Prevalence Of The Cytolethal Distending Toxin Gene In Foodborne Pathogens Isolated From Animals And Humans In Qatar

Abstract

Background and objectives-Foodborne illness has been determined to be one of the major limitations to the advancement of world health and with the ease of travel around the world and the increase in trade of food and animal products, the risk has been exacerbated in recent years. It has been proclaimed as one of the high priority issues in the Qatar National Food Security Master Plan. Different estimates of burden of disease consistently indicate a high cost per episode, irrespective of the country where the study is conducted. The mechanism by which foodborne pathogens cause disease is complex and the cytolethal distending toxin (CDT) has been identified as one of the virulence factors that contributes to gastroenteritis. The CDT is a trimeric subunit toxin produced by gram-negative bacteria that causes cell-cycle arrest and causes affected cells to die by apoptosis. In an effort to understand the mechanisms by which foodborne pathogens put humans at risk of chronic gastroenteritis sequelae, this study investigated the occurrence of the CDT among Salmonella spp., Escherichia coli serogroups and Campylobacter spp. isolates recovered from animals and humans in Qatar. Methods—Samples collected from animals and humans were screened for the presence of these three foodborne pathogens using a combination of bacterial enrichment and molecular detection. Positive samples were further examined for the presence of the CDT gene and its three subunits (cdtA, cdtB, cdtC) using a polymerase chain reaction (PCR) approach. Results—To date the cdtB gene was detected in C. jejuni and C. coli isolates from animals at a rate of 70 and 89%, respectively. The cdtC gene was detected in 72% of the C. jejuni animal samples examined to date. Only cdtB was detected in Salmonella spp. and E. coli spp. isolates from animals and at a much lower rate. Both cdtB and cdtC were detected at a higher rate among C. jejuni and C. coli recovered from human cases enrolled in this study (Figure 1). Conclusions—The high prevalence of the CDT genes among Campylobacter isolates in both animal samples and human clinical cases suggests a possible critical role for the toxin in the pathogenesis of the diseases caused by these pathogens. By virtue of its toxicity, CDT has been incriminated in the risk of chronic gastroenteritis sequelae, including Inflammatory Bowel Disease and is likely to play role in the risk of this disease among human population in Qatar.