Characterization of virulence genes in Escherichia coli strains isolated from pre-weaned calves in the Republic of Korea

Abstract

Background Escherichia coli is an important cause of diarrhea in calves and its diarrheagenic properties are related to presence of certain virulence genes. In this study, the prevalence of virulence genes F5 , F17 , F41 , sta , stx1 , stx2 , eae , and saa in E. coli isolated from pre-weaned calves presenting with (n= 329) or without diarrhea (n= 360) was explored using multiplex polymerase chain reaction. We also evaluated the association between detection of E. coli and the presence of diarrhea. Results Escherichia coli was detected in 56.3% (388/689) of the fecal samples and showed the highest prevalence (66.5%) in 21–40-day-old calves and the lowest (46.3%) among those that were 1–20 days old. The prevalence of the enterotoxigenic E. coli (ETEC) and Shiga toxin-producing E. coli (STEC) pathotypes was detected in 73.9% and 15.9%, respectively. The results showed no association between diarrhea and the presence of E. coli in general, ETEC or STEC. The F17 gene was the most frequently detected virulence factor in E. coli of calves of all ages regardless of diarrhea. Interestingly, the results show that the calves aged 41–60 days with F17 -positive E. coli are at a higher risk for production of Shiga toxin ( Stx1 ; 95% confidence intervals: 1.86–31.95; P = 0.005) compared to calves aged 1–20 days; no association between this finding and diarrhea was observed among the calves of this age group. Moreover, the virulence genes associated with the ETEC and STEC strains were not significantly associated with pathogenicity in this study cohort. Conclusions These results suggest that while the incidence of E. coli is age-related, there was no relationship linking E. coli virulence genes to calf age and diarrhea. Furthermore, the present study demonstrated that detection of E. coli strains either with or without virulence factors was not associated with diarrhea in pre-weaned calves.

Occurrence of Escherichia coli Pathotypes in Diarrheic Calves in a Low-Income Setting

“…In our study, stx1, stx2, and st VGs were more frequent than eae , hly , aatA , and lt . In another report, however, stx1 and eae were found at a higher rate than st and stx2 [ 35 ]. In the isolates where virulence genes were found in combination, stx2-st , sx1-st, stx1-stx2 , and lt-st represented the dominant combinations.…”

“…Virulence genes are extensively used in determining E. coli pathotypes and have been found in multiple combinations [ 34 , 35 ]. In our study, stx1, stx2, and st VGs were more frequent than eae , hly , aatA , and lt .…”

“…These inconsistent results indicate that stx1, stx2 , and stx1-stx2 play a role in causing diarrhea among calves. In addition, STEC was reported in 34% of non-diarrheic water buffalo calves in Brazil [ 48 ] and 5.5% of healthy cattle calves in Korea [ 35 ]. This is in line with previous suggestions that animals are important reservoirs of STEC [ 35 , 49 ].…”

Sandwich-Based Immunosensor for Dual-Mode Detection of Pathogenic F17–Positive Escherichia coli Strains

“…In fact, we recently found that camels affected by diarrhea expressed a higher prevalence of fimbriae F17 than clinically healthy camels (46.5% vs. 14.5%) [ 9 ]. Several other studies also reported the association of this adhesin with diarrhea and/or sepsis observed in newborn alpacas [ 10 ], calves [ 11 , 12 , 13 , 14 ], lambs [ 5 , 15 ] and horses [ 16 ]. All this justifies the growing interest in this virulence factor as a therapeutic target and for the design of diagnostic tools such as ELISA and biosensing platforms.…”

Non-Coding Transcriptome Provides Novel Insights into the Escherichia coli F17 Susceptibility of Sheep Lamb

“…The fimbrial adhesins, F5 [9], F17 [10], F18 [11], and F41 [12] are associated with ETEC mainly in young animals. E. coli F17, one of the main subtypes of ETEC, has been reported as the major pathogen associated with ETEC-related diarrhea worldwide, responsible for high morbidity and mortality [13][14][15]. The growing prevalence of E. coli F17 has renewed the sense of urgency for E. coli F17 research.…”