Frequency of hemolysin BL and non-hemolytic enterotoxin complex genes of Bacillus cereus in raw and cooked meat samples in Zanjan, Iran

Abstract

Food safety has emerged as an important global issue with international trade and public health implications. Bacillus cereus is an important cause of food poisoning worldwide. A total of 200 individual meat samples were collected from meat retail outlets and restaurants and investigated the frequency of B. cereus and hemolysin BL (Hbl), non-hemolytic enterotoxin (Nhe) complex genes. The meat samples were immediately homogenized and cultured on Bacillus cereus selective agar and subjected for confirmatory biochemical tests and molecular detection of gyrB, hblA, hblC, hblD, nheA, nheB and nheC genes. A total of 29 (14.5 %) meat samples were positive for the presence of B. cereus. The frequency of B. cereus in raw meat (14.1 %) was similar to cooked beef samples (15 %) (P > 0.05). Twenty six (89.6 %) isolates carried at least one or more enterotoxin genes. We found nheA (58.6 %) and hblD (51.7 %) genes with higher frequency than others. Hemolysin BL complex genes were found in lower frequency than Nhe complex (P > 0.05). Detection of enterotoxigenic B. cereus in meat samples shows a probable risk for public health. Therefore, the reliable molecular methods for monitoring of potentially pathogenic B. cereus are strongly recommended for the routine food examination.

The Food Poisoning Toxins of Bacillus cereus

“…In fact, the hbl genes alone or a combination of ces and hbl have only been reported for the very few emetic Bacillus weihenstephanensis isolates described so far [ 79 ]. There are further studies showing “unusual” results, particularly low or no prevalence of nhe [ 45 , 74 , 80 , 81 , 82 , 83 , 84 ] or extraordinarily high prevalence of hbl [ 76 , 85 , 86 , 87 , 88 ] or ces [ 89 ], which must be interpreted cautiously, especially as nhe is well known for its molecular heterogeneity [ 48 , 51 , 52 ]. Thus, the choice of detection methods, especially primer pairs for nhe , can have a crucial influence on the results.…”

The Bacillus cereus Food Infection as Multifactorial Process

“…Overall, it is particularly remarkable that strains producing diarrheal enterotoxins are reported much more frequently than emetic isolates. However, it must be pointed out that in several studies the ces gene cluster (encoding cereulide synthetase) is not investigated or not mentioned [119][120][121], and that several studies do not distinguish between emetic and enteropathogenic B. cereus at all [122,123]. If the emetic toxin genes are investigated, their occurrence is rather rare compared to the enterotoxin genes ( Table 2 and [124][125][126][127][128][129]).…”

Meat Borne Diseases

“…Is a pore forming toxin consisting of two lytic elements NheA and NheB, and a protein NheC with unknown function encoded by nheA, nheB, and nheC, respectively [66].…”