Investigation On The Antibacterial Acticity Of Polymyxin B Against Multi-drug Resistant Pesudomonas Aeruginosa And Acinetobacter Bamannii In Vitro

PART 1 Antimicrobial Resistance Surveillance among Pesudomonas aeruginosa and Acinetobacter baumannii IsolatesBackground:Pesudomonas aeruginosa (P.A) and Acinetobacter baumannii(A.b) are two kinds of conditional Gram negative pathogenic bacteria. Recent years, the infection rate which caused by Pesudomonas aeruginosa and Acinetobacter baumannii have been increased gradually, and Pesudomonas aeruginosa and Acinetobacter baumannii have been the most usual bacteria which caused hospital infections. Pesudomonas aeruginosa and Acinetobacter baumannii own a high survival ability. They can permanent plant in hospital for a long time and even cause the outbreak of nosocomial infection. Accordingly, it's important to monitor Pesudomonas aeruginosa and Acinetobacter baumannii's clinical feature and drug resistance. Objective: To investigate the Pesudomonas aeruginosa and Acinetobacter baumannii's distribution feature,the antimicrobial resistance during the past 4 years and compare antibacterial activity of Polymyxin B against multi-drug resisitant (MDR) Pesudomonas aeruginosa and MDR Acinetobacter baumannii with that of imipenem in vitro.Methods: The distribution feature of infections which caused by Pesudomonas aeruginosa and Acinetobacter baumannii were supervised. Disk diffusion test was used to study their antimicobial agent resistance and transition of drug resistance.The results were evaluated based on Clinical and laboratory Standards Institute (CLSI).WHONET 5.4 was applied for analysis.The MDR Pesudomonas aeruginosa and Acinetobacter baumannii were screened by WHONET 5.4. MICs (minimal inhibitory concentration) of polymyxin B and imipenem were detected by broth dilution method.Results: Constituent ratio of infections caused by Pesudomonas aeruginosa remained among 20%-23% in the 4 years and infections caused by Acinetobacter baumannii had been raised obviously in the recent 4 years, especially in ICU. Although carbapenems were the most active antibiotics tested against Pesudomonas aeruginosa and Acinetobacter baumannii, their resistance had been sharply rised since 2008.In addition , the ratio of MDR Pesudomonas aeruginosa and Acinetobacter baumannii had also been raised in the 4 years. The MICs displayed that polymyxin B had the higher antibacterial activity against the MDR Pesudomonas aeruginosa and Acinetobacter baumannii than imipenem.Conclusion: The drug resistance of Pesudomonas aeruginosa and Acinetobacter baumannii had been rised obviously and the number of MDR Pesudomonas aeruginosa and Acinetobaeter baumannii had been increased sharply. Monitoring of the antimicrobial resistance to Pesudomonas aeruginosa and Acinetobacter baumannii should be strengthened . The change of the antimicrobial resistance should be investigated for rational drug usage in the clinic and prevent resistance bacterial strain from being transmitted.We can consider using polymyxin B to treat the severe infections caused by MDR Pesudomonas aeruginosa and Acinetobacter baumannii. PART 2 Investigation on the antibacterial acticity of Polymyxin B against multi-drug resistant Pesudomonas aeruginosa and Acinetobacter bamannii in vitroBackground: Pesudomonas aeruginosa and Acinetobacter baumannii are important pathogenic bacteria. They are both conditional pathogenic bacteria, along with the growing usage ofβ-lactamase antibiotics,immunosuppressive agent,tumor chemothereputics and virulence operations,the drug resistance of Pesudomonas aeruginosa and Acinetobacter baumannii are grave increasingly. The treatment to the severe infections caused by these multi-drug resistant bacteria has been a big problem in clinical healings. Therefore, there is an urgent need of a drug which can treat these infections.Objective: To measure the minimal concentration (MIC) of the polymyxin B,ceftazidime,ciprofloxacin,amikacin,imipenem and measure the time-kill curve of the polymyxin B.Methods: Fifty MDR Pesudomonas aeruginosa and fifty MDR Acinetobacter baumannii were screened from our bacterial division, and they were resistant to at least three kinds of thess drugs as follows:β- lactamases,carbapenems,aminoglycosides and fluoroquinolones. MICs were detected by broth dilution method. The optical density of the culture fluid was determined by spectrophotometer. With the OD values , the logarithm of bacterial fluid's concentration was calculated by differential formula and time-kill curve was drawn according to logarithm of bacterial fluid's concentration.Results: Compared to ceftazidime,ciprofloxacin,amikacin,imipenem, polymyxin B displayed a much higher antibacterial activity . According to the time-kill curve, polymyxin B killed the bacteria in a concentration -dependent manner.Conclusion: Compared to other drugs, polymyxin B showed more antibacterial activity in killing MDR Pesudomonas aeruginosa and Acinetobacter baumannii. We should consider using polymyxin B as the last resort in curing sever infections which caused by MDR Gram-negative bacteria.