Prevalence and characterization of human Shigella infections in Henan Province, China, in 2006

Abstract

In 2006, 3,531 fecal samples were collected from patients with diarrhea in Henan Province, China. A total of 467 (13.2%) Shigella strains were isolated and serotyped. Seventy-one Shigella flexneri strains were characterized by MIC determination, pulsed-field gel electrophoresis (PFGE), and detection of genes encoding cephalosporin resistance. Most infections were caused by S. flexneri variant X [IV:(7),8] (27.6%), S. sonnei (24.2%), and S. flexneri 2a (20.8%). However, large regional differences were observed. Significantly higher odds (2.0) of females compared to males were infected with S. flexneri 2a. Untypeable S. flexneri (-:6) isolates were absent among males, as were untypeable S. flexneri [I:(7),8] isolates among females. Patient ages ranged from 2 months to 82 years, with 231 subjects (49.7%) <5 years of age. Most of the patients were male (62.1% [n = 290]). Infections peaked in July; week 27 with 38 cases (8.1%). All of the 71 S. flexneri conferred resistance to nalidixic acid; in addition, 21% (n = 15) and 79% (n = 56) were high- and low-level resistant to ciprofloxacin, respectively. Six S. flexneri isolates {serotype 2b [II:7,(8)] and 2b [II:(3),4;7,(8)]} harbored the bla(CTX-M-14) or bla(CTX-M-15) gene. A total of 52 unique XbaI PFGE patterns were observed among the 71 S. flexneri isolates with 11 distinct PFGE clusters. This study revealed a high prevalence of shigellosis with geographical differences in the distribution of serotypes in the distribution of serotypes and also differences in comparisons by gender. A high frequency of resistance, including 100% resistance to ciprofloxacin and resistance to extended-spectrum cephalosporins, was observed. We detected several isolates exhibiting the same PFGE type and MIC profile, indicating multiple undetected outbreaks.

FIG. 1.

Location of the six surveillance points in Henan Province, China.

FIG. 2.

Distribution of the serotypes between genders among Chinese patients with shigellosis from 2006 in Henan Province, China.

FIG. 3.

Seasonal variation in the numbers of Shigella infections among Chinese patients during 2006 in Henan Province, China.

FIG. 4.

PFGE (XbaI) analysis of 71 S. flexneri serotypes from Chinese patients during 2006 in Henan Province, China. Black spots in the dendrogram indicate the isolates are resistant. Abbreviations: AMP, ampicillin; AUG2, amoxicillin plus clavulanic acid; APR, apramycin; CEF, cefalothin; POD, cefpodoxime; XNL, ceftiofur; CHL, chloramphenicol; CIP ciprofloxacin; COL colistin; FFN, florfenicol; GEN, gentamicin; NAL, nalidixic acid; NEO, neomycin; SPE, spectinomycin; STR, streptomycin; SMX, sulfamethoxazole; TET, tetracycline; TMP, trimethoprim. *, High-level resistance to ciprofloxacin with an MIC of >4 μg/ml.