Clinical characteristics and antimicrobial susceptibility of , and isolated from human urine in Japan.

The three species , and are difficult to distinguish, owing to their similar biochemical properties, and are often confused in medical practice. There is a scarcity of data comparing the clinical characteristics and antimicrobial susceptibility of , and . We believe that knowledge of the characteristics of each species will help in their better identification. Further, knowing the antimicrobial susceptibility of the species will help physicians in prescribing an effective treatment course for infections. This study aimed to determine the clinical characteristics and antimicrobial resistance of , and isolated from human urine samples. This study included 125 . strains isolated from human urine samples. Multiplex polymerase chain reaction was performed to identify , and . We retrospectively investigated the patient background, complications of bacteraemia, antimicrobial susceptibility and extended-spectrum β-lactamase (ESBL). We identified 84 (67.2 %), 31 (24.8 %) and 10 strains (8 .0%) of , and , respectively. There was no difference in patient background and frequency of bacteraemia complications among these species. was significantly less susceptible than to ampicillin/sulbactam (=0.03) and piperacillin (<0.01). Furthermore, (79.8 %) was less susceptible to trimethoprim/sulfamethoxazole than (96.8 %) and (100 %). There were nine ESBL-producing strains (7.2 %), all of which were . There was no difference in patient background and frequency of bacteraemia complications between , and isolated from urine. The three species showed a varying extent of antimicrobial susceptibility and ESBL production, and accurate identification is needed to understand the epidemiology of these species.