Mechanisms of antibiotic resistance of Clostridioides difficile.

Clostridioides difficile (CD) is one of the top five urgent antibiotic resistance threats in USA. There is a worldwide increase in MDR of CD, with emergence of novel strains which are often more virulent and MDR. Antibiotic resistance in CD is constantly evolving with acquisition of novel resistance mechanisms, which can be transferred between different species of bacteria and among different CD strains present in the clinical setting, community, and environment. Therefore, understanding the antibiotic resistance mechanisms of CD is important to guide optimal antibiotic stewardship policies and to identify novel therapeutic targets to combat CD as well as other bacteria. Epidemiology of CD is driven by the evolution of antibiotic resistance. Prevalence of different CD strains and their characteristic resistomes show distinct global geographical patterns. Understanding epidemiologically driven and strain-specific characteristics of antibiotic resistance is important for effective epidemiological surveillance of antibiotic resistance and to curb the inter-strain and -species spread of the CD resistome. CD has developed resistance to antibiotics with diverse mechanisms such as drug alteration, modification of the antibiotic target site and extrusion of drugs via efflux pumps. In this review, we summarized the most recent advancements in the understanding of mechanisms of antibiotic resistance in CD and analysed the antibiotic resistance factors present in genomes of a few representative well known, epidemic and MDR CD strains found predominantly in different regions of the world.