Usefulness of antimicrobial susceptibility test using fully automated bacteriological analyzer RAISUS ANY for anaerobic Bacteroides spp. and Clostridium spp.

Abstract

Recently, the emergence of drug-resistant anaerobic bacteria has been observed worldwide, and antimicrobial susceptibility tests play a significant role in routine examination. In this study, we compared the result of susceptibility tests using the fully automated bacteriological analyzer RAISUS ANY (RAISUS method) with that of the Eiken dry plate (current method) using 111 anaerobic bacterial strains, namely, 68 strains of Bacteroides spp. and 43 strains of Clostridium spp. The results of the comparisons between the RAISUS method and current manual methods were as follows: RAISUS method: 87–100% for Bacteroides spp. and 63–100% for Clostridium spp. with +/−1 difference in each well; and for the current method: 78–100% for Bacteroides spp. and 51–100% for Clostridium spp. with agreement in the CLSI category. On the other hand, discordance of the susceptibility pattern was seen in cefotaxime and moxifloxacin for Bacteroides spp. and clindamycin for Clostridium spp., presumably due to the individual variability in visual judgement. The RAISUS method is a laboratory procedure with high objectivity and might be useful in routine examination.