Study Of Typing Integrons And Plasmid-mediated Quinolone Resistance In Clinical Isolates Of Proteus

Proteus is the important pathogen belongs to Enterobacteriaceae.The Proteus consists of four named species(P.mirabilis,P.penneri,P.vulgris and P.myxofaciens).And P.mirabilis is a frequent cause of urinary tract infections that are often persistent and difficult to treat.The extensive use and misuse of antimicrobials lead to the emergence and dissemination of mutidrug-resistant bacterial pathogens.In recent years,a novel system known as integrons,which are mobile DNA elements with a specific structure consisting of two conserved segments flanking a central region containing unknown open reading frames or"cassettes"encoding specific antimicrobial resistance,has been identified in multiple resistant bacteria and is considered to play an important role in the acquisition and dissemination of antibiotic resistance genes.Quinolones is the first complete synthesis antimicrobial agents.With extensive use, Clinical isolates of proteus with decreased susceptibility or resistance to fluoroquinolones are growing.To date,two main mechanisms of quinolone resistance have been established:alterations in the targets of quinolones,and decreased accumulation inside the bacteria due to impermeability of the membrane and/or an overexpression of efflux pump systems.Both of these mechanisms are chromosomally mediated.Furthermore,mobile elements have been described carrying the qnr gene which confers resistance to quinolones.These mobile elements have the potential for horizontal transfer of quinolone resistance genes.In 1998,low level quinolone resistance was found to be transfered by a plasmid firstly discovered in a clinical isolate of Klebsiella pnermoniae by Martinez-Martinez. The gene responsible,named qnr,proved to be the quinoloneresistance gene,which can protect DNA gyrase and /or topoisomeraseâ…£from inhibition by quinolone,Many analysis of the gene structure indicated that qnr was always located in class 1 integrons which included many cassttes especially ESBLs gene.Nowadays qnr was reported in worldwide including East Asia,American and Europe,et al.Subsequently,two novel Qnr homologues,QnrB and QnrS are characterised.The first qnr gene is named qnrA.By now,there is not report on qnr-producing Proteus in China.We collected 146 clinical isolates of proteus from the Center of Control and Supervision for Bacterial Resistance of Anhui Province(from October 2004 to October 2006),and investigate their antimicrobial resistance patterns and the distribution of integrons and detect their qnr gene.ObjectiveTo investigate the distribution of class 1 and class 2 integrons in the clinical proteus and to analyze the correlation between integrons and its resistance.To reserch the distribution of qnr gene in the clinical proteus.Materials and Methods146 clinical isolates of Proteus were collected from the Center of Control and Supervision for Bacterial Resistance of Anhui Province(from October 2004 to October 2006).PCR were used for screening of class 1 and class 2 integrons.The M-H broth microdilution method was used to determine the MIC values of a range of antibiotics for these isolates,qnr gene was detected by PCR in clinical isolates of 146 proteus. Antimicrobial susceptibility was tested by M-H broth microdilution.Plasmid DNA is isolated from small-scale(1-2 ml) bacterial cultures by treatment with alkali and SDS. Preparation and Transformation of Competent E.coli Using Calcium Chloride.Results54 strains(36.9%)of 146 clinical isolates were observed in class 1 integron and 56(38.4%) were observed in class 2 integron.27 of them(18.5%) were showed in class 1 integron and in class 2 integron.Of the 146 proteus,qnr gene were found in 3 clinical isolates:qnrA,qnrB₂,qnrS₁.There was one contains qnrB₂ and qnrS₁.Mutation was found in qnrB₂(position 295 C→A).3 qnr gene were submitted to the GenBank database,accession numbers:EF488761,EF488762,EF501989.2 of 3 Strains with qnr gene were ESBLs producing and multi-drug resistance strains.ConclusionsClass 1,2 integron occurrence rate were 36.9%and 38.4%in the clinical Proteus isolates,and closely associated with the multi-drug resistance of proteus.The presence of qnr gene was lower in proteus.