Abstract
In this study, we evaluated the performance of three blood culture systems in a Chinese tertiary-care hospital. Samples of simulated bacteremia were prepared using 10 mL of fresh blood from healthy humans and bacterial suspensions of known cell density. Portions of the specimens were treated with an antibiotic or antifungal drug at specified concentrations to simulate antibacterial drug treatment. We analyzed three blood culture systems: BACTEC Plus, BacT/Alert, and VersaTREK. Both time-to-detection (TTD) of 10 types of bacteria and five types of yeasts in samples without antibiotic treatment and positive detection rate of samples treated with different concentrations of antibiotic or antifungal drugs were compared among the culture systems. We also retrospectively analyzed the use of the culture systems in our hospital from 2015 to 2018. In the simulated study, in the absence of antibiotics, the VersaTREK REDOX 1 displayed the shortest TTD for Pseudomonas aeruginosa, Haemophilus influenzae, Staphylococcus aureus, Streptococcus pneumoniae, Candida albicans, and Candida glabrata (P < 0.001). Among the anaerobically cultured samples, BACTEC lytic/10 anaerobic/F displayed the shortest TTD for Escherichia coli, S. aureus, Enterococcus faecalis, S. pneumoniae, Bacteroides fragilis, and Bacteroides vulgatus (P < 0.001). Comparatively, BacT/Alert FA/FN showed no advantages. In antibiotic-treated samples, overall recovery rates for the BACTEC, BacT/Alert, and VersaTREK systems were, were 70.2, 43.7, and 27.4%, respectively. BACTEC facilitated higher recovery rate than the other two systems (P < 0.001). In antifungal treatment, the overall recovery rates for the BACTEC, BacT/Alert, and VersaTREK systems were 93.9, 98.3, and 69.4%, respectively. BACTEC Plus showed a recovery rate comparable to that of BacT/Alert (P = 0.835), and the recovery rate of both these systems was higher than that of VersaTREK (P < 0.001). The TTD values and positive rates determined in the retrospective study were consistent with those obtained in the simulated study. The combination of BACTEC PLUS Aerobic/F and BACTEC lytic/10 anaerobic/F culture systems displayed the best clinical performance. Furthermore, the BacT/Alert FAN culture system was found to be more resistant to antifungal drugs and levofloxacin, whereas the VersaTREK system is considered more suitable for primary blood cultures without antibiotic supplementation.
Highlights
Systemic infections are a prominent cause of morbidity and mortality worldwide and influence the duration of hospitalization and associated healthcare costs (Tumbarello et al, 2007; Goto and Al-Hasan, 2013)
P. aeruginosa grew exclusively in the Redox2 system, whereas H. influenzae grew exclusively in the BacT/Alert FN system, and B. melitensis failed to grow in anaerobic culture systems
We performed a simulation study using a larger range of pathogens and antibiotics or antifungals to compare the differences in TTD and recovery among the three blood culture systems
Summary
Systemic infections are a prominent cause of morbidity and mortality worldwide and influence the duration of hospitalization and associated healthcare costs (Tumbarello et al, 2007; Goto and Al-Hasan, 2013). The BacT/Alert automated microbial detection system uses an internal colorimetric sensor that changes from gray to yellow in the presence of CO2 produced by growing microorganisms and utilizes active carbon to remove antibiotics from blood samples. The BD Bactec Plus is based on a chemical sensor that can detect increases in CO2 produced as a consequence of microbial growth. The sensor in this system is monitored at 10-min intervals for an increase in fluorescence, which is proportional to the amount of CO2 present, and the system uses cationic-exchange and adsorbent nonionic resins to remove antibiotics from blood samples. The detection of positive cultures using this system is based on the measurement of pressure changes in the sample bottle headspace (due to consumption and production of gases by microorganisms) using an external pressure sensor, and relies on an optimal 1:9 blood:broth dilution to neutralize the effects of antibiotics
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