Prevalence and mechanisms of erythromycin resistance in streptococcal isolates of fish in Taiwan
| Autor: | Shu-fang Kao, 高淑芳 |
|---|---|
| Rok vydání: | 2001 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 89 From 1995 to June 2001, different hemolytic type of streptococcus spp. were isolated from rainbow trout (Oncorhynchus mykiss), ayu (Plecoglossus altivelis), tilapia (Oreochromis spp.), grey mullet(Mugil cephalus Linnaeus) and salmon (Oncorhynchus keta), etc. A total of 66 streptococcus spp. isolates collected from Taiwan were examined. Of the 66 isolates, 49(74.2%) isolates were susceptible to erythromycin and 17(25.8%) isolates were resistant to erythromycin. The minimal inhibitory concentrations (MICs) to erythromycin were distributed between 16mg/L and 32mg/L for 15 isolates collected from 1995 to July 1997. Erythromycin MICs were distributed between 32mg/L and 64mg/L for 31 isolates collected from August 1997 to March 1999. And Erythromycin MICs been tested shown distribution between 128mg/L and 256mg/L for 20 isolates collected from April 1999 to June 2001. The breakpoint MICs for 66 isolates are ≦8 mg/L for susceptibility and >16 mg/L for resistance. And in 1999 the MICs to erythromycin shown greater antimicrobial activity than before. Besides, the higher resistant isolates can achieve greater erythromycin-resistant activity by artificial resistance induction. The 17 isolates of erythromycin resistance were coresistant to macrolide and lincosamide (MLSB-resistance). By double disk diffusion assay, resistance phenotypes of all isolates expressed constitutive resistance (CR) of MLSB resistance. Detection of erythromycin resistance genes by PCR indicated that, 11 γ- hemolytic isolates had erythromycin resistance methylase A (ermA) gene, and the mechanism of resistance is therefore proposed to be target site modification. The genetic location of the ermA gene appeared to be carried on the chromosome. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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