ABSTRACT
Escherichia coli strains of serogroup O26 comprise two distinct groups of pathogens, characterized as enteropathogenic E. coli (EPEC) and enterohemorrhagic E. coli (EHEC). Among the several genes related to type III secretion system-secreted effector proteins, espK was found to be highly specific for EHEC O26:H11 and its stx-negative derivative strains isolated in European countries. E. coli O26 strains isolated in Brazil from infant diarrhea, foods, and the environment have consistently been shown to lack stx genes and are thus considered atypical EPEC. However, no further information related to their genetic background is known. Therefore, in this study, we aimed to discriminate and characterize these Brazilian O26 stx-negative strains by phenotypic, genetic, and biochemical approaches. Among 44 isolates confirmed to be O26 isolates, most displayed flagellar antigen H11 or H32. Out of the 13 nonmotile isolates, 2 tested positive for fliCH11, and 11 were fliCH8 positive. The identification of genetic markers showed that several O26:H11 and all O26:H8 strains tested positive for espK and could therefore be discriminated as EHEC derivatives. The presence of H8 among EHEC O26 and its stx-negative derivative isolates is described for the first time. The interaction of three isolates with polarized Caco-2 cells and with intestinal biopsy specimen fragments ex vivo confirmed the ability of the O26 strains analyzed to cause attaching-and-effacing (A/E) lesions. The O26:H32 strains, isolated mostly from meat, were considered nonvirulent. Knowledge of the virulence content of stx-negative O26 isolates within the same serotype helped to avoid misclassification of isolates, which certainly has important implications for public health surveillance.
Subject(s)
Enterohemorrhagic Escherichia coli/isolation & purification , Enteropathogenic Escherichia coli/isolation & purification , Phenotype , Adhesins, Bacterial/genetics , Bacterial Adhesion/genetics , Brazil , Caco-2 Cells , Enterohemorrhagic Escherichia coli/classification , Enterohemorrhagic Escherichia coli/genetics , Enteropathogenic Escherichia coli/classification , Enteropathogenic Escherichia coli/genetics , Escherichia coli Proteins/genetics , Genetic Markers , HeLa Cells , Hemolysin Proteins/genetics , Humans , Phylogeny , Polymerase Chain Reaction , Polymorphism, Restriction Fragment Length , Sequence Analysis, DNA , Virulence Factors/geneticsSubject(s)
Acinetobacter Infections/microbiology , Acinetobacter baumannii , Carbapenems/pharmacology , Intensive Care Units , Pneumonia, Ventilator-Associated/microbiology , beta-Lactamases/genetics , Acinetobacter Infections/epidemiology , Acinetobacter baumannii/classification , Acinetobacter baumannii/drug effects , Acinetobacter baumannii/genetics , Acinetobacter baumannii/isolation & purification , Anti-Bacterial Agents/pharmacology , Brazil , Critical Care , Drug Resistance, Bacterial , Humans , Pneumonia, Ventilator-Associated/epidemiology , beta-Lactamases/metabolismABSTRACT
Recently, a mechanism of negative regulation of immune responses by a specialized population of so-called regulatory T cells (Tregs) has become a focus of intense investigation. Through the discovery of transcription factor Foxp3 as a central molecular determinant of Tregs differentiation and function, the complex biology of these cells, including maintenance of immunological tolerance to "self" and regulation of immune responses to pathogens, commensals, and tumors, has become the focus of intense investigation. The ability to control the infection and to delay the progression of the infection to AIDS and/or death is probably regulated by a balance between host factors, such as immunologic response and viral factors. Different rates of disease progression among HIV-1 infected individuals have been observed. In this context, Tregs may play an important role in the immunopathology of HIV-1 infection due to their potent suppressive activity of both T cell activation and effector function. In this review, we present the molecular and immunological aspects of Tregs in the HIV system and the association between Tregs and highly active antiretroviral therapy (HAART).
Subject(s)
HIV Infections/immunology , HIV Infections/pathology , HIV-1/immunology , HIV-1/pathogenicity , Immune Tolerance , T-Lymphocytes, Regulatory/immunology , Forkhead Transcription Factors/physiology , HumansABSTRACT
Um mutante (407-P) da linhagem Bacillus thuringiensis subsp. thuringiensis 407 produtor de melanina foi obtido após tratamento com o agente mutagênico etil-metano-sulfonato. Diversas propriedades microbiológicas e bioquímicas das duas linhagens foram analisadas e os resultados foram similares. O mutante 407-P foi incorporado em amostras de solo não esterilizado, recuperado, facilmente identificado e quantificado, possibilitando seu uso em estudos de ecologia de B. thuringiensis.
Subject(s)
Bacillus thuringiensis , Melanins , Mutation , SoilABSTRACT
Foi investigada a produçäo de SLTs por 41 amostras de Escherichia coli O 26, pertencente a diferentes sorotipos, isolados de humanos, bezerros e produtos cárneos. Foram realizados ensaios em culturas de células HeLa e Vero e hibridizaçäo de colênias com sondas para SLTI e SLTII. Nenhuma das amostras brasileiras foram produtoras de SLTs, enquanto 8 amostras padräo O26:H11 confirmaram a produçäo de SLTI. Este resultado sugere que produçäo de SLTs näo é característica frequente dentre amostras brasileiras deste sorogrupo
Subject(s)
Humans , Animals , Bacterial Toxins/isolation & purification , Diarrhea/microbiology , Escherichia coli/isolation & purificationABSTRACT
O presente estudo foi realizado para verificar a frequência de linhagens de Escherichia coli enteropatogênica clássica (EPEC) em 100 amostras de carne moída de segunda qualidade e 93 amostras de quibe cru. Das 193 amostras de alimentos analisados 93,78% continham E. coli, sendo que 8,84% apresentaram algum sorogrupo de EPEC. Em 7,2% das amostras de carne moída de segunda foram evidenciados os sorogrupos O26, O19 e O125. Em 10,71% das amostras de quibe cru foram isoladas os sorogrupos O26, O142, O55 e O127. As cepas de EPEC isoladas apresentaram resistência múltipla a no máximo três das 15 drogas testadas. A ampicilina foi a droga com maior populaçäo de EPEC resistente (68,75% das EPEC isoladas) seguida da tetraciclina (43,75%. A populaçäo de EPEC estudada mostrou sensibilidade acima de 93% para as aioutras drogas testadas, exceçäo à gentamicina (81,25%)
Subject(s)
Humans , Escherichia coli/isolation & purification , Food Microbiology , Meat/analysis , Meat Products , Escherichia coli Infections/epidemiology , Pedigree , Tetracycline/metabolism , Tetracycline/therapeutic use , Brazil , Cattle , Ampicillin/metabolism , Ampicillin/therapeutic use , Escherichia coli Infections/drug therapy , Drug Resistance, MicrobialABSTRACT
A capacidade toxigênica de 924 amostras de Escherichia coli isoladas de 100 amostras de carne mooída de segunda qualidade e de 93 amostras de quibe cru foi pesquisada pelos testes de Dean e alça ligada de intestino de coelho para detecçäo de enterotoxina termoestável (ST). Os testes de imunohemólise passiva, imunohemólise radial e alça ligada de intestino de coelho foram utilizados apra detecçäo de enterotoxina termolábil (LT). Nenhuma cepa de E. coli enterotoxigênica foi isolada dos alimentos analisados, embora 93% das amostras de carne moída de segunda e 90,32% das de quibe cru estivessem contaminada por E. coli.
