Antimicrobial Susceptibilities of Clostridium difficile Isolates from 12 Asia-Pacific Countries in 2014 and 2015

Clostridium (Clostridioides) difficile causes toxin-mediated diarrhea and pseudomembranous colitis, primarily among hospital inpatients. Outbreaks of C. difficile infection (CDI) have been caused by strains with acquired antimicrobial resistance, particularly fluoroquinolone resistance, including C. difficile ribotype (RT) 027 in North America and Europe and RT 017, the most common strain in Asia. Despite being the most common cause of hospital-acquired infection in high-income countries, and frequent misuse of antimicrobials in Asia, little is known about CDI in the Asia-Pacific region. We aimed to determine the antimicrobial susceptibility profiles of a collection of C. difficile isolates from the region. C. difficile isolates (n = 414) from a 2014 study of 13 Asia-Pacific countries were tested for susceptibility to moxifloxacin, amoxicillin-clavulanate, erythromycin, clindamycin, rifaximin, metronidazole, vancomycin, and fidaxomicin according to the Clinical and Laboratory Standards Institute's agar dilution method. All isolates were susceptible to metronidazole, vancomycin, amoxicillin-clavulanate, and fidaxomicin. Moxifloxacin resistance was detected in all countries except Australia, all RT 369 and QX 239 strains, and 92.7% of RT 018 and 70.6% of RT 017 strains. All C. difficile RT 012, 369, and QX 239 strains were also resistant to erythromycin and clindamycin. Rifaximin resistance was common in RT 017 strains only (63.2%) and was not detected in Australian, Japanese, or Singaporean isolates. In conclusion, antimicrobial susceptibility of C. difficile varied by strain type and by country. Multiresistance was common in emerging RTs 369 and QX 239 and the most common strain in Asia, RT 017. Ongoing surveillance is clearly warranted.