Colistin Heteroresistance And Drug Combination Study Of Psoudomonas Aeruglnosa

Objective:To identify the current situation of colistin heterogeneity and its in vitro susceptibility when in combination use with other drugs against Pseudomonas aeruginosa.Methods:297 carbapenem-resistant Pseudomonas aeruginosa isolates were selected. Broth microdilution method was used to determine the minimum inhibitory concentration of colistin and other drugs. Population analysis profiles was used to analyze colistin heterogeneity of colistin-susceptible isolates, as well as time-kill curves of several isolates. Chequer-board method was used to reveal the combination efficacy of colistin with imipenem, meropenem, biapenem, ceftazidime, levofloxcin, piperacillin/tazobactam and cefoperazone/sulbactam.Results:99.66% of the 297 isolates were susceptible to colistin. Population analysis profiles displayed that 35% of the 20 isolates were colistin heteroresistant, and 20% were heterogeneous. It showed that when colistin was used in combination with other drugs, heteroresistant isolates were mainly synergistic and additive, while heterogeneous isolates were mostly additive and indifferent.Conclusion:Multidrug resistant Pseudomonas aeruginosa is highly susceptible to colistin, while its heteroresistant and heterogeneous phenomenon is common. Colistin in combination use with other drugs can enhance the efficacy to heteroresistant isolates.