| Many Gram-negative bacteria are resistant to antibiotics due to the production of plasmid-mediated extended-spectrum β-lactamases (ESBLs). ESBL production confers resistance to all β-lactams except for cephamycins and carbapenems. The prevalence of ESBL-producing bacteria is increasing world-wide. The ESBL producers most frequently isolated in the hospital setting are Klebsiella pneumoniae and Escherichia coli. Infections due to these organisms often occur during outbreaks and therefore ESBL-producing bacteria represent a serious problem for hospitalized patients. In the last few years, ESBL-producing P.mirabilis strains have been isolated with increasing frequency, and infection caused by these strains is becoming a serious therapeutic issue, especially in hospital settings.Consequently, Fluoroquinolones may be an effective alternative antimicrobial therapy. However, similar to Escherichia coli and Klebsiella pneumoniae, the mechanism of drug multiple resistance is complicated. the incidence of ciprofloxacin resistance in P.mirabilis isolates is increasing. Plasmid mediated fluoroquinolones resistance genes qnr and aac(6’)-Ib-cr become the main mechanism of drug resistance. In order to study the resistance and the feature of molecular epidemiology, we detected and analyzed them in this area in P.mirabilis isolates.Objective The purpose of this study was to investigate the prevalence of P.mirabilis, to examine the genetic mechanisms of resistance and to analyse molecular epidemiology by molecular methods. we studied the resistance in P.mirabilis isolates in the first affiliated hospital of Anhui medical university. To provide laboratory basis for the areas to develop P.mirabilis infection control and monitoring of drug resistance.Methods1) A total of33isolates of P.mirabilis of clinical isolates were collected from samples.The agar dilution test was performed for each of the strains.The laboratory data were analyzed. The rates of examined the extent of drug resistance by microdilution method. ESBLs producers were screened by ESBLs initial screening test and phenotype confirmatory test in accordance with the guidelines of CLSI (Clinicaland Laboratory Standards Institute)in2010. Antibacterial susceptibility of ESBLs-positive and ESBLs-negative isolates and the distribution of ESBLs producers of the resistant isolates were analyzed according to the breakpoints of S19and S20.2) QnrB and aac(6’)-Ib gene was detected by PCR in clinical isolates of33P.mirabilis.3) The homology with qnrB gene or ESBLs were analyzed by Enterobacterial Repetitive Intergenic Consensus polymerase chain reaction (ERIC-PCR).Results The results showed the resistant rate of P.mirabilis to Imipenem was0%. The resistance rates to Piperacillin, Cefuroxime, Ceftazidime, Cefotaxime, Cefepimeand Aztreanam are12.1%,30.3%,24.2%,27.3%、18.2%and21.2%respectively. The highest resistance rate of these was Cefazolin(100%). Compared to other drugs, the resistance rate to Gatifloxacin (45.5%), Ciprofloxacin(39.4%) and Levofloxacin (39.4%) were higher. The incidence of ESBLs-producing P.mirabilis was18.1%. Except for Imipenem, Cefazolin and Piperacillin, the resistance rates of ESBLs producers were significant higher than non-ESBLs producers (P<0.01).The resistance rates of some drugs were higher to100%. If use the CTX, CFZ CLSI S20new breakpoints, the concordance of antibacterial susceptibility results and ESBL phenotype will increase greatly. It is no longer necessary to confirmed by CLSI phenotype confirmatory test. As to CAZ, further evaluate and research is required.12strains (36.4%) of33clinical isolates were observed with qnrB,3strains (9.1%) of33aac(6’)-Ib gene.2strains qnrB strains were detected aac(6’)-Ib.Among the2strains,1strains were type of qnrB with aac(6’)-Ib-Cr gene positive.The rates of resistence to fluoroquinolones were all69.2%(9/13). The6ESBLs isolates were divided into5types and12qnrB isolates were divided into7types with ERIC-PCR, in which a homology was observed in isolates from the same hospital. There were41.7%(5/12)strains with ESBLs of12qnrB strains, and there were4.8%(1/21) strains with ESBLs of21non-qnrB strains (P<0.05). and The5strains with qnrB and ESBLs were all resistant to fluoroquinolones.Conclusions1)The resistance rates of P.mirabilis were multi-resistance. To Imipenem was the lowest,there were some extend resistence to the second and third cephalosporins and most fluoroquinolones.To the first cephalosporin,the rate of resistence was the highest. The incidence of ESBLs producers was high in P.mirabilis isolates.2) The rate of Plasmid-mediated qnrB quinolone resistance gene was high in the clinical P.mirabilis isolates, but aac(6’)-Ib-Cr was low.Compared with the resistance rates of non-qnrB/aac(6’)-Ib-Cr gene strains, qnrB/aac(6’)-Ib gene-Cr strains were more resistant to fluoroquinolones (P<0.05).3) The clone dissemilation between strains may exist in resistance to P.mirabilis clinical isolates by themselves and there were correlations between ESBLs with qnrB gene, they play roles together on multiple-drug-resistance. we must detect them at the same time. |
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