Ceftazidime/avibactam activity tested against Gram-negative bacteria isolated from bloodstream, pneumonia, intra-abdominal and urinary tract infections in US medical centres (2012)

Abstract

Objectives: The activity of ceftazidime/avibactam and comparator agents was monitored at 73 medical centres across all nine US census bureau regions during 2012.

Methods: Bacterial isolates were collected from patients hospitalized with pneumonia, urinary tract infections (UTI), intra-abdominal infections (IAI) and bloodstream infections (BSI). The study protocol predetermined the target numbers of strains for each of the requested bacterial species that sites were to collect. Isolates were determined to be clinically relevant at the medical centre and only one isolate per patient episode was collected.

Results: There were 1466 Gram-negative isolates from BSI, 3245 from pneumonia patients, 501 from IAI and 2356 from UTI. Ceftazidime/avibactam was active against Enterobacteriaceae from each infection type. The MIC90 values for ceftazidime/avibactam against Enterobacteriaceae isolates from BSI, pneumonia patients, IAI or UTI were 0.25 mg/L. The extended-spectrum cephalosporin resistance rates for Escherichia coli were 8.5% (UTI), 10.4% (IAI), 12.7% (BSI) and 17.5% (pneumonia patients). The extended-spectrum cephalosporin resistance rates for Klebsiella spp. were 13.0% (UTI), 13.9% (BSI), 16.3% (IAI) and 19.3% (pneumonia patients). A total of 96.5% of the Pseudomonas aeruginosa isolates from BSI, 95.8% from pneumonia patients, 96.3% from IAI and 98.7% from UTI exhibited a ceftazidime/avibactam MIC of ≤8 mg/L (CLSI susceptible breakpoint for ceftazidime when tested alone against P. aeruginosa). Most tested agents showed limited activity against Acinetobacter baumannii, except for colistin. A total of 31.2% of A. baumannii displayed ceftazidime/avibactam MIC values of ≤8 mg/L.

Conclusions: Ceftazidime/avibactam demonstrated potent broad-spectrum activity against Gram-negative pathogens collected in the USA during 2012 from BSI, pneumonia patients, IAI and UTI.

Keywords: Enterobacteriaceae; Pseudomonas aeruginosa; β-lactamase inhibitors.