Update on antimicrobial resistance in Clostridium difficile.

Clostridium difficile is the leading cause of healthcare-associated diarrhea. Since 2002, the morbidity and mortality rates of C. difficile infection have increased dramatically in Europe and North America. The emergence of C. difficile strains that are resistant to multiple antimicrobial agents can complicate prevention programs and potential treatment. Although most clinical isolates are still susceptible to metronidazole and vancomycin, heteroresistance to metronidazole and increasing vancomycin MICs (minimum inhibitory concentrations) have been reported. The prevalence of resistance to other antimicrobial agents, including erythromycin and moxifloxacin, is highly variable in different countries and regions. The exact mechanism of reduced susceptibility to metronidazole or vancomycin is still not clear. The principal mechanism of erythromycin, fluoroquinolones and rifamycins resistance in C. difficile is determined by target alterations. This review will focus primarily on the antimicrobial susceptibility patterns and resistance mechanisms of C. difficile in order to provide an up-to-date review on the topic.