Characterization of Escherichia coli virulence genes, pathotypes and antibiotic resistance properties in diarrheic calves in Iran

Abstract

BackgroundCalf diarrhea is a major economic concern in bovine industry all around the world. This study was carried out in order to investigate distribution of virulence genes, pathotypes, serogroups and antibiotic resistance properties of Escherichia coli isolated from diarrheic calves.ResultsTotally, 76.45% of 824 diarrheic fecal samples collected from Isfahan, Chaharmahal, Fars and Khuzestan provinces, Iran were positive for E. coli and all of them were also positive for cnf2, hlyA, cdtIII, f17c, lt, st, stx1, eae, ehly, stx2 and cnf1 virulence genes. Chaharmahal had the highest prevalence of STEC (84.61%), while Isfahan had the lowest (71.95%). E. coli serogroups had the highest frequency in 1–7 days old calves and winter season. Distribution of ETEC, EHEC, AEEC and NTEC pathotypes among E. coli isolates were 28.41%, 5.07%, 29.52% and 3.49%, respectively. Statistical analyses were significant for presence of bacteria between various seasons and ages. All isolates had the high resistance to penicillin (100%), streptomycin (98.25%) and tetracycline (98.09%) antibiotics. The most commonly detected resistance genes were aadA1, sul1, aac[3]-IV, CITM, and dfrA1. The most prevalent serogroup among STEC was O26.ConclusionsOur findings should raise awareness about antibiotic resistance in diarrheic calves in Iran. Clinicians should exercise caution when prescribing antibiotics.

Detection of virulence and antimicrobial resistance genes in Escherichia coli isolates from diarrhoiec dogs in Iran

“…In this study, isolation of 33 (47.1%) E. coli strains from 70 diarrhoeic dogs suggested the involvement of E. coli in a sizeable percentage of canine diarrhoea in Iran. The fact that virulence genes were detected in the isolates investigated indicates that they were pathogenic E. coli strains (Bentancor et al 2007, Shahrani et al 2014. Although the serotypes of the isolates in this study were not determined, they could belong to the serogroups capable of causing zoonotic infections (Morato et al 2009, de Almeida et al 2012, Tramuta et al 2014.…”

“…It is noteworthy that 13 (92.8%) of the 14 isolates examined haboured stx gene. The stx genes encode shiga-like toxin (stx) also called verocytotoxin/verotoxin, a putative virulent factor involved in the pathogenicity of STEC also known as verocytotoxin-producing E. coli (VTEC) and EHEC strains (Paton and Paton 1998, Goldwater et al 2012, Nguyen and Speradio 2012, Shahrani et al 2014. The stx inhibits protein synthesis and allows invasion of the intestinal mucosa similar to what is observed in human shigellosis (Nguyen and Speradio 2012).…”

“…In the present study, detection of stx and eae in 7 (50%) of the investigated isolates enabled their placement in the EHEC group (Bentancor et al 2007, Aslani et al 2008, Goldwater and Bettelheim 2012, Nguyen and Speradio 2012, Shahrani et al 2014, Ali and Metwaly 2015. The eae gene encodes intimin which enables adhesion of the E. coli isolates to the intestinal epithelial cells resulting in the classical histopathological attaching and effacing (A/E) lesions (Nataro and Kaper 2003, Goldwater and Bettelheim 2012, Shahrani et al 2014.…”

“…Diarrhoeagenic E. coli isolate may belong to the enteroinvasive E. coli (EIEC), enterohaemorrhagic E. coli (EHEC), enteropathogenic E. coli (EPEC), entroaggregative E. coli (EAEC), necrotoxic E. coli (NTEC), enterotoxigenic/shiga-like toxin producing E. coli (STEC) or diffusely adherent E. coli (DAEC) strain/ pathotypes, depending on the type of virulent factor(s) elaborated and the type of lesion produced (Bien et al 2011, De Rycke et al 1999, Puno-Sarmiento et al 2013, Salvadoris et al 2003. Nevertheless, canine diarrhoea may not primarily be caused by E. coli, although pathogenic strains of E. coli has been widely incriminated in cases of diarrhoea in humans and animals (Aslani et al 2008, Salvadoris et al 2003, Shahrani et al 2014. In many clinical conditions of dogs such as canine distemper, parvoviral enteritis, coronavirus infection, helminthosis, etc and a myriad of non-infectious and toxic conditions, the integrity of intestinal mucosa is altered resulting in enteritis and diarrhoea (Hammermueler et al 1995, Torkan et al 2015.…”

“…In these conditions, secondary opportunistic infections by pathogenic E. coli following immune depression and their subsequent discharge in diarrhoeic faeces may occur. Diarrhoeagenic E. coli strains have been reported to harbour genes which encode virulent factors responsible for their pathogenicity (Aslani et al 2008, Bien et al 2011, Shahrani et al 2014. Virulent factors often possessed by pathogenic E. coli strains and used for their classification into pathotypes include: Shiga-like/Shiga toxin (stx) encoded by Shiga toxinogenic (stx) genes 1 and 2 (stx1 and stx2), cytotoxic necrotizing factor (cnf) encoded by cytotoxic necrotizing factor genes 1 and 2 (cnf1 and cnf2), and intimin encoded by E. coli attaching and effacing (eae) gene (De Rycke et al 1999, Landraud et al 2000, Salvadoris et al 2003, Bentancor et al 2007, Puno-Sarmiento et al 2013.…”