Evaluation of BacT/ALERT plastic culture bottles for use in testing pooled whole blood-derived leukoreduced platelet-rich plasma platelets with a single contaminated unit

BACKGROUND: In certain countries, whole blood-derived platelet (PLT)-rich plasma PLTs can only be pooled within 4 hours of transfusion. One prerequisite for prestorage pooling is the ability to detect low levels of bacteria from a single unit (approx. 10 colony-forming units [CFUs]/mL) once pooled (10/6 approx. 2 CFUs/mL). This study evaluated the BacT/ALERT (bioMérieux) for detection of bacteria in 1 unit of a 6-unit pool. STUDY DESIGN AND METHODS: Bacillus cereus, Clostridium perfringens, Enterobacter cloacae, Escherichia coli, Klebsiella pneumoniae, Staphylococcus aureus, Staphylococcus epidermidis, Serratia marcescens, Streptococcus viridans, and Propionibacterium acnes were inoculated into single PLT units (target, 10 and 100 CFUs/mL; mean recovered, 5 and 92 CFUs/mL) and then pooled with 5 sterile units. Four milliliters was inoculated into both plastic aerobic and anaerobic bottles, and 0.5 mL was plated (10 sets). RESULTS: All cases were detected when the single unit had at least 6 CFUs per mL. With B. cereus (< or =2 CFUs/mL), all bottles were reactive. With K. pneumoniae and S. viridans (< or =3 CFUs/mL), all samples were detected with a two-bottle set, but not all bottles were reactive. With S. marcescens (< 2 CFUs/mL), only 7 of the 10 sets were reactive. With C. perfringens (0.2 CFUs/mL), only 3 of 10 samples were detected in the anaerobic bottles. CONCLUSIONS: This study evaluates the use of the BacT/ALERT system for detection of bacteria in PLT pools. Overall, the BacT/ALERT detected all contaminated pooled PLTs when the single inoculated unit had a calculated or recovered concentration at least 3 CFUs per mL with 10 different species of bacteria. Low recovered concentrations (< or =2 CFUs/mL) were, in some cases, only detected with a two-bottle set.     

False-positive alarms for bacterial screening of platelet concentrates with BacT/ALERT new-generation plastic bottles: a multicenter pilot study

BACKGROUND: The microbial detection system BacT/ALERT (bioMérieux) is widely used to monitor bacterial contamination of platelet concentrates (PCs). Recently, the manufacturer introduced polycarbonate culture bottles and a modified pH-sensitive liquid emulsion sensor as microbial growth indicator. This reconfigured assay was investigated in a routine setting. STUDY DESIGN AND METHODS: In each of eight transfusion centers, samples from 500 consecutive PCs were monitored for 1 week. For all PCs with a positive BacT/ALERT signal, retained samples and, if available, original PC containers and concomitant red blood cell concentrates were analyzed independently. Initially BacT/ALERT-positive PCs without bacterial identification in any sample were defined as false-positive. BacT/ALERT-positive PCs with bacteria in the first sample only were called potentially positive. PCs with bacteria in the first sample and the same strain in at least one additional sample were accepted as positive. RESULTS: Five PCs (0.13%) were positive, 9 PCs (0.23%) were potentially positive, and 35 PCs (0.9%) were false-positive. The rate of false-positive BacT/ALERT results varied substantially between centers (<0.2%-3.2%). Tracings from false-positive cultures lacked an exponential increase of the signal during incubation. Most of these false-positives were due to malfunctioning cells in various BacT/ALERT incubation units. CONCLUSION: Careful assessment of individual tracings of samples with positive signals helps to identify malfunctioning incubation units. Their early shutdown or replacement minimizes the high rate of unrectifiable product rejects attributed to false-positive alarms and avoids unnecessary concern of doctors and patients after conversion to a reconfigured BacT/ALERT assay.     

Comparative study of BacT/alert FAN bottles and standard BacT/alert bottles

A total of 5,230 paired blood cultures were studied. One sample was divided between aerobic and anaerobic BacT/Alert standard bottles, and the other divided between aerobic and anaerobic BacT/Alert FAN bottles. There were 44 occasions where Staphylococcus aureus was recovered only from the FAN bottles, compared to six where only the standard bottles were positive (p <0.001), and 21 occasions where Escherichia coli was isolated only from FAN bottles, compared to eight occasions where only the standard bottles were positive for this organism (p <0.05). In 21 of 28 cases reviewed where S. aureus was isolated from FAN bottles only the patient had been receiving anti-staphylococcal antibiotics. However, only 2 of 30 cases where Gram-negative bacilli were isolated from FAN bottles had documented recent appropriate antibiotic therapy. Patients in whom FAN bottles are more likely to recover organisms cannot be selected on the basis of documented antibiotic treatment.     

Viability of Leptospira in BacT/ALERT MB media

Recovery of Leptospira in the clinical setting is typically low as specialized culture media is needed. Previous data demonstrated that blood culture media commonly available to most clinical laboratories do not adequately sustain viable Leptospira. We hypothesized that mycobacterial blood culture medium, which is often readily available to most clinical laboratories, might be able to support the growth of Leptospira. Leptospires and fresh human blood were inoculated into BacT/ALERT (bioMérieux, Durham NC) mycobacterial (MB) and enriched mycobacterial bottles. Standard aerobic (FA) and anaerobic (SN) bottles were also inoculated as a control group. Inoculated bottles were then evaluated for their ability to support Leptospira growth using dark-field microscopy, subculture, and an automated growth detection system. Viable leptospires were detected in MB bottles up to day 14. FA and SN were performed in accordance with prior data. We conclude that MB and enriched MB bottles of the BacT/ALERT blood culture system can support viable leptospires.     

Reassessment of the routine anaerobic culture and incubation time in the BacT/Alert FAN blood culture bottles

A total of 9,130 blood cultures were collected from adult patients with suspected bloodstream infections. The recommended 20 mL sample of blood was divided equally between the aerobic and anaerobic FAN bottles and monitored in the BacT/Alert Microbial Detection System for a total of 5 days. There were 757 clinically significant positive culture pairs from 291 patients. Significant differences were found with greater recovery of Pseudomonas aeruginosa (p < 0.001), Acinetobacter spp. (p = 0.002), coagulase-negative staphylococci other than Staphylococcus epidermidis (p = 0.002), and Candida spp. (p < 0.001) from the aerobic bottle and greater recovery of anaerobic bacteria (p < 0.001) from the anaerobic bottle. Significantly more episodes of P. aeruginosa bacteremia (p < 0.003) and candidemia (p < 0.001) were detected by the aerobic FAN bottle and significantly more episodes of anaerobic bacteremia (p < 0.001) were detected by the anaerobic FAN bottle (Table 2). No other significant differences between systems in their detection of bacteremias were noted. Anaerobic bacteremias were encountered in diverse and often unpredictable clinical settings. All clinically significant episodes of bloodstream infection were detected within 4 days of incubation of their cultures. We conclude routine, rather than selective, use of the anaerobic FAN bottle in the blood culture set and a 4-day incubation of blood cultures in the BacT/Alert aerobic and anaerobic FAN bottles is an appropriate routine procedure.     

A comparison of prestorage WBC-reduced whole-blood-derived platelets and bedside-filtered whole-blood-derived platelets in autologous progenitor cell transplant

BACKGROUND: Prestorage WBC-reduced platelet concentrates (PCs) can be manufactured from platelet-rich plasma (PRP) by in-line filtration of PRP. There are few published data on the clinical use of these products, as compared to bedside-filtered pools of standard PCs (S-PCs) manufactured from PRP. STUDY DESIGN AND METHODS: A prospective, randomized trial was conducted in autologous progenitor cell transplant patients requiring platelet transfusions with each patient as his or her own control who was given a pool of 5 units of WBC-reduced PCs and a pool of 6 units of S-PCs within a 3-hour period. The pools were characterized before transfusion for platelet and WBC content, P-selectin expression, and IL-8. The patients were monitored with platelet counts and vital signs and observed for reactions. Data were analyzed using Mann-Whitney U tests. RESULTS: Thirty-three transfusions were administered to 13 patients. Median platelet content in the WBC-reduced PC pools was lower than that in the S-PC pools (3.3 vs. 4.0 x 10(11), p<0.01). Median WBC content was 4 to 5 log less in the WBC-reduced PC pools (2.5 x 10(4) vs. 4.6 x 10(8), p<0.01). Median IL-8 levels (pg/mL) were lower in the WBC-reduced PC pools (2 vs. 36, p<0.01). No differences were observed in CCI, but the median absolute increase after transfusion of the S-PC pools was higher (25 vs. 19 x 10(9)/L, p<0.01), which reflected the larger size of the S-PC pools. No overall differences in vital signs were recorded. Two reactions were observed, both in temporal association with the transfusion of pools of S-PCs. CONCLUSIONS: A pool consisting of 5 units of WBC-reduced PCs gave a median platelet increment of 19 x 10(9) per L in these thrombocytopenic patients and has a median WBC content 1 to 2 log below the accepted threshold for primary alloimmunization or CMV transmission.     

Use of simulated blood cultures for time to detection comparison between BacT/ALERT and BACTEC 9240 blood culture systems

In order to avoid the influence of pre-analytical steps, the following study was performed by using sterile blood spiked with defined loads of microorganisms as inoculum. Time-to-Detection (TTD) was evaluated for the most frequently encountered bacteria and fungi in septicemia, comparing two commercially available blood culture systems, BACTEC 9240 (Becton Dickinson) and BacT/ALERT (Organon Teknika). A specific medium, Bactec Mycosis IC/F (Becton Dickinson), was compared with the Bactec Plus Aerobic (Becton Dickinson) and FAN Aerobic (Organon Teknika) media for recovery of fungi in general and in case of mixed bacterial/fungal septicemia. The results show that the BACTEC system detects nearly all enrolled microorganisms significantly faster than the BacT/ALERT; the anaerobic vial contributes to the detection of anaerobes and facultative anaerobes and, in the case of BACTEC, shortens TTD; the Bactec Mycosis IC/F bottle shortens TTD of fungi.     

Evaluation of the 3D BacT/ALERT automated culture system for the detection of microbial contamination of platelet concentrates

Bacterial transmission remains the major component of morbidity and mortality associated with transfusion-transmitted infections. Platelet concentrates are the most common cause of bacterial transmission. The BacT/ALERT 3D automated blood culture system has the potential to screen platelet concentrates for the presence of bacteria. Evaluation of this system was performed by spiking day 2 apheresis platelet units with individual bacterial isolates at final concentrations of 10 and 100 colony-forming units (cfu) mL-1. Fifteen organisms were used which had been cited in platelet transmission and monitoring studies. BacT/ALERT times to detection were compared with thioglycollate broth cultures, and the performance of five types of BacT/ALERT culture bottles was evaluated. Sampling was performed immediately after the inoculation of the units, and 10 replicates were performed per organism concentration for each of the five types of BacT/ALERT bottles. The mean times for the detection of these 15 organisms by BacT/ALERT, with the exception of Propionibacterium acnes, ranged from 9.1 to 48.1 h (all 10 replicates were positive). In comparison, the time range found using thioglycollate was 12.0-32.3 h (all 10 replicates were positive). P. acnes' BacT/ALERT mean detection times ranged from 89.0 to 177.6 h compared with 75.6-86.4 h for the thioglycollate broth. BacT/ALERT, with the exception of P. acnes, which has dubious clinical significance, gave equivalent or shorter detection times when compared with the thioglycollate broth system. The BacT/ALERT system detected a range of organisms at levels of 10 and 100 cfu mL-1. This study validates the BacT/ALERT microbial detection system for screening platelets. Currently, the system is the only practically viable option available for routinely screening platelet concentrates to prevent bacterial transmission.     

Evaluation of BACTEC Plus aerobic and anaerobic blood culture bottles and BacT/Alert FAN aerobic and anaerobic blood culture bottles for the detection of bacteremia in ICU patients

Blood culture is the most valuable laboratory test for the diagnosis of bacteremia and sepsis. The BACTEC FX and BacT/Alert 3D automated blood culture systems are commonly used in Korean health care facilities. A controlled clinical evaluation of the resin-containing BACTEC Plus aerobic (BA) and anaerobic (BN), and the charcoal-containing FAN aerobic (FA) and anaerobic (FN) bottles using blood from intensive care unit (ICU) patients was designed. The performances of these 2 systems with media containing particle absorbing antimicrobial agents were evaluated using the culture positivity rate and time to detection (TTD). TTD was collected using data management systems, either the Epicenter (BD Diagnostic Systems) or the hospital laboratory information system. A total of 1539 four-bottle sets were collected from 270 patients in medical and surgical ICUs. Blood culture samples included 1539 bottles each of BA, BN, FA, and FN, and yielded 113 (7.3%), 90 (5.8%), 104 (6.8%), and 80 (5.2%) positive bacterial or fungal isolates, respectively. There were significant differences between the resin-containing BA and BN samples in culture positivity and also between the charcoal-containing FA and FN samples, especially for Escherichia coli (25/27 versus 17/27, P < 0.05) and Acinetobacter baumannii (14/15 versus 7/15, P < 0.05). Significantly shorter recovery time was observed in BACTEC Plus aerobic bottles than in FAN aerobic bottles (17.2 and 24.7 h, respectively) (P < 0.001).     

Bacterial contamination of whole-blood-derived platelets: the introduction of sample diversion and prestorage pooling with culture testing in the American Red Cross

BACKGROUND: Bacterial sepsis following whole blood–derived platelet (WBP) transfusion has remained a substantial patient risk, primarily due to a lack of practical and effective means to limit or detect bacterial contamination. We describe the risk of reported septic reactions to WBPs and the introduction of prestorage‐pooled whole blood–derived platelets (PSPs) collected using initial sample diversion and cultured for bacterial contamination. STUDY DESIGN AND METHODS: Product qualification and quality control (QC) testing with the Acrodose PL system (Pall Medical) were evaluated in four regional blood centers. Bacterial contamination risk was assessed by review of reported septic transfusion reactions to WBPs and by aerobic QC culture of leukoreduced PSPs utilizing automated microbial detection system cultures (BacT/ALERT 3D, bioMérieux). RESULTS: Before implementing PSPs (January 2003‐December 2006), we distributed 2,535,043 WBP units and received 20 reports of septic reactions including 2 fatalities (7.9 per million [1:126,752] reactions and 0.79 per million [1:1,267,522] fatalities). In October 2006, PSPs were effectively implemented with a product qualification success rate of 99.6 percent and a mean yield of 4.0 × 10¹¹ platelets (PLTs) per pool. Whole blood collection sets with sample diversion technology were introduced during the operational trial and decreased the rate of confirmed‐positive bacterial culture of PSPs from 2111 (1:474) to 965 (1:1036) per million (odds ratio, 0.46; 95% confidence interval, 0.22‐0.95). No septic reactions to PSPs were reported (25,936 PSP units distributed). CONCLUSION: Sample diversion and bacterial culture are effective methods to reduce bacterial risk with WBP transfusion. Bacterial contamination of PSPs was assessed at 5.8‐fold our current rate for apheresis PLTs utilizing comparable culture protocols.     

Prestorage pooled whole-blood-derived leukoreduced platelets stored for seven days, preserve acceptable quality and do not show evidence of a mixed lymphocyte reaction

BACKGROUND: Prestorage pooling of whole-blood-derived PCs (WBD-PCs) would be advantageous to transfusion services in that it would make the product available in a more timely manner, reduce wastage of untransfused pools, and simplify bacterial screening by allowing testing of the pool rather than each single PLT concentrate (PC). STUDY DESIGN AND METHODS: Four to six individual leukoreduced PCs were pooled into a 1.5-L CLX-HP PLT storage bag using a sterile connecting device. Controls were individual prestorage leukoreduced PCs that were stored as single products. Products were sampled on Days 5 and 7 for measures of PLT quality; coagulation, fibrinolytic and complement activation; and for evidence of a mixed lymphocyte reaction. RESULTS: The pH level was well maintained to Day 7 with no prestorage pool having a pH below 6.7. Day 7 studies showed no evidence of coagulation or difference in complement activation. F1.2 levels did not differ between Days 5 and 7, but a 10- to 15-percent increase in C3a des-Arg was observed between these days in all product types. Day 7 activated lymphocyte surface markers (CD69, CD71, HLA-DR) were all at lower limits of detection in the prestorage pooled products, and levels of supernatant cytokines were either not different between product types on either study day or, if different, were lower in the prestorage pooled products. CONCLUSION: There is no evidence of a deterioration in quality, activation of coagulation or complement, or a mixed lymphocyte reaction attributable to the prestorage pooling process with up to 7 days of storage.     

Detection of bacteria and fungi in BacT/Alert standard blood-culture bottles

Incubation periods of aerobic (AE) and anaerobic (AN) blood-culture bottles with the BacT/Alert system were assessed in our laboratory. We reviewed the results of 6229 blood-culture sets collected at Kyoto University Hospital from January 1999 to December 2000. Of these sets, 731 (11.7%) were positive for bacteria or yeast. Excluding 87 sets with growth evidence on arrival, of the 644 positive blood-culture sets from 341 patients, a total of 691 organisms were isolated. Of the 691 organisms, 413 (59.8%) were recovered from both bottles, 206 (29.8%) were recovered only from the AE bottle, and 72 (10.4%) were recovered only from the AN bottle. The AE bottle was significantly superior to the AN bottle in terms of both recovery rate and detection time for overall organisms, but there was no significant difference in detection time for facultative anaerobic bacteria between the two bottles. Of the 691 organisms, 530 (76.7%) were classified as usual pathogens. Of the 530 usual pathogens, 501 (94.5%) were recovered in at least one bottle of each set within the first 3 days, and 523 (98.7%) within the first 5 days of incubation. Twenty-nine organisms initially isolated on day 4 or later were recovered from 19 patients. Of these, chart reviews indicated that 21 organisms recovered from 11 patients were considered clinically significant bacteria, and the reviews also revealed that no patient had a treatment plan altered based on the results of positive blood culture. Seven organisms initially isolated on day 6 or later were recovered from 7 patients. Chart reviews revealed that 5 of these organisms from 5 patients were considered to be clinically significant. In conclusion, if the incubation period had been less than 3 days, 11 patients with clinically significant bacteremia or fungemia, (3.2% of all patients with bacteremia or fungemia) would have been undiagnosed. Similarly, with an incubation period of 5 days, 5 such patients (1.5%) would have been undiagnosed.     

全自动微生物监测系统在脐血细菌检测中的应用

目的研究BacT/ALERT 3D全自动微生物监测系统在脐带血细菌检测中的应用。方法将1376份脐带血制备后的血浆和红细胞样本分别以10ml、20ml接种量接种,用BacT/ALERT 3D全自动微生物监测系统进行细菌检测,并和硫乙醇酸盐/改良马丁法检测结果进行比较。结果BacT/ALERT 3D全自动微生物监测系统对10ml、20ml血浆样本的检出率分别为1.16%和1.24%,对20ml红细胞样本的检出率为3.20%,硫乙醇酸盐/改良马丁法对红细胞样本的检出率为1.00%。结论采用BacT/ALERT 3D全自动微生物监测系统可大大提高脐带血细菌污染的检出率,特别是厌氧菌污染的检出率,提高临床脐带血造血干细胞移植的安全性。     

Evaluation of the BacT/ALERT PZA kit in comparison with the BACTEC 460TB PZA for testing Mycobacterium tuberculosis susceptibility to pyrazinamide

OBJECTIVES: To compare the performance of the BacT/ALERT PZA kit (BioMerieux, Marcy l'Etoile, France) with the radiometric BACTEC 460TB PZA test (Becton-Dickinson method) for testing Mycobacterium tuberculosis susceptibility to pyrazinamide. METHODS: A total of 50 M. tuberculosis strains were tested. Thirty of these strains had been previously considered pyrazinamide-susceptible and 20 pyrazinamide-resistant by BACTEC 460TB. RESULTS: Final overall agreement was 100%. Time needed for the susceptibility test was 6.69 days for the BacT/ALERT PZA kit versus 8.07 days for the BACTEC 460TB PZA test. CONCLUSIONS: BacT/ALERT PZA test is an excellent alternative to BACTEC 460TB for pyrazinamide susceptibility testing.     

BacT/ALERT 3D检测系统在快速检测结核分支杆菌中的应用

目的评价BacT/ALERT 3D检测系统在快速检测结核分枝杆菌中的应用价值。方法对336例结核患者的痰液,胸腔积液,病灶组织,脑脊液等标本同时采用BacT/ALERT 3D检测系统和涂片法进行检测。结果 BacT/ALERT 3D检测系统快速培养分支杆菌的阳性率为39.9%,阳性检测时间为14.1天,涂片法阳性率为14.7%,阳性检测时间为1天。结论 BacT/ALERT 3D检测系统能快速,准确的检测分支杆菌,是一种值得推广的分支杆菌快速检测方法。     

全自动血液分析仪在检测血小板细菌污染中的应用

目的评价BacT/ALERT系统在检测血小板细菌污染中的应用。方法用BacT/ALERT系统对所制备的血小板悬液2164袋(含手工采去白细胞混合血小板及机器采集血小板)进行细菌污染检测,阳性标本作细菌鉴定。结果2164袋血小板悬液中细菌培养阳性25袋(1.16%),其中厌氧菌0.60%,需氧菌0.42%,厌氧菌与需氧菌均阳性0.14%。手工采混合血小板的阳性率为1.60%,厌氧菌占0.80%,需氧菌占0.58%,两者均阳性占0.22%。机采血小板的阳性率为0.38%,厌氧菌占0.25%,需氧菌占0.13%。细菌鉴定结果1袋为假阳性。结论BacT/Alert系统全自动血液分析仪具有快速、灵敏度较高以及假阳性率较低的优点。     

Novel method for clearing red blood cell debris from BacT/ALERT blood culture medium for improved microscopic and antimycobacterial drug susceptibility test results

Even though automation in mycobacterial culture has immensely improved the detection of organisms, identification of species and antimycobacterial susceptibility testing from blood culture bottles remain cumbersome and error-prone due to the presence of intact red blood cells (RBCs). The removal or lysis of these RBCs and excessive protein from the blood components could theoretically help improve this process. The present study reports an effective method that uses ammonium chloride (NH(4)Cl) and Triton X-100 to lyse the RBCs in blood culture medium. The method was optimized by preparing various concentrations of NH(4)Cl and Triton X-100, and incubation conditions, leading to eight protocols. The lysis protocol with a concentration of 150 mM of NH(4)Cl, 0.5% Triton X-100, and 1% potassium bicarbonate, pH 7.0, and incubation at 37 degrees C for 15 min was found to be optimal. This method not only made the culture medium clear, the protein concentration decreased from 753.5+/-39.4 to 53.2+/-4.2 mg/mL in the M. tuberculosis-spiked culture medium and in the blood culture medium inoculated with the blood from tuberculosis patients. The method had no adverse effect on mycobacteria, and no depletion of M. tuberculosis colony-forming units was found. The lysate could be used for antimycobacterial susceptibility testing with no difficulty in setting the mycobacterial concentration of inoculum to 0.5 McFarland standards. Furthermore, this method had the added advantage in the microscopy and molecular methods for the speciation of Mycobacterium sp.     

BacT/ALERT 3D在结核分枝杆菌快速培养和药敏试验中的应用

目的探讨BacT/ALERT 3D在结核分枝杆菌快速培养中的应用。方法应用BacT/ALERT 3D检测结核分枝杆菌,并与传统L-J法比较。结果 523份痰标本BacT/ALERT 3D法检出阳性217份(41.52%),阳性报告时间平均14.05 d;L-J法检出阳性178份(34.03%)。BacT/ALERT法培养结核分枝杆菌的阳性率明显高于L-J法(P<0.05);阳性报告时间提前14.66 d,差异有统计学意义(P<0.05)。BacT/ALERT 3D快速药敏法表明总耐药率为56.2%,药敏报告时间平均8.5 d,L-J法则为30 d,两种方法药敏符合率为96.38%(213/221);使用BacT/ALERT 3D快速法进行结核分枝杆菌的培养和药敏试验,报告时间比L-J法总计提前35 d以上。结论 BacT/ALERT 3D法是目前较理想的一种快速检测结核分枝杆菌的方法。     

Comparison of the effect of delayed entry into 2 different blood culture systems (BACTEC 9240 and BacT/ALERT 3D) on culture positivity

The effect of delayed entry (2-48 h) into BacTAlert 3D and BACTEC 9240 and the effect of 2 storage temperatures (22 degrees C vs 35 degrees C) on bacterial growth was evaluated. The delay in transportation of blood culture bottles stored at room temperature had no effect on the recovery rate for the first 12 h. Culture positivity was between 74.4% and 100% for different microorganisms at less than 24 h preincubation time. The positivity rate decreased significantly for Acinetobacter baumannii, Bacteroides fragilis, Escherichia coli, Enterococcus faecalis, Pseudomonas aeruginosa, Klebsiella pneumoniae, and Streptococcus pneumoniae for more than 24 h of delay. Culture positivity was higher at 22 degrees C for all microorganisms especially for Enterococcus faecalis and P. aeruginosa. Effects of instrument, preincubation time, and temperature showed that the risk of culture negativity increased 1.5 times for BACTEC compared with BacTAlert 3D and increased 2.5 times for 35 degrees C compared with 22 degrees C. The negativity increased 5.5 times and 8.5 times at 24 and 48 h of delay respectively, compared with no delay.     

Detection of bacterial contamination of platelet components: six years' experience with the BacT/ALERT system

BACKGROUND: Hemovigilance has shown that bacteria cause more fatalities than other infections together. Surveillance for detection of bacteria in platelets (PLTs) was initiated. Concomitantly, the storage period for PLTs was extended from 5 to 7 days to reduce cost. STUDY DESIGN AND METHODS: Analysis was performed of all cases of a positive signal in a screening procedure for contaminated PLTs taking into account results of confirmative cultures and results of culture from blood components including bacteria strains. Records were assessed from patients transfused with blood components issued before the screening culture became positive. RESULTS: Samples were collected from 22,057 PLT units. An initial reaction was seen in 84 (0.38%). Growth was confirmed in 70 of these. Of the associated PLT units, 26 had been issued or outdated at the time when the culture was found to be reactive, in 27 bacteria were found, and in 17 cultures were negative. The bacteria found were mainly from normal skin flora. Sixty-six patients received 75 blood components issued before the screening system alarmed. None of these patients had a transfusion reaction reported. The outdating fell to less than 5 percent. CONCLUSION: A screening system for detection of bacterial contamination was implemented without increase in cost owing to extension of storage time to 7 days. Transfusion of several contaminated blood components was prevented.