1004. Frequency of Occurrence and Antimicrobial Susceptibility of Bacteria Isolated From Patients Hospitalized With Bloodstream Infections in United States Medical Centers (2015–2017)

Abstract

BackgroundBloodstream infections (BSIs) cause significant morbidity and mortality. We evaluated the frequency and antimicrobial susceptibility of bacteria causing BSIs in the United States.MethodsA total of 9,210 bacterial isolates were consecutively collected (1/patient) from 33 US medical centers in 2015–2017 and tested for susceptibility by reference broth microdilution methods in a central laboratory (JMI Laboratories) as part of the International Network for Optimal Resistance Monitoring (INFORM) program. Whole-genome sequencing was performed on carbapenem-resistant Enterobacteriaceae (CRE).ResultsThe most common organisms were S. aureus (SA; 24.3%), E. coli (EC; 20.8%), K. pneumoniae (KPN; 9.1%), coagulase-negative staphylococci (7.3%), E. faecalis (5.5%), P. aeruginosa (PSA; 4.7%), and β-hemolytic streptococci (4.7%). Overall, 50.0% of isolates were Gram-negative bacilli (GNB) and 41.4% were Enterobacteriaceae (ENT). All SA were susceptible (S) to dalbavancin (MIC90, 0.03 μg/mL), linezolid, tigecycline (TGC), and vancomycin; >99.9% S to daptomycin, 97.6% S to ceftaroline, and 57.8% S to oxacillin. The most active agents against ENT were CAZ-AVI (99.9% S; table), amikacin (AMK; 99.7% S), and the carbapenems meropenem (MEM) and doripenem (99.1% S). Ceftolozane-tazobactam (C-T; tested in 2017 only) was active against 96.9% of ENT. Ceftriaxone (CRO)-S rates were 83.0% and 86.5% among EC and KPN, respectively. CRO-non-S KPN exhibited low S rates to most agents, except CAZ-AVI (99.1% S), TGC (93.6%), AMK (93.8%), and colistin (COL; 93.4%). Among 28 CRE isolates (0.7% of ENT), 21 produced a KPC-like, 2 an NMD-like, and 1 a KPC-17 and an NDM-1. COL (100.0% S), C-T (98.7%S), CAZ-AVI (98.2% S), AMK (97.9% S), and tobramycin (95.6% S) were very active against PSA. CAZ-AVI and C-T remained active against most PSA isolates non-S to MEM (93.0 and 95.0% S, respectively) and/or piperacillin–tazobactam (P-T; 88.9 and 91.3% S) and/or CAZ (86.9 and 88.2% S).ConclusionGNB represented 50.0% of bacteria isolated from patients with BSIs and the most active agents against these organisms were CAZ-AVI and AMK. Various agents exhibited excellent overall coverage against Gram-positives, including dalbavancin, daptomycin, linezolid, and TGC. Disclosures H. S. Sader, Allergan: Research Contractor, Research support. R. K. Flamm, Allergan: Research Contractor, Research support. M. A. Pfaller, Allergan: Research Contractor, Research support. M. Castanheira, Allergan: Research Contractor, Research support.