Trends of Antimicrobial Susceptibility of Clostridium difficileIsolates in West China Hospital of Sichuan University from 2015 to 2017

Objective To summarize the drug sensitivity and its trends of Clostridium difficile diarrhea pathogenic strains in a large tertiary hospital, so as to provide basic reference data for the treatment and control of Clostridium difficile infection. Methods There were 73 toxigenic isolates collected from fecal sample of diarrheal patients in West China Hospital of Sichuan University during two periods. One was from August to December in 2015 （44 strains）, and another was from July 2016 to July 2017 （29 strains）. Enhanced nosocomial infection control measures were implemented during the second sample collection period. The toxin gene was amplified by PCR and sequenced for identification. Minimum inhibitory concentration (MIC) of metronidazole, vancomycin, clindamycin, moxifloxacin, rifaximin, fidaxomicin and linezolid were determined using agar double dilution method. We analyzed the drug resistance characteristics of Clostridium difficile and compared the changes of antimicrobial resistance before and after the enhanced control measures implementation. Results All 73 strains tested were sensitive to metronidazole and vancomycin. Resistance rate to clindamycin, moxifloxacin, tetracycline and rifaximin were 79.5%, 26.0%, 27.4%, and 9.5%, respectively. Fidaxomicin and nitazoxanide were highly susceptible in vitro against these strains with MIC ranges <0.008-0.5 mg/L ( P<0.05). Resistance to clindamycin and moxifloxacin were significantly decreased after enhanced control measures implementation (resistance rates were 99.5% vs. 44.8%, 36.4% vs. 10.3%,P<0.05). Additionally, isolate with decreased susceptibility to tinezolid as MIC 16 mg/L was found. Conclusion Clostridium difficileis highly resistant to clindamycin and quinolones. Since strains remain highly sensitive to metronidazole and vancomycin in our hospital, empirical application is reasonable without routine antimicrobial susceptibility testing.