Evaluation of the BacT/Alert and VITAL blood culture systems for the diagnosis of bacteremia

Objective: To evaluate the detection of bacterial growth in the BacT/Alert (Organon Teknika) and VITAL (bioMérieux) automated blood culture systems.
Methods: In accordance with the protocol of study, 1021 blood sample pairs for culture were obtained from adult patients admitted to the Emergency Room and Intensive Care Unit.
Results: In total, 139 (13.6%) clinically significant blood cultures were detected, of which 79 (56.8%) were detected by both systems, 48 (34.5%) only by BacT/Alert and 12 (8.6%) only by VITAL (P <0.0001). The BacT/Alert system detected positive blood cultures more rapidly for all groups of microorganisms. The VITAL system showed six false-negative blood cultures, while the BacT/Alert system showed none ( P =0.03). There was no significant difference between the number of false-positive blood cultures detected by the two systems.
Conclusions: In our study, overall the BacT/Alert system achieved a better recovery of microorganisms than the VITAL system.     

Brucella detection in blood: comparison of the BacT/Alert standard aerobic bottle, BacT/Alert FAN aerobic bottle and BacT/Alert enhanced FAN aerobic bottle in simulated blood culture

The objective of this study was to compare the performances of the standard aerobic bottle (StAe), FAN aerobic (FANAe) and enhanced FAN aerobic (E-FANAe) (the charcoal component of the FANAe was revised recently to improve the feasibility of Gram smear interpretation) blood culture bottles for BacT/Alert system for the detection of Brucella melitensis in simulated blood culture. Triplicate strains of eight clinical isolates of B. melitensis were studied. Each bottle was inoculated with 5 mL of freshly collected human blood at three different targeted bacterial inocula (10¹, 10² and 10³ CFU/bottle). All bottles were monitored for up to 21 days or until they became positive. The results of time to detection (TTD) on the eight B. melitensis samples were as follows: at 10¹ CFU/bottle, the E-FANAe had a mean TTD significantly shorter than the StAe (48 h vs. 56.2 h, P  < 0.05); and at 10³ CFU/bottle, the FANAe and E-FANAe had a mean TTD significantly shorter than the StAe (41.2 h and 40 h vs. 45.6 h, P  < 0.05). The reproducibilities (no.of positive signals/no.of all bottles) of three bottle systems were as follows: at 10¹ CFU/bottle, the reproducibilities of StAe, FANAe and E-FANAe were 96, 83 and 58%, respectively. At 10³ CFU/bottle, the reproducibilities of StAe, FANAe and E-FANAe were 95, 95 and 91%, respectively. Positive results for the presence of bacteria in Gram smears were confirmed in 68% of StAe, 54% of FANAe and 90% of E-FANAe. In case of suspected brucellosis, the combination of one StAe bottle and one E-FANAe bottle seems to provide the highest and fastest recovery of the organism.     

Comparison of BACTEC 9240 and BacT/Alert blood culture systems in an adult hospital.

In a study comparing the BACTEC 9240 (Becton Dickinson, Canada Inc., Mississauga, Ontario, Canada) and the BacT/Alert (Organon Teknika, Scarborough, Ontario, Canada) blood culture systems, 6,437 sets of four bottles of 10,412 cultures submitted were deemed acceptable for evaluation. There were 586 clinically significant isolates from 544 positive blood cultures. Of the 544 positive blood cultures, 329 were positive in both systems, 157 were positive in the BACTEC 9240 system alone, and 58 were positive in the BacT/Alert system alone (P < 0.001). These cultures represented 421 bacteremic episodes, of which 290 were detected by both systems, 84 were detected by the BACTEC 9240 system alone, and 47 were detected by the BacT/Alert system alone (P < 0.001). The difference between the two systems in terms of microbial recovery was attributable largely to differences in the ability to grow staphylococci. Of 82 monomicrobial isolates of Staphylococcus aureus, 46 were isolated by both systems, 30 were isolated by the BACTEC 9240 system alone, and 6 were isolated by the BacT/Alert system alone (P < 0.0001). A similar pattern was noted in the case of coagulase-negative staphylococci, of which 48 were isolated in both systems, 46 were isolated in the BACTEC 9240 system alone, and 5 were isolated in the BacT/Alert system alone (P < 0.0001). The false-positive rate in the BACTEC 9240 system was 0.5%, and that in the BacT/Alert system was 1.2%. Both systems provided satisfactory service mechanically, and in terms of computer software and costs, both systems were similar.(ABSTRACT TRUNCATED AT 250 WORDS)     

Comparison of BacT/Alert and BACTEC NR 860 blood culture systems in a laboratory not continuously staffed

Objective: To evaluate the performance of continuously working blood culture systems in a discontinuous laboratory system.
Method: The systems used were BacT/Alert (Organon Teknika Corp., Durham, NC) and BACTEC NR 860 (Becton Dickinson Diagnostic Instruments, Sparks, Md) in a comparison in a laboratory staffed 8 1/2 h on Mondays to Fridays and 4 1/2 h on Saturdays. Blood culture bottles (BacT/Alert aerobic and anaerobic, BACTEC NR 26 A and NR 27 A) were received thrice daily.
Results: From 1824 pairs of blood culture vials, 110 clinically significant microorganisms were recovered by both BACTEC and BacT/Alert, 43 by BACTEC alone, and 33 by BacT/Alert alone. The differences between the systems in total recovery and in recovery of individual species were not statistically significant. The average detection times were 13.36 h for BACTEC and 13.93 h for BacT/Alert ( P >0.1). These times represent only 35.6% (BACTEC) and 32.6% (BacT/Alert) of the total timespans from collection of blood to informing the ward of a positive result ( t _crd, clinically relevant detection time). If 24 h per day blood culture processing conditions and continuous transport of vials to the laboratory had been available, these percentages would have risen to 87% (BACTEC) and 87.5% (BacT/Alert). Under such 'ideal' conditions, t _trd could have been reduced by 22.16 h using BACTEC and by 26.81 h using BacT/Alert. The BacT/Alert system showed more false-positive results than the BACTEC system (80 (4.39%) versus 23 (1.26%), P <0.001).
Conclusions: No time benefit for detection of positive blood cultures is gained with continuously measuring systems, if loading and processing of vials is organized discontinuously, as in our laboratory.     

Assessment of routine use of an anaerobic bottle in a three-component, high-volume blood culture system.

The relative value of routine anaerobic blood culture for recovery of organisms and identification of episodes of bloodstream infection was assessed in a three-component, high-volume blood culture system which employs aerobic and anaerobic bottles of BacT/Alert (Organon-Teknika, Durham, N.C.) and aerobic cultures of Isolator (Wampole Laboratories, Cranbury, N.J.). The results of 5,595 blood culture sets from patients with suspected bloodstream infection were analyzed. Compared with either the aerobic BacT/Alert bottle or aerobic culture of Isolator, the BacT/Alert anaerobic bottle recovered significantly fewer isolates (242 versus 294, P < 0.05; 242 versus 298, P < 0.05) but did not detect significantly fewer episodes of bloodstream infection (141 versus 157, P > 0.05; 141 versus 147, P > 0.05). The BacT/Alert anaerobic bottle recovered significantly more isolates of obligately anaerobic bacteria (16 versus 4, P < 0.05; 16 versus 0, P < 0.05) and detected significantly more episodes of bloodstream infection caused by obligately anaerobic bacteria (10 versus 3, P < 0.05; 10 versus 0, P < 0.05) than either the aerobic bottle of BacT/Alert or the aerobic culture of Isolator. The combination of the BacT/Alert anaerobic bottle and the aerobic culture of Isolator recovered as may isolates (374 versus 377) and detected as many episodes of bloodstream infection (194 versus 191) as the combination of the aerobic bottle of BacT/Alert and the aerobic culture of Isolator, and both of these combinations identified at least 8% more isolates and detected at least 3% more bloodstream infections than the combination of the BacT/Alert aerobic and anaerobic bottles. Further analysis of the data revealed that the utility of the BacT/Alert anaerobic bottle, especially when combined with the aerobic culture of Isolator, resulted from not only enhanced recovery of obligately anaerobic bacteria but also effective recovery of facultatively anaerobic bacteria. These results demonstrate the utility of the anaerobic BacT/Alert bottle for detecting bloodstream infection caused by either facultatively anaerobic bacteria or obligately anaerobic bacteria and support the routine inclusion of anaerobic blood culture in the three-component blood culture system used in our hospital.     

Controlled clinical laboratory comparison of BACTEC plus aerobic/F resin medium with BacT/Alert aerobic FAN medium for detection of bacteremia and fungemia.

Blood specimens collected from adult patients with suspected sepsis in four medical centers were inoculated into BACTEC Plus/F and BacT/Alert FAN aerobic culture bottles. Both bottles of 7,401 bottle pairs contained the prescribed blood volume of 8 to 12 ml. Bottles were incubated in their respective instruments for a standard 7-day protocol or until the instruments signaled that they were positive. A total of 720 isolates that were judged to represent true infections were recovered from 338 patients; 451 isolates were recovered from both bottles, 143 were recovered from only the Plus/F bottle, and 126 were recovered from only the FAN bottle (P was not significant). Although more Histoplasma capsulatum isolates were recovered from Plus/F bottles (P < 0.005), there were no other statistically significant differences in recovery rates of individual species or groups of organisms between the two systems. Of 329 monomicrobic patient septic episodes, 244 episodes were detected by both blood culture systems, 40 were detected only by the BACTEC system, and 45 were detected only by the BacT/Alert system (P was not significant). There was no significant difference between the two systems in the detection of septic episodes among patients receiving antibiotic therapy at the time of blood cultures. Of the cultures found to be positive within the first 72 h of incubation, detection was on average earlier by the BACTEC system (16.9 h) than by the BacT/Alert system (18.7 h). Larger differences in average time to detection were seen with streptococci (10.7 h by the BACTEC system and 17.9 h by the BacT/Alert system) and yeasts (an average of 29.4 h by the BacT/Alert system versus 37.2 h by the BACTEC system). With the exception of the differences noted above, BACTEC Plus/F aerobic resin and BacT/Alert aerobic FAN blood culture bottles were comparable in their abilities to recover aerobic and facultative organisms.     

Comparison of the BacT/Alert pediatric blood culture system, Pedi-BacT, with conventional culture using the 20-milliliter Becton-Dickinson supplemented peptone broth tube.

The performance of the Pedi-BacT system, the BacT/Alert (Organon Teknika Corp., Durham, N.C.) pediatric blood culture bottle, was compared with that of a conventional 20-ml supplemented peptone broth tube (Becton-Dickinson Corp., Cockeysville, Md.) (BD system) in matched aerobic cultures. The tubes of the BD system were visually examined daily for 7 days and were subcultured during the first 24 h of incubation. Pedi-BacT cultures were mechanically agitated and continuously monitored for growth by the instrument. Of the 6,628 compliant pairs, 331 (5.0%) were positive in both systems, 220 (3.3%) were positive in the Pedi-BacT system only, and 170 (2.6%) were positive in the BD system only. One (0.02%) false-negative culture and 15 (0.2%) false-positive cultures occurred with the Pedi-BacT system while 20 (0.3%) false-negative cultures and 35 (0.5%) false-positive cultures occurred with the BD system. Of 288 clinically significant organisms detected in matched pairs from which a single isolate was recovered, 176 (61%) were recovered from both systems, 83 (29%) were recovered from the Pedi-BacT system only (P < 0.0001), and 29 (10%) were recovered from the BD system only. Members of the family Enterobacteriaceae (P < 0.01), miscellaneous nonfermenters (P < 0.05), and Candida spp. (P < 0.01) were isolated more frequently in the Pedi-BacT system than in the BD system. No significant difference in recovery of other organisms was found between the systems. The average time to detection for the Pedi-BacT system ranged from 11.5 h for streptococci to 29.7 h for enterococci, while that for the BD system ranged from 20.3 h for streptococci to 66.4 h for some nonfermenters. The BacT/Alert system is a reliable, labor-saving alternative to conventional blood culture methods.     

Comparison of the BacT/Alert PF pediatric FAN blood culture bottle with the standard pediatric blood culture bottle, the Pedi-BacT

The performance of the BacT/Alert PF (Organon-Teknika Corp., Durham, N.C.), a new nonvented pediatric FAN blood culture bottle, was compared to that of the original pediatric bottle, the Pedi-BacT, with matched aerobic cultures obtained from two separate facilities. A total of 244 clinically significant isolates were recovered from 4,015 compliant pairs. Among the positive cultures, 170 (70%) isolates were detected in both the BacT/Alert PF and the Pedi-BacT bottles, while 47 (19%) isolates were recovered in the BacT/Alert PF bottle only and 27 (11%) isolates were recovered in the Pedi-BacT bottle only. Although isolation of specific microorganisms was comparable for the two bottles, the total number of organisms recovered by the BacT/Alert PF was greater than that by the Pedi-BacT (P = 0.0272). In addition, more organisms were recovered by the BacT/Alert PF bottle from the blood of patients receiving antimicrobial therapy (P = 0.0180). Overall time to detection was similar for the two bottles; however, a significantly decreased mean time to detection was recorded for yeast from the BacT/Alert PF bottle (22.9 h; P = 0.0001) and staphylococci from the Pedi-BacT bottle (22.5 h; P = 0.0056). One false-negative culture and five false-positive cultures occurred with the Pedi-BacT bottle, compared to one false-positive culture with the BacT/Alert PF bottle. The BacT/Alert PF bottle is a reliable blood culture bottle for pediatric blood culture specimens and may offer improved recovery of microbes from patients on antimicrobial therapy. The use of the nonvented bottle will both facilitate bottle processing and decrease expenditures for materials due to the elimination of the venting needles required for the original vented bottles.     

Controlled comparison of the BacT/Alert and BACTEC 660/730 nonradiometric blood culture systems.

In a collaborative study at three university hospitals, the recovery of microorganisms and the speed of detection of microbial growth by the BacT/Alert (Organon Teknika Corporation, Durham, N.C.) and BACTEC 660/730 (Becton-Dickinson Diagnostic Instrument Systems, Sparks, Md.) nonradiometric blood culture systems were compared. A total of 5,918 comparisons were made between BacT/Alert aerobic and BACTEC NR 6A bottles and 5,992 comparisons were made between BacT/Alert anaerobic and BACTEC NR 7A bottles. Each bottle was inoculated with 5 ml of blood. The overall recoveries of microorganisms from the two aerobic bottles were comparable; members of the family Enterobacteriaceae were recovered more often from BacT/Alert aerobic bottles alone (P less than 0.001). The overall recoveries of microorganisms from the anaerobic bottles were not significantly different. Growth of Staphylococcus aureus (P less than 0.001), coagulase-negative staphylococci (P less than 0.01), streptococci (P less than 0.001), Escherichia coli (P less than 0.01), other members of the family Enterobacteriaceae (P less than 0.02), and Pseudomonas aeruginosa (P less than 0.05) was detected earlier in BacT/Alert aerobic bottles. Growth of S. aureus (P less than 0.001), coagulase-negative staphylococci (P less than 0.05), enterococci (P less than 0.01), Streptococcus pneumoniae (P less than 0.02), viridans group streptococci (P less than 0.05), E. coli (P less than 0.001), Klebsiella pneumoniae (P less than 0.01), and other members of the family Enterobacteriaceae (P less than 0.001) was detected earlier in BacT/Alert anaerobic bottles. In a system-versus-system comparison, more gram-positive cocci were recovered from the BACTEC system alone (P < 0.05), and more members or the family Enterobacteriaceae were recovered from the BacT/Alert system alone (P < 0.001). As a system, the BacT/Alert system detected growth of S. aureus (P < 0.001), coagulase-negative staphylococci (P < 0.01), streptococci (P < 0.001), E. coli (P < 0.001), other members of the familyEnterobacteriaceae (P < 0.001), and P. aeruginosa (P < 0.05) earlier than the BACTEC system did.Significantly fewer (40 versus 1,183) false-positive results occurred with the BacT/Alert system. We conclude that the BacT/Alert and BACTEC 660/730 nonradiometric systems are comparable for recovering clinically significant microorganisms form adult patients with bacteremia or fungemia, but that the BacT/Alert system detects microbial growth earlier than the BACTEC system does, with significantly fewer false-positive results.     

Time to detection of positive BacT/Alert blood cultures and lack of need for routine subculture of 5- to 7-day negative cultures.

Consecutive BacT/Alert blood cultures which were instrument negative following a 7-day incubation were subcultured. Eighteen (0.2%) of 11,476 bottles had growth on subculture. Eleven of these eighteen isolates were considered contaminants on the basis of the identity of the organism and lack of other positive blood cultures from the same patient. In addition, analysis of time to instrument detection for approximately 2,900 positive blood cultures indicates that 5 or 6 days of incubation is sufficient for the routine detection of clinically significant organisms from BacT/Alert blood cultures. These data indicate that subculture of 5- to 7-day instrument-negative BacT/Alert blood culture bottles is not necessary.     

Three days of incubation may be sufficient for routine blood cultures with BacT/Alert FAN blood culture bottles

BacT/Alert FAN blood culture bottles have been shown to enhance the recovery of bacteria and yeast from blood compared with standard BacT/Alert bottles. It is well established that standard BacT/Alert blood culture bottles require no more than 5 days of incubation for the detection of routine bacteria and yeast. It is less clear, however, whether FAN bottles also routinely require 5 days of incubation. To address this question, we recently reviewed the results of 17,887 blood culture sets collected in FAN blood culture bottles at Geisinger Medical Center. Of these cultures, 1,780 were positive for bacteria or yeast, yielding a total of 1,242 clinically significant isolates. The numbers of isolates recovered on days 1, 2, 3, 4, and 5 were as follows: (values in parentheses are percentages of total significant isolates): 877 (71%), 269 (22%), 65 (5%), 18 (1%) and, 13 (1%), respectively. In total, 97.5% of all clinically significant isolates were detected in the first 3 days of incubation. Of the 31 significant isolates detected on day 4 or 5 of incubation, 17 were detected in concurrent blood cultures within the first 3 days of incubation. Chart reviews were conducted for the 13 patients with the remaining 14 isolates detected on day 4 or 5 to determine whether therapy was changed due to this blood culture result. Therapy was changed for only 1 patient. These results suggest that it may not be necessary to routinely incubate FAN blood culture bottles for more than 3 days.     

Controlled Clinical Laboratory Comparison of Two Supplemented Aerobic and Anaerobic Media Used in Automated Blood Culture Systems To Detect Bloodstream Infections

A 20-ml blood sample was collected from adult patients with suspected bloodstream infections and distributed equally into the four volume-controlled bottles of a blood culture set consisting of aerobic and anaerobic BACTEC Plus/F bottles and aerobic and anaerobic BacT/Alert FAN bottles. All bottles were incubated in their respective instruments for a standard 5-day protocol or until the instruments signalled positivity. Samples in all bottles with negative results by these instruments were terminally subcultured. A total of 8,390 blood culture sets were obtained during the study period, of which 4,402 (52.5%) met the study criteria. Of these, 946 (21.5%) were positive either by instrument signal or by additional terminal subculture of all negative bottles and yielded growth of microorganisms. Five hundred eighty-nine (13.4%) blood culture sets were considered to have recovered 663 clinically significant organisms. When both the BACTEC and the BacT/Alert systems were used, 465 positive sets were detected; BACTEC alone detected 52 positive sets and BacT/Alert alone detected 72 (P = 0.09). No differences were found between the two systems in microbial recovery rate from blood cultures obtained from patients on antibiotic therapy. Significantly more members of the family Enterobacteriaceae (P < 0.01) were detected from patients without antimicrobial therapy by BacT/Alert than by BACTEC. The false-negative rates were 0.20% for BACTEC and 0.32% for BacT/Alert. A significantly higher false-positive rate was found for BACTEC (P < 0.0001). Both systems were comparable for the time to detection of microorganisms. However, gram-positive bacteria were detected faster by BACTEC and Enterobacteriaceae were detected faster on average by BacT/Alert. We concluded that both systems are comparable in their abilities to recover aerobic and anaerobic organisms from blood cultures and a terminal subculture might not be necessary for either of the two systems. The increased positivity rate when using an anaerobic bottle in a two-bottle blood culture set is due to the additional blood volume rather than to the use of an anaerobic medium.     

Isolation of Kingella kingae from Synovial Fluids Using Four Commercial Blood Culture Bottles

 According to the literature, Kingella kingae may be an underdiagnosed cause of joint and bone infections in children. The use of the Bactec blood culture system for culture of joint fluids has dramatically improved the isolation of this fastidious bacterium. The aim of this study was to test the recovery rate and detection time of four commercial blood culture systems: three different BacT/Alert (Organon Teknika, USA) bottles and one Bactec (Becton Dickinson Microbiology Systems, USA) bottle, all inoculated with Kingella kingae strains mixed with pooled synovial fluids. For each strain the same inoculum and volume of synovial fluid was distributed into each of the four bottles. All 24 strains tested grew in the BacT/Alert Aerobic (100%) and the BacT/Alert Pedi-BacT (100%) bottles. Twenty-one strains grew in the BacT/Alert FAN aerobic (88%) bottle, and 15 strains grew in the Bactec Plus Aerobic F (63%) bottle, in both systems within 12 days (P<0.01). The Kingella kingae strains were first detected in the BacT/Alert Pedi-BacT bottles (P<0.001). The results were reproducible. The BacT/Alert blood culture bottles were superior to previously described blood culture systems in isolating Kingella kingae from synovial fluid, even with small inoculums and small volumes of synovial fluid.     

Improved detection of bacterial growth in continuous ambulatory peritoneal dialysis effluent by use of BacT/Alert FAN bottles.

Culture-negative peritonitis is a major complication for patients on continuous ambulatory peritoneal dialysis (CAPD) and precludes organism-specific therapy. The aim of the present study was to compare inoculation of 10 ml of CAPD effluent into BacT/Alert blood culture bottles (FAN [fastidious antimicrobic neutralizing], BacTAlert aerobic [BTA], and BacT/Alert anaerobic [BTAn] bottles) to our conventional method of using 50 ml of concentrated CAPD effluent to inoculate peptone broth bottles (BD bottles) and MacConkey agar and blood agar medium (BA-MAC). The FAN, BTA, and BTAn bottles were monitored automatically in the BacT/Alert blood culture instrument. A total of 207 CAPD effluents were studied, and in 97 bacteria were detected by at least one method. Compared to BTA bottles (79 of 97; 81.4%), BTAn bottles (78 of 97; 80.4%), and BD bottles (88 of 97; 90.7%), the single best broth medium for detecting bacterial growth in CAPD effluents was the FAN bottle (90 of 97 effluents; 92.8%). A total of 125 bacterial species were detected by any method, and the majority (91.8%) of CAPD effluents were infected with a single species. A combination of FAN and BTAn bottles detected 111 of 125 (88.8%) of all organisms, whereas a combination of BD bottles and BA-MAC detected 107 of 125 (85.6%) of all organisms. One or more organisms that would have been completely missed by the conventional method with BD bottles and BA-MAC were detected in 18 CAPD effluents. Of these 18 CAPD effluents, 6 showed no growth by the conventional method with BD bottles and BA-MAC. On the basis of our data, the most sensitive and least labor intensive method was direct inoculation of 10 ml of CAPD effluent into a FAN bottle and a BTAn bottle, which could be automatically monitored by the BacT/Alert blood culture instrument. On the basis of case definitions for peritonitis, the sensitivities and specificities of the methods with FAN and BTAn bottles and with BD bottles and BA-MAC were 81.1 and 98.8% and 74.5 and 96.5%, respectively.     

Comparison of BacT/Alert with Signal blood culture system.

The BacT/Alert (Organon Teknika Corp., Durham, N.C.) is an automated blood culture system. It is based on the detection of CO2 by means of a colorimetric sensor internally attached to the bottom of culture bottles. The aerobic and anaerobic media of this system were compared with one bottle of the Signal system (Oxoid Ltd., Hampshire, United Kingdom). At bedside, 20 ml of blood was drawn from each adult patient. The two BacT/Alert bottles were inoculated with 5 ml of blood each; the Signal bottle was inoculated with 10 ml. A total of 5,284 sets (2,483 patients; 2.1 cultures per patient) consisting of three bottles each were evaluated, of which 781 sets (14.8%) revealed microorganisms (n = 892); 642 of these were considered to be pathogenic. Significantly more (P < 0.0001) pathogens were isolated from the two BacT/Alert bottles together (n = 584) than from the single Signal bottle (n = 515). Escherichia coli (P = 0.007), gram-negative bacteria other than members of the family Enterobacteriaceae or Pseudomonas spp. (P = 0.006), and yeasts (P = 0.02) were isolated more often from both or either BacT/Alert bottle. Comparing the systems in terms of 388 different organisms per septic episode, the difference between BacT/Alert and Signal was significant for the total number of septicemia cases (P = 0.003). More contaminants grew in the BacT/Alert system (173 versus 116; P = 0.0001). False-positive indications were more frequent in the BacT/Alert system, 198 (3.7%) aerobic bottles and 57 (1.1%) anaerobic bottles, than in the Signal bottles, 24 (0.5%) bottles.(ABSTRACT TRUNCATED AT 250 WORDS)     

Blood culture bottles for transportation and recovery of anaerobic bacteria from non-blood samples

Using bacterial suspensions as simulated non-blood specimens, the capacity of three different BacT/ Alert blood culture bottles for the transportation and recovery of anaerobic bacteria with different sensitivity to air was evaluated. To better assess the performance of the BacT/Alert bottles, three other liquid media specially designed for anaerobes were included in the study. Attention was paid to recovery rates in relation to species, initial bacterial concentration, and time needed for detection. Of the BacT/Alert blood culture bottles, the anaerobic FAN bottle yielded the highest recovery rates, but its performance was limited compared with chopped meat broth in tubes. This broth allowed detection of all the tested species within 48 h. Since collection and transportation of anaerobic bacteria are of major importance for a reliable culture result, improvements are necessary.     

Rapid Identification of Bacteria and Yeasts from Positive-Blood-Culture Bottles by Using a Lysis-Filtration Method and Matrix-Assisted Laser Desorption Ionization–Time of Flight Mass Spectrum Analysis with the SARAMIS Database

Rapid identification of microorganisms causing bloodstream infections directly from a positive blood culture would decrease the time to directed antimicrobial therapy and greatly improve patient care. Matrix-assisted laser desorption ionization–time of flight (MALDI-TOF) mass spectrometry (MS) is a fast and reliable method for identifying microorganisms from positive culture. This study evaluates the performance of a novel filtration-based method for processing positive-blood-culture broth for immediate identification of microorganisms by MALDI-TOF with a Vitek MS research-use-only system (VMS). BacT/Alert non-charcoal-based blood culture bottles that were flagged positive by the BacT/Alert 3D system were included. An aliquot of positive-blood-culture broth was incubated with lysis buffer for 2 to 4 min at room temperature, the resulting lysate was filtered through a membrane, and harvested microorganisms were identified by VMS. Of the 259 bottles included in the study, VMS identified the organisms in 189 (73%) cultures to the species level and 51 (19.7%) gave no identification (ID), while 6 (2.3%) gave identifications that were considered incorrect. Among 131 monomicrobic isolates from positive-blood-culture bottles with one spot having a score of 99.9%, the IDs for 131 (100%) were correct to the species level. In 202 bottles where VMS was able to generate an ID, the IDs for 189 (93.6%) were correct to the species level, whereas the IDs provided for 7 isolates (3.5%) were incorrect. In conclusion, this method does not require centrifugation and produces a clean spectrum for VMS analysis in less than 15 min. This study demonstrates the effectiveness of the new lysis-filtration method for identifying microorganisms directly from positive-blood-culture bottles in a clinical setting.     

Comparison of the BacT/Alert FAN aerobic and the Difco ESP 80A aerobic bottles for pediatric blood cultures.

We compared the BacT/Alert system using the aerobic FAN bottle with the ESP system using the 80A aerobic bottle for the detection of pediatric bloodstream pathogens at a children's hospital. From 6,636 blood culture sets complying with the inclusion criteria, 308 pathogens were detected, including 177 that were detected by both systems, 69 that were detected by BacT/Alert FAN only, and 62 that were detected by ESP 80A only (P = 0.6; not significant). BacT/Alert FAN detected more isolates of Staphylococcus aureus (47 versus 34; P = 0.02), while ESP 80A detected more episodes of streptococcal and enterococcal infection. BacT/Alert FAN detected more pathogens from patients receiving antibiotic therapy (107 versus 93; P = 0.04). Of 248 separate episodes of bacteremia or fungemia, 146 were detected by both systems, 56 were detected by ESP 80A only, and 46 were detected by BacT/Alert FAN only (P = 0.37; not significant). The median times to detection were 13.6 h for ESP 80A and 15.7 h for BacT/Alert FAN (P < 0.001). Both systems were considered easy to operate and were free from significant mechanical difficulties. False-positive or false-negative signals were rare or nonexistent with both systems. We conclude that both systems rapidly detect a broad range of pediatric bloodstream pathogens. BacT/Alert FAN provides better detection of Staphylococcus aureus, especially from patients receiving antibiotics. ESP 80A provides better detection of streptococci and enterococci.     

Controlled comparison of BacT/Alert MB system, manual Myco/F lytic procedure, and isolator 10 system for diagnosis of Mycobacterium tuberculosis Bacteremia

We compared the performance of the BacT/Alert MB system, that of the manual Bactec Myco/F Lytic procedure, and that of the Isolator 10 lysis-centrifugation system in the detection of Mycobacterium tuberculosis bacteremia. Mean times to detection were 16.4 days for BacT/Alert MB versus 20.0 days for Myco/F Lytic, 16.5 days for BacT/Alert MB versus 23.8 days for Isolator 10, and 21.1 days for Bactec Myco/F Lytic versus 22.7 days for Isolator 10. There were no significant differences in yields. The mean (range) magnitude of mycobacteremia was 30.0 (0.4, 90.0) CFU/ml and was correlated with the time to positivity in the BacT/Alert MB system (r = -0.4920). M. tuberculosis bacteremia was detected more rapidly in a continuously monitored liquid blood culture system, but the mean time to positivity exceeded 3 weeks.     

Controlled Clinical Comparison of Three Commercial Blood Culture Systems

 In a controlled clinical comparison, three commercial blood culture systems – the standard aerobic BacT/Alert bottle (STD), the aerobic BacT/Alert FAN bottle (FAN) and the Isolator system (ISO; Wampole Laboratories, USA) were compared for their ability to detect aerobic and facultatively anaerobic microorganisms. A total of 945 BacT/Alert (STD and FAN) blood culture sets were compared. Of these, 110 blood culture sets (11.6%) yielded growth of 116 clinically significant bacterial and fungal isolates. Microorganisms were recovered from 10.7% (101/945) of the FAN bottles compared to 8.9% (84/945) of the STD bottles. Of the significant isolates, 78 (67.2%) were recovered by both bottles, 29 (25%) by the FAN bottle only and nine (7.8%) by the STD bottle only (P<0.01). Along with 56.1% (530/945) of BacT/Alert blood culture sets, a concomitant ISO tube was obtained. Of the triple (STD+FAN+ISO) blood culture sets, 54 (10.2%) yielded growth of 59 clinically relevant isolates. Microorganisms were detected in 9.1% (48/530) of the FAN bottles, 8.3% (44/530) of the STD bottles and 4% (21/530) of the ISO tubes (P<0.001). Overall, the BacT/Alert system detected more clinically significant microorganisms than the ISO tube; the STD and the FAN bottle each recovered significantly more staphylococci (P<0.01 and P<0.001, respectively) and gram-negative rods (P<0.01, both). In conclusion, the BacT/Alert FAN bottle performed better than the BacT/Alert STD bottle; both BacT/Alert bottles, however, were superior to the ISO tube in terms of recovery of clinically significant microorganisms, including gram-positive and gram-negative bacteria.