Bacteroides fragilis interferes with iNOS activity and leads to pore formation in macrophage surface.

Bacteroides fragilis is the anaerobe most commonly recoverable from clinical specimens. The wide genetic diversity of this bacterium related with virulence potential is still an open question. In this study, we analyzed the morphological aspects and microbicide action of MØ during interactions with B. fragilis. A filamentous cytoplasm content release and a different actin organization colocalized with iNOS were detected. It was also possible to observe the reduction of NO production in the same conditions. The scanning electron microscopy showed the formation of pore-like structures in the surface of macrophages in the bacterial presence and by transmission electron microscopy we could observe the extrusion of cytoplasm contents as well as the condensation of chromatin in the nucleus periphery. These data suggest the existence of an inhibitory mechanism developed by B. fragilis strains for one of the macrophage microbicide actions.

Non-toxigenic pattern II and III Bacteroides fragilis strains: coexistence in the same host.

Diarrhoeic stool samples from 334 0-5-year-old children were analysed with respect to the incidence of Bacteroides fragilis as well as other enteropathogens. B. fragilis was recovered in 9.3% (31/334) of the samples, and 79 strains were examined for the presence of the bft gene or the BfPAI flanking region using polymerase chain reaction assays. No enterotoxigenic B. fragilis strains were detected. In 29% (9/31) of the samples the coexistence of both II and III non-toxigenic B. fragilis (NTBF) patterns could be seen. In 51.6% (16/31) of the samples there existed a pattern II NTBF only, and in 19.4% (6/31) only pattern III could be detected. Strains from the same patient representing different patterns were submitted to pulsed-field gel electrophoresis assays. Fingerprints obtained by this technique showed that there was strong heterogeneity among strains from different individuals. However, different patterns from the same individual shared 100% similarity.

Aeromonas hydrophila vacuolating activity in the Caco-2 human enterocyte cell line as a putative virulence factor.

A non-enterotoxigenic strain of Aeromonas hydrophila isolated from diarrheic stools of an 8-month-old child was found to cause vacuolation in Caco-2 cells. The vacuoles became prominent 60 min after addition of the bacterial culture to the cell monolayers and, after 120 min, a complete disruption of the monolayers was observed. Cell vacuolation was not detected when Caco-2 monolayers were tested with sterile filtrates of overnight cultures of the A. hydrophila vacuolating strain AH14846. This strain produced a diffuse adherence pattern in Caco-2 cell monolayers, but did not produce detectable cytotonic enterotoxin in the suckling mouse test and only produced small quantities of aerolysin. By demonstrating the ability to induce vacuolation in mammalian cells of enterocytic lineage, the current study raises the possibility that such activity might contribute to gastrointestinal symptoms in infections involving Aeromonas strains which do not express well-established enterotoxins.

Transfer of clindamicyn resistance between Bacteroides fragilis group strains isolated from clinical specimens

Clindamycin resistance was trasferred by a conjugation-like from Bacteroides thetaiotaomicron 52, a multiple antibiotic-resistant strain isolated from clinical specimens, to other Bacteroides species. A possible association between a plasmid detected in the donor strain and clindamycin resistance in discussed

Epidemiology and antimicrobial resistance of B. fragilis group organisms isolated from clinical specimen and human intestinal microbiota

Alguns aspectos epidemiologicos e o perfil de sensibilidade a antimicrobianos de amostras do grupo B. fragilis isoladas de especime clinico e microbiota intestinal humana foram delineados neste estudo. As especies do grupo B. fragilis foram isoladas de 46 (37 por cento) de 124 especimes clinicos, como segue: hemocultura (3), infeccao intra-abdominal (27), abscesso cerebral (2), infeccao de tecido mole (17), seios da face (3), aspirado pleural (9), abscesso pulmonar (3), ferida cirurgica (22), doenca inflamatoria pelvica (22), otite media cronica (9) e diversos (7). Mais da metade destes microorganismos foram isolados de infeccao intra-abdominal e infeccao de tecido mole...

Atividade de hemaglutinante de Bacteroides fragilis como marcador de virulência / Hemagglutination activity of Bacteroides fragilis as a virulence marker

Atividade hemaglutinante (AH) de Bacteroides fragilis foi estudada. Vários padröes de comportamento foram encontrados com eritrócitos de diferentes espécies (humano, cobaio, carneiro) e 4 grupos distintos foram formados. A perda da AH, após tratamento com calor, de algumas cepas demonstrou ter, provavelmente, as adesinas de B. fragilis, uma natureza proteica. Por outro lado, tratamentos com algumas proteases e neuraminidase näo interferiram na AH. Estudos ao microscópio ótico e eletrônico, com as mesmas cepas, sugeriram que as adesinas estejam associadas com proteínas de membrana externa ou com a presença de uma estrutura definida como "microcápsula". Parece improvável o envolvimento de estruturas como cápsula e fimbrias nesta atividade, uma vez que tanto cepas hemaglutinantes como näo hemaglutinantes apresentaram cápsula, e, fimbrias näo foram encontradas em todas as cepas hemaglutinantes. A maior freqüência de isolamento de cepas hemaglutinantes a partir de especimens clínicos (84.2 por cento) do que a partir de flora normal (15.8 por cento), e, a diferença observada na capacidade de induçäo de abscesso sub-cutâneo em camundongos por cepas hemaglutinantes e näo hemaglutinantes sugerem a AH de B. fragilis como um marcador de virulência.

Adherence of bacteroides fragilis strains to a primary cell culture

Foi avaliada a capacidade de aderência de cepas de dBacteroides fragilis a várias linhagens de células de mamíferos. Algumas cepas, definidas como capazes de aglutinar eritrócitos humanso, foram capazes de aderir a células primárias, obtidas de carcaça de cobaio, nas näo às demais células testadas. Apenas uma cepa, näo aglutinante, näo demonstrou qualquer capacidade de aderência às linhagens celulares testadas.