碳青霉烯类药物对铜绿假单胞菌体外抗菌行为比较

目的:比较不同碳青霉烯类药物对临床分离铜绿假单胞菌体外抗菌行为差异,包括体外抗菌活性以及细菌形态学改变.方法:采用纸片法和标准琼脂稀释法测定临床分离的铜绿假单胞菌对亚胺培南、美洛培南、帕尼培南和头孢他啶的敏感性;电镜观察铜绿假单胞菌在不同浓度的亚胺培南、美洛培南、帕尼培南和头孢他啶中不同时间细菌形态变化.结果:14%的铜绿假单胞菌在美洛培南纸片周围呈"双环"抑菌形态;在MH培基中,帕尼培南的MIC值明显高于亚胺培南和美洛培南,但在MM培养基中,帕尼培南的MIC值是原来的1/8～1/2;亚胺培南和帕尼培南使铜绿假单胞菌细胞呈圆球形改变,头孢他啶使细菌伸长如丝状,低浓度美洛培南的细菌呈纺锤形改变.结论:帕尼培南体外抗菌作用受培养基种类影响大,MH培养基测定结果可能无法准确反映其抗菌活性;美洛培南杀菌作用不完全且诱导细菌呈纺垂体样改变,可能导致内毒素释放增加,影响临床严重感染的预后.

Comparing in vitro antibacterial behaviors of carbapenems against Pseudomonas aeruginosa

AIM:To compare the antibacterial behaviors of carbapenems against Pseudomonas aeruginosa,including the in vitro antibacterial activity and the morphological changes of bacterium.METHODS:In vitro the sensitivity of different antibiotics against P.aeruginosa were determined by standard KB method and agar dilution method on Mueller-Hinton (MH) agar,diluted MH agar (1:16) and Minimum Medium (MM) agar.The bacterial morphological changes after incubating with different antibiotics were observed with electronic microscope.RESULTS:14% clinical isolates of P.aeruginosa show double-circle phenomena around meropenenm disc.The MIC values of panipenem were higher than those in imipenem and moropenem on MH agar,while decreased 8-16 times on MM agar.lmipenem and panipenem induced bacterial cell ovoid formation,ceftazidime induced bacterial filamentous elongation and lower concentration meropenem led bacterial cell fusiform change.CONCLUSION:In vitro antibacterial activity of panipenem was affected by the medium type and lower basic amino acid concentration medium favored its bactericidal effect.Meropenem did not have complete bactericidal effect and more bacterial endotoxin could be released at lower drug concentration.