Prevalence of O-serogroups, virulence genes, and F18 antigenic variants in Escherichia coli isolated from weaned piglets with diarrhea in Korea during 2008–2016

To diagnose colibacillosis, detection of O-serogroups and virulence genes has been recommended worldwide. The prevalence of virulence factors can fluctuate over time. The objectives of this study were to determine the prevalence of O-serogroups, virulence genes, and F18 subtypes among pathogenic Escherichia coli isolated from weaned piglets with diarrhea in Korea. Between 2008 and 2016, 362 E. coli were isolated from weaned piglets with diarrhea. Hemolysis was determined in blood agar, and O-serogroups were identified using the slide agglutination technique. The genes for the toxins and fimbriae were amplified by polymerase chain reaction (PCR). Real-time PCR was conducted to discriminate between F18 subtypes. Although the most prevalent serogroup was O149 (11.3%) in the last 9 years, O139 (19.1%) became the most prevalent in recent years (2015–2016). The most predominant pathotype was enterotoxigenic E. coli (61.3%). The frequencies of Shiga-like toxin-producing E. coli (STEC) (23.4%), O139 (19.1%), Stx2e (35.1%), and F18ab (48.7%) increased over the most recent years. Although enterotoxigenic E. coli was the most predominant pathotype, the frequencies of O139, Stx2e, STEC, and F18ab have increased in recent years. These results demonstrate that there have been temporal changes in the predominant O-serogroups and virulence genes over the last decade in Korea. These findings can be practicable for use in epidemiology and control measures for enteric colibacillosis in Korean piggeries.

Caracterización genotipica de aislamientos de Escherichia coli obtenidos de cerdos con diarrea posdestete y enfermedad de los edemas / Genotypic characterization of toxigenic Escherichia coli isolated from pigs with postweaning diarrhea (PWD) and edema disease (ED)

El objetivo del trabajo fue caracterizar mediante PCR 47 aislamientos de Escheríchia coli recuperados de 32 cerdos con diagnóstico clínico de diarrea posdestete (DPD) y de 3 cerdos con enfermedad de los edemas (ED). Sobre 44 aislamientos provenientes de cerdos con DPD, 42 (95,5 %) fueron caracterizados como E. coli enterotoxigénicos (ETEC) y 2 (4,5 %) como E. coli productores de toxina Shiga (STEC). Catorce aislamientos de ETEC (33,3 %) fueron positivos para los genes estl/estlI/fedA. El genotipo más complejo fue eltA/estll/east1/faeG/aidA. Los aislamientos provenientes de cerdos con ED se clasificaron como STEC porcinos y fueron portadores de stxJaidA. Once aislamientos (25 %) fueron portadores del gen que codifica la expresión de la adhesina AIDA-I. Sin embargo, en ningún aislamiento se detectaron los genes que codifican la expresión de las adhesinas F5, F6, F41, de intimina y de "Paa". La prevención de la DPD y de la ED podría realizarse mediante el desarrollo de vacunas que generen anticuerpos contra las adhesinas de las cepas de E. coli prevalentes en la Argentina.

The purpose of this work was to characterize 47 Escherichia coli strains isolated from 32 pigs diagnosed with postweaning diarrhea and tree pigs with edema disease by PCR. Forty two (95.5 %) of the strains isolated from diarrheic pigs were characterized as enterotoxigenic E. coli (ETEC) and 2 (4.5 %) as Shiga toxin-producing E. coli (STEC). Fourteen (33.3 %) ETEC strains were positive for est/estll/fedA genes. The most complex genotype was eltA/estl/faeG/aidA. Strains isolated from pigs with ED were classified as porcine STEC and were stxjaidA carriers. Eleven (25 %) strains carried the gene encoding adhesln protein AIDA-I. However, genes coding for F5, F6, F41, intimin and Paa were not detected. The development of vaccines generating antibodies against prevalent E. coli adhesins in Argentina could be useful for the prevention of PWD and ED.