Detection of cytolethal distending toxin and other virulent factors in Escherichia coli samples from animal livestock, retail foods and gastroenteritis human cases in Qatar

Abstract

Cytolethal distending toxin (CDT) is a heterotrimeric AB-type genotoxin produced by several clinically important bacterial pathogens. To better understand the risk of CDT within the food supply and human gastroenteritis patients in Qatar, we investigated the frequency of the CDT gene (cdtB) among Escherichia coli (E. coli) strains recovered from food products, animal livestock, and human gastroenteritis patients. In this cross-sectional study, E. coli isolates were screened for cdtB using polymerase chain reaction (PCR). cdtB positive strains were further examined for E. coli cdtB gene types (cdt I, cdt II, cdt III, cdt IV and cdtV), serotypes O157: H7, and non-O157 Shiga toxin-producing E. coli O26, O45, O103, O111, O121, and O145. Screening for other virulent factors, stx (Shiga toxin gene) and eae (gene that encodes intimin) genes were also performed. The cdtB gene was detected in E. coli isolates sourced from all three groups; animal livestock (17%), retail foods (8%), and human gastroenteritis patients (3%). Although the incidence of cdtB gene harboring E. coli is relatively low among gastroenteritis patients, there is still a risk of infection from animal reservoirs as well as retail food products. Among the three groups, E. coli isolates from humans had the lowest occurrence of cdtB, stx, eae, and O157: H7. Furthermore, we advise implementing monitoring at the food production and preparation level.