 reported reactions per 1000 platelet pools transfused during July 1991 (p less than 0.001, chi-square for linear trend).

The hospital continues pretransfusion Gram staining and culturing of all platelets and now requires a negative Gram stain before releasing the platelets for transfusion. Reported by: TJ Halpin, MD, State Epidemiologist, Ohio Dept of Health. S Kilker, Cincinnati District; J Epstein, MD, Div of Transfusion Science, M Tourault, Div of Inspection and Surveillance, Office of Compliance, Center for Biologics Evaluation and Research, Food and Drug Administration. Investigation and Prevention Br, Hospital Infections Program, National Center for Infectious Diseases, CDC.

Editorial Note

Editorial Note: Platelets may be obtained from plasmapheresis or from whole blood donations; the latter are produced by a closed two-step centrifugation system within 8 hours of obtaining whole blood from the donor. Individual platelet units are then stored at room temperature for less than or equal to 5 days before being transfused or pooled with one to 10 other individual units (1); once pooled, the platelets must be transfused within 4-6 hours. During 1986, the FDA established the maximum storage time for platelets as 5 days (2-4).

In the United States, up to 10% of platelet pools used in transfusions may be contaminated, a potentially serious complication of platelet transfusion (4). Most episodes of bacterial contamination of platelets involve skin saprophytes such as S. epidermidis and Bacillus sp.

In this investigation, the findings of high colony counts in some individual platelet units suggest that the individual units were contaminated at the time of donation and that the contaminating organisms proliferated at room temperature during the interim between donation and pooling. Conversely, the short interval between pooling and transfusion was insufficient for bacteria to proliferate to the high colony counts present in the pooled platelets at the time of transfusion. The increased discovery of contaminated units at this hospital probably occurred because of rigorous reporting of platelet-transfusion reactions and the subsequent culturing of those platelets.

The findings in this investigation are consistent with those in a previous report in which six (less than 0.06%) of 10,219 platelet pools transfused were contaminated with bacteria (5). Both the hospital involved in that report and the hospital reported here had established protocols for intensive surveillance for platelet-transfusion reactions and routine culturing of those platelets associated with reactions. Hospitals that institute such measures will identify more units of bacterially contaminated platelets; CDC recommends that all platelets involved in transfusion reactions be evaluated for bacterial contamination to more accurately estimate the incidence of bacterial contamination of platelets. Clinicians and blood center personnel are requested to report all episodes of transfusion reactions related to bacterial contamination of platelets through state health departments to CDC's Investigation and Prevention Branch, Hospital Infections Program, National Center for Infectious Diseases; telephone (404) 639-1550. Fatal reactions to platelet transfusions must be reported to the FDA; telephone (301) 295-8191.

References

1. Murphy S, Gardner FH. Effect of storage temperature on maintenance of platelet viability--deleterious effect of refrigerated storage. N Engl J Med 1969;280:1094-8.

2. Myhre BA. Fatalities from blood transfusion. JAMA 1980;244:1333-5.

3. Heal JM, Jones ME, Forey J, Chaudhry A, Stricof RL. Fatal Salmonella septicemia after platelet transfusion. Transfusion 1987;27:2-5.

4. Goldman M, Blajchman MA. Blood product-associated bacterial sepsis. Transfusion Medicine Reviews 1991:73-83.

5. Morrow JF, Braine HG, Kickler TS, Ness PM, Dick JD, Fuller AK. Septic reactions to platelet transfusions: a persistent problem. JAMA 1991;266:555-8.

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