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.

Mouse models are widely used for studying gastrointestinal (GI) tract-related diseases. It is necessary and important to develop a new set of primers to monitor the mouse gut microbiota. In this study, 16S rRNA gene-targeted group-specific primers for Firmicutes, Actinobacteria, Bacteroidetes, Deferribacteres, "Candidatus Saccharibacteria," Verrucomicrobia, Tenericutes, and Proteobacteria were designed and validated for quantification of the predominant bacterial species in mouse feces by real-time PCR. After confirmation of their accuracy and specificity by high-throughput sequencing technologies, these primers were applied to quantify the changes in the fecal samples from a trinitrobenzene sulfonic acid-induced colitis mouse model. Our results showed that this approach efficiently predicted the occurrence of colitis, such as spontaneous chronic inflammatory bowel disease in transgenic mice. The set of primers developed in this study provides a simple and affordable method to monitor changes in the intestinal microbiota at the phylum level.

Bacterial biofilm formation is thought to enhance survival in natural environments and during interaction with hosts. A robust colonizer of the human gastrointestinal tract, Escherichia coli Nissle 1917, is widely employed in probiotic therapy. In this study, we performed a genetic screen to identify genes that are involved in Nissle biofilm formation. We found that F1C fimbriae are required for biofilm formation on an inert surface. In addition, these structures are also important for adherence to epithelial cells and persistence in infant mouse colonization. The data suggest a possible connection between Nissle biofilm formation and the survival of this commensal within the host. Further study of the requirements for robust biofilm formation may improve the therapeutic efficacy of Nissle 1917.

Xonghong Xiao and colleagues analyze the challenge of antimicrobial resistance in China. A government strategy to promote rational use of antimicrobials in health care reduced antibiotic sales and percentage of prescriptions for antimicrobials for both hospitalized patients and outpatients, and offers insights to shape future initiatives. Please see later in the article for the Editors' Summary

The majority of riboswitches are regulatory RNAs that regulate gene expression by binding small-molecule metabolites. Here we report the discovery of an aminoglycoside-binding riboswitch that is widely distributed among antibiotic-resistant bacterial pathogens. This riboswitch is present in the leader RNA of the resistance genes that encode the aminoglycoside acetyl transferase (AAC) and aminoglycoside adenyl transferase (AAD) enzymes that confer resistance to aminoglycoside antibiotics through modification of the drugs. We show that expression of the AAC and AAD resistance genes is regulated by aminoglycoside binding to a secondary structure in their 5' leader RNA. Reporter gene expression, direct measurements of drug RNA binding, chemical probing, and UV crosslinking combined with mutational analysis demonstrate that the leader RNA functions as an aminoglycoside-sensing riboswitch in which drug binding to the leader RNA leads to the induction of aminoglycosides antibiotic resistance.