Abstract
BackgroundDespite the importance of the B. cereus group as major foodborne pathogens that may cause diarrheal and/or emetic syndrome(s), no study in Tunisia has been conducted in order to characterize the pathogenic potential of the B. cereus group. The aim of this study was to assess the sanitary potential risks of 174 B. cereus group strains isolated from different foodstuffs by detecting and profiling virulence genes (hblA, hblB, hblC, hblD, nheA, nheB, nheC, cytK, bceT and ces), testing the isolates cytotoxic activity on Caco-2 cells and antimicrobial susceptibility towards 11 antibiotics.ResultsThe entertoxin genes detected among B. cereus isolates were, in decreasing order, nheA (98.9%), nheC (97.7%) and nheB (86.8%) versus hblC (54.6%), hblD (54.6%), hblA (29.9%) and hblB (14.9%), respectively encoding for Non-hemolytic enterotoxin (NHE) and Hemolysin BL (HBL). The isolates are multi-toxigenic, harbouring at least one gene of each NHE and HBL complexes associated or not to bceT, cytK-2 and ces genes. Based on the incidence of virulence genes, the strains were separated into 12 toxigenic groups. Isolates positive for cytK (37,9%) harbored the cytK-2 variant. The detection rates of bceT and ces genes were 50.6 and 4%, respectively. When bacteria were incubated in BHI-YE at 30 °C for 18 h and for 5 d, 70.7 and 35% of the strains were shown to be cytotoxic to Caco-2 cells, respectively. The cytotoxicity of B. cereus strains depended on the food source of isolation. The presence of virulence factors is not always consistent with cytotoxicity. However, different combinations of enterotoxin genetic determinants are significantly associated to the cytotoxic potential of the bacteria. All strains were fully sensitive to rifampicin, chloramphenicol, ciprofloxacin, and gentamycin. The majority of the isolates were susceptible to streptomycin, kanamycin, erythromycin, vancomycin and tetracycline but showed resistance to ampicillin and novobiocin.ConclusionOur results contribute data that are primary to facilitate risk assessments in order to prevent food poisoning due to B. cereus group.
Highlights
Despite the importance of the B. cereus group as major foodborne pathogens that may cause diarrheal and/or emetic syndrome(s), no study in Tunisia has been conducted in order to characterize the pathogenic potential of the B. cereus group
The enterotoxins produced by B. cereus group bacteria that are recognized as playing a major role in the diarrheal disease are the Hemolysin BL (HBL) encoded by hblA, hblB, hblC, and hblD; the NonHemolytic Enterotoxin (NHE) encoded by nheA, nheB and nheC, and the Cytotoxin K (CytK) encoded by cytK [8, 9]
Distribution of enterotoxin and emetic toxin-encoding genes among B. cereus collection In order to characterize the virulence potential of foodborne B. cereus group bacteria in Tunisia, 174 isolates from different kinds of foods were screened by Polymerase Chain Reaction (PCR) for the presence of nine diarrhoeal toxin-encoding genes and one emetic toxin-encoding gene
Summary
Despite the importance of the B. cereus group as major foodborne pathogens that may cause diarrheal and/or emetic syndrome(s), no study in Tunisia has been conducted in order to characterize the pathogenic potential of the B. cereus group. The contamination of foods with B. cereus group bacteria may lead to food poisoning events that usually occur under the emetic and/or the diarrheal syndromes [1]. These foodborne outbreaks are generally benign and spontaneously resolved. The emetic type of food poisoning is caused by the ingestion of cereulide, which is preformed in food. This toxin is a small cyclic dodecadepsipeptide encoded by the ces gene. CytK-1 shows 89% protein sequence homology with that of CytK-2, but carries much higher toxicity
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
