Association between aggregative adherence fimbriae types including putative new variants and virulence‐related genes and clump formation amongaggR‐positiveEscherichia colistrains isolated in Thailand and Japan

Abstract

Enteroaggregative Escherichia coli (EAggEC) are an important cause of diarrhea. Four types of AAF have been identified; however, their prevalence and association with virulence properties remain unclear. E. coli strains carrying the aggR gene as EAggEC that were isolated in Japan and Thailand (n ¼ 90) were examined for AAF subunit genes, two toxin genes (pet/astA), and clump formation. The most prevalent AAF gene was hdaA (28%), followed by aafA (20%), aggA (12%), and agg3A (4%), as well as a putative new AAF sequence (25.6%). Retention status of the toxin genes and intensities of clump formation appeared to vary according to the AAF type.Key words aggregative adherence (AA), aggregative adherence fimbriae (AAF) type, aggR-positive Escherichia coli, toxin gene.Enteroaggregative Escherichia coli (EAggEC) comprise an emerging group of pathogens that cause pediatric and adult diarrhea worldwide and are known to be heterogeneous in their symptoms (1, 2) and patterns of retaining virulence genes (3-5). EAggEC exhibits characteristic AA at the surface of cultured cells by means of AAF (2). Four distinct AAF variants have been identified to date based on the sequences of fimbrial AAF subunits encoded by aggA (6), aafA (7), agg3A (8), and hdaA (alias agg4A) (9).Many putative virulence factors have been reported in addition to AAF, including EAST1, a 104-kDa cytotoxin designated as a Pet, and a global transcriptional regulator (AggR). AggR is the central regulator of virulence functions in EAggEC; therefore, the term 'typical EAEC List of Abbreviations: AA, aggregative adherence; AAF, aggregative adherence fimbriae; EAggEC, enteroaggregative Escherichia coli; EAST1, enteroaggregative E. coli heat stable enterotoxin 1; Pet, plasmid encoded toxin.

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

“…In fact, EAEC O126:H27 caused an outbreak in Shizuoka, Japan, in 2005 (5). 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.…”

Rapid and Accurate Diagnosis Based on Real-Time PCR Cycle Threshold Value for the Identification of <i>Campylobacter jejuni</i>, <i>astA</i> Gene-Positive <i>Escherichia coli</i>, and <i>eae</i> Gene-Positive <i>E. coli</i>

“…Bacterial culture (BC): BC was performed by directand enrichment-culture techniques as described previously (16)(17)(18). For isolation of diarrheagenic E. coli, we screened 5-40 colonies grown on Chromocult coliform agar (Merck, Darmstadt, Germany) using PCR as described (19). If C. jejuni and astA gene-positive E. coli were detected with RFBS24 ver.5 but not with BC, isolation of C. jejuni was performed using modified charcoal-cefoperazone-deoxycholate (CCDA) agar (Oxoid, Basingstoke, UK) followed by enrichment culture at 42 C for 24 h in Preston Campylobacter selective enrichment broth (Oxoid).…”

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.…”