Clinical Features Associated with Blood Cultures According to the Use of Antimicrobial Agents Prior to Blood Collection

Background: Previous antibiotic exposure may inhibit the growth of microorganisms in blood culture bottles. The authors investigated the frequency of previous antibiotic usage and analyzed the relationships among antibiotic usage, microbiological culture results and mortality of sepsis patients. Methods: From April to May 2011, all blood cultures requested from inpatients were analyzed according to the admitted ward and antibiotic prescription records. The BacT/Alert 3D system (bioMerieux Inc.) was used with a standard bottle (SA, SN) for blood culture. Results: Of 900 inpatients, 48% had been receiving antimicrobial agents when blood cultures were ordered. This group had a significantly higher mortality rate (36.2%) compared to the patients who had not received antibiotics (11.1%). Gram-negative rod bacteremia (37.1%) and candidemia (100%) resulted in a significantly higher mortality rate compared to Grampositive cocci bacteremia (16.4%). In the analysis of 21 cases resulting in death, 15 (71.4%) patients died before or on the date when blood culture results were reported. Conclusion: Patients who receive antibiotics prior to blood collection may be at a higher risk for mortality. In the present study, Gram-negative rod bacteremia and candidemia cases showed a rapid progression of sepsis as indicated by Gram staining and thus should be regarded seriously. (Korean J Clin Microbiol 2012;15:21-26)