Hogan, Stephen F.

The relative value of routine anaerobic blood culture for recovery of organisms and identification of episodes of bloodstream infection was assessed in a three-component, high-volume blood culture system which employs aerobic and anaerobic bottles of BacT/Alert (Organon-Teknika, Durham, N.C.) and aerobic cultures of Isolator (Wampole Laboratories, Cranbury, N.J.). The results of 5,595 blood culture sets from patients with suspected bloodstream infection were analyzed. Compared with either the aerobic BacT/Alert bottle or aerobic culture of Isolator, the BacT/Alert anaerobic bottle recovered significantly fewer isolates (242 versus 294, P < 0.05; 242 versus 298, P < 0.05) but did not detect significantly fewer episodes of bloodstream infection (141 versus 157, P > 0.05; 141 versus 147, P > 0.05). The BacT/Alert anaerobic bottle recovered significantly more isolates of obligately anaerobic bacteria (16 versus 4, P < 0.05; 16 versus 0, P < 0.05) and detected significantly more episodes of bloodstream infection caused by obligately anaerobic bacteria (10 versus 3, P < 0.05; 10 versus 0, P < 0.05) than either the aerobic bottle of BacT/Alert or the aerobic culture of Isolator. The combination of the BacT/Alert anaerobic bottle and the aerobic culture of Isolator recovered as may isolates (374 versus 377) and detected as many episodes of bloodstream infection (194 versus 191) as the combination of the aerobic bottle of BacT/Alert and the aerobic culture of Isolator, and both of these combinations identified at least 8% more isolates and detected at least 3% more bloodstream infections than the combination of the BacT/Alert aerobic and anaerobic bottles. Further analysis of the data revealed that the utility of the BacT/Alert anaerobic bottle, especially when combined with the aerobic culture of Isolator, resulted from not only enhanced recovery of obligately anaerobic bacteria but also effective recovery of facultatively anaerobic bacteria. These results demonstrate the utility of the anaerobic BacT/Alert bottle for detecting bloodstream infection caused by either facultatively anaerobic bacteria or obligately anaerobic bacteria and support the routine inclusion of anaerobic blood culture in the three-component blood culture system used in our hospital.

The performance characteristics of the Isolator (Wampole Laboratories, Cranbury, N.J.) and the BacT/Alert (Organon Teknika Corporation, Durham, N.C.) aerobic blood culture systems were compared for 6,009 blood culture sets obtained from patients with suspected bloodstream infections. The BacT/Alert aerobic bottle [BTA(O2)] was continuously agitated while it was incubated in 5% CO2 at 36 degrees C; culture plates prepared from the Isolator tube [I(O2)] were incubated in 5% CO2 at 37 degrees C. From 394 blood cultures, 416 clinically significant isolates of bacteria and yeasts were recovered. The overall yields for BTA(O2) and I(O2) were not significantly different (319 versus 336; P = 0.20). I(O2) recovered significantly more staphylococcus (P < 0.05) and yeast isolates (P < 0.01). BTA(O2) recovered significantly more aerobic and facultatively anaerobic gram-negative bacilli (P < 0.05). In blood culture sets which produced growth of the same organisms in both the BTA(O2) and I(O2) systems, the BTA(O2) system detected growth sooner, but more rapid identification was possible with the I(O2) system by virtue of earlier isolation of colonies on solid media.