Varacha Singhsuwan. Prevalence and van gene of vancomycin-resistant enterococci isolated from ark shell (arca granulosa) in Thailand. Master's Degree(Medical Microbiology). Chulalongkorn University. Office of Academic Resources. : Chulalongkorn University, 2006.
Prevalence and van gene of vancomycin-resistant enterococci isolated from ark shell (arca granulosa) in Thailand
Abstract:
Prevalence of vancomycin resistant enterococci (VRE) in Thailand had been studied in farm animals, food of animal origins, domesticated animals and human. However, VRE in environment has not been reported in Thailand. Therefore this study was used ark shells which cultivated from the Gulf of Thailand as biological marker of VRE in the environment. They were filter feeders which could concentrate materials presented in water in their digestive tracts. Ark shell samples were collected from August 2005 to August 2006. Samples were pooled and individual counts; pooled of ark shell from same source approximately 10 shells which give total weight 25g as one sample, and individual shell from one source as one sample. All samples were screened for VRE by selective media contained 6 g of vancomycin per mL. Individual ark shell samples were found 0.36% of low level resistant VRE and all 5 isolates (100%) were classified as E.gallinarum. Pooled ark shell samples were found 26 isolates (4.3%) and classified as E.faecium 15 isolates (57.7%), E.faecalis 6 isolates (23.1%), E.gallinarum 3 isolates (11.5%) and E.casseliflavus 2 isolates (7.7%). Antimicrobial susceptibility test had been performed by using agar dilution method for six antibiotics; vancomycin (VN), ampicillin (AP), cholramphenicol (CHPC), erythromycin (ET), tetracycline (TE) and tylosin (TS) and E-test for teicoplanin (TP). All of 5 VRE isolated from individual ark shell samples were low level resistance (MIC = 8 g/ml) to VN and sensitive to all of other antibiotics. All of VRE isolated from from pooled ark shell samples were low level resistance to VN and sensitive to TP. E.faecium 15 isolates were resistance to AP, CHPC, TE and TS 13.3% and resistance to ET 33.3%. E.faecalis 6 isolates were susceptible to AP and CHPC and resistance to ET, TE and TS 16.7%. E.gallinarum were susceptible to AP and resistance to CHPC and TS 33.3% and resistance in ET and TE 66.7% and one from two of E.casseliflvus was resistance to only antibiotics; ET. Detection of van gene from all of low level resistance VRE by polymerase chain reaction (PCR) were found gene vanC1 in all of E.gallinarum isolates and vanC2/C3 in all of E.casseliflavus isolates. The low prevalence of VRE found in this study which showed low level resistance to vancomycin and susceptible to teicoplanin. Therefore VRE should not be a public health threat in Thailand.