Methicillin抗性金黃色葡萄球菌對Ciprofloxacin，Cotrimoxazole與Rifampin單一及合併使用之體外抑制效果評估

Evaluation of in vitro efficacies of ciprofloxacin，cotrimoxazole，and rifampin used alone and in combination against methicillin-resistant Staphylococcus aureus

康玉嬋(Yu-Chan Kang)

指導教授 ： 陳素惠 ； 劉建衛

高雄醫學大學/藥學院/藥學研究所/碩士(2004年)

摘要

本篇研究以ciprofloxacin、cotrimoxazole 與 rifampin對一隨機取樣之臨床分離methicillin抗性金黃色葡萄球菌（methicillin-resistant Staphylococcus aureus,MRSA）進行time-kill體外感受性試驗，試圖模擬治療某些因局部抗生素濃度不足，而造成療效不佳的感染，尤其是成人MRSA慢性骨髓炎。成人慢性骨髓炎正因藥物無法有效到達病灶死骨區，而導致其復發率高居不下，故被公認為是最難治療的慢性疾病之一，想要治癒更是臨床醫學上的一大挑戰。目前成人MRSA慢性骨髓炎之住院病患以外科手術及靜脈注射vancomycin或teicoplanin為標準療法，但對於出院後的抗生素持續治療仍缺乏適當的準則；此外，處於現今醫療資源取得不易的大環境下，與其消極尋找超級抗生素倒不如積極開發傳統藥物的新用法，本實驗目的即希望能以抗生素合併之方式，為出院病患找到一個有效的口服療法。實驗採ciprofloxacin、cotrimoxazole 與rifampin三種不同藥理作用機轉之抗生素，以單獨使用、任兩種或三種藥物合併方式，並嘗試延長實驗時間至48小時及降低藥物濃度至1 × MIC及1/2 × MIC，在近乎10 6 CFU/ml之初始菌量下進行。結果首次證實ciprofloxacin + cotrimoxazole與ciprofloxacin + cotrimoxazole + rifampin能分別以1 × MIC及1/2 × MIC的低藥物濃度，有效抑制MRSA長達48小時；至於ciprofloxacin + rifampin 及cotrimoxazole + rifampin 則是首次以如此低的濃度來支持先前的文獻，證明其確實可有效抑制MRSA。若能利用不同作用機轉的藥物合併法，在低濃度下達到良好抑菌效果之特性，應用於抗藥性發生頻繁與病灶藥物濃度不足而難以治癒的感染，理應更能降低抗藥性的發生率並提高治癒率。如果這種口服合併抗生素治療的模式能建立，醫療品質將大為改善，病患也無須為了靜脈注射住院而影響正常生活作息，如此醫療支出也會大幅降低。因此我們認為MRSA對於本實驗提出的抗生素合併法感受性極佳，且值得做更進一步的活體及臨床研究。

關鍵字

Methicillin抗性金黃色葡萄球菌 ； 慢性骨髓炎 ； 合併使用 ； time-kill 試驗 ； 協同作用 ； ciprofloxacin ； cotrimoxazole ； rifampin

並列摘要

We conducted an in vitro time-kill study to evaluate the efficacies of ciprofloxacin, cotrimoxazole, and rifampin used alone and in combination against a randomly chosen clinical isolate of methicillin-resistant Staphylococcus aureus (MRSA), with an attempt to improve the therapeutic outcomes of infections, such as chronic osteomyelitis, in which local antibiotic concentrations are often inadequate. Chronic osteomyelitis caused by MRSA is one of the therapeutically intractable infections, and the suboptimal local antibiotic concentrations in the sequestrum account for the high recurrence rates of osteomyelitis.Currently, intravenous therapy with vancomycin or teicoplanin coupled with surgical debridement is the standard therapy for inpatients with chronic osteomyelitis caused by MRSA. However, the standard of subsequent long-term oral antibiotic treatment of chronic osteomyelitis has not yet been established. With the limited optional antibiotics available, the synergistic effect of combination of the readily widely used drugs in the treatment of chronic osteomyelitis cannot be overemphasized. Combined use of antibiotics additionally hampers the development of antimicrobial resistance. In the time-kill study presented in this paper, ciprofloxacin, cotrimoxazole, and rifampin (each at 1×MIC and 1/2×MIC) were used alone, in two-drug and three-drug combinations, respectively. A starting MRSA inoculum of approximate 10 6 CFU/ml was used in each experiment whose experimental time lasted for 48 hours.Our study demonstrated the excellent inhibitory activities against MRSA by ciprofloxacin plus cotrimoxazole and by ciprofloxacin plus cotrimoxazole and rifampin, respectively, for 48 hours at merely 1×MIC and 1/2×MIC of each drug. Our result also confirms the previous study indicating the inhibitory effects of the combinations of ciprofloxacin plus rifampin and cotrimoxazole plus rifampin against MRSA, when these antibiotics each were used at such a low concentration.The synergistic antimicrobial effects by combined antibiotics each with a subinhibitory concentration suggest the potential for the applicability of combined antibiotics for treatment of osteomyelitis caused by MRSA, because in such circumstances adequate local individual antibiotic concentration is hardly achieved due to compromised tissue perfusion.As aforementioned, the synergistic antibiotic effect can also prevent the inevitable development of antimicrobial resistance in the presence of the subinhibitory concentration of an antibiotic should it be used alone. Theoretically, the synergistic effect of combined antibiotics each with a subinhibitory concentration additionally makes oral antibiotic therapy for osteomyelitis caused by MRSA possible. In conclusion, our in vitro study shows that the combination of ciprofloxacin, cotrimoxazole, and rifampin is synergistically highly active against MRSA. Our study discloses important experimental data, and in view of their potentially beneficial value in applicability, further in vivo and clinical studies are deserved.

並列關鍵字

methicillin-resistant Staphylococcus aureus ； chronic osteomyelitis ； combined use ； time-kill study ； synergistic effect ； ciprofloxacin ； cotrimoxazole ； rifampin

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