RESUMEN
Escherichia coli O157:H7 causes food and waterborne enteric infections that can result in hemorrhagic colitis and life-threatening hemolytic uremic syndrome. Intimate adherence of the bacteria to intestinal epithelial cells is mediated by intimin, but E. coli O157:H7 also possess several other putative adhesins, including curli and two operons that encode long polar fimbriae (Lpf). To assess the importance of Lpf for intestinal colonization, we performed competition experiments between E. coli O157:H7 and an isogenic ΔlpfA1 ΔlpfA2 double mutant in the infant rabbit model. The mutant was outcompeted in the ileum, cecum, and midcolon, suggesting that Lpf contributes to intestinal colonization. In contrast, the ΔlpfA1 ΔlpfA2 mutant showed increased adherence to colonic epithelial cells in vitro. Transmission electron microscopy revealed curli-like structures on the surface of the ΔlpfA1 ΔlpfA2 mutant, and the presence of curli was confirmed by Congo red binding, immunogold-labeling electron microscopy, immunoblotting, and quantitative real-time reverse transcription-PCR (qRT-PCR) measuring csgA expression. However, deletion of csgA, which encodes the major curli subunit, does not appear to affect intestinal colonization. In addition to suggesting that Lpf can contribute to EHEC intestinal colonization, our observations indicate that the regulatory pathways governing the expression of Lpf and curli are interdependent.
Asunto(s)
Adhesinas Bacterianas/metabolismo , Adhesión Bacteriana , Proteínas Bacterianas/metabolismo , Escherichia coli O157/patogenicidad , Proteínas de Escherichia coli/metabolismo , Proteínas Fimbrias/metabolismo , Fimbrias Bacterianas/metabolismo , Adhesinas Bacterianas/genética , Adhesinas Bacterianas/ultraestructura , Animales , Animales Recién Nacidos , Proteínas Bacterianas/genética , Ciego/microbiología , Línea Celular , Extensiones de la Superficie Celular/ultraestructura , Colon/microbiología , Células Epiteliales/microbiología , Escherichia coli O157/genética , Escherichia coli O157/ultraestructura , Proteínas de Escherichia coli/genética , Proteínas Fimbrias/genética , Fimbrias Bacterianas/genética , Fimbrias Bacterianas/ultraestructura , Eliminación de Gen , Perfilación de la Expresión Génica , Humanos , Íleon/microbiología , ConejosRESUMEN
Strawberry disease (SD) in the USA is a skin disorder of unknown etiology that occurs in rainbow trout Oncorhynchus mykiss and is characterized by bright red inflammatory lesions. To identify a candidate bacterial agent responsible for SD, we constructed 16S rDNA libraries from 7 SD lesion samples and 2 apparently healthy skin samples from SD-affected fish. A 16S rDNA sequence highly similar to members of the order Rickettsiales was present in 3 lesion libraries at 1%, 32% and 54% prevalence, but this sequence was not found in either healthy tissue library. Based on phylogenetic analysis, this Rickettsia-like organism (RLO) sequence is most closely related to 16S rDNA sequences of bacteria that may form a novel lineage within the Rickettsiales. We used nested PCR assays to screen 25 SD-affected fish for RLO or Flavobacterium psychrophilum DNA. Sixteen lesion samples were positive for the RLO sequence and 4 of the matched healthy samples were positive resulting in a significant association between SD lesions and presence of RLO DNA. While F. psychrophilum is reportedly associated with 'cold water strawberry disease' in the UK, we found no significant association between SD lesions and the presence of F. psychrophilum DNA. The statistical association between SD lesions and presence of RLO DNA is not proof of etiology, but these data suggest that RLO may play a role in SD in southern Idaho, USA.
Asunto(s)
ADN Bacteriano/aislamiento & purificación , Enfermedades de los Peces/microbiología , Oncorhynchus mykiss , Rickettsiaceae/aislamiento & purificación , Enfermedades de la Piel/veterinaria , Animales , ADN Bacteriano/genética , Enfermedades de los Peces/epidemiología , Idaho/epidemiología , Filogenia , Rickettsiaceae/genética , Enfermedades de la Piel/microbiologíaRESUMEN
Shiga toxin-producing Escherichia coli (STEC) serotypes, particularly E. coli O157:H7, possess a variety of fimbrial and afimbrial adhesins which have emerged as important contributors to intestinal colonization. E. coli O157:H7 possesses two chromosomal operons encoding long polar fimbriae (Lpf), which have been found to influence adherence in vitro and colonization in vivo. In a recent Infection and Immunity paper, we further explored the role of Lpf in E. coli O157:H7 intestinal colonization by using the infant rabbit model of STEC infection. We found that an E. coli O157:H7 Lpf-deficient mutant was outcompeted in the rabbit intestine by its parental strain, which may suggest that Lpf contributes to colonization. In contrast, the Lpf-deficient mutant showed an increased adherence to cultured intestinal epithelial cells, and we discovered that this strain overexpressed curli fibers. In this addendum article, we provide a continued perspective on the predicted roles of Lpf and curli, both in vivo and in vitro.