Optimum Detection Times for Bacteria and Yeast Species with the BACTEC 9120 Aerobic Blood Culture System: Evaluation for a 5-Year Period in a Turkish University Hospital

Abstract

We tracked and documented the time of positivity of blood cultures by using the BACTEC 9120 (Becton Dickinson Diagnostic Instrument Systems) blood culture system over a 5-year study period. A 7-day protocol of the incubation period was selected, and a total of 11,156 blood cultures were evaluated. The clinically significant microorganisms (32.95%) were isolated in 3,676 specimens. Gram-positive and -negative bacterial isolation rates were found to be 41.07 and 44.88%, respectively. Yeasts were found in 14.03% of all pathogens. Both the false-positivity and -negativity rates were very low (0.1 and 0.3%, respectively). The mean detection times for all of the pathogens were determined to be 19.45 h. Yeasts, nonfermentative gram-negative bacteria, and Brucella melitensis strains were isolated within 5 days. By taking these data into account, we decided to establish a 5-day-incubation protocol in our laboratory instead of the 7 days that are commonly used.Bloodstream infection is one of the most serious problems in all infectious diseases. Despite recent developments, like nucleic acid probes, PCR, and other molecular techniques for microbiological diagnosis, blood cultures still remain the most practical and reliable method in the diagnosis of bloodstream infections. Blood culture is one of the most important tools in the clinical microbiology laboratory. Rapid isolation and identification of the microorganisms in blood samples and directing of the treatment accordingly are critically important in order to reduce the mortality rate (2). The fact that conventional methods are not sufficient for a low mortality rate has resulted in the extensive usage of various continually monitored blood culture systems in many clinical microbiology laboratories over the past 25 years. In the end, these systems were proven to be highly reliable. One of these, BACTEC 9120, is based on the monitoring of the CO 2 concentration produced by growing microorganisms with a fluorescent sensor located at the bottom of each bottle (8). The aim of this study was to determine the detection times and the distribution of the bacteria and yeasts isolated from the blood samples by using BACTEC 9120 (Becton Dickinson Diagnostic Instrument Systems, Sparks, Md.) over a 5-year period. We also had it in mind to analyze the data to decide which incubation protocol would be more suitable for practical purposes.This study was conducted in the Clinical Microbiology Laboratory of Osmangazi University Medical Faculty Hospital from August 1996 to December 2001. Most of the patients were adults from intensive care and hematology units. Two bottles were used in the culturing for every patient. All of the phlebotomies were performed with peripheral sticks, and the blood samples were drawn by a clinician by the bedside after cleansing the skin with 70% isopropyl alcohol and applying 10% povidone-iodine for 1 min. The blood samples were inoculated at a volume of 1 to 5 ml into BACTEC Peds Plus/F and a volume of 10 ml into PlusϩAerobic/F blood culture bottles and wer...

Evaluation of blood cultures in a children’s hospital located in Southeastern Anatolia

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Detection of Bacterial and Yeast Species with the Bactec 9120 Automated System with Routine Use of Aerobic, Anaerobic, and Fungal Media

“…Of the microorganisms involved in all of the infections, 58.4% were grampositive cocci, 33.5% were fermentative gram-negative bacilli, 29.0% were nonfermentative gram-negative bacilli, 0.9% were corynebacteria, 1.8% were anaerobes, and 13.1% were yeasts. When these results are compared with those obtained in other epidemiological studies of nosocomial bloodstream infections recently carried out in Italy (15) and other parts of the world (1,3,5,14,17,20), our hospital presents a very low incidence of anaerobic infections and, conversely, relatively high rates of isolation of nonfermentative gram-negative bacilli and yeasts. Nonfermentative gram-negative bacilli were more frequently isolated during bloodstream infections in patients from the ICU and HU than in those from all other units, and yeasts (C. albicans) were more frequently isolated in patients from the ICU.…”

Investigation of Rapid Identification of Metisillin Resistance of Staphylococcus Aureus (MRSA) in Blood Culture Bottles at Three Different Pre-Incubation Periods

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