Genetic basis for antibiotic resistance in anaerobes.

This review focuses on genetic and molecular data regarding antibiotic resistance in anaerobes, particularly Clostridium perfringens, Clostridium difficile, Bacteroides species, and Prevotella species. The determinants of resistance are frequently transferable through a conjugation-like process; plasmid self-transfer, plasmid mobilization, or (in Bacteroides species) chromosomal conjugative elements can be involved. The determinants can be localized on transposons. At the genetic level, resistance determinants can be highly specific for one or several anaerobes or may exhibit homology with genes from aerobes. The latter observation suggests that anaerobes are able to exchange genetic material from a "gene pool" shared with aerobic organisms.