RESUMEN
Streptococcus suis infection is considered to be a major problem in the swine industry worldwide. Most virulent Canadian isolates of S. suis serotype 2 do not produce the known virulence markers for this pathogen. PCR-based subtraction hybridization was adapted to isolate unique DNA sequences which were specific to virulent strains of S. suis isolated in Canada. Analysis of some subtracted DNA clones revealed significant homology with bacteriophages of gram-positive bacteria. An inducible phage (named Ss1) was observed in S. suis following the incubation of the virulent strain 89-999 with mitomycin C. Phage Ss1 has a long noncontractile tail and a small isometric nucleocapsid and is a member of the Siphoviridae family. Ss1 phage DNA appears to be present in most Canadian S. suis strains tested in this study, which were isolated from diseased pigs or had proven virulence in mouse or pig models. To our knowledge, this is the first report of the isolation of a phage in S. suis.
Asunto(s)
Fagos de Streptococcus/aislamiento & purificación , Streptococcus suis/patogenicidad , Streptococcus suis/virología , Animales , Canadá , ADN Bacteriano/genética , ADN Bacteriano/aislamiento & purificación , ADN Viral/genética , ADN Viral/aislamiento & purificación , Datos de Secuencia Molecular , Serotipificación , Infecciones Estreptocócicas/microbiología , Infecciones Estreptocócicas/veterinaria , Fagos de Streptococcus/genética , Streptococcus suis/clasificación , Streptococcus suis/genética , Sus scrofa , Enfermedades de los Porcinos/microbiología , VirulenciaRESUMEN
Escherichia coli O115:F165 strains are associated with septicaemia in young pigs and possess at least two types of fimbriae. F165(1) fimbriae belong to the P fimbrial family and F165(2) fimbriae belong to the S fimbrial family. Regulatory regions of foo (F165(1)) and fot (F165(2)) fimbrial gene clusters from wild-type strain 4787 were sequenced and characterised. Expression of F165(1) and F165(2) fimbrial genes was analysed by using lacZ and/or luxAB as reporter genes under the control of the native fimbrial promoters. Differential expression of fimbrial genes was observed. Global regulatory mechanisms such as catabolite repression, leucine-responsive regulatory protein (Lrp), methylation and DNA supercoiling were demonstrated to influence foo and fot expression. foo and fot expression was optimal at 37 degrees C and under aerobic conditions. Expression of foo was higher on minimal medium, whereas fot expression was higher on complex Luria-Bertani medium. This could reflect an in vivo differential expression.
Asunto(s)
Antígenos Bacterianos , Proteínas Bacterianas/genética , Proteínas de Escherichia coli , Escherichia coli/genética , Proteínas Fimbrias , Fimbrias Bacterianas/genética , Regulación Bacteriana de la Expresión Génica , Genes Reguladores , Secuencia de Aminoácidos , Animales , Bacteriemia/microbiología , Bacteriemia/veterinaria , Proteínas Bacterianas/metabolismo , Secuencia de Bases , ADN Superhelicoidal , Escherichia coli/patogenicidad , Infecciones por Escherichia coli/microbiología , Infecciones por Escherichia coli/veterinaria , Genes Reporteros , Datos de Secuencia Molecular , Operón , Regiones Promotoras Genéticas , Porcinos , Enfermedades de los Porcinos/microbiología , VirulenciaRESUMEN
In the present study, attaching and effacing Escherichia coli (AEEC) O45 isolates from post-weaning pigs with diarrhoea were examined for the presence of the LEE (locus of enterocyte effacement) using various DNA probes derived from the LEE of human enteropathogenic E. coli (EPEC) strain E2348/69. The LEE fragment was conserved among the eae -positive pig isolates. The attaching and effacing activity of PEPEC (pig EPEC) O45 isolates is highly correlated with the presence of the LEE. Nevertheless, for some PEPEC isolates, the insertion site of the LEE is different or has diverged during evolution. The presence of the LEE fragment in PEPEC isolates provides further evidence that the LEE region is conserved among AEEC of different animal origins. In addition, the nucleotide sequence of the region containing the eae gene and esp genes of a pig AEEC isolate, strain 1390, was determined. Among examined Eae proteins, Eae of strain 1390 showed the highest similarity with Eae belonging to the beta intimin group such as the Eae of rabbit AEEC. Moreover, all pig strains that produced attaching and effacing lesions in piglets and pig ileal explants belonged to the beta intimin group. The deduced amino acid sequences of the EspA, EspB and EspD proteins of strain 1390 showed particularly strong homology to those of AEEC strains presenting a beta intimin allele. Thus, pig AEEC possess the LEE sequences, and for the strain 1390, sequences of the eae and esp regions are related to those of other AEEC, in particular, strains presenting a beta intimin allele, such as the rabbit AEEC.