The Antibiotic-resistance And Its Mechanisms Of β-lactamases In Pseudomonas Aeruginosa

Objective：Pseudomonas aeruginosa(PA) is the causative agent of Pneumonia and is a commonpathogenic bacterium in hospital. PA leads to a high rate of fatality to patientsinfected．In recent years, Imipenem，an important antibiotic of carbapenems，isfrequently used as the last extended-spectrum beta-lactamases for the treatment ofserious infections caused by PA. As its large ammount of clinical application，theresistance of PA against imipenem has been popular all over the world．It was reportedthat kinds of β-1actamase (such as TEM，SHV,OXA,PER,VEB,GES and so on),metallo-β-lactamase (such as IMP, VIM, SPM and GIM) and plasmid-cephalosporinase(AmpC) produced by P. aeruginosa，and the absence of outer porin D2(OprDE) wereprincipal mechanisms for the drug-resistance to β-lactam Antibiotics．In this researchwe examined P.aeruginosa’s drug-resistance genes and tested its sensitivity to β-1actam antibiotics in order to provide evidence clinical medication．To analyze theresistance profile of PA isolated from the first affiliated hospital of Bengbu MedicalCollege to16antimicrobial agents，we confirmed the role of metallo-β-lactamases andextended-spectrum beta-lactamases in order for appropriate use of antibiotics and theclinical microbiology laboratory monitoring for the beta lactamase．Methods:1．otally208clinical isolates of PA were collected from the first affiliated hospital ofBengbu Medical College from Jan2012to Jan2013. Bacteria were identified by Usingautomatic microbial analyzer VITEK2compact. Disc diffusion method recommended by the Clinical and Laboratory Standards Institute (CLSI2011) was utilized to detect thedrug sensitivity against16antimicrobial agents in208strains of P. aeruginosa．2．The metallo-β-lactamase(MBLs) screened genotype of53imipenem-resistant PAwasdetected by EDTA disc synergy test．Genotype of bacteria procucing MBLs wasidentified by Polymerase chain reaction(PCR)．3．The phenotypic confirmatory test recommended by CLSl was employed to detect theESBLs in the multi-drug resistant PA， and PCR were introduced to detect theextended-spectrum beta-lactamases(ESBLs) gene of PA． The results of CLSIrecommended methods and PCR were comparatively analyzed．Results:1． Bacterial drug-sensitive test showed that208PA strains were mainly distributed inICU，and the department of respiratory diseases, geriatrics department, etc；the rateswere25.0％，13.94％，and9.13％，respectively．Isolating rate of sputa was60.57％．53of208strains were resistant to imipenem．Most of them were multi-drugresistant PA，and had a high drug resistant rate to CTE,CZ, AMS, FTN, and low rate toAN,TZP, CAZ；the rates were92.45%,86.79%,88.68%,90.56%,37.73%,39.62%, and45.28%，respectively．2．Phenotype of metallo-beta-lactamases(MBLs) in PA was screened in the improveddisc synergy test in53isolates of imipenem-resistant PA，among them4strains werepositive．PCR methods showed that3strains were VIM genotype，and no othergenotypes were noted．3． Fourteen of ESBLs positive stains were ascertained in53strains ofimipenem-resistant PA by the phenotypic confirmatory test as recommended byCLSI．For the purpose of detection of the ESBLs genotype in these strains，PCR werecarried out，the results indicated that23strains were ESBLs genotype positive((43.39 ％)，and14strains were TEM genotype(60.9%，14/23)，4strains were OXA-10genotype(17.39%，4/23)，3strains were PER genotype(13.04%，3/23)；the OXA-2,SHV, and VEB were found to be negative．Conclusion:1．The phenomina of drug-resistance of PA was crucial, and most of them weremulti-drug resistant．PA was widely detectable in each department of the hospitalinvestigated，especially in intensive care units(ICU)，and the isolating rate in sputumkept the highest．2．The mechanism of PAagainst imipenem is diverse in the hospital．But the phenotypicconfirmatory test recommended by CLSI is unsuitable for the screening of PA withESBLs phenotype.however PCR have the reasonable coincidence in it．3．Beta-lactamases contribute to the mechanisms of PAdrug-resistance...