Frequency of occurrence and antimicrobial susceptibility of bacteria isolated from patients hospitalized with bloodstream infections in United States medical centers (2015-2017).

The frequency and antimicrobial susceptibility of organisms causing bloodstream infections in the United States were evaluated by consecutively collecting (1/patient) 9210 bacterial isolates from 33 US medical centers in 2015-2017. Isolates were susceptibility tested by reference broth microdilution methods. Whole genome sequencing was performed on carbapenem-resistant Enterobacteriaceae (CRE). The most common organisms were Staphylococcus aureus (24.3%), Escherichia coli (20.8%), and Klebsiella pneumoniae (9.1%). Overall, 50.0% of isolates were gram-negative bacilli and 41.4% were Enterobacteriaceae. The most active agents against Enterobacteriaceae were ceftazidime-avibactam (99.9% susceptible), amikacin (99.7% susceptible), and the carbapenems meropenem and doripenem (99.1% susceptible). Among 28 CRE isolates (0.7% of Enterobacteriaceae), 21 produced a KPC-like carbapenemase, 2 an NMD-like, and 1 a KPC-17 and an NDM-1. Colistin (100.0% susceptible), ceftolozane-tazobactam (98.7% susceptible), ceftazidime-avibactam (98.2% susceptible), amikacin (97.9% susceptible), and tobramycin (95.6% susceptible) were very active against Pseudomonas aeruginosa. Among S. aureus isolates, 57.8% were oxacillin-susceptible.