| Enterococcus faecium is a gram-positive cocci commonly found in environment and the gastrointestinal tracts of human and animals, whichhas been regarded as one of important pathogens that can cause urinary tract infections, skin and soft tissue infections,abdominal cavity infections,sepsis and meningitis,endocarditis. In recent years, there are a lot of reports about drug-resistant E. faeciumisolated from patients,healthy people, animals(dogs, pigs, cattle, chickens, cats, etc.), environment and food.However, there is little study on the characteristics of E. faecium isolated from wild animals.In this study, we intensively study the characteristics of the E. faecium in yaks and marmots that live in special geographical environment in Qinghai-Tibetan plateau,China. Sixty-five E. faecium strains were isolated from 320 yak fecal samples and 200 marmot fecal samples, 33 of which were isolated from yaks, and 32 were isolated from marmots. All the strains were characterized for antibiotic susceptibility, relevant resistance genes, virulence genes, and genotyped by pulsed-field gel electrophoresis(PFGE) and multi-locus sequencing typing (MLST). Of the 33 strains isolated from yaks, we found 19 antibiotic-resistant strains,including 4 multidrug resistance strains and 15 strains resistant to only one drug; the 19 antibiotic-resistant strains showed resistance to 10 antibiotics with variable prevalence:rifampicin 36.4% (12/33),erythromycin 9.1% (3/33) , penicillin G 15.2% (5/33) , ampicillin 6.1% (2/33),high-level gentamicin 6.1% (2/33) , tetracycline 12.1% (4/33) , doxycycline 12.1%(4/33) , ciprofloxacin 6.1% (2/33) , levofloxacin 6.1% (2/33) , fosfomycin 6.1%(2/33) . Of the 32 strains isolated from marmots, we found 13 strains that were resistant to only one antibiotics: 10 rifampicin resistance strains(31.3%) and 3 erythromycin resistance strains(9.4%). All of the strains were 100% susceptible to vancomycin, teicoplanin and chloromycetin.Antibiotic resistance genes screened positive included ermB, tetM, tetL, aac (6') -Ie-aph(2"),and negative genes included ermA,ermC,mef, ereA,ereB,mphA,tetW,tetQ, tetS,fosA,fosB,fosC,vanA,vanB. The C-terminal region and N-terminal region of the pbp5 gene were amplified ,sequenced and translated to amino acids sequences , then compared with a pbp5 reference sequence (GenBank accession no. X84860).We found 3 new specific amino acids alterations associated with ampicillin resistance.Concering quinolone resistance,we found mutations in both gyrA and parC genes in quinolone resistant strains. A total of six virulence genes were detected by PCR method, including enterococcalsurface protein (esp), hyalronidase (hyl), collagen-binding-adhesin (acm),cytolysin (cylA), gelatinase (gelE) and aggregation substance (asal). The gene asa1 was found in 7.7% strains tested,followed by hyl 3.1%and acm 1.5%. None of isolates were tested positive for the rest three virulence genes. Sixty-five E. faecium strains displayed 58 PFGE patterns and then were divided into 8 clusters from A to H, all strains in 4 groups (A,C,F,G) were antibiotic-resistance.WithMLST,65 E.faecium strains displayed 32 sequence type(ST), including 22 new STs; of the 10 known STs,2 STs belonged to clonal complex 17(CC17), and the strains belong to these 2 STs were multidrug resistance.This study analysised the characteristics of Efaecium strains isolated from yaks and marmots in Qinghai-Tibetan Plateau, revealing that some of the E.faecium strains isolated from yaks and marmots are resistant to antibiotics and carry antibiotic resistance genes and virulence genes, indicating potential hazard to human health,implying important public health significance. |
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