Characteristics of enteroaggregative Escherichia coli isolated from healthy carriers and from patients with diarrhoea

Abstract

The aim of this study was to compare the virulence characteristics and phylogenetic features of enteroaggregative Escherichia coli (EAEC) strains from adults with and without diarrhoea and to search for associations between the analysed genes and carrier or diarrhoeagenic strains, respectively. Faecal samples of 487 healthy humans were screened for EAEC strains and compared with isolates from diarrhoeal patients. Virulence and virulence-associated gene typing, serotyping, multilocus sequence typing and antibiotic susceptibility testing were performed for characterization of the isolates. Characteristics significantly linked to carrier strains or to diarrhoeagenic strains were determined. From 487 stool samples, 24 EAEC strains were obtained. Comparison with strains originating from diseased persons showed a statistically significant association of the genes sat (P50.002) and agg3C (P50.0139) with the carrier strains, and of pCVD432 (P50.0001), aap (P50.003), aggR (P50.0048) and air (P50.031) with the diarrhoeagenic strains. Our study indicates that a certain subset of EAEC is unrelated to diarrhoea, for which sat and agg3C may be markers. Our results further suggest that diarrhoeagenic EAEC strains are distinguishable from carrier strains and suggest that, in addition to well-established markers such as pCVD432 and aggR, aap and air may be useful additional markers to define EAEC as an aetiological agent of diarrhoea in adults. INTRODUCTIONEnteroaggregative Escherichia coli (EAEC) infection is a common cause of diarrhoea worldwide and is frequently seen as an aetiological agent of persistent paediatric diarrhoea in developing as well as in industrialized countries (Huang et al., 2006). In industrialized countries, EAEC has been described as a cause of diarrhoeal illness in individuals with immune deficiency syndrome and in travellers visiting less developed areas of the world (Kaur et al., 2010). EAEC is becoming increasingly recognized as a major cause of sporadic diarrhoea in otherwise healthy adults and children in industrialized countries. As well as sporadic cases, outbreaks of EAEC-caused diarrhoea that include foodborne outbreaks have been described (Smith et al., 1997;Morabito et al., 1998;Scavia et al., 2008). The outbreak of Shiga toxin-producing EAEC in northern Germany in 2011, with related cases in 15 other countries, received international attention, afflicting some 3000 people and causing over 800 cases of haemolytic uraemic syndrome and 46 deaths (Rasko et al., 2011). This outbreak revealed the alarming capability of this pathogen to genetically recombine, resulting in a phenotype of devastating proportions (Mellmann et al., 2011).Because EAEC can persist in recovered or subclinical cases (Huang et al., 2003) and thereby contribute to cryptic dissemination, its detection and prediction of its virulence and pandemic potential are of challenging importance. EAEC are traditionally defined by their ability to adhere to HEp-2 cells in culture in a so-called 'stacked-brick' aggregative formation (Natar...

Phylogenetic Analysis of Enteroaggregative Escherichia coli (EAEC) Isolates from Japan Reveals Emergence of CTX-M-14-Producing EAEC O25:H4 Clones Related to Sequence Type 131

“…Three EAEC O25:H4 strains in Vietnam have been reported, although the ST and virulence gene patterns have not been described (46). Nuesch-Inderbinen et al reported that three EAEC O25:H4/ST131 strains in Germany possessed agg3C and sat but not aggR or aap (24). EAEC O25:H4/CG131 strains cannot form strong biofilms, compared to canonical EAEC strains, and rarely harbor the toxin genes tested in this study.…”

“…Ito et al also recently reported that these three serotypes are frequently found in Japan (45). However, these three serotypes have not been reported to be prevalent in other countries (15,24,46,47), suggesting that the dominant EAEC serotypes differ geographically.…”

“…We previously reported that 36.8% of the aggR gene-positive EAEC strains isolated from diarrheal children in Kagoshima, Japan, were cefotaxime resistant (22), suggesting ESBL production. Subsequently, some CTX-M-producing EAEC strains were reported worldwide (23)(24)(25)(26), including an EAEC-Shiga toxin-producing E. coli (STEC) hybrid clone of O104:H4 that caused a large outbreak in Germany in 2011 (27).…”

Phenotypic and Molecular Characterization of Enteroaggregative <i>Escherichia coli</i> Isolated in Kawasaki, Japan

“…Furthermore, PCR results revealed that 5 AAF-negative OUT:H10 strains harbored the O99 antigen. Many OUT EAEC strains have been reported domestically and overseas (28,29 (22,30,31). Therefore, the prevalence of O:H types is likely to vary among countries.…”

“…Of the dominant O:H types we detected, the O126:H27 EAEC strain was reported as a causative pathogen of a food poisoning and diarrhea outbreak in Shizuoka, Japan (9). In addition, the O131:H27 and O176:H34 EAEC strains were reported to be isolated from diarrhea cases (31,32,33).…”