Abstract
BackgroundIn order to investigate the epidemiology, molecular characteristics, and distribution of extended-spectrum β-lactamase (ESBL)- and AmpC-producing Escherichia coli from community-onset infections in Chinese county hospitals.MethodsE. coli isolates were collected from patients with community-onset infections in 30 county hospitals. ESBL activity was confirmed by double-disc diffusion. Genetic confirmation and molecular typing of ESBL- and AmpC-producing isolates was determined by PCR and DNA sequencing. ESBL-positive isolates were further characterised by multi-locus sequence typing.ResultsOf 550 E. coli isolates, 256 (46.5%) carried ESBL genes and all were of the CTX-M type. The prevalence of ESBL-producing strains varied from 30.2% to 57.0% across different regions of China. Overall, 12 blaCTX-M subtypes were detected; the most abundant were blaCTX-M-14 (163/256 isolates, 64.5%), blaCTX-M-55(47/256, 18.4%), and blaCTX-M-15 (31/256, 12.1%). CMY-2-like AmpC β-lactamases were detected in 11 strains, three of which co-existed with blaCTX-M. A total of 64 sequence types (STs) were detected in 256 ESBL-producing strains, including nine that were new. ST131 was the most abundant type (27 isolates, 12.7%), followed by ST69 (14 isolates, 6.6%), ST405 (14 isolates, 6.6%), and ST38 (12 isolates, 5.6%).ConclusionsThis study revealed that the widespread prevalence of ESBLs among outpatient infections has reached a high level in county hospitals. The CTX-M genotype was most dominant, comprising a variety of subtypes. This is the first time the incidence of CTX-M-55 has exceeded that of CTX-M-15 in China. No predominant ST was detected, suggesting that ESBL-producing E. coli strains originate in different clones.Electronic supplementary materialThe online version of this article (doi:10.1186/s12879-014-0659-0) contains supplementary material, which is available to authorized users.
Highlights
In order to investigate the epidemiology, molecular characteristics, and distribution of extended-spectrum β-lactamase (ESBL)- and AmpC-producing Escherichia coli from community-onset infections in Chinese county hospitals
CTX-M-14 (CTX-M-9 group) was the most common ESBL genotype detected in this study; the results suggest that CTX-M-55 (CTX-M-1 group) is becoming prevalent, with the ratio of the number of CTX-M-55positive isolates to the number of ESBL-positive isolates being 5:8 in SC4, 4:8 in SC5, 6:9 in EC2, and 4:8 in NE1
The results indicate that 46.5% of clinical E. coli isolates carried genes for ESBLs, and that this figure varied significantly across the different regions, Figure 2 Phylogenetic tree of sequence types (STs) detected in this study using Phylodendron
Summary
In order to investigate the epidemiology, molecular characteristics, and distribution of extended-spectrum β-lactamase (ESBL)- and AmpC-producing Escherichia coli from community-onset infections in Chinese county hospitals. A national monitoring program of antimicrobial resistance in E. coli caused bacteriaemia (mostly nosocomial infections) in Chinese tertiary hospitals reported an increase in ESBLproducing E. coli from less than 20% to 72.2% between 2000 and 2011 [21,22,23]. Another survey of Chinese tertiary hospitals reported that the incidence of ESBLproducing E. coli among community-associated intraabdominal infections increased from 19.1% in 2002–2003 to 61.6% in 2010–2011 [20]. None of these studies focused on bacteria isolated from outpatients in primary and noncentral city hospitals. In light of the increasing importance of ESBL-producing E. coli within communities, it is important to understand the pattern of antibiotic resistance and the prevalence of ESBLs in bacterial isolates from primary and non-central city healthcare institutions that provide medical services to patients in China
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