Molecular and Toxigenic Characterization of Bacillus cereus and Bacillus thuringiensis Strains Isolated from Commercial Ground Roasted Coffee

Abstract

<jats:p>Thirty samples of roasted ground coffee beans from 10 different commercial brands were analyzed to investigate the occurrence and levels of Bacillus cereus and Bacillus thuringiensis strains. Strains were evaluated for their genetic diversity by repetitive element sequence polymorphism PCR (Rep-PCR) and for their toxigenic profiles, i.e., the presence of hblA, hblC, hblD, nheA, nheB, nheC, cytK, ces, and entFM. Survival and multiplication of B. cereus sensu lato in the ready-to-drink coffee was determined to evaluate this beverage as a possible vehicle for B. cereus infection. B. cereus was detected in 17 (56.7%) of the 30 samples, and B. thuringiensis was detected in 8 (26.7%) of the 30 samples. Five samples did not produce any characteristic growth. The most common gene, entFM, was detected in 23 strains (92%). The NHE complex (nheA, nheB, and nheC genes) was found in 19 strains (76%). The HBL complex (hblA, hblC, and hblD) was found in 16 strains (64%). All strains were negative for ces. The cytK gene was found in 16 strains (64%). The computer-assisted cluster analysis of Rep-PCR profiles using a clustering criterion of 80% similarity revealed four main clusters. Cluster 1 was the predominant and comprised three B. thuringiensis strains with 100% similarity, cluster 2 comprised two B. cereus strains (100% similarity), cluster 3 comprised two B. thuringiensis strains (90% similarity), and cluster 4 comprised one B. thuringiensis strain and one B. cereus strain (85% similarity). The cluster analysis of fingerprints generated by Rep-PCR revealed a high genetic diversity among the B. cereus strains, suggesting that the contamination could have originated from different sources. In our experiments, when sugar was added and the beverage was kept in thermic bottles there was a significant increase in B. cereus sensu lato levels, which may increase the risk of food poisoning. These results highlight the need for additional studies on this subject to better evaluate coffee as a food poisoning vehicle.</jats:p>

Incidence, Antibiotic Susceptibility, and Toxin Profiles of Bacillus cereus sensu lato Isolated from Korean Fermented Soybean Products

“…Among the enterotoxins produced by B. cereus sensu lato , HBL, NHE, and cytotoxin K are considered the primary virulence factors that mediate the diarrheal disease (Granum and others ; Lund and others ). The isolated B. cereus sensu lato strains commonly harbored nheABC and entFM genes and this finding was consistent with previous studies (Guinebretiere and others ; Yang and others ; Chaves and others ; Kim and others ). However, the prevalence of hblCDA genes determined in this study (34.5%) was relatively lower than those previously reported (81% to 90%) (Guinebretiere and others ; Park and others ; Chon and others ).…”

Characteristics of enterotoxin distribution, hemolysis, lecithinase, and starch hydrolysis of Bacillus cereus isolated from infant formulas and ready-to-eat foods

“…In addition, the isolates from all food samples harbored nhe. These results are consistent with the available results of B. cereus harboring nhe (Guinebretière et al, 2002;Ankolekar et al, 2009;Chaves et al, 2012;Chon et al, 2012). The CytK toxin is known to induce diarrhea similarly to the HBL and Nhe toxins .…”

“…Thus, the isolation ratio of 347 B. cereus strains from 687 food samples was 50%. The prevalence of the isolates from the food items of dried milk product, rice, ground roasted coffee, and German infant formula was similar to this ratio reported here (Becker et al, 1994;Shaheen et al, 2006;Reyes et al, 2007;Ankolekar et al, 2009;Chaves et al, 2012). However, the prevalence of the isolates for the weaning cereal was found to be less than the reported value (Kunene et al, 1999).…”

“…More than 95% of the strains isolated from RTE foods possessed hbl and approximately 30% of isolates from infant formulas possessed hbl. Some previous studies have reported that 60 to 90% of the strains isolated from various food items harbored hbl (Ankolekar et al, 2009;Chaves et al, 2012;Chon et al, 2012). Here, although the RTE food isolates complied with these earlier reports, unpredictably, only 30% of the infant formula isolates possessed hbl.…”

Prevalence, virulence factor genes and antibiotic resistance of Bacillus cereus sensu lato isolated from dairy farms and traditional dairy products

“…The isolated B. cereus s. l. commonly possessed cytk (75%) as the most prevalent toxin gene followed by entFM (67%). Similar results of high prevalence of nheABC and entFM gene complexes have previously been reported to be widespread among wild B. cereus isolates from various food and environmental sources [30, 45–48], as well as some reference strains [31]. Similarly, various studies have reported higher prevalence rates, usually between 40 and 70.6% of the HBL gene complex in B. cereus isolated from milk and dairy products [28, 49–51].…”