Aerobic Bottles Research Articles

Reduction of Platelet Transfusion Associated Sepsis by Short‐Term Bacterial Culture

Abstract Background and Objectives: There is as yet no suitable routine laboratory test for a blood transfusion service to detect bacterial contamination in platelets. This study evaluates the effectiveness and the applicability of short‐term bacterial culture for such a purpose. Materials and Methods: Samples from 5‐unit platelet pools were inoculated into an aerobic culture bottle, then monitored for 48 h at 35°C in an automated monitoring and detection system. Results: 26,210 whole‐blood‐derived platelet components were tested, of which 14 (0.053%) platelet units were found to be contaminated. In addition, nine of the associated red cell units and 4 fresh‐frozen plasma units grew the same organisms on culture. Conclusion: Short‐duration bacterial culture by an automated system is effective and suitable for routine screening in a regional transfusion center.

Reduction of Platelet Transfusion– Associated Sepsis by Short–Term Bacterial Culture

Background and Objectives: There is as yet no suitable routine laboratory test for a blood transfusion service to detect bacterial contamination in platelets. This study evaluates the effectiveness and the applicability of short–term bacterial culture for such a purpose. Materials and Methods: Samples from 5–unit platelet pools were inoculated into an aerobic culture bottle, then monitored for 48 h at 35°C in an automated monitoring and detection system. Results: 26,210 whole–blood–derived platelet components were tested, of which 14 (0.053%) platelet units were found to be contaminated. In addition, nine of the associated red cell units and 4 fresh–frozen plasma units grew the same organisms on culture. Conclusion: Short–duration bacterial culture by an automated system is effective and suitable for routine screening in a regional transfusion center.

Survival and function of phagocytes in blood culture media.

The survival and function of human phagocytes in sterile aerobic and anaerobic blood culture media were investigated using neutrophil morphology, white blood cell count in a haemoanalyser, flow cytometry, oxidative burst response, and bactericidal effect in Colorbact and Septi-Chek blood culture media and Bact/Alert. When comparing agitation to stationary incubation no difference in phagocytic activity was found. The methods showed the same trends demonstrating that the phagocytes' viability and activity were prolonged by oxygen and shortened by anaerobic conditions and sodium polyethanol sulfonate (SPS). Best preserved activity and viability were found in the aerobic media containing less than 0.5 g/l SPS, in which significant phagocyte oxidative burst and bactericidal activity were found up to 4 days after inoculation. Considering that the majority of bacteremias are due to aerobic or facultatively anaerobic bacteria, the present data suggest that most bacteria may be recovered by the use of one aerobic bottle with SPS concentration below 0.5 g/l to protect meningococci and other SPS-sensitive bacteria and one above 0.5 g/l to stop phagocytic activity, plus one anaerobic bottle with SPS below 0.5 g/l.

Saponin, an inhibitory agent of carbon dioxide production by white cells: its use in the microbiologic examination of blood components in an automated bacterial culture system.

Blood components with a white cell count > 100 x 10(9) per L may cause false-positive results when the BacT/Alert system is used for the microbiologic examination. The effects of different concentrations of saponin on bacterial growth and on carbon dioxide production by blood fractions with a high white cell count, in particular peripheral blood progenitor cells and buffy coats, were investigated. The effect of saponin on carbon dioxide production was studied by adding different fractions of white cell-rich material (buffy coat or leukapheresis material) to BacT/Alert culture bottles with or without saponin and incubating these bottles. Five bacterial strains were used to inoculate the culture bottles at four levels ranging from about 1 colony-forming unit per mL to about 10(3) colony-forming units per mL. Aerobic and anaerobic bottles with and without saponin were used. It was demonstrated that the addition of 0.5 percent saponin to BacT/Alert culture bottles effectively inhibited carbon dioxide production, without affecting bacterial growth. Saponin at a concentration of 0.5 percent is a valuable additive to BacT/Alert culture media because it prevents false-positive results in the examination of white cell-rich blood components.

Reassessment of the incubation time in a controlled clinical comparison of the BacT/Alert aerobic FAN bottle and standard anaerobic bottle used aerobically for the detection of bloodstream infections

This study assessed the minimum incubation time required to detect bloodstream infections during a controlled clinical comparison of the performance characteristics of the BacT/Alert aerobic FAN bottle and the standard anaerobic bottle used aerobically except on a selective basis. Blood was collected from adults with suspected bloodstream infections and inoculated into each bottle, which was monitored in the BacT/Alert Microbial Detection System. The anaerobic bottle was vented before incubation except when cultures were obtained from patients on the colorectal and gynecologic surgical and emergency services. Statistical analysis was limited to those culture sets in which each bottle was inoculated with ≥8 mL of blood and bacterial growth was considered to be clinically significant. A total of 682 positive cultures from 243 patients satisfied the inclusion criteria. Significantly more isolates of Staphylococcus aureus ( p <0.001), S. epidermidis ( p <0.001), other coagulase-negative staphylococci ( p <0.001), Enterococcus spp. ( p = 0.04), Escherichia coli ( p = 0.03), all Enterobacteriaceae ( p <0.001), Pseudomonas aeruginosa ( p = 0.001), and Candida spp. ( p <0.001) were detected by the aerobic FAN bottle. Significantly more septic episodes due to S. aureus, S. epidermidis, other coagulase-negative staphylococci, Enterobacteriaceae, P. aeruginosa, and Candida spp. were detected by the aerobic FAN bottle. Significantly more bacterial isolates were detected by the aerobic FAN whether or not antibiotics were being administered at the time of blood culture, whereas there were significantly fewer positive cultures in the vented standard anaerobic bottle when patients were receiving antimicrobial therapy than when they were not. All but 5% of positive cultures were detected within three days. Only six of the cultures requiring four or five days of incubation represented true misses, and only one of these six resulted in a change in therapy which, however, did not affect the patent’s outcome.

Comparison of Bedside- and Laboratory-Inoculated Bactec High- and Low-Volume Resin Bottles for the Recovery of Microorganisms Causing Peritonitis in CAPD Patients

There is not yet a universally accepted protocol for the recovery of microorganisms causing peritonitis in patients on continuous ambulatory peritoneal dialysis (CAPD). We prospectively analyzed 343 peritoneal effluent specimens by three protocols: 1) 10 ml of effluent centrifuged and the pellet plated onto blood, MacConkey agars, and into thioglycolate broth (routine method); 2) 5 ml and 10 ml inoculated at the bedside into Bactec 16A and 26A aerobic resin-containing blood culture bottles, respectively; and 3) 5 ml and 10 ml inoculated in the laboratory into Bactec 16A and 26A media, respectively. One hundred and forty (41%) peritoneal effluent specimens had microorganisms recovered, and, of these, 101 were recovered by routine culture compared to 117 ( p < .021), 125 ( p < .0001), 115 ( p < .047), and 116 ( p < .032) for bedside-inoculated 16A and 26A and for laboratory-inoculated 16A and 26A, respectively. Bedside-inoculated bottles were not significantly better than laboratory-inoculated bottles, and high-volume bottles were not significantly better than low-volume bottles for detection of patients positive for microorganisms; however, the number of total microorganisms recovered were significantly better from all inoculated blood culture bottles compared to routine culture. Bedside- and laboratory-inoculated resin-containing blood culture bottles are superior to the routine method for recovery of microorganisms causing peritonitis in CAPD patients.

Comparative Study of Three Different BACTEC Culture Media for the Detection of Bacteremia in Ambulatory and Hospitalized Children

To compare the yield of two aerobic and an anaerobic BACTEC blood culture media in detecting bacteremia in ambulatory and hospitalized care settings at a children's hospital, a prospective cohort study was completed. Over an 18-month period, equal blood volumes (minimum of 1 mL/bottle) were inoculated into a three-bottle culture set including aerobic BACTEC NR 6A, aerobic BACTEC PEDS Plus and anaerobic NR 7A broths. Chart reviews were completed on all children with bacteremia to determine whether the isolate was clinically significant based on predefined criteria. Among 5328 evaluable blood culture sets, 323 clinically significant organisms (110 from ambulatory and 213 from hospitalized children) were isolated. Most Streptococcus pneumoniae, Haemophilus species, and Neisseria or Moraxella species were recovered from children attending the emergency department or out-patient clinics. Important isolates in hospitalized children included most of the staphylococci and Enterobacteriaceae, and all group D enterococci, Gram-negative nonfermentative bacilli and all Candida species. Overall, significantly more isolates were detected only in the anaerobic bottle from ambulatory children (P<0.0001), including 13 of 54 (24%) patients with S pneumoniae bacteremias presenting to the emergency department. This study indicated that different BACTEC blood culture media combinations are needed in ambulatory and hospitalized pediatric care settings to ensure the optimal recovery of all types of isolates. Whereas aerobic blood culture bottles are adequate for detection of bacteremia in hospitalized children, the common occurrence of fastidious organisms mandates the need for a combined aerobic/anaerobic culture set in ambulatory pediatric care settings.

Bacteraemia caused by periodontal probing.

Bacteraemia of oral origin may result in infective endocarditis in susceptible individuals. The aim of this pilot study was to investigate the occurrence of bacteraemia due to periodontal probing. Thirty patients (15 male, 15 female; mean age 42.7 years) with untreated periodontitis were investigated. All were free of significant medical disorders and none had taken antibiotics in the previous month. Prior to and immediately following periodontal probing, 20 mL of venous blood were obtained from each patient and inoculated into aerobic and anaerobic blood culture bottles and incubated. Negative bottles were monitored continuously for three weeks before being discarded. Periodontal probing consisted of measuring pockets at six points around each tooth and recording the presence or absence of bleeding. A positive bacteraemia was recorded for three of the patients prior to probing. One patient exhibited Prevotella species whilst two exhibited skin commensals. Following probing, 13 patients (43 per cent) exhibited bacteraemia of oral origin. Viridans streptococci were the most common isolates (45 per cent). No significant correlations were found between bacteraemia and the severity of periodontitis or extent of bleeding on probing. The results indicate that periodontal probing can cause bacteraemia in patients with periodontitis. It would be advisable for patients considered at risk of developing infective endocarditis to receive antibiotic prophylaxis for periodontal probing if they have radiographic evidence of periodontitis.

Assessment of the yield of anaerobic blood cultures

Because of the declining incidence of anaerobic bacteremia, the predictable sites of anaerobic infection and the increasing importance of aerobic isolates (eg; yeasts), the practice of routinely culturing half the volume of blood collected anaerobically has been questioned. We have assessed the yield of routine anaerobic blood cultures in our clinical setting. Blood culture isolates from November 1994 through October 1995 at Auckland (AKH) and Green Lane/National Women's Hospitals (GL/NWH) were recorded. The medical records of patients with anaerobic bacteremia were examined. For the three month period April to June 1996, all positive blood cultures were analysed with respect to which bottle (aerobic or anaerobic or both) was positive. For the period November 1994 to October 1995, 5.6% and 5.3% of blood cultures at AKH and GLH respectively were positive. At AKH and GLH anaerobes constituted 0.16% and 0.19% of all blood cultures and 3.1% and 3.5% of all positive blood cultures respectively. Twenty-one of 25 (84%) significant anaerobes were from patients in whom anaerobic infection was predictable. More isolates were recovered from aerobic than anaerobic bottles, 178 versus 71, p < 0.001. Aerobic culture also recovered more pathogens (76 versus 38, p < 0.001 more yeasts (10 versus 0) and more Pseudomonas spp. (10 versus 1) than did anaerobic culture. Only obligate anaerobes were isolated more frequently in anaerobic bottles (5 versus 0, p = 0.03). Most instances of anaerobic bacteremia occurred in patients where anaerobes could be expected. We conclude that routine use of two aerobic bottles with clinically directed use of anaerobic blood culture bottle is an appropriate and effective approach in our setting.

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.

Evaluation of an extended blood culture protocol to isolate fastidious organisms from patients with AIDS.

Recent reports of fastidious pathogens suggest the need for special blood cultures for immunocompromised patients. Blood cultures from 45 human immunodeficiency virus (HIV)-infected patients with unexplained fever (> or = 38.0 degrees C) and CD4 counts of < 125 cells per mm3 were collected into a vacuum tube with sodium polyanetholsulfonate, an Isolator tube, and BACTEC aerobic and anaerobic bottles. Blood from the sodium polyanethosulfonate tube was inoculated into BACTEC 13A bottles, which were read weekly for 16 weeks. Isolator sediment was divided among eight agar media, including four sheep blood agar media: chocolate agar, brain heart infusion blood agar, heart infusion blood agar, and brucella blood agar. Other agar plates included Sabouraud's, buffered charcoal-yeast extract, Middlebrook 7H11 (M7H11) with hemoglobin, and M7H11 with mycobactin J. Incubation conditions included air and CO2-enriched aerobic, microaerophilic, and anaerobic atmospheres. Aerobic BACTEC broths received an acridine orange stain on day 8 and were subcultured at 2, 4, and 8 weeks. Anaerobic BACTEC bottles were subcultured at 4 weeks. All solid media, including subcultures, were incubated for 8 weeks, providing a total of 16 weeks of incubation for each specimen. Clinically significant isolates included eight Mycobacterium avium complex isolates and one each of Bartonella henselae, Bartonella quintana, Shigella flexneri, Klebsiella oxytoca, and Cryptococcus neoformans. All isolates were detected with commercially available media and, with the exception of Bartonella spp., were recovered within incubation times routinely used in most clinical laboratories.

Clinical importance of increased sensitivity of BacT/Alert FAN aerobic and anaerobic blood culture bottles.

Two recent multicenter blood culture studies found that BacT/Alert FAN (FAN) bottles (Organon Teknika, Durham, N.C.) had increased yields in detecting bacteremia and fungemia compared with standard BacT/Alert (STD) bottles. Because the clinical importance of this increase in microbial recovery is unknown, we performed a retrospective analysis to determine the frequency with which FAN bottles were the sole means of detecting an episode of bacteremia. There were 1,047 positive blood cultures in which both study bottles were adequately filled and the organism isolated was judged to be the cause of sepsis: 240 (23%) were positive only in FAN bottles and 73 (7%) were positive only in STD bottles. Of a total of 664 episodes of bacteremia, 126 (19%) were identified only by FAN bottles and 43 (7%) were identified only by STD bottles (P < 0.0001). Episodes detected only by FAN bottles more often were recurrent events (23 of 126, or 18%) than episodes detected only by STD bottles (2 of 43, or 5%) (P < 0.05) and more commonly occurred in patients receiving theoretically effective antibiotic therapy (33 of 126 [26%] versus 4 of 43 [9%]) (P < 0.05). The medical records for patients with 127 of these episodes (92 FAN bottles only; 35 STD bottles only) were available for review. More than half of both FAN bottle-only (60 of 92, or 65%) and STD bottle-only (20 of 35, or 57%) episodes were judged to be clinically important. We conclude that FAN bottles improve the detection of bacteremia and that the majority of the additional episodes detected are clinically important. The benefits of the greater yield in specific patient populations must be balanced against the higher costs of FAN bottles.

Impact of the resin blood culture medium on the treatment of critically ill patients

To assess the relevance, both clinical and bacteriologic, of the use of resin-containing blood culture media in blood cultures taken from critically ill patients receiving antibiotics. A prospective, open clinical trial. The mixed medical surgical intensive care unit (ICU) of a 550-bed urban hospital. All ICU patients admitted during a 3-month period (n = 49) with suspected sepsis requiring blood cultures as part of their laboratory investigations. The use of an aerobic resin-containing blood culture medium, in addition to the regular aerobic and anaerobic media for all blood cultures taken. Each blood culture result was classified as to its clinical significance. Changes in patient management were recorded. Culture sets in which the resin-containing bottle provided the information central to the change in patient management were identified. Bacteriologically, the results from the resin-containing medium were compared with the results from the aerobic and anaerobic media. Of 266 blood culture sets, 103 (39%) were positive, growing 278 bacterial and fungal isolates. Clinically, the resin-containing medium alone provided relevant data leading to changes in patient management on three occasions. On two of these occasions, cultures from the regular media provided the same data within 72 hrs. Bacteriologically, 77 (29%) aerobic bottles, 55 (21%) anaerobic bottles, and 89 (33%) resin-containing bottles were positive (statistical comparison of percentages: aerobic vs. resin-containing bottles, nonsignificant; aerobic vs anaerobic bottles, p < .046; anaerobic vs. resin-containing bottles, p < .0027). A similar proportion of pathogens was isolated from the resin-containing bottles only (9%) and aerobic bottles only (6%). A higher proportion of contaminants was isolated from the resin-containing bottles only than the aerobic bottles only in the various sets (17% vs. 7%, p < .046). The resin-containing bottle showed a trend toward increased detection of Staphylococcus aureus and Pseudomonas aeruginosa bacteremia. The resin-containing medium offers little clinical benefit to the majority of ICU patients. Bacteriologically, it seems to have a similar overall sensitivity as the regular aerobic medium (with the possible exception of a higher sensitivity for the isolation of S. aureus and P. aeruginosa), but a lower specificity. The wide-spread use of the resin-containing bottle cannot be recommended.

Clinical comparison of the BACTEC 9000 Standard Anaerobic/F and Lytic/F blood culture media

An 8-month prospective, volume controlled, comparison of Standard Anaerobic/F media with a new anaerobic high blood volume lytic medium (Lytic/F) was performed. A total of 2,092 compliant sets, consisting of an aerobic resin bottle or standard aerobic bottle, Standard Anaerobic/F, and Lytic/F bottle were evaluated. A total of 220 (10.6%) positive specimens were detected from the paired anaerobic bottles. These consisted of 194 true positive and 26 false positive bottles. Of 207 total organisms isolated, 122 were considered clinically significant. A comparison of significant organism recovery revealed 79 isolates in both anaerobic bottles, 7 isolates in the standard Anaerobic/F bottle only, and 36 isolates in the Lytic/F bottle only (p < 0.001). The Lytic/F bottle detected significantly more Enterobacteriaceae (p < 0.005) and Streptococci (p < 0.05). There were 24 false positive Standard Anaerobic/F bottles and 2 false positive Lytic/F bottles (p < 0.001). When both bottles were positive the Standard Anaerobic/F bottle was positive 12 hours earlier in 1 instance whereas the Lytic/F bottle was positive 12 hours earlier in 8 instances. The mean time for detection in the Standard Anaerobic/F bottle was 18.2 hours versus 13.2 hours for the Lytic/F bottle. The new Lytic/F anaerobic blood culture media was found to be superior to Standard Anaerobic/F media for both total organism recovery and time to organism detection.

Nosocomial coagulase-negative staphylococcal infections in bone marrow transplantation recipients with central vein catheter. A 5-year prospective study.

The purpose of this study was to examine coagulase-negative staphylococcal infections in bone marrow transplantation (BMT) patients with central vein catheters by investigating incidence, clinical relevance, risk factors, methicillin resistance, clinical impact of initial empiric antimicrobial therapy without vancomycin, and management of documented catheter-related infections. A 5-year prospective study was conducted with daily evaluation of 242 BMT patients during hospitalization, including clinical assessment and blood culture via the Hickman/Broviac catheter. If fever or infected appearance occurred, peripheral blood cultures or exit site cultures, respectively, were done. Results showed a septicemia incidence of 7.0%, including in 6 patients following colonization, in 1 patient with tunnel infection, in 1 patient with thrombophlebitis, in 1 patient with exit site infection, and in 8 patients with septicemia of unknown origin. Total colonization incidence was 7%, with colonization only in 11 patients who had 16 episodes; incidence of exit site infection was 3.7%. Age > or = 18 years was the only identified risk factor for developing staphylococcal infection (P = 0.03). Despite a methicillin resistance rate of 45% and omission of vancomycin from the routine initial empiric antimicrobial regimen, the clinical course of coagulase-negative staphylococcal infections was relatively benign. A single patient, who experienced marrow rejection, died on day +31 with septicemia and only one patient experienced microbiological failure with recurrent colonization. Bacteria grown in both aerobic and anaerobic bottles were more likely true bacteremia than contaminant (P = 0.03). We conclude that the hazard of coagulase-negative staphylococcal infection does not mandate inclusion of a glycopeptide in the initial empiric antimicrobial regimen in BMT patients, even during febrile neutropenia. Hickman/Broviac-related staphylococcal infections, except for tunnel infection or thrombophlebitis, can usually be treated successfully without removing the catheter.

Evaluation of routine anaerobic blood cultures in the BacT/Alert blood culture system.

To evaluate the use of routine anaerobic blood cultures with the BacT/Alert system, results of 12,289 blood culture sets collected from adults over a 9-month period were reviewed. Of the sets included in the study, 1,306 (10.6%) from 808 patients grew 1 or more organisms. Anaerobes were present in 39 sets from 38 patients. Of the positive sets, both bottles were positive in 60.7% of cases, the aerobic bottle only in 23.7%, and the anaerobic bottle only in 15.6%. When only the 254 patients who had 2 or more positive sets were considered, both bottles were positive in 71.5% of cases, the aerobic bottle only in 20.7%, and the anaerobic only in 7.8%. In this subset of patients gram-positive bacilli, gram-negative bacilli other than Enterobacteriaceae, and yeasts grew significantly more frequently in aerobic bottle. No organisms preferred the anaerobic bottle. These data support the selective use of the BacT/Alert anaerobic blood culture bottle in patients at risk for anaerobic bacteremia.

Value of routine anaerobic blood cultures for pediatric patients

Objective: Anaerobic bacteremia rarely occurs in children. Therefore we assessed the usefulness of routinely obtaining anaerobic blood cultures in our pediatric patients. Study design: Records of 9360 paired aerobic and anaerobic blood culture bottles (Bactec NR660 System) containing blood specimens from pediatric inpatients and outpatients at Duke University Medical Center, Durham, N.C., were reviewed retrospectively. Yield and speed of detection were calculated for each bottle and compared for statistical significance by the McNemar test. Results: A total of 723 clinically important microorganisms were isolated; only 15 (2.1%) were strict anaerobes. Significantly more microorganisms ( p <0.001), especially staphylococci, nonfermenting gram-negative rods, enteric gram-negative rods, and yeasts, were detected by use of the aerobic bottle. The anaerobic bottle was important in identifying an anaerobic microorganism as the cause of sepsis in only five patients, all of whom were at increased risk of having anaerobic infection. Conclusions: Anaerobic blood cultures are rarely helpful in the majority of pediatric patients and usually show positive results only in clinical settings associated with anaerobic infection. Microorganisms that prefer an aerobic environment, such as Pseudomonas aeruginosa and yeasts, are now far more common than anaerobes in children; aerobic culturing of the entire volume of blood collected might increase the yield from pediatric blood cultures. (J P EDIATR 1995;127:263-8)

Value of terminal subcultures for blood cultures monitored by BACTEC 9240.

Blood cultures collected in BACTEC Plus Aerobic/F bottles and BACTEC Plus Anaerobic/F bottles were monitored for 5 days by BACTEC 9240 and subsequent terminal subcultures. Of the 13,471 bottles subcultured, 11.0% (1,477 of 13,471) were culture positive. Of these, 94.0% (1,388 of 1,477) were detected by BACTEC 9240; the additional 6.0% (89 of 1,477) were considered to be false negatives by BACTEC 9240 since they were detected by terminal subculture only. The false-negative bottles consisted of 17 BACTEC Plus Aerobic/F and 72 BACTEC Plus Anaerobic/F bottles, accounting for 2.2 (17 of 786) and 10.4% (72 of 691) of the total positive aerobic and anaerobic bottles, respectively. The positive blood culture bottles most frequently not detected by BACTEC 9240 grew Pseudomonas spp. (24), Staphylococcus spp. (21), and yeasts (24). Of the 86 blood cultures represented by the 89 false-negative bottles, 41 would not have been identified as positive since the other bottle in the blood culture set was either a false negative or a true negative. In general, terminal subcultures of false-negative BACTEC bottles had heavy growth, indicating that BACTEC Plus media were able to support the growth of microorganisms, but the BACTEC 9240 instrument was unable to detect this growth.

Comparison of automated Difco ESP blood culture system with biphasic BBL Septi-Chek system for detection of bloodstream infections in pediatric patients

We compared the Difco ESP 384 blood culture system with the pediatric Septi-Chek system for the detection of bloodstream infections in pediatric patients. A total of 10,762 blood culture sets included an ESP aerobic bottle and a Septi-Chek bottle. From these cultures, a total of 278 organisms classified as probable pathogens were isolated, including 237 from ESP bottles and 221 from Septi-Chek bottles. This difference was not statistically significant. More organisms classified as possible contaminants were also isolated from ESP bottles (for ESP, 480 bottles; for Septi-Chek, 418 bottles; P < 0.01). The time to detection was shorter for probable pathogens isolated from ESP bottles (median times for organisms isolated from both systems: ESP, 14.0 h; Septi-Chek, 34.5 h; P < 0.001). The proportions of all probable pathogens detected by 24 and 48 h after inoculation were 78 and 96%, respectively, for ESP compared with 31 and 74%, respectively, for Septi-Chek. The time to final identification was also shorter for organisms grown in ESP bottles (median times for organisms isolated from both systems: ESP, 48.8 h; Septi-Chek, 58.5 h; P < or = 0.001). A subset of 4,442 cultures also included an ESP anaerobic bottle in addition to an ESP aerobic bottle and a Septi-Chek bottle. There were no significant differences in the recovery of probable pathogens by any of the possible two bottle combinations, but five anaerobic pathogens were recovered only in the anaerobic bottle. We conclude that the ESP 384 is an excellent system for culturing pediatric blood samples and that it provides for the very rapid detection of bloodstream pathogens.

Controlled evaluation of BacT/Alert standard aerobic and FAN aerobic blood culture bottles for detection of bacteremia and fungemia

A new medium, FAN, designed to enhance the recovery of microorganisms, has been developed for the BacT/Alert blood culture system (Organon Teknika Corp., Durham, N.C.). We compared the yield and speed of detection of microorganisms in 6,847 adequately filled paired aerobic standard and FAN bottles at four university hospitals. Of 499 clinically significant microorganisms isolated from one or both bottles, significantly more Staphylococcus aureus isolates (P < 0.001), coagulase-negative staphylococci (P < 0.001), yeasts (P < 0.01), and all microorganisms combined (P < 0.001) were recovered from the FAN bottles. Overall, the speeds of detection of positive cultures did not differ between the two medium formulations; mean times to detection in the standard and FAN bottles were 16.1 and 16.0 h, respectively. When a subset of patients on antimicrobial therapy was evaluated, significantly enhanced yield from the FAN bottle was evident for staphylococci. Overall, the FAN bottle outperformed the standard aerobic BacT/Alert bottle.