ABSTRACT
Bacillus cereus is a human pathogenic bacterium that produces emetic and diarrheal foodborne diseases. This study evaluated the genetic and toxigenic diversity in B. cereus group isolates from powdered foods collected in public educational institutions, bakeries and powdered food companies located in Medellín, Colombia. B. cereus was detected in 35 of 305 (11%) powdered food samples and 52 B. cereus were isolated. The presence of ten toxin genes, hblCDAB, nheABC, cytK2, entFM and cesB, was evaluated in the isolates by multiplex PCR. The nheABC operon was found in all isolates (100%), hblCDAB in 22 (42%), hblCDA in 8 (15%) and hblCD in 3 (6%); the cytK2 gene was detected in 32 isolates (62%) and entFM in 32 (62%). Notably, the cesB gene was not detected. According to the presence of toxin genes, fifteen profiles were identified. The predominant toxigenic profile contained all toxin genes but cesB. A large genetic diversity was observed by GTG5 fingerprinting with 46 isolates grouped in seven clusters and the remaining six clustering individually. There was no relationship between toxigenic profiles and genetic clusters, but some genetic clusters seemed to be related to particular powdered food types. In general, the results evidenced high genetic and enterotoxigenic diversity among the B. cereus group isolates.
ABSTRACT
Bacillus cereus is a human pathogenic bacterium found in foods with the potential to cause emesis and diarrhea. This study estimated the presence, toxigenic and genomic diversity of B. cereus s.l. obtained from cassava starch samples collected in bakeries and powdered food companies in Medellín (Colombia). Bacillus cereuss.l. was found in 43 of 75 (57%) cassava starch samples and 98 isolates were obtained. The nheABC, hblCDAB, cytK2, entFM and cesB toxin genes were detected by multiplex PCR and the most frequent operon was nheABC, whereas cesB gene was not found. Twelve toxigenic profiles were determined by the detection of toxin genes, and the most frequent profiles harbored all enterotoxin genes. A broad genomic diversity was detected according to GTG5-PCR fingerprinting results with 76 B. cereus s.l. grouped in sixteen clusters and the 22 isolates clustering separately. No relationship was observed between genomic background and toxigenic profiles. In general, the results showed a high genomic and enterotoxigenic diversity in B. cereus s.l. found in cassava starch. These results should incentive future studies to understand the distribution of B. cereus s.l. isolated on raw materials in comparison with finished products.
Subject(s)
Bacillus cereus/genetics , Bacterial Proteins/genetics , Bacterial Toxins/genetics , Enterotoxins/genetics , Food Microbiology , Hemolysin Proteins/genetics , Manihot/microbiology , Starch/analysis , Bacillus cereus/isolation & purification , Bacillus cereus/metabolism , Bacterial Proteins/metabolism , Bacterial Toxins/metabolism , Enterotoxins/metabolism , Food Handling , Gene Expression Regulation, Bacterial , Genotype , Hemolysin Proteins/metabolismABSTRACT
Bacillus cereus sensu lato (s.l.) is a group of bacteria commonly found in diverse environments, including foods, with potential to cause emesis and diarrhea. In Colombia, it is one of the main foodborne pathogens. The aim of this study was to determine the genomic and toxigenic heterogeneity of B. cereus s.l. isolated from ready-to-eat foods and powdered milk collected in day care centers of Medellin, Colombia. Of 112 B. cereus s.l. isolates obtained, 94% were ß-hemolytic. Toxigenic heterogeneity was established by the presence of nheABC, hblCDAB, cytK2, entFM, and cesB toxigenic genes. The nheABC operon and entFM gene were most frequently detected in the isolates, whereas the cesB gene was not found. According to the toxin genes content, nine toxigenic profiles were identified. A 44% of isolates had profiles with all genes for nonhemolytic enterotoxin, hemolysin BL, and enterotoxin FM production (profiles II and IV). Pulsed-field gel electrophoresis analysis indicated a high genomic heterogeneity among the B. cereus s.l., with 68 isolates grouping into 16 clusters and 33 placed separately in the dendrogram. This study provides useful information on the safety of ready-to-eat foods and powdered milk in day care centers where children, a susceptible population, are exposed and it should incentive for more studies to understand the distribution of different toxin-encoding genes among B. cereus s.l. isolates, enabling detailed risk assessment.
Subject(s)
Bacillus cereus/genetics , Bacterial Toxins/genetics , Fast Foods , Milk , Animals , Bacillus cereus/isolation & purification , Colombia/epidemiology , DNA, Bacterial , Fast Foods/microbiology , Food Contamination , Food Microbiology , Genes, Bacterial , Hemolysin Proteins/genetics , Milk/microbiology , Operon , Powders , Risk AssessmentABSTRACT
Introducción: Bacillus cereus es una bacteria contaminante de alimentos y patógena en humanos, cuya toxina emética o cereúlida (Ces) causa el síndrome emético y las enterotoxinas hemolítica o hemolisina BL (Hbl), no hemolítica (Nhe) y citotoxina K (CytK), el síndrome diarreico. Objetivo: Determinar la presencia de genes toxigénicos de Bacillus cereus en muestras de ADN obtenido directamente de fécula de maíz y de harina de trigo, mediante reacción en cadena de la polimerasa múltiple. Materiales y métodos: Se determinaron los genes toxigénicos de Bacillus cereus en muestras de ADN extraído directamente de fécula de maíz y harina de trigo, utilizando una reacción en cadena de la polimerasa múltiple específica para los genes cesB, hblC, nheA y cytK. Resultados: De 76 muestras de fécula de maíz, el 60,5% presentó los genes toxigénicos de Bacillus cereus, que fueron agrupados en seis consorcios: I: hblC, cytK (30,4%), II: nheA, hblC, cytK (21,7%), III: hblC (19,6%), IV: nheA (15,2%), V: nheA, hblC (10,9%), VI: nheA, hblC, cytK, cesB (2,2%). De 79 muestras de harina de trigo, el 65,8% presentó los genes toxigénicos de Bacillus cereus, que se agruparon en cuatro consorcios: I: nheA, hblC, cytK (80,8%), II: hblC, cytK (11,5%), III: hblC (5,8%), IV: nheA, hblC (1,9%)...
Introduction: Bacillus cereus is a human pathogen that causes two kinds of foodborne diseases, the emetic syndrome caused by emetic toxin or cereulide (Ces), and the diarrheal syndrome caused by three different enterotoxins, the hemolytic enterotoxin or hemolysin BL (Hbl), the nonhemolytic enterotoxin (Nhe) and the cytotoxin K (CytK). Objective: To determine the presence of toxigenic genes of Bacillus cereus in DNA samples directly obtained from corn starch and wheat flour using multiplex polymerase chain reaction. Material and methods: The presence of toxigenic genes of Bacillus cereus were determinedin DNA samples directly extracted from corn starch and wheat flour, using a multiplex polymerase chain reaction technique specific for cesB, hblC, nheA and cytK genes. Results: From a total of 76 corn starch samples, 60.5% had toxigenic genes of Bacillus cereus and were grouped in six consortia: I: hblC, cytK (30.4%), II: nheA, hblC, cytK (21.7%), III: hblC (19.6%), IV: nheA (15.2%), V: nheA, hblC (10.9%) and VI: nheA, hblC, cytK, cesB (2.2%). From 79 wheat flour samples tested, 65.8% had toxigenic genes of Bacillus cereus and were grouped into four consortia: I: nheA, hblC, cytK (80.8%), II: hblC, cytK (11.5%), III: hblC (5.8%) and IV: nheA, hblC (1.9%)...
