Prevalence and characteristics of cytolethal distending toxin‐producing Escherichia coli from children with diarrhea in Japan

Abstract

In the present study, we examined the prevalence and characteristics of CTEC among diarrheal children in Japan during a year-long surveillance study. A PCR-RFLP assay for the detection and differentiation of five types of E. coli cdtB gene (types I through V) was developed, and 362 stool specimens collected from patients reporting to pediatric departments in two hospitals were analyzed. Of the 35 samples (9.7%) that were positive for the cdtB gene, 21 were positive for cdt-I, three for cdt-II, four for cdt-III, three for cdt-IV and four samples were positive for cdt-V , as determined by different molecular techniques. The recovery of CTEC having cdt alleles was a little less, which included 19 with cdt-I, one cdt-II, three cdt-III, three cdt-IV and four with cdt-V . Among 30 CTEC strains isolated, the majority of them (43%) belonged to serogroup O2. The other virulence genes such as astA, cnf1, eaeA, cnf2 and bfpA genes were detected in 14 (47%), 11 (37%), four (13%), three (10%) and one (3.3%) strains of CTEC, respectively. However, the other common virulence-associated genes specific for DEC were not detected in these strains. Interestingly, an untypable cdt gene was detected by PCR-RFLP in Providencia alcalifaciens. Our data indicate that CTEC may be associated with diarrheal children in Japan and most of them do not belong to a conventional enteropathogenic pathovar and thus differ from strains isolated in developing countries.

Distribution of Virulence Genes Related to Adhesions and Toxins in Shiga Toxin-Producing Escherichia coli Strains Isolated from Healthy Cattle and Diarrheal Patients in Japan

“…CDT [13] and SubAB [28] were identified as new types of toxin in STEC strains isolated from HUS patients. Although there are at least five types of CDT in E. coli [10], CDT-III and CDT-V have been detected in STEC strains [2,13]. It has been reported that cdt in eae-negative STEC was significantly more frequent in those from patients with HUS and in those from patients with diarrhea than in those from asymptomatic carriers [2].…”

“…STEC O113:NM isolated in this study was used as a positive control for saa, lpfA O113 , cdt-V and subAB genes. These 4 PCR products were confirmed to be the corresponding genes by sequencing as described previously [10]. E. coli strain C600 was used as a negative control.…”

“…For cdt-gene probe, a mixture of cdt-IB, cdt-IIIB and cdt-IVB genes specific PCR products which could react with so far identified all 5 types of cdt (I to V) was used. The cdtgene positive strains were amplified by PCR using cdt-common primer set and were subtyped by PCR-RFLP with EcoRI, EcoRV and MspI, and by specific PCR for cdt-V as described previously [10]. The eae-gene positive strains were amplified by PCR using eae-F and eae-R primer set and were subtyped by PCR-RFLP with MspI as described previously [39].…”

Prevalence of Providencia Strains among Children with Diarrhea in Japan

“…The sequences of all PCR products were matched with the 16S rRNA gene of the genus Providencia, but further differentiation at the species level was not possible, indicating that the PCR developed in this study was genus-specific. All positive samples were examined for other enteric pathogens such as enterohemorrhagic E. coli, enteroaggregative E. coli, Salmonella spp., Shigella spp., Campylobacter jejuni, C. coli, C. fetus, Norovirus, Adenovirus, and Rotavirus, by PCR or immune chromatography (10). P. rettgeri was the only pathogen that was isolated from the specimen from 1 child, while the other 3 children were shown to have had mixed infection with other pathogens (Table 2).…”

“…in children with diarrhea in Japan. Recently we identified 2 isolates of P. alcalifaciens from children with diarrhea in Japan during a survey of cytolethal distending toxin-producing Escherichia coli in children with diarrhea (10,11). Therefore, we conducted a survey to determine the prevalence of Providencia spp.…”