In vitro activity of ceftazidime–avibactam, ceftolozane–tazobactam, and other comparable agents against clinically important Gram-negative bacilli: results from the 2017 Surveillance of Multicenter Antimicrobial Resistance in Taiwan (SMART)

Objectives: We investigated the in vitro antimicrobial susceptibilities of clinically important Gram-negative bacteria (GNB) from 16 major teaching hospitals in Taiwan in 2017. Materials and methods: Escherichia coli (n=686) and Klebsiella pneumoniae bloodstream isolates (n=673), non-typhoid Salmonella (NTS; n=221) from various sources, Shigella species (n=21) from fecal samples, and Neisseria gonorrhoeae (n=129) from the genitourinary tract were collected. Antibiotic minimum inhibitory concentrations (MICs) were determined using the broth microdilution method. Alleles encoding K . pneumoniae carbapenemases (KPCs), New Delhi metallo-β-lactamases (NDMs), Verona integron-encoded metallo-β-lactamase, imipenemase, OXA-48-like, and mcr -1-5 genes were detected by molecular methods in Enterobacteriaceae isolates. Results: Five (0.7%) E . coli isolates harbored mcr -1 alleles. Twenty-four (3.6%), seven (1.0%), four (0.6%), and one (0.15%) K . pneumoniae isolates contained bla KPC , bla OXA-48-like , mcr -1, and bla NDM , respectively. Three (1.4%) NTS and no Shigella isolates harbored mcr -1 genes. Seventy-one (10.5%) K . pneumoniae isolates displayed non-susceptibility (NS) to carbapenem agent(s). Phenotypically extended-spectrum β-lactamase (ESBL)-producing K . pneumoniae isolates showed significantly higher rates of ertapenem, tigecycline, and ceftolozane–tazobactam (CLZ–TAZ) NS (40.2%, 16.3%, and 71%–80%, respectively) than E . coli isolates exhibiting ESBL phenotypes (5.4%, 0.7%, and 18%–28%, respectively). All phenotypically ESBL-producing E . coli isolates were ceftazidime–avibactam (CAZ–AVB) susceptible. Two (8.3%) KPC-producing K . pneumoniae isolates showed CAZ–AVB NS. Hospital-acquired K . pneumoniae isolates were significantly less susceptible to ertapenem and CLZ–TAZ than hospital-acquired E . coli isolates. Conclusion: Third-generation cephalosporins remain the optimal choice for treating NTS, Shigella , and gonococcal infections in Taiwan. Hospital-acquired and phenotypically ESBL-producing K . pneumoniae are a heavy resistance burden in Taiwan.