Evaluation of antimicrobial activity of β-lactam antibiotics using Etest against clinical isolates from 60 medical centres in Japan

An antimicrobial resistance surveillance study was carried out in 60 medical centres across Japan. Resistance to piperacillin was 10.8% in clinical isolates of Escherichia coli, while 1.3% or fewer isolates were resistant to other β-lactams. Klebsiella spp. were more susceptible to imipenem, cefepime and cefpirome. Isolates of Enterobacter spp., Citrobacter spp., indole-positive Proteus and Serratia spp. were susceptible to imipenem, cefepime and cefpirome, while Acinetobacter spp. were most susceptible to cefoperazone/sulbactam, imipenem, ceftazidime (5.8% resistance) and cefepime (7.6%). Isolates of Pseudomonas aeruginosa were more susceptible to ceftazidime (12.3% resistance), cefoperazone/sulbactam (12.5%) and cefepime (12.6%) than to piperacillin (15.0%), cefpirome (22.6%) and imipenem (30.8%). The percentage of Japanese imipenem resistant P. aeruginosa clinical isolates was around 30%.