인위적으로 유도한 퀴놀론제제 내성 Mycoplasma hominis의 gyrA, parC, parE 유전자의 돌연변이 분석 = Analysis of gyrA, parC, and parE Mutations in Quinolone-Resistant Mutants of Mycoplasma hominis obtained In Vitro

다국어 초록 (Multilingual Abstract)

Background/Aims : Fluoroquinolones are broad-spectrum antibacterial agents that inhibit DNA gyrase and topoisomerase IV activities. Both enzymes are encoded by the gyrA and gyrB genes for DNA gyrase and parC and parE genes for topoisomerase IV. Mutations in the quinolone resistance-determining regions (QRDRs) of GyrA and ParC mainly and GyrB and ParE less frequently have been described as the major mechanism for quinolone resistance. The aim of the study described here is to investigate the relationship between mutations in the gyrA, parC, and parE Gene and cirofloxacin resistance in M.hominis.
Methods : Ciprofloxacin-resistant mutants of M.hominis (Mycoplasma hominis) were generated by stepwise selection at increasing drug concentrations. Sequence analysis of PCR products from the strains were used to examine the quinolone resistance-determining regions of the GyrA, ParC, and ParE proteins.
Results : Sixteen strains of M.hominis were isolated and were examined for susceptibility to ciprofloxacin, levofloxacin and moxifloxacin. The MIC range for M.hominis were as follows: ciprofloxacin, 0.5-8 ㎍/㎖; levofloxacin, 0.13-2 ㎍/㎖; moxifloxacin, ≤ 0.06-0.13 ㎍/㎖. M.hominis was highly susceptible to moxifloxacin. Ciprofloxacin - resistant mutants were isolated by serial passing of M.hominis M30 in broth culture. Two mutants, C10-2 and C21, displaying high-level ciprofloxacin resistance (MIC > 128 ㎍/㎖) were found to have a change in GyrA at Ser83 to Leu and in ParC at Ser80 to Ile or Glu84 to Lys, but no changes in ParE.
Conclusion : Two mutants displaying high-level ciprofloxacin resistance (MIC > 128 ㎍/㎖) were isolated and the gyrA, parC, and parE genes were sequenced. They harbored amino acid substitution of Ser83 to Leu in the GyrA, and of Ser80 to Ile or Glu84 to Lys in the ParC. These findings indicate that resistance to ciprofloxacin may be due to amino acid substitution in the GyrA and ParC.

목차 (Table of Contents)

• 서론
• 재료와 방법
• 1. 균 분리
• 2. 항생제
• 3. 최저발육저지농도 (minimal inhibitory concentration, MIC)의 측정
• 4. 인공돌연변이 유도
• 5. Polymerase chain reaction (PCR)
• 결 과
• 1. 항생제 감수성 검사
• 2. PCR과 염기서열분석
• 3. 돌연변이의 유도와 염기서열분석
• 고찰
• 결론
• References