Genetic relationship of diarrheagenic Escherichia coli pathotypes among the enteropathogenic Escherichia coli O serogroup

The genetic relationship among the Escherichia coli pathotypes was investigated. We used random amplified polymorphic DNA (RAPD) data for constructing a dendrogram of 73 strains of diarrheagenic E. coli. A phylogenetic tree encompassing 15 serotypes from different pathotypes was constructed using multilocus sequence typing data. Phylogram clusters were used for validating RAPD data on the clonality of enteropathogenic E. coli (EPEC) O serogroup strains. Both analyses showed very similar topologies, characterized by the presence of two major groups: group A includes EPEC H6 and H34 strains and group B contains the other EPEC strains plus all serotypes belonging to atypical EPEC, enteroaggregative E. coli (EAEC) and enterohemorrhagic E. coli (EHEC). These results confirm the existence of two evolutionary divergent groups in EPEC: one is genetically and serologically very homogeneous whereas the other harbors EPEC and non-EPEC serotypes. The same situation was found for EAEC and EHEC.

Production, characterization, and application of antibodies against heat-labile type-I toxin for detection of enterotoxigenic Escherichia coli

Strains of enterotoxigenic Escherichia coli (ETEC) are responsible for significant rates of morbidity and mortality among children, particularly in developing countries. The majority of clinical and public health laboratories are capable of isolating and identifying Salmonella, Shigella, Campylobacter, and Escherichia coli O157:H7 from stool samples, but ETEC cannot be identified by routine methods. The method most often used to identify ETEC is polymerase chain reaction for heat-stable and heat-labile enterotoxin genes, and subsequent serotyping, but most clinical and public health laboratories do not have the capacity or resources to perform these tests. In this study, polyclonal rabbit and monoclonal mouse IgG2b antibodies against ETEC heat-labile toxin-I (LT) were characterized and the potential applicability of a capture assay was analyzed. IgG-enriched fractions from rabbit polyclonal and the IgG2b monoclonal antibodies recognized LT in a conformational shape and they were excellent tools for detection of LT-producing strains. These findings indicate that the capture immunoassay could be used as a diagnostic assay of ETEC LT-producing strains in routine diagnosis and in epidemiological studies of diarrhea in developing countries as enzyme linked immunosorbent assay techniques remain as effective and economical choice for the detection of specific pathogen antigens in cultures.

Diarrheagenic Escherichia coli categories among the traditional enteropathogenic E. coli O serogroups: a review

The socalled enteropathogenic Escherichia coli (EPEC) O serogroups include typical and atypical EPEC, enterohaemorrragic E. coli, enterotoxigenic E. coli, and enteroaggregative E. coli. The aim of this article is to review the composition of each O serogroup and the major serotypes, clones, and additional virulence characteristics of each of these diarrheageniccategories. Their adherence patterns and genetic relationships are also presented. The review is based on the study of 805 strains of serogroups O26, O55, O86, O111, O114, O119, O125, O126, O1127, O128, and O142 most of which isolated in São Paulo from children with diarrhea between 1970 and 1990. Since some O serogroups include more than one diarrheageniccategory O serogrouping only should be abandoned as a diagnostic method. However serotyping is a reliable method for those serotypes that correspond to clones.

Characaterization of typical and atypical enteropathogenic Ëscherichia coli (EPEC) strains of the classical O55 serogroup by RAPD analysis

The genetic diversity of 41 typical and atypical enteropathogenic Ëscherichia coli" (EPEC) strains of the serogroup O55 was analysed by using the random amplified polymorphic DNA (RAPD) method. All typical EPEC O55 strains were grouped in two clusters (A and C) and belonged to serotype O55:H6, while cluster B included all atypical strains, which were of the serotype O55:H7. The three groups also included non-motile strains. RAPD may be a useful method for epidemiological studies on "E. coli" O55 infection

Characterization of lactose-fermenting Salmonella agona strains isolated in a pediatric unit

Eight lactose-fermenting Salmonella agona strains isolated in a pediatric unit were characterized by classic and molecular methods. The strains were classified as biotypes 1a, corresponding to the most frequen one in Brazil. None of the strains produced colicin. Multiple resistence to antimicrobials was observed among the strains studied, It was demonstrated that the lactose-fermenting character was encoded by a plasmid with spontaneous segregaton at a frequency of 1 percer center. This plasmid was transferable by conjugation at a frequency between 4x10(-8) and 5x10(-10). The lac+ plasmid, which molecular weight was approximately 90 MDa, encoded both lactose fermentation and multiple resistance to antimicrobials. Replicon typing showed that this plasmid did not belong to the known types, suggesting the present of a new replicon type. Classic methods showed that the studied strains had the same characteristics as the clone widely occurring in our area, differing only by lactose-fermenting ability. This conclusion was supported by the results of ribotyping study.

Isolamento de Yersinia enterocolitica em um laboratório particular da cidade de Säo Paulo / Isolation of Yersinia enterocolitica in São Paulo, Brazil

Comunica-se o isolamento de 10 amostras de Y. enterocolítica, das fezes de crianças e adultos, atendidos no Laboratório Bio-Ciência Lavoisier. O isolamento destas 10 amostras sugere que a Y. enterocolítica é mais frquente em São Paulo do que era indicado por trabalhos anteriores.

Valor do exame bacterioscópico de urina para o diagnóstico de infecçäo das vias urinárias / Value of the urine bacterioscope examination for the diagnosis of urinary tract infections

O diagnóstico preciso de infecçäo urinária depende da cultura na urina. O exame bacteriológico completo compreende o bacterioscópico (esfregaço de urina centrifugada, corado pelo gram e examinada ao microscópico de grande aumento) e a cultura quantitativa. Os autores estudaram 3.030 exames bacteriológicos consecutivos: a) idade: rcém-nascidos - 3%, lactentes - 42%, crianças - 42%, adolescentes 3%, näo conhecida - 10%; b) sexo: feminino - 62% c) método de coleta: saquinho plástico - 66%; jato intermediário - 24% näo conhecido - 10%; d) resultados - 2.456 bacteriscópicos negativos e 574 positivos; 2.747 culturas negativas e 556 positivas. Considerando a cultura quantitativa como o padräo para o diagnóstico de infecçäo urinária, o bacterioscópico apresentou 100% de sensibilidade e 99% de especificidade. Assim, o exame bacterioscópico é o meio mais fideligno, acurado e rápido para estabelecer o diagnóstico de infecçäo urinária

Atividade in vitro da associaçäo sulbactam-ampicilina frente a amostras de Staphylococcus aureus produtoras de beta-lactamase / In vitro activity of sulbactam-ampicilin to beta-lactamase producing Staphylococcus aureus strains

A incidência cada vez maior de resistência bacteriana aos antibióticos é um fato de grande relevância principalmente aquela causada pelas beta-lactamases. Seguindo-se esta linha de pensamento, foi avaliada a atividade in vitro de uma associaçäo de Sulbactam (inibidor irreversível das beta-lactamases) com Ampicilina, frente a 100 amostras de S. aureus produtoras de beta-lactamase. As duas substâncias foram usadas na proporçäo de uma parte da primeira para duas da segunda. Para fins de comparaçäo, as 100 amostras foram também estudadas com relaçäo às concentraçöes inibitórias da Ampicilina, isoladamente. A associaçäo Sulbactam-ampicilina, que continha 8 microng/ml da primeira droga e 16 microng/ml da segunda, inibiu o crescimento de todas as amostras de S. aureus. Na concentraçäo 16 microng/ml, a Ampicilina, isoladamente, inibiu o crescimento de somente 60% das amostras. Considerando-se os níveis séricos que a Ampicilina e o Sulbactam podem alcançar quando administrados em associaçäo, as 100 amostras de S. aureus foram consideradas sensíveis à associaçäo das duas substâncias

Estudio microbiológico de la diarrea aguda en niños pertenecientes a una comunidad urbana de bajos recursos de la ciudad de Sao Paulo-Brasil / Microbiological study of the acute diarrhea in children belonging to an urbane community of the city of Sao Paulo-Brasil

Con la finalidad de identificar los microorganismos responsables por la diarrea aguda infantil en un barrio de Sao Paulo, se estudian las heces de 224 niños menores de 5 años de edad, 107 diarréicos y 117 no diarréicos (controles), en el barrio "Cidade Leonor", comunidad caracterizada por presentar condiciones desfavorables de higiene ambiental y alto grado de promiscuidad. El estudio microbiológico se realiza por métodos convencionales (coprocultivos) y la detección de Rotavirus mediante el test inmunoenzimático. También se estudia el comportamiento "in vitro" de las bacterias enteropatógenas frente a 12 drogas antimicrobianas. Se detectan microorganismos enteropatógenos en 46.7% de los niños diarréicos y en 32.5% de los controles. E. coli enteroinvasora es el enteropatógeno más frecuente, sobre todo en niños diarréicos, aislándose con mayor frecuencia los serotipos 028ac:H y 0136:H. Campylobacter ocupa el segundo lugar, siendo C. jejuni la especie más frecuentemente aislada. Enteropatógenos tales como E. coli enteropatogénica clásica, Salmonella y Rotavirus son aislados con baja frecuencia, a pesar de que los mismos se encuentran ampliamente difundidos en Sao Paulo. La mayoría de las muestras de enterobacterias enteropatógenas fueron sensibles a los agentes antimicrobianos utilizados, llamando la atención la elevada sensibilidad de E. coli enteropatogénica clásica y de Salmonella. Los barrios parecen constituir un medio adecuado para la proliferación de organismos patógenos, por lo que sería conveniente realizar mayor número de estudios microbiológicos y epidemiológicos en este tipo de población