PCR evaluation of false-positive signals from two automated blood-culture systems
- 1 January 2006
- journal article
- research article
- Published by Microbiology Society in Journal of Medical Microbiology
- Vol. 55 (1) , 53-57
- https://doi.org/10.1099/jmm.0.46196-0
Abstract
Rapid detection of micro-organisms from blood is one of the most critical functions of a diagnostic microbiology laboratory. Automated blood-culture systems reduce the time needed to detect positive cultures, and reduce specimen handling. The false-positive rate of such systems is 1–10 %. In this study, the presence of pathogens in ‘false-positive’ bottles obtained from BACTEC 9050 (Becton Dickinson) and BacT/Alert (Biomérieux) systems was investigated by eubacterial and fungal PCR. A total of 169 subculture-negative aerobic blood-culture bottles (104 BacT/Alert and 65 BACTEC) were evaluated. Both fungal and eubacterial PCRs were negative for all BACTEC bottles. Fungal PCR was also negative for the BacT/Alert system, but 10 bottles (9·6 %) gave positive results by eubacterial PCR. Sequence analysis of the positive PCR amplicons indicated the presence of the following bacteria (number of isolates in parentheses): Pasteurella multocida (1), Staphylococcus epidermidis (2), Staphylococcus hominis (1), Micrococcus sp. (1), Streptococcus pneumoniae (1), Corynebacterium spp. (2), Brachibacterium sp. (1) and Arthrobacter/Rothia sp. (1). Antibiotic usage by the patients may be responsible for the inability of the laboratory to grow these bacteria on subcultures. For patients with more than one false-positive bottle, molecular methods can be used to evaluate the microbial DNA in these bottles. False positives from the BACTEC system may be due to elevated patient leukocyte counts or the high sensitivity of the system to background increases in CO2 concentration.Keywords
This publication has 6 references indexed in Scilit:
- Verification of false-positive blood culture results generated by the BACTEC 9000 series by eubacterial 16S rDNA and panfungal 18S rDNA directed polymerase chain reaction (PCR)Diagnostic Microbiology and Infectious Disease, 2004
- Can BacT/Alert FA and FN blood culture bottles increase the recovery of microorganisms in the clinical laboratory?Journal of Infection and Chemotherapy, 2004
- 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 HospitalJournal of Clinical Microbiology, 2003
- Direct Identification of Bacteria from Positive Blood Cultures by Amplification and Sequencing of the 16S rRNA Gene: Evaluation of BACTEC 9240 Instrument True- Positive and False-Positive ResultsJournal of Clinical Microbiology, 2001
- A simple and sensitive method to extract bacterial, yeast and fungal DNA from blood culture materialJournal of Microbiological Methods, 2000
- Identification of medically significant fungal genera by polymerase chain reaction followed by restriction enzyme analysisFEMS Immunology & Medical Microbiology, 1999