Controlled comparison of two supplemented aerobic and anaerobic blood culture bottles to detect simulated bacteremia specimens

Objective To compare BACTEC Plus aerobic and anaerobic bottles with BacT/ALERT FA aerobic bottles and FN anaerobic bottles in the ability of detecting simulated bacteremia specimens.Methods The 202 pairs of specimens were composed of 5ml sterile blood and defined loads of microorganisms.112 pairs of specimens in them also contained defined doses of antibiotics to simulate the patients undertaking antibiotic therapy.Time-to-detect(TTD)and positive percentages were evaluated in four groups,including aerobic bottles detecting aerobic bacteria,anaerobic bottles detecting anaerobic bacteria and facultative anaerobic bacteria,and aerobic bottles contained antibiotics detecting aerobic bacteria.Results The positive percentages of two kinds of aerobic bottles were both 100%.For the specimens with bacterial concentration of 10~2 and 10~3 CFU/ml,average TTDs of BACTEC Plus aerobic bottles[(13.69±3.74)h,(11.54±2.87)h]were faster than those of BacT/ALERT FA bottles [(16.76±5.62)h,(14.47±4.30)h;t=-5.674,-7.294,P0.01].To anerobic bacteria,the positive percentages of BACTEC Plus anaerobic bottles and BacT/ALERT FN bottles were 92% and 100%. respectively.Average TTDs of BacT/ALERT FN bottles[(22.60±9.16)h,(22.10±13.46)h]were faster than those of BACTEC Plus anaerobic bottles[(40.24±35.07)h,(34.88±17.34)h;t=2.389, 2.712,P0.05].To facultative anaerobic bacteria,the positive percentages of BACTEC Plus anaerobic bottles and BacT/ALERT FN bottles were 100% and 60%,respectively.Average TTDs of BACTEC Plus anaerobic bottles[(13.24±7.82)h,(11.33±7.61)h]were faster than those of BacT/ALERT FN bottles [(16.79±8.00)h,(19.27±14.71)h;t=-3.440,-2.604,P0.05].To the specimens containing antibiotics,the positive percentages of BACTEC Plus aerobic bottles and BacT/ALERT FA bottles were 100% and 57%,respectively.Most TTDs of BACTEC Plus aerobic bottles were faster than those of BacT/ ALERT FA bottles.The addition of antibiotics delayed the TTDs,and the more the antibiotics specimens contained,the slower the TTDs was.Conelusions According to the condition of the patients,different blood culture bottles and systems should be selected to shorten the TTDs and enhance the positive percentage.To the patient maybe infected with aerobic or facultative aerobic bacteria and those undertaking antibiotic therapy,BACTEC Plus aerobic and anaerobic bottles are recommended to be used.To the patients maybe infected with anaerobic bacteria,BacT/ALERT FN bottles are recommended to be used.