RESUMO
BACKGROUND: Antimicrobial resistance is continuously increasing. Adding tazobactam to ceftolozane improves the latter's activity spectrum against resistant strains. We aimed to determine the susceptibility of recently collected bacterial isolates to ceftolozane/tazobactam (C/T) and other antibiotics. METHODS: This was a prospective cohort study conducted between March 2017 and March 2018. The in-vitro activities of C/T and 14 other antibiotics were assessed against 192 gram-negative bacterial (GNB) isolates (P. aeruginosa, K. pneumonia, E. coli, and other Enterobacterales) prospectively collected from two hospitals in Saudi arabia; in the laboratories of the International Health Management Associates Inc. Samples were obtained from intensive care units (ICUs) and non-ICU locations. The minimum inhibitory concentrations (MICs) of the antibiotics were determined by broth microdilution. Isolates were obtained from different infection sites [urine (31.8%), urinary bladder samples (15.1%), abscess/pus (20.3%), endotracheal aspirates (18.8%)]. RESULTS: Our sample showed substantial drug resistance; 66.1% of the collected isolates showed either multiple or extensive drug resistance. Susceptibility rates of P. aeruginosa (n = 50), E.coli (n = 40), K. pneumoniae (n = 64) and other Enterobacterales (n = 38) to C/T were 74%, 87.5%, 48.4% and 71.1%, respectively. According to MIC50 values (1 µg/mL for both P. aeruginosa and other Enterobacterales, 0.5 µg/mL for E.coli, and 4 µg/mL for K. pneumoniae), C/T was among the most potent antibiotics against these isolates. CONCLUSIONS: C/T displayed high potency against all examined bacterial isolates. It was mainly active against E.coli followed by P.aeruginosa and other Enterobacterales and its lowest susceptibility rate was reported against K. pneumoniae.