Comparison of BACTEC Plus Aerobic/F Media and BacT/ Alert FA Media to Detect Bacteria in Blood Culture Bottles Containing Peak Therapeutic Levels of Antimicrobials

Background: Blood culture bottles with an antimicrobial removal system have been developed for patients treated with antibiotics. This study compared the ability of BACTEC Plus Aerobic/F bottles (Becton Dickinson, USA, BACTEC Plus) and BacT/Alert FA bottles (bioMerieux Vitek, France) to effectively remove antimicrobials. Methods: BACTEC Plus and BacT/Alert FA bottles were spiked with 5 mL human blood, peak therapeutic concentrations of 9 antimicrobials and 7 type strains. Three rounds of duplicate testing were completed per antimicrobial/strain combination and growth control without antimicrobials. The time to detection (TTD) and recovery rates for bacteria were compared for both systems. Results: Overall, the BACTEC Plus and BacT/Alert FA recovered 76% (128/168) and 34% (57/168) of strains from test bottles, respectively. BACTEC Plus detected all of gram-positive bacteria except S. pneumoniae with ampicillin and ceftriaxone, but BacT/Alert FA detected 0∼50% of gram-positive bacteria except E. faecalis with vancomycin and methicillin-resistant S. aureus with oxacillin. In presence of cefepime, cefotaxime, cefoxitin and ceftriaxone, BACTEC Plus detected 33∼100% of gram-negative bacteria, but BacT/ Alert FA did not detect gram-negative bacteria at all. In presence of ciprofloxacin, BacT/Alert FA detected 100% of E. coli and K. pneumoniae compared with 33% of those for BACTEC Plus. Overall, TTD of BACTEC Plus was shorter than that of BacT/Alert FA except in detecting gram-negative bacteria with ciprofloxacin (P＜0.05). Conclusion: BACTEC Plus Aerobic/F media containing peak therapeutic levels of antimicrobials are more effective and faster detection of bacteria than BacT/ Alert FA media. (Korean J Clin Microbiol 2010;13: 151-156)