Antibiotic resistance in animal isolates of enterococci is a public health concern, because of the risk of transmission of antibiotic-resistant strains or resistance genes to humans through the food chain. This study investigated phenotypic and genotypic resistances profile of tetracycline in 245 Enterococcus isolates from bovine milk. A total of 245 enterococci were isolated from 950 milk samples. The predominant strain was E. faecalis (n = 199, 81.2%) and E. faecium (n = 25, 10.2%). E. avium (n = 7, 2.9%), E. durans (n = 6, 2.5%), E. gallinarum (n = 4, 1.6%), and E. raffinosus (n = 4, 1.6%) were also isolated. Of the 245 enterococcal isolates 76.3% (n = 187) displayed tetracycline resistance (≥ 16 μg/ml). Of the 187 tetracycline-resistant isolates, 83.4% (n = 156), 16.1% (n = 30), and 26.7% (n = 50) possessed the genes tet(M), tet(L), tet(S) respectively. While 3.2% (n = 6) of the tetracycline- resistant isolates possessed all three genes tet(M) + tet(L) + tet(S), 8.6% (n = 16), 16.0% (n = 30), and 2.7% (n = 5) of them possessed two genes tet(M) + tet(L), tet(M) + tet(S), and tet(L) + tet(S) respectively. The tetracycline resistance pattern investigated in this study was attributable mainly to the presence of tet(M).

ABSTRACT
 재료 및 방법
  원유시료의 수집 및 장구균 분리
  최소저지농도(minimum inhibitory concentration, MIC)의 측정
  중합효소연쇄반응에 의한 tetracycline 내성 유전자의 검색
  내성 유전자의 염기서열 분석
 결과 및 고찰
 감사의 글
 요 약
 참고문헌

• 김지훈(삼육대학교 동물과학부, Division of Animal Science, Sahmyook University) | JiHoon Kim
• 최성숙(삼육대학교 약학대학, College of Pharmacy, Sahmyook University) | SungSook Choi Correspondence to