RESUMEN
Shiga toxin-producing Escherichia coli belonging to serotype O26:H11 was isolated from a 2-month-old guanaco with severe watery diarrhea. E. coli colonies carried the stx1 and eae genes, showed localized adherence to HEp-2 cells, and produced enterohemolysin. A serological response to lipopolysaccharide O26 was observed at the onset of diarrhea.
Asunto(s)
Camélidos del Nuevo Mundo , Diarrea/veterinaria , Infecciones por Escherichia coli/veterinaria , Escherichia coli/aislamiento & purificación , Toxina Shiga/biosíntesis , Animales , Adhesión Bacteriana , Línea Celular , Diarrea/microbiología , Escherichia coli/genética , Escherichia coli/metabolismo , Escherichia coli/fisiología , Infecciones por Escherichia coli/microbiología , Heces/microbiología , Humanos , Reacción en Cadena de la Polimerasa , América del SurRESUMEN
Faecal samples from 76 diarrhoeic calves belonging to 36 farms located in the Pampas plain, Argentina, were examined for Shiga toxin-producing Escherichia coli (STEC). A total of 15 STEC strains were isolated from 12 (15.8%) calves which came from six different farms. All stx positive strains assayed by PCR were also positives in the Vero cell cytotoxicity test. The majority (60.0%) of the STEC strains carried the stx(1) gene. Twelve (80.0%) of the STEC isolates which belonged to serotypes O5:H- (n = 4), O26:H11 (n = 4), O26:H- (n = 1), O111:H- (n = 2), and O123:H38 (n = 1) were also enterohaemolysin (EHly) positive and carried the gene encoding for intimin (eae). All the stx positive strains were negative for the bfpA gene. Localized adherence to HEp-2 cells were observed in 83.3% of the eae+ STEC strains. STEC belonging to serotype O5:H- showed atypical biochemical properties, including urease production. Urease was also produced by two strains belonging to serotypes O153:H? and non-typeable, respectively. Resistance to three or more antibiotics was observed in 12 (80.0%) of the STEC isolates. Most of the serotypes of STEC recovered in this survey carried virulence traits that are associated with increased human and bovine pathogenicity. The present study shows that highly virulent STEC strains are being shed by diarrhoeic calves from farms located in a high incidence area of human STEC infections.
Asunto(s)
Antiinfecciosos/farmacología , Enfermedades de los Bovinos/epidemiología , Diarrea/veterinaria , Escherichia coli/efectos de los fármacos , Escherichia coli/aislamiento & purificación , Animales , Animales Recién Nacidos , Argentina/epidemiología , Adhesión Bacteriana , Bovinos , Enfermedades de los Bovinos/etiología , Enfermedades de los Bovinos/microbiología , Cartilla de ADN , ADN Bacteriano/análisis , Diarrea/epidemiología , Farmacorresistencia Bacteriana , Escherichia coli/genética , Escherichia coli/fisiología , Pruebas de Sensibilidad Microbiana , Fenotipo , Reacción en Cadena de la Polimerasa/veterinaria , Toxinas ShigaRESUMEN
CS31A is a K88-related non-fimbrial adhesin first described on Escherichia coli strains isolated from diarrhoeic and septicaemic calves. In this report, CS31A antigen was screened by immunological methods and confirmed by PCR among bovine E. coli isolates. In addition, CS31A-producing strains were characterized with respect to different fimbrial antigens, O-serogroup and other properties related to virulence. Faecal or tissue specimens of 100 diarrhoeic or septicaemic calves and 27 older cattle with different pathologies from 71 outbreaks or individual cases that occurred in Buenos Aires province, Argentina, were examined. CS31A + E. coli strains were isolated from 21 (21.0%) calves from 16 outbreaks or individual cases. No CS31A + E. coli was detected in samples from cattle more than 1 year old. Fimbriae F5, F41, F17a and F17b were not detected among the CS31A-producing strains. Three (14.3%) of the CS31A+ E. coli strains expressed the F17c fimbria. All of the 21 isolates exhibited at least one property of septicaemic strains (resistance to serum, production of aerobactin or colicins) but none of them demonstrated heat-stable enterotoxigenic activity. CS31A + E. coli isolates belonged to 10 serogroups, more commonly O8, O7, O17 and O21. The results obtained here confirm the worldwide distribution of CS31A antigen in bovine E. coli strains. However, CS31A + or CS31A + /F17c + E. coli were less frequently isolated than they were in North hemisphere countries.