The Distribution And The Analysis Of Drug Resistance Of Non-fermentative Bacteria In Burn Department And Investigation On Mechanism Of Pseudomonas Aeruginosa Against To Imipenem

Objective:To analyze the distribution and drug resistance of non-fermentative bacteria which isolated from the burn department of the First Affiliated Hospital of Anhui Medical University from 2001 to 2008 for guiding the clinical practice. To study the mechanism of 13 Pseudomonas aeruginosa isolated from clinical burn patients.Materials and Methods:A total of 235 non-reputitive non-fermentative bacterias were collected from the burn department of the First Affiliated Hospital of Anhui Medical University from 2001 to 2008. M-H agar dilution method was used to detect the minimal inhibitory concentration (MIC) of antimicrobials against wild-type isolates through referring antimicrobial agents susceptibility standards of CLSI 2008.M-H agar dilution method was used to detect the minimal inhibitory concentration (MIC) of antimicrobials against to 13 Pseudomonas aeruginosa. Metallo-beta-lactamase was screened by imipenem-EDTA double disc synergy test, PCR methods was employed to examine the genes of IMP-1, IMP-2, VIM-1, VIM-2 and the gene of PER and outer membrane encoded by OprD2 gene, and so on. Carbonyl cyanide 3-chlorophenylhydrazone(CCCP) was used to study the affection on the MIC of imipenem and active efflux pumps system in 13 P. Aeruginosa. Results:235 strains were isolated from bum patients. Pseudomonas aeruginosa (75.3%), Acinetobacter baumannii (14.0%) which were the dominant in the infection of non-fermentative bacteria. The resistant rates of P. aeruginosa to Ceftriaxone, Ceftazidime, Cefotaxime and Piperacillin were 90.4%, 95.5%, 87.7%, 100% respectively. Especially the resistant rates of P. aeruginosa to Imipenem was up to 74.1%. Meanwhile the resistant rates of A.baumanni to Amikacin, Cefepime, Imipenem were 90.6%, 100%, 50% respectively. The results showed obviously that the wound infection is influenced by the extent of burn(χ2=13.014, P<0.05).The 13 strains of Pseudomonas aeruginosa displays a highly drug-resistance to antimicrobial agents. The strains of metallo-beta- lactamase-producing are screened by imipenem-EDTA double disk synergy test. But no any gene of metallo-beta-lactamase was found. OprD2 gene was screened in one imipenem-resistant Pseudomonas aeruginosa strains, OprD2 gene were not found in any other imipenem-resistant Pseudomonas aeruginosa strain. 1 strains had active efflux pumps system because their MICs to imipenem were cut down to 1/4 affected by CCCP.Conclusions:In vitro antimicrobial sensitivity test against clinical isolates of 235 non-reputitive non-fermentative strains, most of the resistant rates are high and more common phenomenon of multi-drug resistance in commonly used clinical antimicrobial agents. Aztreanam, the third-generation fluoroquinolones are not selected to treat clinical burn infection caused by Pseudomonas aeruginosa. At present carbapenems was the first choice to the treatment of burn infection caused by Pseudomonas aeruginosa, the followed is including inhibitors ofβ-lactam and cephalosporin or assoiating with aminoglycoside when conditions permit. The loss of outer membrane OprD2 was the first reason to imipenem-resistant P. aeruginosa. The second reasons were Extended-spectrumβ-lactamases and active efflux pumps systems. Metallo-beta-lactamase was detected by imipenem-EDTA double disc synergy test, which was an accurate, easy, economic, easy operating method. In addition, two kinds resistant mechanism were found in 8 strains(1,2,3,4,5,6,11,13) of 13 strains Pseudomonas aeruginosa.