3 years ago

Effects of Clinically Meaningful Concentrations of Anti-Pseudomonal β-Lactams on Time to Detection and Organism Growth in Blood Culture Bottles.

Tanner, Aslanzadeh, Grupper, Nicolau, Kuti
The effectiveness of antimicrobial binding resins present in blood culture (BC) bottles in removing meropenem, ceftolozane/tazobactam, and ceftazidime/avibactam is unknown. We assessed the time to detection (TTD) and growth of 2 Pseudomonas aeruginosa isolates in the presence of clinically meaningful concentrations of these antibiotics. BACTEC Plus Aerobic/F and BacT/ALERT FA Plus BC bottles were inoculated with one of two isolates (1 meropenem susceptible, 1 resistant), followed by fresh whole blood containing the peak, midpoint, or trough plasma concentrations for meropenem, ceftolozane/tazobactam, and ceftazidime/avibactam. Matching bottles were loaded into their respective detection instrument and a standard incubator at 37° C, with TTD and colony forming units monitored for up to 72 hours. Bacterial growth was observed for 11/48 (22.9%), 22/48 (45.8%) and 47/48 (97.9%) of all BC bottles inoculated with the peak, mid-point and trough concentrations, respectively (p≤0.001). When P. aeruginosa was isolated, TTD was typically <26 hours, and no differences were observed between BACTEC and BacT/ALERT bottles. In both systems, meropenem was removed greater than ceftolozane and ceftazidime; however, concentrations for all antibiotics remained above the MIC for the susceptible organisms at 12 hours. BC bottles containing antibiotic binding resins may not sufficiently inactivate achievable concentrations of meropenem, ceftolozane/tazobactam and ceftazidime/avibactam. Consistent identification of both P. aeruginosa was observed only in the presence of antibiotic trough concentrations. To minimize false negative BC results in patients already receiving these antibiotics, cultures should be collected just prior to the next dose when antibiotic concentrations are lowest.

Publisher URL: http://doi.org/10.1128/JCM.01241-17

DOI: 10.1128/JCM.01241-17

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