Isolation, Identification, Prevalence, and Genetic Diversity of Bacillus cereus Group Bacteria From Different Foodstuffs in Tunisia

Abstract

Bacillus cereus group is widespread in nature and foods. Several members of this group are recognized as causing food spoilage and/or health issues. This study was designed to determine the prevalence and genetic diversity of the B. cereus group strains isolated in Tunisia from different foods (cereals, spices, cooked food, fresh-cut vegetables, raw and cooked poultry meats, seafood, canned, pastry, and dairy products). In total, 687 different samples were collected and searched for the presence of the B. cereus group after selective plating on MYP agar and enumeration of each sample. The typical pink-orange uniform colonies surrounded by a zone of precipitate were assumed to belong to the B. cereus group. One typical colony from each sample was subcultured and preserved as cryoculture. Overall, 191 (27.8%) food samples were found positive, giving rise to a collection of 191 B. cereus-like isolates. The concentration of B. cereus-like bacteria were below 103 cfu/g or ml in 77.5% of the tested samples. Higher counts (>104 cfu/g or ml) were found in 6.8% of samples including fresh-cut vegetables, cooked foods, cereals, and pastry products. To verify whether B. cereus-like isolates belonged to the B. cereus group, a PCR test targeting the sspE gene sequence specific of the group was carried out. Therefore, 174 isolates were found to be positive. Food samples were contaminated as follows: cereals (67.6%), pastry products (46.2%), cooked food (40.8%), cooked poultry meat (32.7%), seafood products (32.3%), spices (28.8%), canned products (16.7%), raw poultry meat (9.4%), fresh-cut vegetables (5.0%), and dairy products (4.8%). The 174 B. cereus isolates were characterized by partial sequencing of the panC gene, using a Sym'Previous software tool to assign them to different phylogenetic groups. Strains were distributed as follows: 61.3, 29.5, 7.5, and 1.7% in the group III, IV, II, and V, respectively. The genetic diversity was further assessed by ERIC-PCR and PFGE typing methods. PFGE and ERIC-PCR patterns analysis allowed discriminating 143 and 99 different profiles, respectivey. These findings, associated to a relatively higher prevalence of B. cereus group in different foods, could be a significant etiological agent of food in Tunisia.

Microbiological safety of ready‐to‐eat foods in low‐ and middle‐income countries: A comprehensive 10‐year (2009 to 2018) review

“…Diverse species of Bacillus , including B. cereus , were also detected in several RTEs including meat pie , buns , and jollof rice from Nigeria (Aruwa & Ogunlade, ). Similarly, in Tunisia, B. cereus contaminated cooked poultry meat and pastry products (Gdoura‐Ben Amor et al., ).…”

Prevalence of Bacillus cereus s.l. in ultra-high temperature chocolate milk from selected milk manufacturers in Malaysia

“…in this study is higher compared to the prevalence of B. cereus in UHT milk mentioned previously in other studies. It can be suggested that it might be due to the high microbial load from raw materials which can lead to the high number of successive spores (Vyletělová et al, 2002;Amor et al, 2018).…”

“…This indicates that most of the raw materials contained B. cereus spores. The spores which might be present in these raw ingredients may successfully be transferred during the milk processing course (Vyletělová et al, 2002;Amor et al, 2018) and surviving the UHT process, if the spores are incompletely inactivated. Generally, B. cereus utilises glucose as its main carbon source (Tallent et al, 2012).…”

Quantitative bioluminescence assay for measuring Bacillus cereus nonhemolytic enterotoxin complex

“…Spores of B. cereus are present in the soil at high concentrations up to 10 6 cfu g −1 [1] and enter the human food chain by contaminating crops used for feed and food. Foods observed to be affected by this contamination include the following: cooked rice [2], infant rice cereal [3], infant formula [4], dried milk products [5], dehydrated potato products [6], eggs, meat and spices [7], causing 47% of the total cases of food poisoning in Iceland (1985Iceland ( -1992, 22% in Finland (1992), 8.5% in the Netherlands (1991), and 5% in Denmark (1990-92) [8]. Most reported outbreaks involving B. cereus were linked to the consumption of heat-treated foods [9] (EFSA 2016) and between 400 and 10 8 B. cereus CFU/g were found in the foods found responsible in those foodborne disease outbreaks [10].…”