Longitudinal analysis of the in vitro activity of ceftazidime/avibactam versus Enterobacteriaceae, 2012-2016.

OBJECTIVES

The in vitro activities of ceftazidime/avibactam and comparator antimicrobial agents were analysed against 59 828 Enterobacteriaceae isolates collected by 190 centres from all global regions except North America from 2012-2016 as part of the International Network for Optimal Resistance Monitoring (INFORM) global surveillance programme.

METHODS

Antimicrobial susceptibility testing was performed using Clinical and Laboratory Standards Institute broth microdilution panels at a central reference laboratory, except for isolates collected in China that were tested using frozen, dehydrated broth microdilution panels at a central laboratory in China. The presence of extended-spectrum β-lactamases (ESBLs) was confirmed by multiplex PCR assays.

RESULTS

Ceftazidime/avibactam was the most active agent against all Enterobacteriaceae (MIC90, ≤1mg/L, ≥98.4% susceptibility). High rates of susceptibility (>88%) were observed amongst Citrobacter freundii, Citrobacter spp., Enterobacter spp., Escherichia coli, Klebsiella pneumoniae and Klebsiella oxytoca to colistin, meropenem, amikacin and tigecycline. Ceftazidime/avibactam showed consistent in vitro activity against ESBL-positive isolates of E. coli (n=5674; MIC90, 0.5mg/L, 99.5% susceptible), K. pneumoniae (n=7097; MIC90, 2mg/L, 97.0% susceptible) and K. oxytoca (n = 565; MIC90, 1mg/L, 96.8% susceptible). Isolates identified as metallo-β-lactamase-positive (n=242) were not susceptible to ceftazidime/avibactam but were susceptible to tigecycline (76.9%) and colistin (n=194 isolates tested; 92.8%).

CONCLUSIONS

Clinical Enterobacteriaceae isolates, including ESBL-positive phenotypes, collected globally (excluding North America) from 2012-2016 were highly susceptible to ceftazidime/avibactam, suggesting it is a useful agent for serious infections caused by multidrug-resistant organisms belonging to the family Enterobacteriaceae when therapeutic options are limited.