CIVETAN   23983
CENTRO DE INVESTIGACION VETERINARIA DE TANDIL
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
O157:H7 VEROCYTOTOXIGENIC Escherichia coli FROM THE PAMPAN REGION: PATHOGENICITY ISLANDS AND EFFECTORS GENES
Autor/es:
GONZALEZ, J.; CADONA, J. S.; SANSO, A.M.; BUSTAMANTE, A.V.
Lugar:
Mar del Plata
Reunión:
Congreso; X Congreso Argentino de Microbiología General SAMIGE; 2014
Institución organizadora:
SAMIGE
Resumen:
Verocytotoxigenic Escherichia coli (VTEC) is one of the pathogens most commonly transmitted to humans through food, the cattle is the main reservoir. E. coli O157:H7 is the serotype most frequently associated whit patients whit hemolytic uremic syndrome (HUS). Subtyping scheme using single nucleotide polymorphisms (SNPs) classifies VTEC O157:H7 isolates in 9 evolutionary clades, the clade 8 is the most virulent. On the other hand, several virulence determinants associated with the pathogenesis of infection with VTEC are encoded in chromosomal pathogenicity islands (PAI). PAIs contain "non-LEE-encoded effector" (nle) genes, that encode translocated substrates of type III secretion system. Some of these effectors contribute to the colonization and persistence of VTEC in cattle and interfere with the inflammatory response in human following infection. The aim was detect which O157: H7 isolates belonging to clade 8 and analyze the distribution of nle genes encoded in different PAIs. 33 isolates were analyzed, obtained from cattle, humans and food, mainly from the pampan region. They had been previously characterized as positive for virulence genes eae and vtx2. The identification of the strains belonging to clade 8 is performed by detecting a SNP located in the rhsA gene. For this was PCR amplified a fragment of this gene and the amplicon obtained was analyzed by RFLP, by cutting with restriction enzymes HaeII and Sau961. In relation to the nle genes were amplified genes encoded in genomic islands O-I 71, nleA, nleH1-2, nleF, nleG, nleG2-1 y nleG9, O-I 122, nleB, nleE y ent/esp L2, O-I 36, nleB2, nleC, nleH1-1 y nleD, O-I 57, nleG2-3, nleG5-2 y nleG6-2. PCR products were visualized in agarose gels stained with SYBR Safe. All isolates belonged to clade 8. Moreover, in relation to nle genes, isolates were grouped into six profiles. 61% of isolates were positive for all nle genes analyzed, while the remaining, except two, showed incomplete O-I 71, particularly lacked the nleF gene. No source-specific profiles were observed. According to these studies, strains O157:H7 circulating in the pampan region are a homogeneous group in relation to the clades assignment. The belonging of the isolates studied to clade 8, which is associated with hypervirulent strains, and the high prevalence nle genes, genetic determinants of a variety of functions that enable the pathogen to persist in the host and cause disease, would assign to most VTEC strains of the pampan region a high risk to public health.