Epidemiologic markers of Clostridium difficile.

A wide range of epidemiologic markers have been identified for Clostridium difficile. These markers are based on phenotypic characteristics of the organism, such as antibiotic resistance, bacteriocin or bacteriophage susceptibility, electrophoretic protein patterns, and immunologic markers. Methods for determining genetic markers include plasmid and DNA restriction endonuclease analysis and ribosomal RNA restriction patterns. These methods have been applied to various degrees in epidemiologic studies and have contributed to a better understanding of C. difficile-associated disease. The method based on the use of [35S]methionine-labeled proteins and the development of an automated scanner with computer analysis made possible the recognition of 15 distinct types of C. difficile, based on the major radiolabeled protein patterns. These proteins were strain-specific and immunogenic, as demonstrated by immunoblotting and DNA restriction endonuclease analysis. Epidemiologic studies revealed cross-infection among patients, nosocomial acquisition, and a direct relation between symptoms and type of C. difficile. The development of DNA probes based on antibiotic resistance genes, toxin A, and cloned specific common antigens is discussed.