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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.

Streptococcus pyogenes causes a broad spectrum of acute infections and is the bacterium most frequently isolated from patients with pharyngitis. A number of antibiotics including penicillin have been shown to be effective, although antibiotic treatment failure in cases of streptococcal pharyngitis have been reported. Herein, we aimed to elucidate the features of recurrent strains using clinical isolates. Ninety-three S. pyogenes organisms were obtained from Japanese patients with recurrent pharyngitis. Following genetic characterization, M-type isolates from patients with recurrent pharyngitis differed from those obtained at initial onset in 11 of 49 episodes, and pulsed field gel electrophoresis analysis showed different patterns in those cases. Additionally, spe genotyping revealed that the Spe type of the strains obtained at secondary onset corresponded with those from the initial onset in 22 cases. Furthermore, antibiotic susceptibility testing revealed that more than half of the strains were resistant to macrolides and lincosamides, which was a much greater ratio as compared with the strains obtained from initial onsets in previous studies. Our results suggest that recurrence and reinfection are often confused during the diagnosis of repetitive and persistent streptococcal pharyngitis. Moreover, the present S. pyogenes organisms were less susceptible to antibiotics, which raises caution about their appropriate use in clinical practice.

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