Virulence profiles of enterotoxigenic Escherichia coli isolated from piglets with post-weaning diarrhea and classification according to fecal consistency

Abstract

The aim of this study was to assess the frequency and association of virulence factors of Escherichia (E.) coli isolated from weaned piglets with diarrhea and to correlate it with fecal consistency. A total of 152 rectal swabs were collected from 25-40 day-old piglets with diarrhea, in farms of Southern Brazil. Phenotypical and molecular techniques were used for bacterial isolation, characterization and classification of enterotoxigenic E. coli (ETEC) pathotypes. Statistical analysis was carried out to determine the frequency of virulence factors and virotypes, of fimbriae F4, F5, F6, F18, F41 and toxins LT, STa, STb and STx2e. Out of 456 E. coli isolates, 287 (62.9%) samples showed significant growth of E. coli. Among them, 194 (67.6%) samples showed at least one virulence factor, indicating that ETEC is an important etiological agent of diarrhea in weaned piglets. Higher frequencies were found of fimbria F4 and F18 and enterotoxins LT, STa and STb. Significant association was found to F4, LT, STa and STb; between F18 and STa and STx2e; between F5 and LT, STa and STb. The most frequent virotypes were F18-STa, F4-LT-STa-STb, F4-STa, F4-LT-STb and F18-STa-STx2e. Beta-hemolysis was observed in 47.4% of samples and there was significant association between hemolytic samples and virulence factors F4, F18, STa and STx2e. Regarding fecal consistency, there was significant association of liquid feces and F4 fimbria, STa toxin and virotypes F4-STa and F4-F5-LT-STa-STb. Since there was significant association of ETEC and liquid feces in nursery piglets, it is important to prioritize the sampling of liquid feces for the diagnosis etiologic cause of diarrhea.

Piglet colibacillosis diagnosis based on multiplex polymerase chain reaction and immunohistochemistry of paraffin-embedded tissues

“…Pathogenic strains of ETEC adhere to enterocytes and produce enterotoxins and therefore require the expression of at least one fimbria and one toxin [ 5 ]. The present study revealed that 40% of the analyzed samples presented pathogenic ETEC, similar to previous reports of 54.8% and 50.5% occurrence [ 14 23 ]. However, expression of a toxin gene with no fimbrial gene expression was observed in 13.6% (18/132) of the samples in the present study.…”

“…Although this value was less than the 94.8% and 92% reported by other authors using cultivated bacterial assessment [ 21 25 ], the results obtained through the extraction from paraffin-embedded tissues were similar to the previously reported 77% based on isolated E. coli assessment [ 26 ], and is greater than the 29.2%, 42%, and 62.9% based on multiplex PCR [ 14 17 23 ]. The frequencies of virulence genes observed in the present study were similar to those in previous reports in which the virulence types for F18 and F4 fimbriae and for STaP and STb toxins were most frequent in cultivated bacteria [ 6 14 21 23 25 ]. The occurrence of high frequencies of F18 and F4 fimbrial genes may be explained by the fact that 53% of the samples were from weaning pigs, which is similar to that in a previous study that evaluated post-weaning E. coli isolates via multiplex PCR [ 26 ].…”

“…More than one fimbria was detected in 27.3% of the samples, which is greater than that observed in a previous study of E. coli samples isolated from weaned piglets (6.3%) [ 23 ]. However, 26.5% of the samples in the current study exhibited more than one toxin, which is similar to a 37% occurrence reported previously [ 23 ].…”

“…More than one fimbria was detected in 27.3% of the samples, which is greater than that observed in a previous study of E. coli samples isolated from weaned piglets (6.3%) [ 23 ]. However, 26.5% of the samples in the current study exhibited more than one toxin, which is similar to a 37% occurrence reported previously [ 23 ]. The predominant virulence types identified in the present study (F18-STaP [7.5%], F18-STaP-STb [5.7%], and F4-STaP [3.8%]) were similar to those observed in previous reports: F18-STaP (11.1%), F4-LT-STaP-STb (9.8%), and F4-STaP (7.3%) [ 23 ].…”

Distribution of Genes Encoding Iron Uptake Systems among the Escherichia coli Isolates from Diarrheal Patients of Iran

“…However, among EPEC isolated from children in Brazil, only 25% indicated the ability of hemolysin production [38] that was lower than the rate we obtained here in this study. Additionally, the rate of hemolysin activity in our ETEC isolates was close to the similar isolates from diarrhea patients in Iran and Brazil [35,39]. The high prevalence of hemolysin activity in DEC isolates suggests its role in the increased pathogenicity of these strains.…”