AUTHOR=Haque Md Atiqul , Wang Fei , Chen Yi , Hossen Foysal , Islam Md Aminul , Hossain Md Amzad , Siddique Naila , He Cheng , Ahmed Firoz 

TITLE=Bacillus spp. Contamination: A Novel Risk Originated From Animal Feed to Human Food Chains in South-Eastern Bangladesh

JOURNAL=Frontiers in Microbiology

VOLUME=12

YEAR=2022

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2021.783103

DOI=10.3389/fmicb.2021.783103

ISSN=1664-302X

ABSTRACT=<p>The current study provides information on <italic>Bacillus</italic> spp. contamination along with present status in commercially available poultry and animal feeds as well as animal-derived products in Bangladesh. The research has been conducted to determine if animal feed and its components are a source of <italic>Bacillus</italic> spp. contamination in feed and food chain. Out of 180 different feeds, milk, egg, and human stool samples, 218 <italic>Bacillus</italic> spp. were isolated and identified by cultural morphology, microscopic, biochemical, and molecular characteristics where <italic>B. cereus</italic>, <italic>B. subtilis</italic>, <italic>B. amyloliquefaciens</italic>, <italic>B. licheniformis</italic>, <italic>B. thuringiensis</italic>, <italic>B. megaterium</italic>, and <italic>B. coagulans</italic> accounted for 51, 22, 9.1, 5.9, 5, 3.6, and 2.2%, respectively. Regarding the enumeration of total viable count and total <italic>Bacillus</italic> count, correspondingly 67 and 39% samples were found to be contaminated with above 10,000 CFU/g, while highest contamination was 85 and 75% in broiler feed, respectively. The total number of bacteria above the regulatory limits in commercially available feeds indicates a poor compliance with regulation and abuse administration in the Bangladeshi market. Moreover, a hospital-based survey showed that food-borne <italic>Bacillus</italic> spp. contributed to 4.5% human diarrhea cases and 25% food contamination associated with vegetables, rice, RTE food, milk, and egg, accounting for 46, 34, 14, 4, and 2%, respectively. <italic>B. cereus</italic> was the dominant isolate correspondingly accounting for 56 and 51% egg and milk contamination followed by <italic>B. amyloliquefaciens</italic> (32%) and <italic>B. thuringiensis</italic> (12%) in egg and <italic>B. subtilis</italic> (25%), <italic>B. amyloliquefaciens</italic> (12%), <italic>B. thuringiensis</italic> (6.4%), and <italic>B. coagulans</italic> (3.2%) in milk, respectively. Toxin gene profiling of <italic>Bacillus</italic> spp. revealed that <italic>B. cereus</italic> constituted a principal part of virulence, while <italic>B. thuringiensis</italic>, <italic>B. licheniformis</italic>, <italic>B. megaterium</italic>, <italic>B. coagulans</italic>, and <italic>B. subtili</italic>s showed genetic diversity and <italic>B. amyloliquefaciens</italic> had not carried any toxin gene. Detection rate of enterotoxin genes (<italic>nheA</italic>, <italic>nheB</italic>, <italic>nheC</italic>, <italic>cytK</italic>, <italic>hblA</italic>, <italic>hblC</italic>, <italic>hblD</italic>, and <italic>entFM</italic>) showed that 55% isolates carried <italic>nheABC</italic> genes, 80% <italic>entFM</italic>, and 71% <italic>cytK</italic>, whereas only 33% of the isolates contained <italic>hblACD</italic> gene clusters. These virulence genes were posing a threat to human health due to spread across the food and feed chain. Finally, our findings support the hypothesis that <italic>B. cereus</italic> might contribute to clinical diarrhea, gizzard erosion, and lung infection in duck and poultry, and that it contaminates animal-derived foods resulting in toxicity and antibacterial resistance to humans. Therefore, maximal tolerance limits of <italic>Bacillus</italic> spp. and their potential risks to the animal industry are urgently needed to clarify. Moreover, <italic>Bacillus</italic> spp.–induced toxin residual must be altered for human health via food chain transmission.</p>