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

Clinical evaluation of FAPlus/FNPlus bottles compared with the combination of SA/SN and FA/FN bottles in the BacT/Alert blood culture system

Background : The comparison of the performance of FAPlus/FNPlus bottles and combination of SA/SN and FA/FN bottles is not yet reported. Methods : We used human blood samples to investigate microorganism detection rates and the time to positivity (TTP) in a before-vs.-after study (a combination of SA/SN and FA/FN bottles from September 2012 to August 2013 vs. FAPlus/FNPlus bottles from September 2013 to August 2014). Results : The microorganism detection rate was significantly higher in the later period than in the earlier period (11.2% vs. 9.6%, P < 0.001), particularly for Enterococcus and Streptococcus species, nonfermentative Gram-negative bacilli, and Helicobacter cinaedi. TTP for pathogens was longer when FAPlus/FNPlus bottles were used than when a combination of SA/SN and FA/FN bottles was used (14.9 vs. 13.3 h, P = 0.014), particularly, in the case of Gram-negative bacilli including Escherichia coli. Conclusion : The microorganism detection rate was improved with the use of FAPlus/FNPlus bottles compared with the combination of SA/SN and FA/FN bottles ; however, FAPlus/FNPlus bottles seemed to be inferior to SA/SN and FA/FN bottles in terms of TTP. J. Med. Invest. 67 : 90-94, February, 2020.

Practical Guidance for Clinical Microbiology Laboratories: A Comprehensive Update on the Problem of Blood Culture Contamination and a Discussion of Methods for Addressing the Problem

In this review, we present a comprehensive discussion of matters related to the problem of blood culture contamination. Issues addressed include the scope and magnitude of the problem, the bacteria most often recognized as contaminants, the impact of blood culture contamination on clinical microbiology laboratory function, the economic and clinical ramifications of contamination, and, perhaps most importantly, a systematic discussion of solutions to the problem. We conclude by providing a series of unanswered questions that pertain to this important issue.

Slow growth of Burkholderia pseudomallei compared to other pathogens in an adapted blood culture system in Phnom Penh, Cambodia

PURPOSE

Burkholderia pseudomallei is a key pathogen causing bloodstream infections at Sihanouk Hospital Center of Hope, Phnom Penh, Cambodia. Here, visual instead of automated detection of growth of commercial blood culture bottles is done. The present study assessed the performance of this system.

METHODOLOGY

Blood culture sets, consisting of paired adult aerobic and anaerobic bottles (bioMérieux, FA FAN 259791 and FN FAN 252793) were incubated in a standard incubator for 7 days after reception. Each day, the bottle growth indicator was visually inspected for colour change indicating growth. Blind subculture was performed from the aerobic bottle at day 3.

RESULTS

From 2010 to 2015, 11  671 sets representing 10  389 suspected bloodstream infection episodes were documented. In 1058 (10.2  %) episodes, pathogens grew; they comprised Escherichia coli (31.7 %), Salmonella Paratyphi A (13.9 %), B. pseudomallei (8.5 %), Staphylococcus aureus (7.8 %) and Klebsiella pneumoniae (7.0 %). Blind subculture yielded 72 (4.1  %) pathogens, mostly (55/72, 76.4 %) B. pseudomallei. Cumulative proportions of growth at day 2 were as follows: E. coli: 85.0 %, Salmonella Paratyphi A: 85.0 %, K. pneumoniae: 76.3  % and S. aureus: 52.2  %; for B. pseudomallei, this was only 4.0  %, which increased to 70.1  % (70/99) at day 4 mainly by detection on blind subculture (55/99). Compared to the anaerobic bottles, aerobic bottles had a higher yield and a shorter time-to-detection, particularly for B. pseudomallei.

CONCLUSIONS

Visual inspection for growth of commercial blood culture bottles in a low-resource setting provided satisfactory yield and time-to-detection. However, B. pseudomallei grew slowly and was mainly detected by blind subculture. The aerobic bottle outperformed the anaerobic bottle.

Rapid Identification of Microorganisms by FilmArray Blood Culture Identification Panel Improves Clinical Management in Children

BACKGROUND

Blood cultures are a common investigation for children admitted to hospital. In routine practice, it takes at least 24 hours to identify an organism as a contaminant or clinically significant. FilmArray Blood Culture Identification Panel (FA-BCIP) is a multiplex polymerase chain reaction that can detect 24 pathogens within 1 hour. We assessed whether results from FA-BCIP lead to changes in clinical management in a tertiary referral paediatric hospital.

METHODS

We prospectively studied children having blood cultures taken at our tertiary children's hospital. Blood cultures were monitored and organisms identified using standard methods. FA-BCIP was performed when growth was initially detected in first positive blood cultures per episode, between January 1 and June 30, 2014. Assessment of whether the FA-BCIP result altered clinical management was made, specifically focused on antimicrobial stewardship and length of stay.

RESULTS

FA-BCIP was done on 117 positive blood cultures; 74 (63%) grew clinically significant organisms, 43 (37%) grew contaminants. FA-BCIP results were judged to alter clinical management in 63 of the 117 episodes (54%). Antimicrobials were started/altered in 23 (19%) episodes and de-escalated/withheld/stopped in 29 (25%) episodes. Ten children were discharged from hospital earlier, which saved a cumulative total of 14 bed days.

CONCLUSIONS

Rapid identification of microorganisms in pediatric blood cultures by FA-BCIP, led to changes in clinical management for half of the episodes. This improved antimicrobial stewardship and allowed early discharge from hospital for 10% of children. Future studies should focus on how best to use this technology in a cost-effective manner.

High medical impact of implementing the new polymeric bead-based BacT/ALERT® FAPlus and FNPlus blood culture bottles in standard care

Blood culture (BC) efficiency is critical for the diagnosis of bloodstream infection (BSI). We evaluated the impact on standard care of implementing the new BacT/ALERT® FAPlus and FNPlus BC bottles containing antibiotic-binding polymeric beads. We measured positivity rates and time to detection (TTD) during the first 10 months of implementation (PF) and during the previous 10-month period (PS) during which we were using standard aerobic (SA) or standard anaerobic (SN) BC bottles. For each period, the same number of consecutive patients (n = 3,918) was included. Per patient, a median of 1 BC set (1 aerobic and 1 anaerobic bottles) has been sampled. A higher positivity rate was measured during PF than PS when counting per BC bottle (7.0 % vs 5.8 % with 1,456 and 1,237 positive bottles respectively, P < 0.0001) and per BC set (9.6 % vs 7.8 % with 995 and 832 positive BC sets respectively, P < 0.0001). In PF, an increased number of cases due to staphylococci (P < 0.0001) and to Gram-negative bacilli (P < 0.005) was observed, whereas the contamination rate was similar during the two periods (2.4 % of BC sets in PF and 2.3 % in PS). Although antibiotic consumption and medical activity were similar during the two periods, BSI case detection increased from 2.2 to 2.6 per 1,000 hospital-days, especially in intensive care units (ICU; 35.1 to 55.7). Mean TTD for pathogenic microorganisms was significantly shorter in PF than in PS (15.5 h vs 18.0 h, P < 0.01). In conclusion, the use of the new FAPlus/FNPlus BC bottles improved the diagnosis of bacteremia in our hospital, especially in ICU patients.

Performance of two resin-containing blood culture media in detection of bloodstream infections and in direct matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) broth assays for isolate identification: clinical comparison of the BacT/Alert Plus and Bactec Plus systems

We compared the clinical performances of the BacT/Alert Plus (bioMérieux) and Bactec Plus (Becton Dickinson) aerobic and anaerobic blood culture (BC) media with adsorbent polymeric beads. Patients ≥ 16 years old with suspected bloodstream infections (BSIs) were enrolled in intensive care units and infectious disease wards. A single 40-ml blood sample was collected from each and used to inoculate (10 ml/bottle) one set of BacT/Alert Plus cultures and one set of Bactec Plus cultures, each set consisting of one aerobic and one anaerobic bottle. Cultures were incubated ≤ 5 days in the BacT/Alert 3D and Bactec FX instruments, respectively. A total of 128 unique BSI episodes were identified based on the recovery of clinically significant growth in 212 aerobic cultures (106 BacT/Alert and 106 Bactec) and 151 anaerobic cultures (82 BacT/Alert and 69 Bactec). The BacT/Alert aerobic medium had higher recovery rates for Gram-positive cocci (P = 0.024), whereas the Bactec aerobic medium was superior for recovery of Gram-negative bacilli (P = 0.006). BacT/Alert anaerobic medium recovery rates exceeded those of the Bactec anaerobic medium for total organisms (P = 0.003), Gram-positive cocci (P = 0.013), and Escherichia coli (P = 0.030). In terms of capacity for diagnosing the 128 septic episodes, the BacT/Alert and Bactec sets were comparable, although the former sets diagnosed more BSIs caused by Gram-positive cocci (P = 0.008). They also allowed earlier identification of coagulase-negative staphylococcal growth (mean, 2.8 h; P = 0.003) and growth in samples from patients not on antimicrobial therapy that yielded positive results (mean, 1.3 h; P < 0.001). Similarly high percentages of microorganisms in BacT/Alert and Bactec cultures (93.8% and 93.3%, respectively) were identified by direct matrix-assisted laser desorption ionization-time of flight mass spectrometry assay of BC broths. The BacT/Alert Plus media line appears to be a reliable, timesaving tool for routine detection of BSIs in the population we studied, although further studies are needed to evaluate their performance in other settings.

Developments for improved diagnosis of bacterial bloodstream infections

Bloodstream infections (BSIs) are associated with high mortality and increased healthcare costs. Optimal management of BSI depends on several factors including recognition of the disease, laboratory tests and treatment. Rapid and accurate identification of the etiologic agent is crucial to be able to initiate pathogen specific antibiotic therapy and decrease mortality rates. Furthermore, appropriate treatment might slow down the emergence of antibiotic resistant strains. Culture-based methods are still considered to be the "gold standard" for the detection and identification of pathogens causing BSI. Positive blood cultures are used for Gram-staining. Subsequently, positive blood culture material is subcultured on solid media, and (semi-automated) biochemical testing is performed for species identification. Finally, a complete antibiotic susceptibility profile can be provided based on cultured colonies, which allows the start of pathogen-tailored antibiotic therapy. This conventional workflow is extremely time-consuming and can take up to several days. Furthermore, fastidious and slow-growing microorganisms, as well as antibiotic pre-treated samples can lead to false-negative results. The main aim of this review is to present different strategies to improve the conventional laboratory diagnostic steps for BSI. These approaches include protein-based (MALDI-TOF mass spectrometry) and nucleic acid-based (polymerase chain reaction [PCR]) identification from subculture, blood cultures, and whole blood to decrease time to results. Pathogen enrichment and DNA isolation methods, to enable optimal pathogen DNA recovery from whole blood, are described. In addition, the use of biomarkers as patient pre-selection tools for molecular assays are discussed.

Controlled clinical comparison of new pediatric medium with adsorbent polymeric beads (PF Plus) versus charcoal-containing PF medium in the BacT/alert blood culture system

We conducted a controlled clinical comparison of PF Plus, the new pediatric medium with adsorbent polymeric beads, versus the charcoal-containing PF medium in the BacT/Alert blood culture system. A total of 2,381 pediatric cultures were enrolled, and 1,703 (71.5%) were deemed to be compliant and acceptable for analysis. Seventy-two cultures (4.2%) had a positive result with 80 clinically significant microorganisms. The results showed that the PF Plus medium yielded more clinically significant microorganisms than the BacT/Alert system (P < 0.05). In addition, the PF Plus bottle yielded positive results an average of 5.0 h earlier than the PF bottle for compliant clinically significant cultures (18.3 h versus 23.2 h, P = 0.004). PF Plus is an improved medium for detecting microorganisms that cause pediatric bloodstream infections.

Identifying and classifying bloodstream infections among hemodialysis patients

Bloodstream infections (BSIs) are a prominent clinical problem in patients undergoing hemodialysis. These infections appear to be more common among patients who have a central line as their dialysis access and can be associated with substantial morbidity and mortality. Accurately diagnosing BSIs clearly influences patient management, but is also an important part of an infection prevention program; particularly as facility BSI rates are becoming a recognized quality measure for which dialysis facilities might be held accountable. Blood cultures remain the gold standard for diagnosing BSIs and a number of practices can affect the sensitivity and specificity of this important laboratory test. Optimizing the collection of blood cultures can assist providers with interpretation of positive blood cultures and can help minimize the impact of false-positive and false-negative cultures. This review will describe differences between BSI definitions, examine the use of blood cultures to identify these infections including the use of recommended best practices to maximize culture yield, and highlight characteristics that can assist in the clinical interpretation of positive blood cultures.

Update on blood cultures: how to obtain, process, report, and interpret

The detection and identification of microorganisms circulating in the bloodstream of patients is arguably one of the most important functions of the clinical microbiology laboratory. Effective implementation of this function requires careful consideration of specimen collection and processing, culture techniques, result reporting, and, perhaps most importantly, result interpretation by the physician. The purpose of this review is to provide a synopsis of the current state of the art for each of these areas, with the intention of providing adequate information to enable clinical laboratory personnel and physicians to critically evaluate and, if required, improve their current blood culture practices.

Relevance of routine use of the anaerobic blood culture bottle

Using the BacT/Alert automated system, we conducted a 1-year retrospective study on blood cultures, focusing on the relevance of routine use of the anaerobic bottle. The rate of patients with positive blood cultures was 19.7%. Among these, 13.5% had a positive anaerobic bottle in the absence of any aerobic bottle, and 2/3 of these grew with nonobligate anaerobes. These patients were hospitalized in 20 out of 26 wards of the hospital group. For 65.4% of the monomicrobial-positive blood cultures growing Enterobacteriaceae, the anaerobic bottle detected growth earlier than the corresponding aerobic bottle. These data suggest that, in our institution, the use of an anaerobic bottle is still relevant.

Comparison of BACTEC PLUS blood culture media to BacT/Alert FA blood culture media for detection of bacterial pathogens in samples containing therapeutic levels of antibiotics

Blood culture bottles with antimicrobial removal systems are recommended for patients who develop fever while on antibiotics. This study compared the ability of Becton Dickinson (Sparks, MD) BACTEC PLUS bottles and bioMerieux (Durham, NC) BacT/Alert FA bottles to effectively remove vancomycin, cefoxitin, ceftriaxone, cefepime, piperacillin-tazobactam, ampicillin, oxacillin, gentamicin, and a combination of gentamicin/penicillin, thus allowing bacterial pathogens to grow. Each bottle was spiked with 10 ml of human blood, antibiotic, and strains of organisms susceptible to the antibiotic evaluated. The organisms used were type strains and clinical isolates of Staphylococcus aureus (methicillin susceptible and resistant), Streptococcus pneumoniae, a viridans streptococcus, Enterococcus faecalis, Enterococcus faecium, Streptococcus agalactiae, Escherichia coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa. Testing was completed in triplicate, using 10 to 100 CFU/ml of organisms with various concentrations of each antibiotic. Two rounds of testing were completed per antibiotic/organism combination. Bottles were mixed and loaded onto their respective instruments as per the manufacturer's instructions. Antimicrobial removal was evaluated on the basis of time to detection of organism growth, for up to 5 days of incubation. Overall, the BacT/Alert FA system recovered 25.1% of strains from test bottles and 96.9% of strains from growth control bottles (no antibiotic added), and the BACTEC PLUS system recovered 95.1% of strains from test bottles and 100% of strains from growth control bottles. Both systems performed well in the detection of Escherichia coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa in the presence of gentamicin. In the presence of ceftriaxone, neither system was able to recover Streptococcus pneumoniae. The ability to remove vancomycin and cefoxitin was also determined by measuring antibiotic levels remaining in bottles after 1 h of incubation. The results demonstrated remaining levels of 72 to 90% of vancomycin and 71 to 72% of cefoxitin in the BacT/Alert system. For the BACTEC system, remaining levels were 0 to 30% of vancomycin and 0% of cefoxitin. Under these simulated conditions, the BACTEC PLUS system was superior to the BacT/Alert FA system in recovering gram-positive and gram-negative bacterial pathogens in the presence of beta-lactam antibiotics, gentamicin/penicillin, and vancomycin.

Updated review of blood culture contamination

Blood culture contamination represents an ongoing source of frustration for clinicians and microbiologists alike. Ambiguous culture results often lead to diagnostic uncertainty in clinical management and are associated with increased health care costs due to unnecessary treatment and testing. A variety of strategies have been investigated and employed to decrease contamination rates. In addition, numerous approaches to increase our ability to distinguish between clinically significant bacteremia and contamination have been explored. In recent years, there has been an increase in the application of computer-based tools to support infection control activities as well as provide clinical decision support related to the management of infectious diseases. Finally, new approaches for estimating bacteremia risk which have the potential to decrease unnecessary blood culture utilization have been developed and evaluated. In this review, we provide an overview of blood culture contamination and describe the potential utility of a variety of approaches to improve both detection and prevention. While it is clear that progress is being made, fundamental challenges remain.

Using the polymerase chain reaction coupled with denaturing gradient gel electrophoresis to investigate the association between bacterial translocation and systemic inflammatory response syndrome in predicted acute severe pancreatitis

AIM

To investigate the use of PCR and DGGE to investigate the association between bacterial translocation and systemic inflammatory response syndrome in predicted severe AP.

METHODS

Patients with biochemical and clinical evidence of acute pancreatitis and an APACHE II score > or = 8 were enrolled. PCR and DGGE were employed to detect bacterial translocation in blood samples collected on d 1, 3, and 8 after the admission. Standard microbial blood cultures were taken when there was clinical evidence of sepsis or when felt to be clinically indicated by the supervising team.

RESULTS

Six patients were included. Of all the patients investigated, only one developed septic complications; the others had uneventful illness. Bacteria were detected using PCR in 4 of the 17 collected blood samples. The patient with sepsis was PCR-positive in two samples (taken on d 1 and 3), despite three negative blood cultures. Using DGGE and specific primers, the bacteria in all blood specimens which tested positive for the presence of bacterial DNA were identified as E coli.

CONCLUSION

Our study confirmed that unlike traditional microbiological techniques, PCR can detect the presence of bacteria in the blood of patients with severe AP. Therefore, this latter method in conjunction with DGGE is potentially an extremely useful tool in predicting septic morbidity and evaluating patients with the disease. Further research using increased numbers of patients, in particular those patients with necrosis and sepsis, is required to assess the reliability of PCR and DGGE in the rapid diagnosis of infection in AP.

Controlled clinical comparison of the BacT/ALERT FN and the standard anaerobic SN blood culture medium

To determine the optimal anaerobic companion bottle to pair with the BacT/ALERT (bioMerieux, Durham, N.C.) nonvented aerobic FA (FA) medium for recovery of pathogenic microorganisms from adult patients with bacteremia and fungemia, we compared the BacT/ALERT FN (FN) anaerobic bottle with the standard BacT/ALERT SN (SN) anaerobic bottle. Each bottle, FA, FN, and SN, was filled with 8 to 12 ml of blood. Of 11,498 blood culture sets received in the clinical microbiology laboratories at two university medical centers, 7,945 sets had all three bottles filled adequately and 8,569 had both anaerobic bottles filled adequately. Of 686 clinically important (based on previously published criteria) isolates detected in one or both adequately filled anaerobic bottles, more staphylococci (P < 0.001), including Staphylococcus aureus (P < 0.001); members of the family Enterobacteriaceae (P < 0.001); and all microorganisms combined (P < 0.001) were detected in FN bottles. In contrast, more Pseudomonas aeruginosa isolates (P < 0.01) and yeasts (P < 0.001) were detected in SN bottles. More Bacteroides fragilis group bacteremias were detected only in the FN (six) than in the SN (one) anaerobic bottle (P = not significant). Overall, the mean time to detection was shorter with FN (16.8 h) than with SN (18.2 h). This difference in time to detection was greatest for the B. fragilis group: FN, 28 h, versus SN, 60.0 h. Many of the facultative microorganisms recovered in either FN or SN were also found in the companion FA. When microorganisms found in the companion FA bottle were omitted from the analysis, significantly more staphylococci (P < 0.001), including S. aureus (P < 0.001), and Enterobacteriaceae (P < 0.005) still were detected in FN bottles, whereas there were no significant differences for P. aeruginosa and yeasts, which were found as expected in FA bottles. We conclude that the companion anaerobic FN bottle detects more microorganisms than does the anaerobic SN bottle when used in conjunction with the nonvented aerobic FA bottle in the BacT/ALERT blood culture system.

Diagnosis of infection in sepsis: An evidence-based review

OBJECTIVE

In 2003, critical care and infectious disease experts representing 11 international organizations developed management guidelines for the diagnosis of infection in sepsis that would be of practical use for the bedside clinician, under the auspices of the Surviving Sepsis Campaign, an international effort to increase awareness and improve outcome in severe sepsis.

DESIGN

The process included a modified Delphi method, a consensus conference, several subsequent smaller meetings of subgroups and key individuals, teleconferences, and electronic-based discussion among subgroups and among the entire committee.

METHODS

The modified Delphi methodology used for grading recommendations built on a 2001 publication sponsored by the International Sepsis Forum. We undertook a systematic review of the literature graded along five levels to create recommendation grades from A to E, with A being the highest grade. Pediatric considerations to contrast adult and pediatric management are in the article by Parker et al. on p. S591.

CONCLUSIONS

Obtaining a precise bacteriological diagnosis before starting antibiotic therapy is, when possible, of paramount importance for the success of therapeutic strategy during sepsis. Two to three blood cultures should be performed, preferably from a peripheral vein, without interval between samples to avoid delaying therapy. A quantitative approach is preferred in most cases when possible, in particular for catheter-related infections and ventilator-associated pneumonia. Diagnosing community-acquired pneumonia is complex, and a diagnostic algorithm is proposed. Appropriate samples are indicated during soft tissue and intraabdominal infections, but cultures obtained through the drains are discouraged.

Can BacT/Alert FA and FN blood culture bottles increase the recovery of microorganisms in the clinical laboratory?

To evaluate whether the use of BacT/Alert FA and FN blood culture bottles increases the yield of microorganisms, we performed a before-after study. BacT/Alert standard aerobic (AE) and anaerobic (AN) bottles were used from January 1999 to May 2001 (before period). FA and FN bottles were used from May 2001 to March 2003 (after period). A total of 7796 AE, 7807 AN, 4798 FA, and 4787 FN bottles were processed. There were 742 (9.5%) AE-, 598 (7.7%) AN-, 521 (10.7%) FA-, and 396 (8.3%) FN-positive bottles. From these positive bottles 776, 631, 585, and 487 microorganisms were isolated, respectively. Among the isolated microorganisms, 58 (7.5%) and 59 (10.1%) Candida species were isolated from AE and FA bottles, respectively, and 17 (2.7%) and 21 (4.3%) obligate anaerobes were isolated from AN and FN bottles, respectively. We conclude that BacT/Alert FA and FN bottles showed a higher percentage of positivity for microorganisms, in particular for Candida species and obligate anaerobes.

Laboratory diagnosis of bacteremia and fungemia

Many of the variables that affect the laboratory diagnosis of bacteremia and fungemia have been addressed in this article. Whereas the scientific basis and principles for blood cultures are well-established, and the methodology has improved, the diagnosis of bacteremia and fungemia still depends greatly on the care that is taken in obtaining the specimens of blood and the skill of the clinician in interpreting positive results.

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 clinical comparison of BACTEC plus anaerobic/F to standard anaerobic/F as the anaerobic companion bottle to plus aerobic/F medium for culturing blood from adults

To determine the optimal anaerobic companion bottle to pair with BACTEC Plus Aerobic/F medium for recovery of pathogenic microorganisms from adult patients with bacteremia and fungemia, we compared Plus Anaerobic/F bottles with Standard Anaerobic/F bottles, each of which was filled with 4 to 6 ml of blood. The two bottles were paired with a Plus Aerobic/F bottle filled with 8 to 12 ml of blood. A total of 14,011 blood culture sets were obtained. Of these, 11,583 sets were received with all three bottles filled adequately and 12,257 were received with both anaerobic bottles filled adequately. Of 818 clinically important isolates detected in one or both adequately filled anaerobic bottles, significantly more staphylococci (P < 0.001), streptococci (P < 0.005), Escherichia coli isolates (P < 0.02), Klebsiella pneumoniae isolates (P < 0.005), and all microorganisms combined (P < 0.001) were detected in Plus Anaerobic/F bottles. In contrast, significantly more anaerobic gram-negative bacilli were detected in Standard Anaerobic/F bottles (P < 0.05). Of 397 unimicrobial episodes of septicemia, 354 were detected with both pairs, 30 were detected with Plus Aerobic/F-Plus Anaerobic/F pairs only, and 13 were detected with Plus Aerobic/F-Standard Anaerobic/F pairs only (P < 0.05). Significantly more episodes of bacteremia caused by members of the family Enterobacteriaceae (P < 0.05) and aerobic and facultative gram-positive bacteria (P < 0.025) were detected with Plus Anaerobic/F bottles only. In a paired-bottle analysis, 810 of 950 isolates were recovered from both pairs, 90 were recovered from Plus Aerobic/F-Plus Anaerobic/F pairs only, and 50 were recovered from Plus Aerobic/F-Standard Anaerobic/F pairs only (P < 0.001). Paired Plus Aerobic/F-Plus Anaerobic/F bottles yielded significantly more staphylococci (P < 0.001), streptococci (P < 0.05), and members of the family Enterobacteriaceae (P <0.001). We conclude that Plus Anaerobic/F bottles detect more microorganisms and episodes of bacteremia and fungemia than Standard Anaerobic/F bottles as companion bottles to Plus Aerobic/F bottles in the BACTEC 9240 blood culture system.

Evaluation of the BacT/Alert microbial detection system with FAN aerobic and FAN anaerobic bottles for culturing normally sterile body fluids other than blood

We evaluated the BacT/Alert Microbial Detection System (Organon Teknika Corporation, Durham, NC, USA) by using FAN bottles compared to conventional culture methods for the recovery of microorganisms from normally sterile body fluids other than blood and dialysates. Clinically significant pathogens were isolated from 116 (11%) of 1, 099 consecutive specimens (80 from both conventional media and FAN bottles; 23 from FAN bottles only; 13 from conventional media only). Gram-positive cocci were more likely to be recovered from FAN bottles than from conventional media (p = 0.04). Contaminants were also more likely to have grown in FAN bottles (3%) than on conventional media (1%) (p = 0.04). The mean time to detection of significant pathogens was 20.9 h using FAN bottles as compared to 30. 9 h using conventional media (p = 0.0001). These results indicate that the BacT/Alert Microbial Detection System using FAN blood culture bottles improves the yield of clinically significant Gram-positive isolates from normally sterile body fluids with a reduced time to detection.

Assessment of the FAN anaerobic bottle for culture of continuous ambulatory peritoneal dialysis fluid using the BacT/Alert system

The purpose of this study was to determine if the newly available FAN anaerobic bottle (FANAN) alone would be comparable to the combination of the FAN aerobic (FANAE) plus the standard BacT/Alert anaerobic (REGAN) bottles for culture of continuous ambulatory peritoneal dialysis (CAPD) fluid from patients with CAPD peritonitis. CAPD fluid (10 mL) was injected into each bottle, which was then monitored by the BacT/Alert instrument by using a 7-day protocol. Aerobic and anaerobic terminal subculture were performed on all bottles before they were classified as being culture negative. There were 181 effluents received that were suitable for analysis. Growth was detected in 76 (42%) effluents by at least one method. FANAE was the single best medium detecting 84/96 (88%) of all organisms whereas the FANAN and REGAN each detected 69/96 (72%). The combination of FANAE and REGAN bottles detected 92/96 (96%) isolates, which was significantly better than the FANAN or FANAE alone for isolate recovery (p < 0.001). The isolates that were missed by the FANAN but that were recovered by either FANAE or REGAN were all facultative anaerobes commonly detected in CAPD fluids. Terminal subculture revealed otherwise undetected pathogens in 3.9% of positive effluents, usually Pseudomonas aeruginosa. Based on our data, FANAE was the single best bottle for detection of CAPD peritonitis and, in combination with an anaerobic bottle, detected growth from the most effluents. FANAN alone could not substitute for the FANAE/REGAN combination. Although terminal subculture remains controversial, we recommend routine aerobic subculture to ensure that no P. aeruginosa isolates are missed.

The detection of pyrogens in sera from patients with symptoms of sepsis using an ex vivo whole blood culture assay

The aim of this study was to investigate whether the ex vivo whole blood culture (WBC) assay system can be used to detect pyrogens in blood from patients with symptoms of sepsis. Blood samples from 35 patients with symptoms of sepsis were assayed for bacterial contamination using the radiometric blood culture assay. Serum from the same patients were screened for IL-6, C-reactive protein (CRP) and pyrogens using the whole blood culture assay. Serum samples from 26 patients tested positive for pyrogens. Of the 26 patients with pyrogenic serum, 15 had elevated serum IL-6 levels and 19 had elevated CRP levels. Only two of the samples had positive blood cultures as detected by the routine radiometric assay. Both of these patients had high serum CRP and pyrogen levels, while only one of them had an elevated serum IL-6 level. These results show that the WBC is very sensitive in detecting pyrogens in serum of patients. This technique can be a useful tool to quantitate pyrogens in sera from patients with symptoms of sepsis and to determine whether their clinical symptoms are caused by pyretic substances in their circulatory system.

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.

Use of the BacT/Alert blood culture system for culture of sterile body fluids other than blood

Studies have demonstrated that large-volume culture methods for sterile body fluids other than blood increase recovery compared to traditional plated-medium methods. BacT/Alert is a fully automated blood culture system for detecting bacteremia and fungemia. In this study, we compared culture in BacT/Alert standard aerobic and anaerobic bottles, BacT/Alert FAN aerobic and FAN anaerobic bottles, and culture on routine media for six specimen types, i.e., continuous ambulatory peritoneal dialysate (CAPD), peritoneal, amniotic, pericardial, synovial, and pleural fluids. Specimen volumes were divided equally among the three arms of the study. A total of 1,157 specimens were tested, with 227 significant isolates recovered from 193 specimens. Recovery by method was as follows: standard bottles, 186 of 227 (82%); FAN bottles, 217 of 227 (96%); and routine culture, 184 of 227 (81%). The FAN bottles recovered significantly more gram-positive cocci (P < 0.001), Staphylococcus aureus (P = 0.003), coagulase-negative staphylococci (P = 0.008), gram-negative bacilli (P < 0.001), Enterobacteriaceae (P = 0.005), and total organisms (P < 0.001) than the routine culture. There were no significant differences in recovery between the standard bottles and the routine culture. The FAN aerobic bottle recovered significantly more gram-positive cocci (P < 0.001), S. aureus isolates (P < 0.001), coagulase-negative staphyococci (P = 0.003), and total organisms (P < 0.001) than the standard aerobic bottle, while the FAN anaerobic bottle recovered significantly more gram-positive cocci (P < 0.001), S. aureus isolates (P < 0.001), Enterobacteriaceae (P = 0.03), and total organisms (P < 0.001) than the standard anaerobic bottle. For specific specimen types, significantly more isolates were recovered from the FAN bottles compared to the routine culture for synovial (P < 0.001) and CAPD (P = 0.004) fluids. Overall, the FAN bottles were superior in performance to both the standard bottles and the routine culture for detection of microorganisms from the types of sterile body fluids included in this study.

Update on detection of bacteremia and fungemia

The presence of microorganisms in a patient's blood is a critical determinant of the severity of the patient's illness. Equally important, the laboratory isolation and identification of a microorganism present in blood determine the etiologic agent of infection, especially when the site of infection is localized and difficult to access. This review addresses the pathophysiology and clinical characteristics of bacteremia, fungemia, and sepsis; diagnostic strategies and critical factors in the detection of positive blood cultures; characteristics of manual and instrument approaches to bacteremia detection; approaches for isolating specific microorganisms associated with positive blood cultures; and rapid methods for the identification of microorganisms in blood cultures.