Molecular Typing And Epidemiology Of Extended-spectrum Beta-lactamases In Escherichia Coli Isolated From Outpatients Of County Hospitals In China

Background and ObjectivesIn China, several studies have been performed to characterize extended-spectrum beta-lactamases (ESBL)-producing Enterobacteriaceae in tertiary hospitals. A national monitor program of antimicrobial-resistant bacteria in Chinese tertiary hospitals which mostly represent nosocomial infection showed a uptrend prevalence of ESBL-producing E. coli between2000to2011, from less than20%to more than60%. However, none of these studies focused on isolates from outpatient in primary and non-central city hospitals. None of these studies focused on bacteria isolated from outpatients in primary and non-central city hospitals. This study focus to investigate the epidemiology, molecular characteristic and geographical distribution of extended-spectrum beta-lactamase and AmpC gene in Escherichia coli isolated from county hospitals in China.Methods E. coli isolates were collected from community-onset infections patients in30county hospitals. Minimum inhibitory concentration testing was performed according to the CLSI recommend agar dilution method. The prevalence of ESBL and AmpC was subsequently determined by PCR, and verified by DNA sequencing. Strain typing (ST) of all ESBLs positive strains were identified with multi-locus sequence typing (MLST).ResultsA total of550clinical E. coli isolates were collected. All isolates were susceptible to biapenem, imipenem, and meropenem, whereas94.1%,93.6%, and91.0%of strains were susceptible to fosfomycin, amikacin, and piperacillin-tazobactam, respectively. In total,249strains produced ESBLs:100%of these were resistant to ampicillin, with high resistance also to cefazolin (99.6%, n=248), ceftriaxone (98.8%, n=246), ampicillin-sulbactam (61.3%, n=153), ciprofloxacin (73.5%, n=183), and levofloxacin (68.8%, n=171).256isolates (46.5%) carried ESBLs, all of which were CTX-M type. The ESBLs genotype positive rate of different regions ranges with30.2-57.0%. Overall, twelve blacTx-M subtypes were detected, of those, the most common blacTK-M genotypes were blaCTX-M-14(163/256isolates,64.5%),blaCTX-M-55(47/256,18.4%) and blaCTX-M-15(31/256,12.1%). It is worthy of note that the rate of CTX-M-55exceeded CTX-M-15in China was first observed. blaTEM-1was the most common spectrum β-lactamases gene in this study (347isolates), followed by blaOXA-1(35isolates) and blaSHV-11(5isolates). One strain carried blaCTX-M-55which showed negative ESBL phenotype, also carried TEM-30, an inhibitor resistance TEM β-lactamases.11strains harbored CMY-2-like AmpC β-lactamases,3of which coexisted with blacrx-M-64STs were detected in256ESBLs-producing strains, including9new STs. ST131is the most prevalent (27/256,10.5%), followed by ST69(14/256,5.5%), ST405(14/256,5.5%) and ST38(12/256,4.7%). Conclusions:1. It’s very common of multiple drug resistance E. coli among outpatients from county hospitals, most of them resistant to β-lactam and fluoroquinolones, in this study73.3%and68.9%ESBLs positive strains resistant to ciprofloxacin and levofloxacin, respectively.2. In summary, strikingly rates of ESBL-carrier among E. coli stains from community-associated infections in county hospital in China is identified, CTX-M-14being also the major molecular type ESBL in community-onset infections.3. The pandemic of CTX-M-55in some provinces are the main epidemic characteristics of ESBL in those isolates, the obvious increase of CTX-M-55may worsen and complicate the resistance in E. coli in China.4. ST131was the most common ST, and the STs were diversity and no evolutionary convergent relationship among ESBL-producing E.coli isolated from community-onset infection in county hospitals of China was founded. The predomination of ST38in Northwest China alert us to continually close monitor the evaluation and spread of the germ.5. Further investigations need to find out the mechanism of the increasing CTX-M-55and the emerging OXA-10in clinical isolates of E. coli.6. The results indicate that the incidence rate of ESBLs varied significantly across the different regions, ranging30.2%to57.0%, although the most common genotype was CTX-M-14, in some hospitals CTX-M-55or CTX-M-15was predominant. These results indicated the epidemiology of ESBLs was complicated in China, and more research should be done to explore suitable empirical therapy regimen for different region and hospitals.