Detection of Clostridium difficile in Louisiana oysters, harvesting water and sewage

ABSTRACT Clostridium difficile infection (CDI) was generally considered as a hospital-associated disease; however, recent studies indicated that foods might also play a role in its epidemical chain. From August-2013 to February-2014, oyster samples and harvesting water samples were collected monthly from 6 commercial oyster harvesting areas along Louisiana Gulf Coast and analyzed for total aerobic bacteria, fecal coliforms, coliphage and pathogenic C. difficile. In this study, C. difficile were isolated from 9 (47.37%) of 19 oyster samples and 3 (37.5%) of 8 harvesting water samples and all isolations were carrying the toxin B-encoding gene (tcdB). Toxin B positive C. difficle was detected in all influent and effluent samples collected from a waste water treatment plant (WWTP) located in New Orleans, LA. However, the PCR-ribotyping showed that different strains of C. difficile were found in sewage effluent and oysters/harvesting water, suggesting the discharge of treated sewage might not contribute to the transmission of C. difficile into the harvesting areas. No statistical significance was found between the density of fecal coliform/E. coli in oysters and the occurrence of C. difficile, according to a binary logistic regression model (odds ratio = 1.025 and 0.997). The concentration of Male-specific (F+) Coiphage and Somatic Coliphage in oysters was also found not to be directly related to the occurrence of C. difficile in oysters due to the low detection rate