Evaluation of a plastic nonvented aerobic blood culture bottle for use with the BacT/ALERT microbial detection system.

The current BacT/ALERT SA (BTA SA) aerobic blood culture bottle is made from glass, does not require venting, and contains a liquid emulsion sensor (LES). Its performance has been shown to be equivalent to that of the vented standard aerobic culture bottle. A further-improved version of the BTA SA bottle, designated the BacT/ALERT plastic SA (BTA PSA) culture bottle, is made from clear plastic to prevent breakage, does not require venting, and contains a modified LES (LES 2) to reduce the possibility of false positives. The BTA PSA provides a practical alternative to the current glass version of this bottle. The plastic bottle is also comparable to the current glass bottle in transparency and growth performance and additionally minimizes the exposure to infectious agents due to glass bottle breakage.

Clinical comparison of nonvented aerobic BacT/Alert blood culture bottle and standard aerobic bottle for detection of microorganisms in blood.

The current BacT/Alert standard aerobic (VA) blood culture bottle was redesigned and designated a nonvented aerobic (NVA) culture bottle; this bottle does not require venting. A total of 3,873 sets of blood samples for culture were obtained from adult patients with suspected bacteremia or fungemia. The NVA bottle showed performance equivalent to that of the VA bottle for recovery and speed of detection of microorganisms from blood without the need for venting the bottle.

Comparative in vitro and bactericidal activity of oxazolidinone antibiotics against multidrug-resistant enterococci.

Increasing resistance among enterococci poses a considerable therapeutic problem. In this study, we evaluated the comparative in vitro activity of two investigational oxazolidinone antibiotics, eperezolid and linezolid, versus clinical isolates of multidrug-resistant enterococci. One hundred isolates (16 Enterococcus faecalis, 69 E. faecium, 10 E. gallinarum, 2 E. casseliflavus, 1 E. avium, 1 E. hirae, and 1 E. raffinosus) evaluated were collected from diverse geographic areas in North America and Europe from 1991 to 1995. Eperezolid MIC50 and MIC90 were 1.0 microgram/mL and 2.0 micrograms/mL (1.0-2.0 micrograms/mL range). Linezolid MIC50 and MIC90 were 2.0 micrograms/mL and 2.0 micrograms/mL (0.5-2.0 micrograms/mL range), respectively. MICs were the same at 10(3) CFU/mL and 10(8) CFU/mL initial inoculum. In time-kill experiments using 10 strains and concentrations of 4 micrograms/mL, 8 micrograms/mL, and 16 micrograms/mL (achievable serum concentrations) of eperezolid and linezolid there was a 2 log10 reduction of growth for 2 of 10 isolates tested using eperezolid and a 1 log10 reduction for 50% of isolates with both agents. There was indifferent bactericidal killing when either oxazolidinone was combined with gentamicin, ampicillin, or streptomycin for isolates lacking these resistances. This study demonstrates these oxazolidinone agents to have excellent in vitro activity versus multidrug-resistant enterococci.

Epidemiologic evaluation of antimicrobial resistance in community-acquired enterococci.

Fecal samples from 200 consecutive patients admitted to a community hospital yielded 107 enterococci. High-level gentamicin resistance occurred in 10 (14%) of the Enterococcus faecalis isolates. Ampicillin resistance occurred in two (3%) of the E. faecalis isolates and six (23%) of the Enterococcus faecium isolates. There were no vancomycin-resistant enterococci. Risk factors for enterococci with high-level aminoglycoside (gentamicin) or ampicillin resistance included prior hospitalization and previous antibiotic use.

Colonization of the respiratory tract with Legionella species.

Pneumonia is the most important manifestation of disease caused by Legionella species. However, it is still not known for certain how these organisms actually enter the lungs. During a 5-month period 318 hospitalized patients without clinical or radiologic features of pneumonia were enrolled in a survey of sputum colonization with Legionella. Diagnostic tests included cultures, direct fluorescent antibody test (DFA) and DNA probe assay of sputum. Colonization was considered to occur when at least one of these tests was positive. According to our definitions, 1.2-10% of of these patients could have been colonized by Legionella spp. However, all cultures were negative and in all but one of these patients the DFA was the only positive test. A case-control study comparing test-positive and test-negative patients failed to identify any different features of disease or epidemiologic characteristics. These findings suggest that a high rate of false-positive DFA results occurred in our study rather than any new evidence of colonization of the respiratory tract with Legionella.

Diagnostic efficacy of a DNA probe in pneumonia caused by Legionella species.

A commercial DNA probe kit (Gen-probe) for the detection of rRNA from legionellae was evaluated for its accuracy in diagnosing Legionnaires' disease in 167 patients with pneumonia. The test was performed on freshly obtained clinical respiratory tract samples. Cultures and direct immunofluorescence antibody (DFA) staining of the samples and serological tests were performed simultaneously for all patients. The probe assay result was positive in six patients; five of them had other laboratory evidence of disease (positive cultures or positive serological results or both). Depending on the diagnostic criteria, the probe test had a sensitivity of 31-67%, a specificity of 99% and positive predictive values of 67-83%. The diagnostic performance of the DNA probe assay in this study was superior to that of the DFA test. The results indicate that the examination of respiratory tract secretions by the Gen-probe kit is a suitable screening test for the diagnosis of Legionnaires' disease.

A cluster of pseudofungemia associated with hospital renovation adjacent to the microbiology laboratory.

OBJECTIVE: To determine the clinical significance and source of fungemia following a cluster of positive blood cultures during a 3-day period. DESIGN: Chart review was used to determine the clinical significance of positive blood cultures. Microbiologic sampling of the laboratory environment was used to determine potential sources of fungal contamination. SETTING: A large, tertiary care, community teaching hospital. PATIENTS: All patients with blood cultures positive for Aspergillus species, Penicillium species, or both during the outbreak period. RESULTS: Thirteen patients, all children, were reported to have positive blood cultures for fungus during a 3-day period in early 1990. None had clinical features consistent with fungemia. Investigation of specimen processing procedures revealed that microbiologic plates were not processed--as per protocol--under the biologic hood but inadvertently were left open to air on the work bench by laboratory technicians. Settling plates left at the workbench, at door entry sites, and at sites of renovation immediately adjacent to the laboratory were positive for Aspergillus and/or Penicillium; control plates placed elsewhere were negative. Airflow patterns suggested spread into the microbiologic laboratory through an open door located near the implicated workbench station and a false ceiling above the workbench area. CONCLUSIONS: Our investigation demonstrates that faulty technique in the laboratory coupled with a change in environmental conditions can result in false-positive cultures and an outbreak of pseudofungemia.