| BACKGROUND AND OBJECTIVE:Extraintestinal pathogenic Escherichia coli (ExPEC) was an important zoonotic pathogen that could cause intestinal tissue infections in humans and animals, it could cause meningitis, septicemia, urinary tract infections and respiratory infections on different hosts.70～95%of community-acquired urinary tract infections and50%of hospital-acquired urinary tract infections were caused by Uropathogenic Escherichia coli (UPEC). Meanwhile E.coli was also one of the main reasons for blood infections, causing more and more bacteremia and sepsis cases. Which had a very high mortality rate. The purpose of this study was to understand the epidemiology of E. coli infection by investigating and analyzing E. coli that was isolated from clinical urine and blood sources in our hospital, and to clarify its phylogenetic group, molecular classification characteristics, the distribution of virulence-associated genes and antibiotic susceptibility, in order to provide a scientific basis for the prevention and treatment of E. coli disease. METHODS:A total of104ExPEC strains (55UPEC strains,49SEPEC strains) were isolated from the First Affiliated Hospital, Zhejiang University from July2011to June2012. Then, phylogenetic grouping and44virulence-associated genes was detected by Multiplex PCR technique. The seven housekeeping genes of E.coli were tested for multiple locus sequence typing (MLST). At the end, antibiotic susceptibility test was performed by K-B method.RESULTS:1. The result showed that104strains of ExPEC mainly belonged to group D (51cases,49.0%). The second was group B2(37cases,35.6%), group A (10cases,9.6%), and group B1(6cases,5.8%). Among55UPEC strains, B2, D, A and B1accounted for43.6%,41.8%,9.1%and5.5%, respectively, in49SEPEC strains, B2, D, A and B1accounted for26.5%,57.2%,10.2%and6.1%respectively.2. The allele numbers of E.coli housekeeping genes adk、fume、gyrB、icd、mdh、 purA、recA were divided into18、21、20、17、15、15and13kinds respectively.34STs among the104isolates were characterized, among which ST131accounted for14.42%as the most one, and ST648, ST69and ST10accounted for10.58%,9.62%and7.69%respectively. There were20STs in55UPEC strains isolated from urine sources and24STs in49SEPEC strains isolated from blood sources. ST131in UPEC was the most, accounting for20.00%, while ST10and ST648in SEPEC was the most, accounting for10.20%respectively. Two new STs (ST3905、ST3907) were reported to the website of http://mlst.ucc.ie/mlst/.3. The virulence-associated genes sfaS、iha、papA、iroN、fyuA、Kps Ⅲ were found in most of the strains, and the positive rate was more than50%. The virulence genes afaE8、cdtB、and pic were not detected in104strains. In55UPEC strains, the number of virulence genes whose positive rate was not less than20.0%is22. The virulence genes with the highest positive rate were fyuA (96.4%) and kps Ⅲ (92.7%).4virulence genes were not detected (bmaE、afaE8、cdtB and pic). Thevirulence scores (number of virulence genes) were5-20, the25th percentile (P25), P50and P75were7,11and14respectively. In49SEPEC strains, the number of virulence genes of which positive rate was not less than20.0%is15. The virulence genes with the highest positive rate were papEF (91.7%)、iha (87.5%) and astA (87.5%).12virulence genes were not detected (f17, afaE8, cvaC, Kl, rfc, vat, cdtB, pic, usp, uidA, malX, H7fliC). The virulence scores were2～20, the25th percentile (P25), P50and P75were6,9and11respectively.4. The resistance rate to ampicillin of104strains of ExPEC was as high as86.5%, while the lowest resistance rate was meropenem (2.9%). The resistance rates to nine antibiotics (ampicillin, tetracycline, cefazolin, cefotaxime, cefuroxime, ciprofloxacin, trimethoprim and sulphame-thoxazole, ampicillin and sulbactam, gentamicin) of55UPEC strains and49SEPEC strains were all more than50%, but none meropenemdrug-resistant strain was detected in UPEC isolates.ESBL-positive rates in UPEC strains and SEPEC strains were60.0%(33/55),61.7%(30/49) respectively, while the multiple drug-resistant bacteria positive rates were80.0%(44/55),87.7%(42/49), and the median number of resistance to antimicrobial agents were7and8. The difference had no statistical meaning.CONCLUSION:1. Phylogenetic group D was a common type of Extraintestinal pathogenic Escherichia coli. ST131occupied a higher proportion and should attract more and more attention.2. Adhesins, Protectins, Siderophores and toxins related virulence-associated genes were widely distributed in ExPEC.3. The antimicrobial resistance of ExPEC clinical isolated locally was very serious. More attention was needed on ESBL-positive strains. Meanwhile, the management of antimicrobial agents and monitor of ST131shoud be continually enhanced. |
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