Isolation, Identification, and Characterization of Bacillus cereus Group Bacteria Isolated from the Dairy Farm Environment and Raw Milk in Tunisia

• Published in: Foodborne pathogens and disease
• Main Authors: Ben Akacha, Randa, Gdoura-Ben Amor, Maroua, Sellami, Hanen, Grosset, Noël, Jan, Sophie, Gautier, Michel, Gdoura, Radhouane
• Format: Journal Article
• Language: English
• Published: United States 18.03.2024
• Subjects: adhesion capacity; antibiotic resistance; B. cereus group; ERIC-PCR; dairy farm; virulence genes
• ISSN: 1556-7125
• DOI: 10.1089/fpd.2023.0154

Members of the group are well-known opportunistic foodborne pathogens. In this study, the prevalence, hemolytic activity, antimicrobial resistance profile, virulence factor genes, genetic diversity by enterobacterial repetitive intergenic consensus (ERIC)-polymerase chain reaction (PCR) genotyping, and adhesion potential were investigated in isolates from a Tunisian dairy farm environment and raw milk. A total of 200 samples, including bedding, feces, feed, liquid manure, and raw bovine milk, were examined. Based on PCR test targeting gene, 59 isolates were detected. The prevalence of group isolates in bedding, feces, liquid manure, feed, and raw milk was 48%, 37.8%, 20%, 17.1%, and 12.5%, respectively. Out of the tested strains, 81.4% showed β-hemolytic on blood agar plates. An antimicrobial resistance test against 11 antibiotics showed that more than 50% of the isolates were resistant to ampicillin and novobiocin, while a high sensitivity to other antibiotics tested was observed in most isolates. The distribution of enterotoxigenic genes showed that 8.5% and 67.8% of isolates carried and , respectively. In addition, the detection rate of cytotoxin K ( ), enterotoxin T ( ), and genes was 72.9%, 64.4%, and 5.1%, respectively. ERIC-PCR fingerprinting genotype analysis allowed discriminating 40 different profiles. The adhesion potential of group on stainless steel showed that all isolates were able to adhere at various levels, from 1.5 ± 0.3 to 5.1 ± 0.1 log colony-forming unit (CFU)/cm for vegetative cells and from 2.6 ± 0.4 to 5.7 ± 0.3 log CFU/cm for spores. An important finding of the study is useful for updating the knowledge of the contamination status of group in Tunisia, at the dairy farm level.