Trends of the Species and Antimicrobial Susceptibility of Microorganisms Isolated from Blood Cultures of Patients / 대한임상미생물학회지

BACKGROUND: Blood culture is an important procedure for the determination of the etiologic agent of septicemia. Analysis of the blood culture results can provide clinicians with very important information for the empirical treatment of patients. METHODS: In this study the blood cuture results at Chosun University Hospital during the years 2002 to 2005 were analysed to determine the species and antimicrobial susceptibility of the isolates. Blood culture bottles were incubated in BACTEC 9240 blood culture system; the isolates were identified by Vitek II, and antimicrobial susceptibility was tested by Vitek II system or the NCCLS disk diffusion method. RESULTS: Positive blood cultures were obtained from 1,520 (18.5%) patients. Among the microorganisms isolated from blood culture, 97.0% were aerobic and facultative anaerobic bacteria and 2.8% were fungi. Frequently isolated organisms in decreasing order were coagulase-negative staphylococci (CNS), Escherichia coli, Staphylococus aureus, Stenotrophomonas maltophilia, Serratia marcescens, and Klebsiella pneumoniae. The proportion of Pseudomonas aeruginosa isolates resistant to ceftazidime and imipenem was increased during the study period. CONCLUSION: E. coli was the most frequent etiologic agent of bacteremia except CNS, common contaminants of skin, at Chosun University Hospital. It seems to be necessary to enhance infection control measures to cope with an increasing number of the resistant bacteria to various antibiotics.

The Clinical Relevance of Four-Day Blood Cultures with the BACTEC 9240 System / 대한임상병리학회지

BACKGROUND: It is well established that automated blood culture systems require no more than five days of incubation for the detection of the majority of pathogens. It is not clear, however, whether continuous monitoring of blood culture systems also routinely require five days of incubation. This study was conducted to determine the clinical impact of incubating blood cultures for 4 days rather than for 5 days using the BACTEC 9240 blood culture system. METHODS: During the 6-month period from July to November 1998, 22,167 blood cultures were performed. Positive culture sets and the isolates were sorted by times to detection of isolates. Chart reviews were done for isolates detected on day 3 or later to determine whether therapy was changed due to this blood culture result. RESULTS: Of 2,426 isolates (2,319 positive cultures), 2,344 (96.6%) were recovered within 3 days and 52 (2.1%) were recovered on day 4, and 30 (1.2%) on day 5. Chart reviews showed that 21 of the 52 isolates detected on day 4 were considered clinically significant and 10 of those affected the treatment of the patients. On day 5, 5 of the 30 isolates were considered clinically significant and 3 of those affected the treatment. CONCLUSIONS: Four-days rather than a 5-day incubation period reduced culture sensitivity by 1.2% but most of those were clinically irrelevant. These data suggest that the 4-day protocol for the BACTEC 9240 system is adequate for detection of positive blood cultures.