Field T R, White A, Elborn J S, Tunney M M
Clinical and Practice Research Group, School of Pharmacy, Queen's University Belfast, Medical Biology Centre, 97 Lisburn Road, Belfast, BT9 7BL, UK.
Eur J Clin Microbiol Infect Dis. 2005 Oct;24(10):677-87. doi: 10.1007/s10096-005-0031-9.
Pseudomonas aeruginosa, the predominant causative pathogen of chronic lung infection in patients with cystic fibrosis, may grow under anaerobic conditions as biofilms in the lungs of cystic fibrosis patients. To determine if growth under anaerobic conditions affects the antimicrobial susceptibility of P. aeruginosa, the susceptibility of clinical isolates of P. aeruginosa grown planktonically and as biofilms to a range of antibiotics was determined. Growth under anaerobic conditions did not reduce the ability of ceftazidime, meropenem, aztreonam, piperacillin, or piperacillin/tazobactam to inhibit planktonic growth, with MIC50 values for these antibiotics remaining unchanged or decreasing. However, tobramycin was less effective at inhibiting planktonic bacterial growth under anaerobic conditions, with the MIC50 of tobramycin increasing twofold. Growth under anaerobic conditions also decreased the bactericidal activity of tobramycin, with the MBC50 of tobramycin increasing fourfold. The killing kinetics of tobramycin was also examined under aerobic and anaerobic conditions for selected isolates. When isolates 6A and 12A were grown aerobically, concentration-dependent decreases in total viable count were apparent with tobramycin. In contrast, when these isolates were grown anaerobically, tobramycin at the same concentrations did not decrease the total viable count. When isolates were grown as biofilms under both aerobic and anaerobic conditions, isolate- and concentration-dependent differences in killing of the biofilms by tobramycin were apparent. However, tobramycin at concentrations up to 128 mg/l was unable to eradicate biofilms of any of the isolates tested, whether biofilms were grown aerobically or anaerobically. These results show that oxygen limitation may reduce, in a strain-dependent manner, the susceptibility to tobramycin of P. aeruginosa grown planktonically and as biofilms.
铜绿假单胞菌是囊性纤维化患者慢性肺部感染的主要致病病原体，可在厌氧条件下于囊性纤维化患者肺部形成生物膜生长。为了确定厌氧条件下的生长是否会影响铜绿假单胞菌的抗菌敏感性，测定了浮游生长和形成生物膜生长的铜绿假单胞菌临床分离株对一系列抗生素的敏感性。厌氧条件下的生长并未降低头孢他啶、美罗培南、氨曲南、哌拉西林或哌拉西林/他唑巴坦抑制浮游生长的能力，这些抗生素的MIC50值保持不变或降低。然而，妥布霉素在厌氧条件下抑制浮游细菌生长的效果较差，妥布霉素的MIC50增加了两倍。厌氧条件下的生长也降低了妥布霉素的杀菌活性，妥布霉素的MBC50增加了四倍。还在需氧和厌氧条件下对选定的分离株检测了妥布霉素的杀菌动力学。当分离株6A和12A在需氧条件下生长时，妥布霉素使总活菌数明显呈浓度依赖性下降。相反，当这些分离株在厌氧条件下生长时，相同浓度的妥布霉素并未降低总活菌数。当分离株在需氧和厌氧条件下均形成生物膜生长时，妥布霉素对生物膜的杀灭存在分离株和浓度依赖性差异。然而，浓度高达128mg/l的妥布霉素无法根除所测试的任何分离株的生物膜，无论生物膜是在需氧还是厌氧条件下生长。这些结果表明，氧限制可能以菌株依赖性方式降低浮游生长和形成生物膜生长的铜绿假单胞菌对妥布霉素的敏感性。
