Occurrence of Clostridium difficile in seasoned hamburgers and seven processing plants in Iran

BACKGROUND: The recent increment of the incidence of Community Associated Clostridium difficile Infection (CA)-CDI has led to speculation that this disease is associated to foodborne transmission. Therefore it is critical to establish the community sources of CDI in order to implement the appropriate interventions. The present study was conducted to evaluate the prevalence of C. difficile in seasoned hamburger and examine the sources of C. difficile dispersal in hamburger processing plants. A total of 211 samples including hamburger ingredients, the final product, processing equipment and food contact surfaces were collected from seven hamburger processing plants to evaluate the routes of dispersal of C. difficile. The samples were assessed for the occurrence of C. difficile using culture and polymerase chain reaction (PCR) methods. All isolates were screened for the existence of toxin A, B and binary toxin genes. In addition, isolates were subjected to PCR ribotyping. RESULTS: Overall, 9/211 (4.2%) samples were positive. Toxigenic C. difficile were detected from 2/7 (28.5%) hamburger processing plants, in (3/54) 5.6% of beef meat samples, (2/56) 3.5% of swabs taken from the environment and (4/56) 7.1% of hamburger samples after both molding and freezing. C. difficile was not found in 45 non-meat ingredients including 14 defrosted onions, 14 textured soy proteins and 17 seasonings. All isolates contained tcdB gene while 7 strains were positive for tcdA and two remaining strains were negative for tcdA. None of the isolates harbored binary toxin gene (cdtB). PCR ribotyping of 9 isolates categorized into four ribotypes (IR21, IR 22, IR 23 and IR24). Ribotype IR 22 was the most common type 6/9 (66.6%) found. This genotype was isolated from raw meat, environmental samples and hamburger after both forming and freezing in one processing plant, suggesting raw beef meat as a possible major source of contamination. CONCLUSIONS: Hyper-virulent strains of ribotype were not found in this study however, occurrence of other toxicgenic strains indicate the public health significance of contamination of this product.