Posible papel de Bacteroides fragilis enterotoxigénico en la etiología de la vaginitis infecciosa / Possible role of enterotoxigenic Bacteroides fragilis in the etiology of infectious vaginitis

La vaginitis es un trastorno ginecológico frecuente producido por distintas causas, algunas de las cuales permanecen desconocidas. Bacteroides fragilis es el anaerobio más importante en bacteriología clínica. Algunas cepas son enterotoxigénicas y se asocian con síndromes intestinales y extraintestinales. Recientemente han sido aisladas de pacientes con vaginitis. En este trabajo se planteó investigar la posible asociación de B. fragilis enterotoxigénico con la vaginitis infecciosa. Fueron procesadas 265 muestras de exudado vaginal. 202 de mujeres sintomáticas y 63 mujeres sanas. La identificación de los microorganismos se realizó por métodos convencionales. En 31,2% de las pacientes sintomáticas se identificaron: Gardnerella vaginalis, Candida albicans, Mobiluncus, Mycoplasma hominis, Ureaplasma urealyticum y Streptococcus agalactiae. En 27 pacientes sintomáticas y en 5 mujeres sanas se identificó B. fragilis. Estas cepas fueron cultivadas en medio líquido e incubadas durante 48 h a 36° C en anaerobiosis. La toxicidad en los sobrenadantes se ensayó en células HT-29. 18 cepas de B. fragilis aisladas de pacientes sintomáticas fueron enterotoxigénicas, ya que indujeron alteraciones en la monocapa celular y en las células. No se identificó en mujeres sanas (P<0,05). 77,7% de las cepas de B. fragilis enterotoxigénicas no se encontraron asociadas con otros patógenos específicos. Este hecho sugiere que pudiera ser un agente causante de vaginitis, ya que el efecto de la enterotoxina sobre la E-cadherina del epitelio vaginal podría facilitar la invasión y su posible papel patógeno en la vagina. Esta es la primera investigación que asocia a Bacteroides fragilis enterotoxigénico como posible causa de vaginitis infecciosa.

Vaginitis is a common gynecologic disorder. It is due to several causes, some even unknown. Bacteroides fragilis is the most important anaerobe in clinical bacteriology, some strains of this group are notable for being enterotoxigenic and they have been associated with intestinal and extraintestinal syndromes. They have recently been isolated from patients with vaginitis. The purpose of this study was to investigate a possible association of enterotoxigenic B. fragilis with infectious vaginitis. 265 samples of vaginal exudate were processed, 202 from symptomatic patients and 63 healthy women. The identification of the microorganisms was carried out by conventional methods. In 31.2% of symptomatic patients were identified: Gardnerella vaginalis, Mobiluncus, Candida albicans, Mycoplasma hominis, Ureaplasma urealyticum and Streptococcus agalactiae. B. fragilis was identified in 27 symptomatic patients and 5 healthy women. These strains were cultivated in liquid medium and incubated during 48 h at 36°C in anaerobe chambers. Supernatant activity was assayed in HT-29 cells. Eighteen B. fragilis strains isolated from symptomatic patients were enterotoxigenic, because induced alterations in target cell morphology. It was not identified in healthy women (P<0.05). 77.7% of enterotoxigenic B. fragilis strains were not associated with other specific pathogens. This fact suggests that enterotoxigenic B. fragilis could be a cause for vaginitis. The effect of enterotoxin on E-cadherin of vaginal epithelium could facilitate invasion and its possible pathogenic role in the vagina. This is the first report that associates enterotoxigenic Bacteroides fragilis as a possible cause of infectious vaginitis.

Enterotoxigenic and nontoxigenic Bacteroides fragilis strains isolated in Brazil

The presence of enterotoxigenic Bacteroides fragilis and nontoxigenic B. fragilis (NTBF) among 109 strains isolated from 1980-2008 in Brazil were investigated by PCR. One strain, representing 0.9 percent of the total analyzed strains, harbored the bft gene which was identified as bft-1 isoform based on PCR-RFLP and sequencing. Forty-nine strains (44.9 percent) exhibited the NTBF pattern III which possesses the flanking region required for pathogenicity island acquisition in which the bftgene is codified. These data reinforce the potential of B. fragilis as an emerging enteropathogen in our country.

Effect of bacterial association on virulence of Entamoeba histolytica to baby hamster kidney cell monolayers.

Axenic E. histolytica trophozoite strain NIH:200 and HMI:IMSS when co-associated with aerobic bacteria Escherichia coli strain K12 and serotype 056 showed marked increase in virulence as observed by destruction of baby hamster kidney (BHK) monolayers. However, when incubated with anaerobic bacterial strains Clostridium perfringens and Bacteroides fragilis virulence remained unaltered. Further, adherence of E. histolytica to BHK monolayer was found to be mediated by N-acetyl-D-galactosamine.

Liver abscess caused by concomitant infection with entamoeba histolytica and metronidazole-resistant bacteroides fragilis

A case of liver abscess caused by concomitant infection with Entamoeba histolytica and Bacteroides fragilis is described. The strain of B. fragilis isolated was found to be resistant to metronidazole. The rarity of such concomitant infection and the importance of carrying out proper anaerobic cultures and growing concerns about the evolution of metronidazole-resistant Bacteroides are discussed in this case report

Ssceptibilidade a antimicrobianos em três meios de cultivo, de cepas do grupo Bacteroides fragilis isoladas de humanos e de micos Callithrix penicillata / Antimicrobial susceptibility in three growth media of isolates of the bacteroides fragilis group abtained fron humans and callithris penicillata marmosets

A Susceptibilidade de 104 cepas do grupo B. fragilis isolados de humanos (52) e de micos C. penicillata (52) para clindamicina, metronidazol, penicillina G e bicloreto de mercúrio, foi determinada em três diferentes meios de cultivos, pelos métodos de diluiçäo em ágar e diluiçäo em caldo. O ágar infuso cérebro coraçäo, suplementado com hemina ou sangue, foi usado para o primeiro método e, o caldo infuso cérebro coraçäo para o último. Nos meios sólidos, somente 10 (por cento) dos isolados humanose, nenhum dos isolados de micos foram resistentes para clindamicina. O metronidazol foi o antimicrobiano mais eficaz contra todos os microrganismos testados nos três meios apresentaram níveis elevados de resistência para penicilina G em todos os meios testados. O bicloreto de mecúrio apresentou menor atividade em ágar sangue, apresentando faixas de CIMs de 2 a 128 ug/ml.

Virulence factors in Bacteroides fragilis group.

Attempts were made to study the virulence factors in some strains of B. fragilis group in the rat model. Subcutaneous wound abscesses could be produced by 10(9) CFU/ml of live cells of all the five species of B. fragilis group tested. For determination of virulence factor cellular components (capsular polysaccharide and lipopolysaccharide) of B. fragilis were separated using gel filtration technique and injected in rats. Abscesses could be produced only by capsular polysaccharide fraction suggesting it to be the virulence factor. Studies with transmission electron microscope showed presence of capsular polysaccharide in B. fragilis and B. thetaiotaomicron, it was doubtful in B. distasonis and absent in B. ovatus and B. vulgatus. This suggested that virulence factors other than capsular polysaccharide may be responsible for pyogenic lesions in the noncapsulated species of B. fragilis group. The abscess could not be produced by 10(9) CFU/ml of heat killed cells of non-capsulated B. ovatus and B. vulgatus indicating that in live bacteria, a heat labile factor was responsible for the development of abscess.

Factores de patogenia de Bacteroides fragilis / Factors of Bacteroides fragilis pathogenicity

El colon humano contiene una flora microbiana compleja y numerosa. Aunque existen por lo menos 400 especies distintas de bacterias, normalmente 70% de aislamientos corresponde sólo a cuatro géneros: dos anaerobios y dos aerobios uno de éstos es bacteroides, con 30% del total, y las especies más numerosas (10*9 -10*10 microrganismos/g de peso seco de heces) de éste son: B. vulgatus, B. distasonis, B. thetaiotaomicron y, en menor cantidad, B. ovatus y B. fragilis (0.5% del total). Es indudable que Bacteroides desempeña un papel importante en el ecosistema del colon. Asimismo algunas especies com B. fragilis y, en menor grado, otras del mismo género, como B. distasonis, B. thetaiotaomicron y B. ovatus pueden causar, en especial, septicemias y abscesos cerebrales, pulmonares o abdominales