[Laboratory-based evaluation of significance to routinely use anaerobic blood culture bottles: analysis of positivity and rapidity to detect positive cultures].

The publications in 1990s have indicated decreased recovery rates of obligate anaerobes from blood cultures and have questioned the need for routine anaerobic blood culture bottles. In this study, we compared positivities of the paired aerobic and anaerobic bottles and rapidity to detect positive cultures by two automated blood culture systems, BACTEC 9120 and BacT/ALERT 3D. Of 401 positive readings by BACTEC 9120, 338(84.3%) aerobic bottles became to be positive, and anaerobic bottles were 318(79.3%). Also, of 437 positive readings by BacT/ALERT 3D, positivities were 90.8% and 67.3% by aerobic and anaerobic bottles, respectively. These results indicated 5.0% and 23.7% more organisms were recovered in aerobic bottles than in anaerobic bottles, including more staphylococci, gram-positive rods, glucose-nonfermentative gram-negative rods and yeasts. Only 4 (0.14%) of 2,799 BACTEC 9120 anaerobic bottles and 2 (0.06%) of 3,428 BacT/ALERT 3D anaerobic bottles recovered obligate anaerobes. We compared time to detect positive cultures during incubation cycle by both aerobic and anaerobic bottles. Aerobic bottles in BACTEC 9120 read more positive cultures >2 hours earlier than anaerobic bottles, whereas BacT/ALERT 3D could not demonstrate a statistical significance in rapid reading of positive cultures. These results support that recovery rates of obligate anaerobes markedly decreased and that the routine use of anaerobic blood culture bottles is not legitimate at this time. In place of anaerobes, it is an urgent and important issue how to recover fungi correctly and rapidly from blood cultures.