국내분리 Actinobacillus pleuropneumoniae의 항생제 내성 패턴에 대한 표현형과 유전적 특성 분석

학위논문 (석사)-- 서울대학교 대학원 : 수의학과(수의미생물학전공), 2013. 2. 유한상.The antimicrobial susceptibility patterns of 102 Actinobacillus pleuropneumoniae isolated from pigs with pleuropneumonia in Korea from 2006 to 2010 were analyzed using the disk diffusion test and microdilution method. Amoxicillin/clavulanic acid, cephalothin, and ceftiofur were active against A. pleuropneumoniae, while most of the isolates were resistant to lincomycin (100 %), erythromycin (99.9 %), and kanamycin (93.2 %). The susceptibility to florfenicol decreased considerably by year from 2006 to 2010, as did that of a minor percentage of ampicillin and amoxicillin in minor percentage. Further studies were focused on the resistance to tetracycline and florfenicol based on the phenotypic analysis of antibiotic susceptibility patterns. Of 11 tetracycline resistance genes [tet (A), tet (B), tet (C), tet (D), tet (E), tet (G), tet (H), tet (K), tet (M), tet (L), and tet (O)], tet (B) was predominant (62 %), followed by tet (H) (12 %) and tet (O) (8 %). The florfenicol resistance (flo R) gene was detected in 35 strains (34%) and β-lactam antibiotic resistance (blaROB-1) gene was detected in 15 strains (15 %) of all isolates. To determine the factor related with the MIC value, the expression levels of the tetracycline repressor gene and resistance gene, as well as biofilm formation, were compared with the MIC values of tetracycline-resistant strains. There was, however, no significant degree of relation. Interspecies transferability of the florfenicol resistance (flo R) gene and tetracycline resistance [tet (B)] / β-lactams antibiotic resistance (blaROB-1) gene were observed with 5.7 X 10-3 and 3.5 X 10-2, respectively. In analyzing digested DNA patterns using PFGE, they showed slight relatedness to serotypes but not to isolated location and year. This study acknowledges the antimicrobial resistance of A. pleuropneumoniae based on the current situation in Korea and may help to control the disease caused by A. pleuropneumoniae.Abstract Contents List of Figures List of Tables List of Abbreviations 1. Introduction 2. Materials and Methods 2.1. Bacterial strains and growth conditions 2.2. Antimicrobial susceptibility testing 2.3. Polymerase Chain Reaction (PCR) for the detection of antibiotic resistance genes 2.4. Real-time PCR assay 2.5. Biofilm formation assay 2.6. Bacterial conjugation 2.7. Pulsed field gel electrophoresis (PFGE) 3. Results 3.1. Serotyping and antimicrobial resistance profile 3.2. Relatedness of MIC values to resistance-gene expression and biofilm formation 3.3. Transfer of resistance gene 3.4. PFGE 4. Discussion 5. References 국문초록Maste