Clinical comparison of difco ESP, Wampole isolator, and Becton Dickinson Septi-Chek aerobic blood culturing systems

Isolation and concentration of bacteria from blood using microfluidic membraneless dialysis and dielectrophoresis

A microfluidic system that combines membraneless microfluidic dialysis and dielectrophoresis to achieve label-free isolation and concentration of bacteria from whole blood is presented. Target bacteria and undesired blood cells are discriminated on the basis of their differential susceptibility to permeabilizing agents that alter the dielectrophoretic behavior of blood cells but not bacteria. The combined membraneless microdialysis and dielectrophoresis system isolated 79 ± 3% of Escherichia coli and 78 ± 2% of Staphylococcus aureus spiked into whole blood at a processing rate of 0.6 mL h^-1. Collection efficiency was independent of the number of target bacteria up to 10⁵ cells. Quantitative PCR analysis revealed that bacterial 16S rDNA levels were enriched more than 307-fold over human DNA in the fraction recovered from the isolation system compared with the original specimen. These data demonstrate feasibility for an instrument to accelerate the detection and analysis of bacteria in blood by first isolating and concentrating them in a microchamber.

Population-based epidemiology and microbiology of community-onset bloodstream infections

Bloodstream infection (BSI) is a major cause of infectious disease morbidity and mortality worldwide. While a positive blood culture is mandatory for establishment of the presence of a BSI, there are a number of determinants that must be considered for establishment of this entity. Community-onset BSIs are those that occur in outpatients or are first identified <48 h after admission to hospital, and they may be subclassified further as health care associated, when they occur in patients with significant prior health care exposure, or community associated, in other cases. The most common causes of community-onset BSI include Escherichia coli, Staphylococcus aureus, and Streptococcus pneumoniae. Antimicrobial-resistant organisms, including methicillin-resistant Staphylococcus aureus and extended-spectrum β-lactamase/metallo-β-lactamase/carbapenemase-producing Enterobacteriaceae, have emerged as important etiologies of community-onset BSI.

A Critical Appraisal of the Role of the Clinical Microbiology Laboratory in the Diagnosis of Bloodstream Infections

The detection of bloodstream infections is one of the most important functions of clinical microbiology laboratories. Despite advances in blood culture technology and clinical studies that have focused on the detection of bacteremia and fungemia, perfection has not been achieved and uncertainties persist. This review provides perspectives on a number of areas, including the recommended number of blood cultures, duration of incubation of blood cultures, use of anaerobic, in addition to aerobic, blood culture media, value of the lysis-centrifugation method, processing and reporting of probable blood culture contaminants, and limitations of current blood culture methods and systems. We also address the handling of blood cultures in point-of-care locations that lack full microbiology capabilities.

Use of a panfungal PCR assay for detection of fungal pathogens in a commercial blood culture system

A panfungal PCR assay was used to evaluate the ability of the ESP blood culture system to detect fungemia. The results showed that the ESP system is reliable for the detection of fungi and showed the applicability of using a molecular-based assay as a potential rapid and reliable method for the identification of fungi.

Effects of rapid detection of bloodstream infections on length of hospitalization and hospital charges

Current automated continuous-monitoring blood culture systems afford more rapid detection of bacteremia and fungemia than is possible with non-instrument-based manual methods. Use of these systems has not been studied objectively with respect to impact on patient outcomes, including hospital charges and length of hospitalization. We conducted a prospective, two-center study in which the time from the obtainment of the initial positive blood culture until the Gram stain was called was evaluated for 917 cases of bloodstream infection. Factors showing univariate associations with a shorter time to notification included higher body temperature and respiratory rate and higher percentage of immature neutrophils. Multiple linear regression models determined that the primary predictors of both increased microbiology laboratory and total hospital charges for patients with bloodstream infection were nonmicrobiologic and included length of stay and host factors such as the admitting service and underlying illness score. Significant microbiologic predictors of increased charges included the number of blood cultures obtained, nosocomial acquisition, and polymicrobial bloodstream infections. Accelerated failure time regression analysis demonstrated that microbiologic factors, including time until notification, organism group, and nosocomial acquisition, were independently associated with length of hospitalization after bacteremia, as were the factors of admitting service, gender, and age. Our data suggest that an increased time to notification of bloodstream infection is independently associated with increased length of stay. We conclude that the time to notification is an obvious target for efforts to shorten length of stay. The newest generation of automated continuous-monitoring blood culture systems, which shorten the time required to obtain a positive result, should impact length of hospitalization.

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.

Performance of five agar media for recovery of fungi from isolator blood cultures

We studied the recovery of 1,270 fungal isolates from 176,144 Isolator blood cultures (0.72% positive) on bacterial and fungal media, under routine and differing incubation conditions. Except with Histoplasma capsulatum, chocolate agar incubated for only 3 days proved to be an excellent medium for the recovery of fungi from the Isolator system.

Controlled comparative evaluation of BacT/Alert FAN and ESP 80A aerobic media as means for detecting bacteremia and fungemia

During a one-year period, a total of 6,305 blood cultures were processed in a tertiary-care teaching hospital; 6 to 12 ml of blood was inoculated into both a BacT/Alert Fan aerobic bottle and an ESP 80A aerobic bottle. The FAN aerobic bottle contains an antimicrobial-absorbing material; the 80A aerobic bottle does not. Bottles were processed on their respective continuous-monitoring blood culture instruments for up to five days of incubation. Four hundred thirty-three cultures (6.9%) representing 301 septic episodes in 235 different patients yielded 490 bacteria or yeasts thought to be clinically significant. Two hundred seventy-five of the 433 presumed clinically significant positive cultures (63.5%) representing 195 septic episodes and yielding 301 isolates were positive in both FAN and 80A bottles. One hundred nine significant positive cultures (25.2%) (i.e., cultures positive with an organism judged to be of probable clinical significance) from 70 septic episodes yielded 126 isolates only in FAN bottles. Conversely, the 80A bottle was exclusively positive in 49 instances (11.3%), representing 36 septic episodes and yielding 63 isolates. The higher rates of significant positive blood cultures, numbers of septic episodes documented, and numbers of isolates recovered in FAN bottles versus 80A bottles were all statistically significant (P < 0.05). Enhanced rates of detection of presumed clinically significant isolates in FAN bottles were largely accounted for by Staphylococcus aureus, members of the Enterobacteriaceae, and non-Pseudomonas aeruginosa miscellaneous gram-negative bacilli from patients receiving antimicrobial therapy at the time blood cultures were obtained. Enhanced recovery of one organism group, the beta-hemolytic streptococci, occurred in 80A. With one exception, detection times were essentially equivalent in the two systems. The single exception pertained to streptococci and enterococci, which were recovered significantly faster in 80A bottles. Three hundred thirty-eight of the 6,305 blood cultures evaluated in this study (5.4%) were judged likely to be contaminated. The percentages of probable contaminated cultures were as follows: 26.6% FAN and 80A; 42.3% FAN only; 31.1% 80A only (P < 0.05). Finally, the instrument false-positive rates for the two systems were 0.7% with FAN and 3.0% with 80A (P < 0.05). We conclude that while contamination rates were slightly higher with FAN than with 80A, use of FAN aerobic bottles in conjunction with the BacT/Alert system will yield significantly higher numbers of clinically significant blood culture isolates than 80A bottles and the ESP system. Furthermore, this enhanced detection is most conspicuous in patients receiving antimicrobial therapy at the time blood cultures are performed, probably due to the presence of an antimicrobial-absorbing material in FAN aerobic bottles.

Investigation of infection in the neutropenic patient with fever

Episodes of infection occurring in neutropenic patients are often associated with high levels of morbidity and mortality and prompt, accurate diagnosis allowing the rapid instigation of appropriate treatment can lead to an improved outcome. Recent developments in laboratory technology have increased the range of investigations available to the physician. The improved sensitivity of traditional microbiological culture, methods for antigen and antibody detection and the advances in molecular biology are among the reasons for an increased ability to detect both familiar and novel pathogens. This article describes the current methods available for determining the aetiology of an infectious episode in these patients. A plan of management for investigation of febrile episodes in neutropenic patients is suggested.

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.

Clinical comparison of BACTEC 9240 plus aerobic/F resin bottles and the isolator aerobic culture system for detection of bloodstream infections

The Plus Aerobic/F resin bottle of the BACTEC 9240 automated blood culture system (Becton Dickinson Diagnostic Instrument Systems, Sparks, Md.) was compared with aerobic culture of the Isolator system (Wampole Laboratories, Cranbury, N.J.) for the detection of bloodstream microorganisms from 6,145 blood cultures collected from adult patients with suspected septicemia. The BACTEC resin bottles were incubated for 7 days, and the sediment from the Isolator tube was inoculated to sheep blood and chocolate agars which were incubated for 72 h and to inhibitory mold, brain heart infusion, and Sabouraud agars which were incubated for 21 days. A total of 622 microorganisms were recovered from 583 blood cultures. The BACTEC resin bottle recovered statistically significantly more pathogens overall than the Isolator system (P = 0.0006). When individual pathogens isolated from either system for a 7-day study period were assessed, it was determined that the BACTEC resin bottle detected statistically significantly more isolates of Staphylococcus aureus (P = 0.0113) and coagulase-negative Staphylococcus spp. (P = 0.0029) than the Isolator system. The BACTEC resin bottle also detected statistically significantly more bloodstream infections (septic episodes) caused by coagulase-negative Staphylococcus spp. (P = 0.0146). The Isolator system recovered statistically significantly more contaminants overall (P < 0.0001), and among this group of microorganisms, recovered statistically significantly more Bacillus spp. (P < 0.0001), coagulase-negative Staphylococcus spp. (P < 0.0001), and viridans group Streptococcus spp. (P = 0.0156). The Isolator system detected statistically significantly more isolates of Histoplasma capsulatum (P = 0.004), but all of these isolates were detected at > or = 7 days of incubation of fungal plates, i.e., after the system to system comparison study period (7 days). In blood culture sets which produced growth of the same pathogen in both systems, there was a statistically significant difference in median time to detection for all pathogens combined favoring the BACTEC resin bottle over the Isolator tube (P < 0.05). When assessing individual microorganisms, the median times for detection of S. aureus, Enterococcus spp., and Pseudomonas spp. were all statistically significantly less for the BACTEC system (P < 0.05). The BACTEC instrument had 79 (1.3%) false positive signals. The BACTEC system required less processing time than the Isolator system and eliminates the hands-on time for detection of positive cultures required with the Isolator system.

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.