健康豬隻與雞隻糞腸球菌對奎諾酮類抗菌劑（Quinolone）抗藥性之研究   全文下載

Characterization of Quinolone-Resistant Enterococcus faecalis Isolates from Healthy Chickens and Pigs in Taiwan

本試驗是檢測即將屠宰之健康豬與雞隻所分離的糞腸球菌（Enterococcus faecalis），對奎諾酮類抗菌劑之抗藥性表現型與基因型間的關係。結果顯示：豬源與雞源糞腸球菌對於西普氟奎林羧酸（ciprofloxacin）抗藥性比例分別為54.0%（162/300）與53.5%（107/200），這269 株對西普氟奎林羧酸具抗藥性的糞腸球菌對於西普氟奎林羧酸、恩氟奎林羧酸（enrofloxacin）與moxifloxacin 的最小抑制濃度範圍分別為4 - 512 mg/L 、8 - 512 mg/L與0.5 - 512 mg/L。分離株若在GyrA（Ser83-Arg/Ile；Glu87-Lys/Gly）與ParC（Ser80-Ile）產生突變，則會對西普氟奎林羧酸造成高程度的抗藥性，但若僅在ParC則不見明顯的影響，此外，本文為首次報告在糞腸球菌的拓樸異構?（topoisomerase）胺基酸發現三點突變。對36 株具有抗藥性但於GyrA與ParC卻無胺基酸突變的菌株而言，由蛇根鹼（reserpine）抑制藥物輸出幫浦（efflux pump）的試驗結果證實：這些分離株所帶有的藥物輸出幫浦基因（emeA）表現量，除均較標準糞腸球菌為高外，蛇根鹼可顯著下降糞腸球菌對於西普氟奎林羧酸的最小抑制濃度。綜合上述結果得知，健康畜禽腸道的糞腸球菌對於西普氟奎林酸產生抗藥性的機制包括：隨胺基酸突變數增加，而抗藥性愈強的拓樸異構?突變外，細菌所帶有的藥物輸出幫浦亦可明顯造成抗藥性的上升。

This study attempted to correlate quinolone-resistant phenotypes and genetic traits in Enterococcus faecalis from healthy chickens and pigs in Taiwan. The percentage of E. faecalis isolates resistant to ciprofloxacin was 54.0% (162/300) in pigs and 53.5% (107/200) in chickens. Two hundred and sixty-nine ciprofloxacin-resistant E. faecalis isolates showed different levels of resistance to ciprofloxacin (MIC 4 - 512 mg/L), enrofloxacin (MIC 8 - 512 mg/L) and moxifloxacin (MIC 0.5 - 512 mg/L). Two mutations associated with resistance were detected in GyrA at Ser83 (to Arg/Ile) and Glu87 (to Lys/Gly) and one mutation was found in ParC at position 80 (Ser to Ile). In addition, triple-point mutation in DNA gyrase (GyrA) and topoisomerase IV (ParC) of E. faecalis was firstly reported. Thirty-six isolates with no amino acid substitution in GyrA or ParC showed high levels of ciprofloxacin resistance. In the presence of reserpine, the levels of resistance to ciprofloxacin for these 36 strains were decreased. The effect of reserpine on ciprofloxacin resistance was correlated with the level of expression of the emeA gene. Our results demonstrate that not only point mutations in topoisomerase IV and DNA gyrase but also the efflux pump can be used by E. faecalis to generate resistance to quinolones.