Abstract
Clostridium difficile is the leading cause of antibiotic-associated diarrheal disease in health care settings across the world. Despite its pathogenic capacity, it can be carried asymptomatically and has been found in terrestrial and marine ecosystems outside hospital environments. Little is known about these environmental strains, and few studies have been conducted on estuarine systems. Although prophage abundance and diversity are known to occur within clinical strains, prophage carriage within environmental strains of C. difficile has not previously been explored. In this study, we isolated C. difficile from sites sampled in two consecutive years in an English estuarine system. Isolates were characterized by PCR ribotype, antibiotic resistance, and motility. The prevalence and diversity of prophages were detected by transmission electron microscopy (TEM) and a phage-specific PCR assay. We show that a dynamic and diverse population of C. difficile exists within these sediments and that it includes isolates of ribotypes which are associated with severe clinical infections and those which are more frequently isolated from outside the hospital environment. Prophage carriage was found to be high (75%), demonstrating that phages play a role in the biology of these strains.
Highlights
Clostridium difficile is the leading cause of antibiotic-associated diarrheal disease in health care settings across the world
It is of major health care importance, as it causes C. difficile infection (CDI), typically a nosocomial disease that has a high incidence of relapse and treatment failure [1]
The bacterium was isolated from sites throughout the estuarine system regardless of assessed trophic status
Summary
Clostridium difficile is the leading cause of antibiotic-associated diarrheal disease in health care settings across the world. We show that a dynamic and diverse population of C. difficile exists within these sediments and that it includes isolates of ribotypes which are associated with severe clinical infections and those which are more frequently isolated from outside the hospital environment. Clostridium difficile is an endospore-forming, anaerobic, lowGϩC-content, Gram-positive bacterium belonging to the phylum Firmicutes It is of major health care importance, as it causes C. difficile infection (CDI), typically a nosocomial disease that has a high incidence of relapse and treatment failure [1]. Carriage of prophages is high, as detected by induction of prophages (see, e.g., reference 28), determination of molecular markers to probe their diversity [29], and identification of prophages in sequenced strains [30] and temperate phages that can infect in a lytic manner other C. difficile isolates [31]. Whether environmental reservoirs are sources of novel strains is not known, as only a few studies have examined the genetic diversity or physiological traits of these strains in detail (see, e.g., references 20 and 22), and none have examined prophage carriage
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