In Vitro Activity of Ceftazidime-Avibactam Against Isolates from Respiratory and Blood Specimens from Patients with Nosocomial Pneumonia, including Ventilator-Associated Pneumonia, in a Phase 3 Clinical Trial.

This study describes the in vitro activity of ceftazidime-avibactam, ceftazidime, and relevant comparator agents against bacterial pathogens isolated from patients with NP, including VAP, enrolled in a ceftazidime-avibactam phase 3 trial (ClinicalTrials.gov identifier NCT01808092). Gram-positive pathogens were included if co-isolated with a Gram-negative pathogen. In vitro susceptibility was determined at a central laboratory using Clinical and Laboratory Standards Institute broth microdilution methods. Of 817 randomized patients, 457 (55.9%) had ≥1 Gram-negative bacterial pathogen isolated at baseline, and 149 (18.2%) had ≥1 Gram-positive pathogen co-isolated. The most common isolated pathogens were Klebsiella pneumoniae (18.8%), Pseudomonas aeruginosa (15.8%), and Staphylococcus aureus (11.5%). Ceftazidime-avibactam was highly active in vitro against 370 isolates of Enterobacteriaceae, with 98.6% susceptible (MIC90 0.5 μg/ml) compared with 73.2% susceptible for ceftazidime (MIC90 >64 μg/ml). The percent susceptibility values for ceftazidime-avibactam and ceftazidime against 129 P. aeruginosa isolates were 88.4% and 72.9% (MIC90 values of 16 μg/ml and 64 μg/ml) respectively. Among ceftazidime-nonsusceptible Gram-negative isolates, ceftazidime-avibactam percent susceptibility values were 94.9% for 99 Enterobacteriaceae and 60.0% for 35 P. aeruginosa MIC90 values for linezolid and vancomycin (permitted per-protocol for Gram-positive coverage) were within their respe...
Source: Antimicrobial Agents and Chemotherapy - Category: Microbiology Authors: Tags: Antimicrob Agents Chemother Source Type: research