Bennie C J M, To J L K, Martin P A, Govendir M
Faculty of Veterinary Science, McMaster Building, B14, The University of Sydney, NSW, 2006, Australia.
Aust Vet J. 2015 Jan-Feb;93(1-2):40-5. doi: 10.1111/avj.12279.
To investigate whether selected drug combinations used to treat rapidly growing mycobacteria (RGM) have drug-drug interactions that affect efficacy and to investigate each isolate's susceptibility to cefovecin and clofazimine, individually.
In vitro susceptibility testing of bacterial isolates.
Initially, five feline isolates and one canine isolate from both Mycobacterium fortuitum and M. smegmatis clusters (n = 12) underwent microbroth susceptibility testing to individual drugs to establish minimum inhibitory concentrations (MIC) of cefovecin, ciprofloxacin, clarithromycin, clofazimine, doxycycline, enrofloxacin, trimethoprim and sulfanilamide (the latter two as a combination). Checkerboard assays were then performed for susceptible M. smegmatis isolates for the following combinations: clarithromycin (one isolate only) versus enrofloxacin, clarithromycin vs doxycycline, clarithromycin vs trimethoprim/sulfanilamide; enrofloxacin vs doxycycline (six isolates); enrofloxacin vs trimethoprim/sulfanilamide (six isolates). Susceptible M. fortuitum isolates were tested against enrofloxacin versus doxycycline (four isolates only).
All six M. fortuitum isolates were susceptible to enrofloxacin, but only four of six were susceptible to doxycycline. All six M. smegmatis isolates were susceptible to doxycycline, enrofloxacin and trimethoprim/sulfanilamide. A single isolate from the 12, a M. smegmatis isolate, was susceptible to clarithromycin. The fractional inhibitory concentration of each drug ranged from 0.64 to 1.84, indicating that neither synergism nor antagonism was evident. All 12 isolates were resistant to cefovecin. The clofazimine MIC50 to inhibit isolate growth was approximately 3.3 μg/mL for both strains.
Drugs commonly used for treatment of RGM, when tested as combinations, do not appear to antagonise one another in vitro. Cefovecin is not efficacious for treatment of RGM infections.
研究用于治疗快速生长分枝杆菌（RGM）的特定药物组合是否存在影响疗效的药物相互作用，并分别研究每种分离株对头孢维星和氯法齐明的敏感性。
细菌分离株的体外药敏试验。
最初，对来自偶然分枝杆菌和耻垢分枝杆菌菌群的5株猫分离株和1株犬分离株（n = 12）进行微量肉汤药敏试验，以确定头孢维星、环丙沙星、克拉霉素、氯法齐明、强力霉素、恩诺沙星、甲氧苄啶和磺胺（后两者为组合）的最低抑菌浓度（MIC）。然后对敏感的耻垢分枝杆菌分离株进行棋盘法试验，用于以下组合：克拉霉素（仅1株分离株）与恩诺沙星、克拉霉素与强力霉素、克拉霉素与甲氧苄啶/磺胺；恩诺沙星与强力霉素（6株分离株）；恩诺沙星与甲氧苄啶/磺胺（6株分离株）。对敏感的偶然分枝杆菌分离株进行恩诺沙星与强力霉素的试验（仅4株分离株）。
所有6株偶然分枝杆菌分离株对恩诺沙星敏感，但6株中只有4株对强力霉素敏感。所有6株耻垢分枝杆菌分离株对强力霉素、恩诺沙星和甲氧苄啶/磺胺敏感。12株分离株中的1株，即耻垢分枝杆菌分离株，对克拉霉素敏感。每种药物的部分抑菌浓度范围为0.64至1.84，表明既无协同作用也无拮抗作用。所有12株分离株对头孢维星耐药。两种菌株抑制分离株生长的氯法齐明MIC50约为3.3μg/mL。
用于治疗RGM的常用药物组合在体外试验时似乎不会相互拮抗。头孢维星对治疗RGM感染无效。
