Abstract
We investigated the phenotypic characteristics by using API20E, APIZYM and determined minimum inhibitory concentrations (MICs) of 7 antibiotics in motile aeromonads isolated from freshwater fishes in Korea and Japan, and 4 American Type Culture Collection (ATCC) strains. All isolates (n=7) were identified as motile Aeromonas species according to API20E test. Lysine decarboxylase activity and acid production from 4 different carbohydrates including mannitol, rhamnose, amygdalin and arabinose were observed in various strains. In enzymatic activities by APIZYM, all isolates showed negative reactions in valine and cystine arylamidases, α-chymotrypsin, α-galactosidase, β-glucuronidase, α-glucosidase, α-mannosidase and α-fucosidase. Although the intensities of each enzymatic activity were diverse in alkaline phosphatase, esterase-lipase, leucine arylamidase, β-galactosidase and N-acetyl-β-glucosaminidase, all isolates showed positive reactions. All isolates were resistant to ampicillin sodium (MIC>100㎍/ml), but sensitive to chloramphenicol (MIC≤1.6㎍/ml). However, recently isolated strains (AC9804, AC0202 and GMA0361) were commonly resistant to tetracycline (MIC=50㎍/ml). Furthermore, AC9804 was resistant to oxolinic acid (MIC=12.5㎍/ml). GMA0361 was resistant to kanamycin sulfate (MIC>100㎍/ml) and streptomycin sulfate (MIC>100 ㎍/ml).
본 연구에서는 우리나라와 일본의 담수어에서 분리된 운동성 aeromonads 7균주와 American Type Culture Collection (ATCC)에서 분양받은Aeromonas hydrophila 4균주의 표현형적 특성을 API20E와 APIZYM 방법으로 평가하고, 7종류의 항생제에 대한 최소 성장 억제 농도 (minimum inhibitory concentrations; MICs) 를 측정하였다. API20E 시험 결과 시험한 모든 균주는 (n=7) 운동성 aeromonads로 동정되었다. API20E시험에서lysine decarboxylase와mannitol, rhamnose, amygdalin, arabinose를 포함한 4종류의 carbohydrates의 산 생성은 균주에 따라 다른 반응을 나타내었다. APIZYM 시험을 이용한 효소 활성능을 평가한 결과, 모든 시험된 균주가valine arylamidase, cystine arylamidase, α-chymotrypsin, α-galactosidase, β-glucuronidase, α-glucosidase, α-mannosidase, α-fucosidase반응에서 음성 반응을 나타내었으나, 비록 그 효소 활성의 강도에서 차이는 있었으나alkaline phosphatase, esterase-lipase, leucine arylamidase, β-galactosidase, N-acetyl-β-glucosaminidase 모든 균주에서 양성 반응이 나타났다. 최소 성장 억제농도를 시험한 결과, 시험된 모든 균주는 ampicillin sodium (MIC>100㎍/ml) 에 내성을 가지며 chloramphenicol (MIC≤1.6㎍/ml) 감수성을 나타내었다. 그러나 1998년 이후에 분리된 3균주 (AC9804, AC0202, GMA0361)는 tetracycline (MIC=50㎍/ml) 모두 저항성이 있었으며, AC9804는 oxolinic acid (MIC=12.5㎍/ml), GMA0361는 kanamycin sulfate (MIC>100㎍/ml)와 streptomycin sulfate (MIC>100㎍/ml)에도 저항성을 나타내었다.