RESUMO
Twenty-three Bacillus cereus isolates from food poisoning outbreaks associated with a diarrheal-type syndrome, fourteen foodborne isolates not associated with food poisoning and fifteen isolates from Brazilian soil samples were analyzed for the presence and genetic diversity (by RE-PCR) of the virulence genes ces (emetic toxin, cereulide), plcR-papR (pleiotropic regulator PlcR and peptide PapR), nheA (a component of the NHE complex), bceT (diarrheal enterotoxin bc-D-ENT), gyrB (B subunit of DNA gyrase), cytK-2 (necrotic enterotoxin cytotoxin K-2), and plcA (phosphatidylcholine-specific phospholipase C). Additionally, these isolates were phenotypically characterized for motility, hemolytic and lecithinase activities, as well as HBL enterotoxin production. The group of isolates associated with food poisoning had the highest occurrence of the phenotypically analyzed factors and the most frequent occurrence and highest genetic diversity of the plcR-papR, nheA, bceT, cytK-2, plcA, and gyrB genes. An analysis of molecular variance (AMOVA), in which all loci were analyzed, demonstrated that the genetic variation intragroup of isolates (92%) was significantly higher than that intergroup (8%) (P<0.05). These results were corroborated by an analysis of the genetic differentiation between the groups, which was low/moderate, the result of a high degree of allele sharing. Our results suggest that B. cereus isolates with the potential to cause food poisoning outbreaks do not have a specific genetic profile characterized by the presence of a particular gene or allele among the genes assessed. On the contrary, different combinations of genes encoding virulence factors may be present in different isolates of B. cereus that potentially cause food poisoning outbreaks.
Assuntos
Bacillus cereus/isolamento & purificação , Doenças Transmitidas por Alimentos/microbiologia , Microbiologia do Solo , Bacillus cereus/química , Bacillus cereus/genética , Bacillus cereus/patogenicidade , Brasil , Enzimas de Restrição do DNA/metabolismo , Diarreia/epidemiologia , Diarreia/microbiologia , Surtos de Doenças , Enterotoxinas/análise , Enterotoxinas/genética , Humanos , Fenótipo , Reação em Cadeia da Polimerase/métodos , Fatores de Virulência/genéticaRESUMO
The aim of this study was to determine the potency (ITU) and efficacy of a liquid formulation of Bacillus thuringiensis israelensis developed by the State University of Londrina named BioUel, against early fourth instar larvae of Aedes aegypti and Culex quinquefasciatus. The ITU/mg of BioUel was 960, the LC50 was of 0.271 (± 0.39) ppm, and the LC95 was 0.634 (± 0.099) ppm, in larvae of C. quinquefasciatus. In A. aegypti larvae, LC50 was 0.332 (± 0.042) ppm and LC95 was 0.694 (± 0.073) ppm. The ITU level of BioUel and its control results were similar to most commercial products tested. Stability was of approximately 90 days, which allows for local production.
Assuntos
Aedes , Bacillus thuringiensis , Culex , Controle Biológico de Vetores/métodos , Animais , Larva , Dose Letal MedianaRESUMO
The bacterial strain Bacillus cereus is closely related to Bacillus thuringiensis, although any genetic relationship between the two strains is still in debate. Using rep-PCR genomic fingerprinting, we established the genetic relationships between Brazilian sympatric populations of B. cereus and B. thuringiensis simultaneously collected from two geographically separate sites. We observed the formation of both B. thuringiensis and B. cereus clusters, as well as strains of B. cereus that are more closely related to B. thuringiensis than to other B. cereus strains. In addition, lower genetic variability was observed among B. thuringiensis clusters compared to B. cereus clusters, indicating that either the two species should be categorized as separate or that B. thuringiensis may represent a clone from a B. cereus background.
Assuntos
Bacillus cereus/genética , Bacillus thuringiensis/genética , Impressões Digitais de DNA/métodos , Variação Genética/genética , Reação em Cadeia da Polimerase/métodos , Bacillus cereus/isolamento & purificação , Bacillus thuringiensis/isolamento & purificação , Análise por Conglomerados , Microbiologia do SoloRESUMO
The bacterial strain Bacillus cereus is closely related to Bacillus thuringiensis, although any genetic relationship between the two strains is still in debate. Using rep-PCR genomic fingerprinting, we established the genetic relationships between Brazilian sympatric populations of B. cereus and B. thuringiensis simultaneously collected from two geographically separate sites. We observed the formation of both B. thuringiensis and B. cereus clusters, as well as strains of B. cereus that are more closely related to B. thuringiensis than to other B. cereus strains. In addition, lower genetic variability was observed among B. thuringiensis clusters compared to B. cereus clusters, indicating that either the two species should be categorized as separate or that B. thuringiensis may represent a clone from a B. cereus background.
Assuntos
Bacillus cereus/genética , Bacillus thuringiensis/genética , Impressões Digitais de DNA/métodos , Variação Genética , Reação em Cadeia da Polimerase/métodos , Bacillus cereus/isolamento & purificação , Bacillus thuringiensis/isolamento & purificação , Análise por Conglomerados , Microbiologia do SoloRESUMO
Three species of the Bacillus cereus group (Bacillus cereus, Bacillus anthracis, and Bacillus thuringiensis) have a marked impact on human activity. Bacillus cereus and B. anthracis are important pathogens of mammals, including humans, and B. thuringiensis is extensively used in the biological control of insects. The microbiological, biochemical, and genetic characteristics of these three species are reviewed, together with a discussion of several genomic studies conducted on strains of B. cereus group. Using bacterial systematic concepts, we speculate that to understand the taxonomic relationship within this group of bacteria, special attention should be devoted also to the ecology and the population genetics of these species.
