Isolation from a sheep of an attaching and effacing Escherichia coli O115:H− with a novel combination of virulence factors

Abstract

Attaching and effacing (AE) lesions were observed in the caecum, proximal colon and rectum of one of four lambs experimentally inoculated at 6 weeks of age with Escherichia coli O157:H7. However, the attached bacteria did not immunostain with O157-specific antiserum. Subsequent bacteriological analysis of samples from this animal yielded two E. coli O115:H 2 strains, one from the colon (CO) and one from the rectum (RC), and those bacteria forming the AE lesions were shown to be of the O115 serogroup by immunostaining. The O115:H 2 isolates formed microcolonies and attaching and effacing lesions, as demonstrated by the fluorescence actin staining test, on HEp-2 tissue culture cells. Both isolates were confirmed by PCR to encode the epsilon (å) subtype of intimin. Supernates of both O115:H 2 isolates induced cytopathic effects on Vero cell monolayers, and PCR analysis verified that both isolates encoded EAST1, CNF1 and CNF2 toxins but not Shiga-like toxins. Both isolates harboured similar sized plasmids but PCR analysis indicated that only one of the O115:H 2 isolates (CO) possessed the plasmid-associated virulence determinants ehxA and etpD. Neither strain possessed the espP, katP or bfpA plasmid-associated virulence determinants. These E. coli O115:H 2 strains exhibited a novel combination of virulence determinants and are the first isolates found to possess both CNF1 and CNF2.

Presence of Escherichia coli carrying the EAST1 toxin gene in farm animals

“…Cookson et al [9] experimentally inoculated four lambs at 6 weeks of age with an E. coli O157:H7. Attaching-effacing lesions were observed in the caecum, proximal colon and rectum of one lamb.…”

Isolation, Characterization, and Epidemiological Assessment of Shiga Toxin-Producing Escherichia coli O84 Isolates from New Zealand

“…Primers intF and (zeta) intR, based on GenBank sequence AJ298279 from STEC O84 537/89 (11), were used to detect the eae subtype. The STEC enterohemolysin (ehxA), serine protease (espP), katalase peroxidase (katP), and type II secretion system (etpD) genes were detected using primers outlined previously (5,6,12). PCR analysis indicated that all 22 of the isolates were stx 1 , eae ( subtype), ehxA, and espP positive (Table 1).…”

“…stx and/or eae detection was performed using a multiplex PCR method outlined previously (6). Primers intF and (zeta) intR, based on GenBank sequence AJ298279 from STEC O84 537/89 (11), were used to detect the eae subtype.…”

Relationship between Virulence Gene Profiles of Atypical Enteropathogenic Escherichia coli and Shiga Toxin- Producing E. coli Isolates from Cattle and Sheep in New Zealand

“…It is uncertain whether ruminants are a reservoir of aEPEC which may cause human diarrheal disease or whether human aEPEC strains are distinct from ruminant aEPEC strains. Previous studies have indicated that plasmid-associated virulence factors more commonly associated with STEC, such as EHEC hemolysin (ehxA) (27), serine protease (espP) (6, 13), a catalase/peroxidise system (katP) (5), and a type II secretion pathway (etpD) (28), are occasionally associated with human aEPEC strains (1,3,16,17) and that these same virulence factors may also be associated with ruminant aEPEC (8,(10)(11)(12). In addition, subtyping of ehxA and espP PCR products has indicated that subtypes of these virulence factors are shared between ruminant aEPEC and STEC (10,12).…”

“…PCR-RFLP analysis of eae, ehxA, and espP amplicons was performed as described previously (10)(11)(12), and amplification of stx 1 , stx 2 , etpD, and katP (catalase/peroxidase) was performed using primers and amplification as outlined in other studies (5,8,9). Only bac-terial strains that were eae positive were included in this study.…”