| Objective: To investigate the distribution of E. coli in a hospital, to confirm the drug resistance and the infection of ESBLs strains in clinic, to trace the transmission mechanism of ESBLs-producing E. coli mediated from plasmid in a hospital, and to explore the homology between different sources of strains; so as to provide management basis on prevention and control of nosocomial infection.Methods: The medical staff hand skin samples and the material surface samples were collected from six key departments in a Class 3A comprehensive hospital in Guizhou Province; as the same time, E. coli strains isolated from the inpatients with extra intestinal infection were collected from the bacteriology laboratory in this hospital. E.coli strains were isolated and identified from all samples by conventional methods of bacteriology. Susceptibility test and extended-spectrum β-lactamase detection were used for all E. coli strains; plasmid elimination and plasmid fingerprint analysis were used for the ESBLs-producing E. coli strains. Results: 718 samples were collected from six key departments in this hospital, 288 samples came from medical staff hand skin, and 430 samples came from material surface. 9 strains of E. coli were isolated from these 718 samples, and the constituent ratio of ESBLs-producing strains was55.6%(5/9). 123 strains of E. coli isolated from the inpatients with extra intestinal infection were collected from the bacteriology laboratory in this hospital, the constituent ratios of nosocomial infection strains and community infection strains were 28.5%(35/123) and 71.5%(88/123) respectively. In these 123 strains of E. coli,81 strains with the constituent ratio of 65.9%(81/123) were ESBLs-producing E. coli,the constituent ratios of nosocomial infection ESBLs-producing strains and community infection ESBLs-producing strains were 29.6%(24/81) and 70.4%(57/81) respectively. In these 81 strains of ESBLs-producing E. coli isolated from the inpatients with extra intestinal infection, the top three departments of 24 strains of ESBLs-producing caused nosocomial infection were general surgery(20.8%, 5/24),hepatobiliary surgery(12.5%, 3/24) and pediatric surgery(12.5%, 3/24); the top three specimens were secretion(50.0%, 12/24), urine(25.0%, 6/24) and pus(12.5%, 3/24).In these 81 strains of ESBLs-producing E. coli isolated from the inpatients with extra intestinal infection, the top three departments of 57 strains of ESBLs-producing caused community infection were pediatrics(19.3%, 11/57), urology(14.0%, 8/57)and nephrology(7.0%, 4/57); the top three specimens were urine(45.6%, 26/57),sputum(26.3%, 15/57) and secretion(10.5%,6/57). According to the results of drug susceptibility, 81 strains of ESBLs-producing E. coli isolated from the inpatients with extra intestinal infection were resistant to Ampicillin, but the resistance rates to Ampicillin/Sulbactam were 46.9%; the resistance rates to Ceftazidime were less than30.0%, in addition to ceftazidime, the resistance rates to the first, second and third generation cephalosporins were more than 90.0%, and the resistance rates to Cefepime were more than 60.0%; these 81 strains of ESBLs-producing E. coli were all sensitive to Carbapenems. The 81 positive strains of ESBLs E. coli solated from the inpatients with extra intestinal infection were resistant to the 13 out of 15 kinds of antimicrobial drugs, the range of resistance rates from 1.2% to 100.0%; and the 42 negative strains of ESBLs E. coli solated from the inpatients with extra intestinal infection were resistant to the 12 out of 15 kinds of antimicrobial drugs, the range of resistance rates from 2.4% to 73.8%. In 123 strains of E. coli isolated from the inpatients with extra intestinal infection, the resistance rates between nosocomial infection strains(35 strains) and community infection strains(88 strains) were not different significantly. In 55 strains of ESBLs-producing E. coli with plasmids, of which 50 strains(90.0%) carried the 20.0 kb plasmid; among them, 18 strains carried the 20.0 kb plasmid with the same plasmid spectrum belonged to three different phenotypes respectively. After several plasmid elimination tests, the resistance of the2 strains was not changed from the beginning, but the resistance of the other 16 strains to part antibiotics was changed. The results of plasmid fingerprint analysis for the resistance plasmids of 16 strains of ESBLs-producing E. coli with the same plasmid spectrum showed that the plasmids of the 2 strains(12.5%, 2/16) isolated from general surgery and orthopedics both possessed the DNA fragments with same number and size; the plasmids of the other 2 strains(12.5%, 2/16) isolated from two bedside cabinets in pediatrics ICU both possessed the DNA fragments with same number and size. Conclusion: 1. In this hospital, nosocomial infection caused by ESBLs-producing E. coli mainly distributed in surgical system. Children is a high-risk population of the infection caused by ESBLs-producing E. coli. Urinary tract is the most common position of the infection caused by ESBLs-producing E. coli. 2.According to the drug susceptibility data, Ceftazidime is the first choice for the therapy of general infections caused by ESBLs-producing E. coli; β-lactamase inhibitor antibacterials( such as Ampicillin/Sulbactam) can be used for the therapy of mild to moderate infections; Imipenem and Meropenem can be considered for the therapy of severe infections. 3. According to the result that the plasmids from different sources have same restriction enzyme fingerprints, it is prompted that the different resistant strains mediated by plasmids all have the certain homology, these strains all have risks or trends of diffusion or prevalence. Plasmid fingerprinting combined with restriction enzyme digestion can be used for molecular epidemiology investigation of nosocomial infection outbreak. |
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