Virulence repertoire of Shiga toxin-producing Escherichia coli (STEC) and enterotoxigenic Escherichia coli (ETEC) from diarrhoeic lambs of Arunachal Pradesh, India

Abstract

A total of 107 faecal samples were collected from diarrhoeic lambs of high altitude terrains (2,000 to 5,000 m above the mean sea level) of Tawang and West Kameng districts of Arunachal Pradesh, India. Total 234 Escherichia coli were isolated and further subjected to PCR for the study of virulence repertoire characteristics of Shiga toxin-producing E. coli (STEC) and enterotoxigenic E. coli (ETEC). Out of the 234 isolated E. coli, 32% were found positive for STEC, and 9% were carrying virulence gene for ETEC. The isolated STEC serogroups were O159, O127, O120, O113, O60, O30, O25, O8 and O2. Of all the 74 STEC strains, PCR showed that 18% isolates carried stx ( 1 ), 26% possessed stx ( 2 ) and 47% produced positive amplicon for both. Other virulent attributes like intimin (eaeA), enterohaemolysin (ehxA) and STEC auto-agglutinating adhesin (saa) were present in 18%, 43% and 44% of the isolates, respectively. The isolated ETEC serogroups were O172, O170, O159, O146, O127, O120, O113, O86, O75, O60, O30, O25, O8, O2, OR and OUT. Of the 22 ETEC-positive isolates, 23%, 18% and 4.5% possessed the gene only for LT, STa and STb, respectively, whereas 54% carried genes for both LT and STb. Some serogroups of E. coli like O159, O127, O120, O113, O60, O30, O25, O8 and O2 possessed genes for both Shiga toxin and enterotoxin. This study is the first report of ETEC isolation from diarrhoeic lambs in India. The moderately high proportion of STEC and ETEC in the diarrhoeic lambs implicated that these animals are important reservoir of STEC and ETEC. This is really a grave concern for the 'brokpas' and nomads (shepherds) who share a close relationship with this animals for their livelihood. This study also indicates that ETEC may be a major cause for frequent diarrhoeal episodes in lambs of this region.

Identification, characterization and molecular epidemiology of Escherichia coli isolated from lamb and goat kids with diarrhoea

“…In our study, the stx2 gene was more prevalent than the stx1 gene. This result contrasts with reports which showed that STEC strains isolated from small ruminants harbour the stx1 gene more frequently (B h a t et al 2008; Wa n i et al 2009) but agrees with Bandyopadhyay et al (2011), who also found a predominance of the stx2 gene in STEC strains isolated from small ruminant with diarrhoea in India. Jenkins et al (2002) reported that among healthy cattle, prevalence of VTEC strains may vary depending on the season.…”

“…in small ruminants from Turkey (Gokce et al 2010) and other states (Wani et al 2004), however, research on classification of enterovirulent E. coli and its virulence genes is limited. Recent studies have reported (Wani et al 2003;Bhat et al 2008;Bandyopadhyay et al 2011), the existence of at least one virulence gene in 41%, 36.7%, and 32.6% of E. coli isolates, respectively. In our study we found at least one virulence gene for EHEC or STEC, EPEC, ETEC, EIEC, and EAEC among 36.4% of the isolates.…”

“…This rate was higher than the findings reported by Wa n i et al (2003) from India (6%), and was the same (17.8%) to the findings of B h a t et al (2008). However, the latest report from India showed that the STEC rate has increased to 32% (Bandyopadhyay et al 2011). This may be an indication that if necessary precautions are not taken, pathogenic E. coli ratio may increase also in our country.…”

“…The latest study from India showed that 9% of the faecal isolates from lambs were ETEC. In India, among 22 ETEC positive isolates, five (23%) possessed lt genes, and another five possessed st genes (Bandyopadhyay et al 2011). In our study, recovery of lt was in high frequency (28.2%) but st was in low frequency (2.6%).…”

Molecular screening of bovine raw milk for the presence of Shiga toxin-producing Escherichia coli (STEC) on dairy farms

“…Environmental contaminations and poor herd and milking managements are important causes of reduction of milk quality. The high frequency of stx2 in faecal samples collected from buffalo, cows, and goats described elsewhere (Islam et al, 2008;Stephan et al, 2008;Bandyopadhyay et al, 2011Bandyopadhyay et al, , 2012 might explain the prevalence of stx2 positive STEC in raw milk. In humans, epidemiologic data suggest that E. coli O157 strains that express stx2 are more important than stx1 in the development of HUS, and that strains that express stx2 alone are more likely to be associated with the progression to HUS than strains that produce both stx1 and stx2 (Griffin, 1995) In this study, the presence of STEC harboring the genes stx1 and stx2 in raw milk sample was detected.…”