Toxigenic potential and antimicrobial susceptibility of Bacillus cereus group bacteria isolated from Tunisian foodstuffs

Abstract

Background 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 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. Results The 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. Conclusion Our results contribute data that are primary to facilitate risk assessments in order to prevent food poisoning due to B. cereus group.

Molecular Characterization of Bacteria, Detection of Enterotoxin Genes, and Screening of Antibiotic Susceptibility Patterns in Traditionally Processed Meat Products of Sikkim, India

“…The widespread use of antibiotics in animals for the treatment of diseases and other purposes may develop antibiotic resistance in bacteria resulting into cross-transmission of resistance genes from animals to humans through food ( Safarpoor Dehkordi et al, 2017 ; Tang et al, 2017 ). The antibiogram of bacterial isolates showed a maximum rate of sensitivity against gentamicin and trimethoprim, which is in accordance with a similar report where 90% of sensitivity was observed in bacterial isolates from street foods ( Amor et al, 2019 ). The majority of isolated strains showed the highest resistance pattern against amoxicillin–clavulanate followed by ampicillin.…”

“…Staphylococcus ( sea ), B. cereus ( nhea , nheb ), and Salmonella ( invA , stn ) by PCR analysis. These enterotoxin genes were selected based on their prevalence associated with foodborne illness ( Kérouanton et al, 2007 ; Wallin-Carlquist et al, 2010 ; Tekale et al, 2015 ; Amor et al, 2019 ). The PCR amplification was performed in a total volume of 25 μl and the reaction mixture contained GoTaq Green Master Mix (Taq DNA polymerase, dNTPs, MgCl 2 , and reaction buffers), 10 μM of each primer [Imperial Life Sciences (P) Ltd, India], and nuclease-free water (P1193, Promega, United States).…”

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“…The widespread use of antibiotics in animals for the treatment of diseases and other purposes may develop antibiotic resistance in bacteria resulting into cross-transmission of resistance genes from animals to humans through food (Safarpoor Dehkordi et al, 2017;Tang et al, 2017). The antibiogram of bacterial isolates showed a maximum rate of sensitivity against gentamicin and trimethoprim, which is in accordance with a similar report where 90% of sensitivity was observed in bacterial isolates from street foods (Amor et al, 2019). The majority of isolated strains showed the highest resistance pattern against amoxicillinclavulanate followed by ampicillin.…”

“…Staphylococcus (sea), B. cereus (nhea, nheb), and Salmonella (invA, stn) by PCR analysis. These enterotoxin genes were selected based on their prevalence associated with foodborne illness (Kérouanton et al, 2007;Wallin-Carlquist et al, 2010;Tekale et al, 2015;Amor et al, 2019). The PCR amplification was performed in a total volume of 25 µl and the reaction mixture contained GoTaq Green Master Mix (Taq DNA polymerase, dNTPs, MgCl 2 , and reaction buffers), 10 µM of each primer [Imperial Life Sciences (P) Ltd, India], and nuclease-free water (P1193, Promega, United States).…”

Sciadopitys verticillata Resin: Volatile Components and Impact on Plant Pathogenic and Foodborne Bacteria

“…Strains were resistant to some antibiotics: ampicillin (90.8%), novobiocin (88%), tetracycline (5.7%), vancomycin (4%), erythromycin (1.2%), and streptomycin (1.1%). All strains were sensitive to rifampicin and ciprofloxacin [29]. In Canada, B. cereus and its enterotoxins were found in pasteurized milk tested at its best-before date.…”