Bacteriocidal properties of platelet concentrates

Evaluation of a new generation of plastic culture bottles with an automated microbial detection system for nine common contaminating organisms found in PLT components

BACKGROUND

A microbial detection system (BacT/ALERT 3D, bioMérieux [formerly Organon Teknika]) has previously been validated with a variety of bacterial contaminants in PLTs. The recovery of nine organisms seeded into PLTs with new plastic culture bottles was studied in comparison to the current glass bottles. The use of plastic instead of glass would be expected to reduce the risk of injury.

STUDY DESIGN AND METHODS

Isolates of Bacillus cereus, Enterobacter cloacae, Escherichia coli, Klebsiella pneumoniae, Staphylococcus aureus, Staphylococcus epidermidis, Serratia marcescens, Streptococcus viridans, and Propionibacterium acnes were inoculated into Day 2 (>24 hr <48 hr) apheresis PLT units to 10 and 100 CFUs per mL. Replicate samples (4 mL) were inoculated into both current- and new-generation standard aerobic and anaerobic bottles.

RESULTS

All organisms (with the exception of P. acnes) were detected in a mean time of 9.3 to 18.9 hours (10 CFUs/mL) or 8.7 to 18.2 hours (100 CFUs/mL). In aggregate (with the exception of P. acnes), the plastic and glass aerobic bottles had a mean difference in detection of 1.2 hours (p < 0.0001), and the plastic and glass anaerobic bottles had a mean difference of 3.3 hours (p < 0.0001). In all cases, the mean detection time was superior or clinically comparable (within 0.1 hr) with the new plastic bottles. P. acnes (an anaerobic organism) was detected with the new and current anaerobic bottles in a mean of 72.8 and 90.4 hours (10 CFUs/mL) or 64.0 and 80.8 hours (100 CFUs/mL), respectively. The narrower bottle neck and smaller inoculation septum present with the new-generation plastic bottles were inoculated with comparable ease to that of the glass bottles.

CONCLUSIONS

These data demonstrate that the new plastic bottles are clinically comparable or superior to the current glass standard aerobic and anaerobic culture bottles.

Evaluation of a new generation of culture bottle using an automated bacterial culture system for detecting nine common contaminating organisms found in platelet components

BACKGROUND

An automated bacterial culture system (BacT/ALERT 3D, bioMérieux) has been previously validated with a variety of bacteria in platelets. The recovery of bacteria in platelets using a new generation of culture bottles that do not require venting and that use a liquid emulsion sensor was studied.

STUDY DESIGN AND METHODS

Bacillus cereus, Enterobacter cloacae, Escherichia coli, Klebsiella oxytoca, Staphylococcus aureus, Staphylococcus epidermidis, Serratia marcescens, Streptococcus viridans, and Propionibacterium acnes isolates were inoculated into Day 2 platelets to concentrations of 10 and 100 CFU per mL. Samples were then studied with current and new aerobic, anaerobic, and pediatric bottles.

RESULTS

All organisms, except P. acnes, were detected in a mean time of 9.2 to 20.4 (10 CFU/mL) or 8.7 to 18.6 (100 CFU/mL) hours. P. acnes was detected in a mean time of 69.2 (10 CFU/mL) or 66.0 (100 CFU/mL) hours. The 10-fold increase in inoculum was associated with a mean 9.2 percent difference in detection time. The aerobic, anaerobic, and pediatric bottles had a mean difference in detection time (hours) between the current and new bottles of 0.10 (p=0.61), 0.4 (p=0.38), and 1.0 (p < 0.001), respectively.

CONCLUSION

No difference in detection time between the current and new aerobic and anaerobic bottles was demonstrated. The new pediatric bottles had a small but significant delay in detection.

Evaluation of an automated culture system for detecting bacterial contamination of platelets: an analysis with 15 contaminating organisms

BACKGROUND

Approximately 1 in 2000 platelet components are bacterially contaminated. The time to detection of 15 seeded organisms in platelets recovered from an automated culture system was studied.

STUDY DESIGN AND METHODS

Isolates of Bacillus cereus, Bacillus subtilis, Candida albicans, Clostridium perfringens, Corynebacterium species, Enterobacter cloacae, Escherichia coli, Klebsiella oxytoca, Propionibacterium acnes, Pseudomonas aeruginosa, Staphylococcus aureus, Staphylococcus epidermidis, Serratia marcescens, Streptococcus pyogenes, and Streptococcus viridans were inoculated into Day 2 apheresis platelet components to obtain a final concentration of approximately 10 and 100 CFU per mL (2 units/organism). Each bag was sampled 10 times (20 mL/sample). Four mL of each sample was inoculated into standard aerobic and anaerobic bottles and into aerobic and anaerobic bottles containing charcoal; 2 mL was inoculated into pediatric aerobic bottles (so as to maintain a 1:10 ratio of sample to media) and 1 mL into thioglycollate broth.

RESULTS

With the exception of P. acnes, all organisms were detected in a mean of 9.2 to 25.6 hours. A range of 10 serial dilutions in inoculating concentrations was associated with an overall 10.1-percent difference in detection time. A mean of 74.4 and 86.2 hours (100 and 10 CFU/mL inocula, respectively) was required for the detection of P. acnes in anaerobic bottles.

CONCLUSION

Bacteria thought to be clinically significant platelet contaminants can be detected in 9.2 to 25.6 hours when the starting concentration is approximately 10 to 100 CFU per mL. P. acnes required considerably longer incubation times for detection (in either aerobic or anaerobic bottles). However, P. acnes is of questionable clinical significance. Such a detection system could be used in either a blood collection center or a transfusion service to screen platelet concentrates for bacterial contamination. Such testing (with sterile sampling performed so as to maintain a closed-bag system) would be expected to save lives and might allow an extension of platelet storage.

Effects of white cell reduction on the resistance of blood components to bacterial multiplication

BACKGROUND

While prestorage white cell (WBC) reduction by filtration may improve platelet and red cell quality, it also may remove an important anti-bacterial defense mechanism, especially if blood is WBC-reduced shortly after collection.

STUDY DESIGN AND METHODS

The question of whether WBC reduction of platelet concentrates and red cells altered bacterial proliferation kinetics in components prepared from deliberately contaminated, freshly collected blood was investigated. Two-unit pools of whole blood were inoculated, at a concentration of approximately one colony-forming unit per mL, with one of 17 bacterial species reported to have caused septicemia in transfusion recipients. Each pool was divided after inoculation, and components were prepared from the 2 units after a 7-hour room-temperature holding period. One unit of each AS-1 red cell or platelet pair was WBC-reduced, and the pairs were then stored for 42 days at 4 degrees C (red cells) or for 10 days at 22 degrees C (platelets). Quantitative bacterial cultures were performed at periodic intervals.

RESULTS

In red cells, clinically significant bacterial proliferation occurred in only one instance (Serratia marcescens), and growth was less rapid in the WBC-reduced unit than in the control. Three patterns of growth were seen in platelet concentrates. In four cases, there was rapid proliferation in both test and control units, while on 13 occasions there was minimal replication in either pair. On six occasions, substantial growth was noted in control units, while few or no bacteria could be found in the WBC-reduced units. There was no evidence in either red cells or platelets that bacteria proliferated more rapidly in units that had been WBC-reduced before storage than they did in units in which WBCs were retained.

CONCLUSION

Rather than increasing the risk of bacterial proliferation through removal of active phagocytic cells, WBC reduction by filtration before blood storage may act to reduce the likelihood of significant bacterial proliferation, possibly by removal of microorganisms along with WBCs.

Microbiologic contamination of peripheral blood stem cell autografts

We have determined the incidence and clinical significance of positive microbiologic cultures in a series of 290 peripheral blood stem cell concentrates in 95 patients undergoing multiple apheresis procedures for autologous stem cell rescue. Specimens for bacterial cultures were obtained after processing of the autografts just prior to freezing. The incidence of microbial contamination was 4.5% (n = 13). The predominant pathogenic microorganism cultured was coagulase-negative Staphylococcus (n = 11). From 8 patients with contaminated leukapheresis products 6 underwent autologous stem cell transplantation. Five patients received 1-5 culture-positive stem cell concentrates without serious sequelae, whereas the sixth patient was autografted with noncontaminated leukapheresis products, 1 concentrate contaminated with Aspergillus fumigatus being not reinfused. No microorganism present in the stem cell autograft was recovered in vivo in the posttransplantation period, although fever as a sign of infection occurred in all but 1 patient. Peripheral blood stem cell collection and ex vivo processing for cryopreservation may result in microbiologic contamination. However, our data show that infusion of contaminated stem cell autografts does not play a significant role as a source for infections in the clinical setting of autologous stem cell rescue.

Transfusion-associated bacterial sepsis

The incidence of sepsis caused by transfusion of bacterially contaminated blood components is similar to or less than that of transfusion-transmitted hepatitis C virus infection, yet significantly exceeds those currently estimated for transfusion-associated human immunodeficiency and hepatitis B viruses. Outcomes are serious and may be fatal. In addition, transfusion of sterile allogenic blood can have generalized immunosuppressive effects on recipients, resulting in increased susceptibility to postoperative infection. This review examines the frequency of occurrence of transfusion-associated sepsis, the organisms implicated, and potential sources of bacteria. Approaches to minimize the frequency of sepsis are discussed, including the benefits and disadvantages of altering the storage conditions for blood. In addition, the impact of high levels of bacteria on the gross characteristics of erythrocyte and platelet concentrates is described. The potentials and limitations of current tests for detecting bacteria in blood are also discussed.

Exercise and the immune response

A growing number of reports have become available which implicate infectious disease with reduced performance in athletes. The immune system consists of both nonspecific and specific components geared to control infections. Adaptive immunity functions through both antibody-mediated and cell-mediated compartments to establish and maintain long term immunity to infectious agents. Evidence is accumulating to support the view that physical exercise can lead to modification of the cells of the immune system. However, studies have often not been well designed to control exercise protocols when examining the effects of exercise on the immune system. Large numbers of peripheral blood lymphocytes are mobilised with exercise and in vitro tests indicate that temporarily these cells may not be capable of responding normally to mitogens. These reactions appear to be influenced by hormones to some degree and there are reports that the cells of the immune system are extremely active biochemically and may depend on products from muscles to maintain their activity. Specific populations within the circulating leucocyte pool vary significantly with exercise and there is some evidence that the T4/T8 lymphocyte ratio may become significantly reduced. This reduction in ratio may be related to the variable responses to T and B cell mitogens recorded in vitro which overall suggests that a temporary immune suppression may exist following certain training or performance schedules. It is argued that this may lead to a temporary susceptibility to infection and could result from overtraining.

Transfusion-related sepsis after prolonged platelet storage

The antecubital fossa venipuncture site in frequent blood donors can become scarred or "dimpled" and colonized with surface and deep bacteria that are not sterilized by standard iodophor preparation techniques. These microorganisms can be introduced into blood or platelets at the time of donation. Recent advances that permit the prolonged storage of platelets at room temperature before transfusion allow proliferation of these contaminating bacteria, particularly gram-positive microorganisms. Documented are three episodes of platelet contamination with gram-positive organisms and four cases of sepsis in recipients of these platelets, which were obtained through the "dimpled" site of a single donor and stored for at least 80 hours at 22 degrees C before transfusion. In contrast, platelets harvested from this donor's "dimpled" site and stored for not more than 50 hours were transfused to 25 patients without complication. Therefore, the extended storage of platelets at 22 degrees C prior to transfusion demands strict awareness of any possible sources of extrinsic contamination, since gram-positive bacteria can proliferate under these conditions and result in infectious complications in recipients.

[Influence of temperature on shear induced platelet aggregation in vitro (author's transl)]

The extent of platelet aggregation (PA) in vitro was investigated in relation to the temperature. The measurements were performed with a newly developed device in which PA is induced by a well-defined viscometric flow without addition of specific aggregation promoting agents. It was found that the PA occurs in two phases as related to temperature: at 4 degrees C and 37 degrees C there is none and a minimal PA respectively, whereas at room temperature strong PA takes place. It is proposed that these results indicate that both physicochemical mechanisms and the availability of metabolic energy linked with activation of contractile processes are prerequisites for platelet aggregation. The clinical aspects are discussed.

Preparation and storage of platelet concentrates. II. Storage variables influencing platelet viability and function

Factors affecting the viability and function of stored platelet concentrates have been investigated in a blood component programme. It was found that platelets could be maintained for up to 72 h without bacterial contamination under the following conditions: (1) surgical skin preparation at venipuncture site; (2) blood collection in CPD or ACD anticoagulant in a closed bag system; (3) centrifugation of PRP at 3000 g for 20 min; (4) storage in Fenwal PL-146, Cutter CL-2383, or McGaw plastic bags; (5) resuspension of the platelet pellet in 70 ml residual plasma; (6) storage at 22+/-2 degrees C; and (7) constant gentle mixing throughout storage. Platelet viability as determined by recovery and survival is largely maintained, as is platelet function measured by template bleeding time. Both viability and function of concentrated platelets stored at 4 degrees C are severely compromised.