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Background: Enterobacter cloacae (E. cloacae) infection has the highest mortality rate among Enterobacter infections. This study aimed to determine the prevalence and the transmission route of the class I integron, qnr genes, and CTX-M ESBLs genes in clinical isolates and to analyse the association between the prevalence of MDR genes and the antibiotic resistance of E. cloacae. Materials and Methods: The antibiotic susceptibility was tested the agar dilution method. The class I integron, qnr genes, and CTX-M ESBLs genes were detected by polymerase chain reaction (PCR). The prevalence data were analysed with the Chi-square test. Results: In the 100 clinical isolates, the class I integron-positive rate was 65%, with 12% on chromosome, 15% on plasmids and 38% on both. The positive rate of qnr genes was 37% with plasmid location. The positive rates for qnrA, qnrB and qnrS were 6%, 23% and 8%, respectively. The CTX-M ESBLs-positive rate was 34%. For CTX-M-1 ESBLs, 15% were on chromosome, 6% on plasmids and 4% on both; for CTX-M-9 ESBLs, 1% was on chromosome and 7% on plasmid; for CTX-M-25 ESBLs, 3% were on chromosome and 1% on plasmid. Conclusion: Antibiotic resistance genes may be horizontally and vertically disseminated among E. cloacae, which helps multidrug-resistant (MDR) strains of E. cloacae to be successful nosocomial agents.
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Objective To investigate the distribution of qnr and aac(6')- Ⅰ b-cr genes of clinical isolates resistant to ciprofloxacin in Enterobacteriaceae in Wenzhou. Methods From August 2005 to April 2008 a total of 461 clinical isolates resistant to ciprofloxacin in Enterobacteriaceae (370 isolates of Escherichia coli, 39 isolates of Enterobacter cloacae and 52 isolates of Klebsiella) were collected from the First Affiliated Hospital of Wenzhou Medical College. qnr and aac(6')- Ⅰ b genes were detected by PCR for all the clinical isolates, DNA sequencing was used for qnr and aac(6')-Ⅰ b-cr identification and conjugation experiment was proved to find ways of transmission of antimicrobial resistance. Results Fifteen qnr-positive isolates were detected among 461 Enterobacteriaceae isolates, including 5 qnrA-positive isolates (4 Enterobacter cloacae isolates and 1 Klebsiella ornithinolytica isolate), 4 qnrB-positive isolates( 2 Klebsiclla paeunoniae isolates and 2 Escherichia coli isolates), 6 qnrS-positive isolates(2 Klebsiella pneunoniae isolates and 4 Escherichia coli isolates). Fifty-two among 461 Enterobacteriaceae isolates harbored aac(6')- Ⅰ b-cr gene, including 42 Escherichia coil isolates, 4 Enterobacter cloacae isolates and 6 Klebsiella isolates. DNA sequencing for 15 qnr-positive isolates found they harbored aac(6')- Ⅰ b-cr gene simultaneously. Fifteen qnr-positive isolates were susceptible to imipenem but resistant to some other drugs. Conjugation experiments were successfully carried out in 7 of 15 isolates harbored qnr and aac(6')-Ⅰ b-cr genes, and their resistance to quinolones and aminoglycosides was partly transmitted to the recipient isolates. Conclusion The qnr genes are few in clinical isolates resistant to ciprofloxaein in Enterubacteriaceae in Wenzhou, however the aac(6')- Ⅰ b-cr gene is popular.
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Objective To explore the prevalence of qnr gene in gram-negative bacteria isolated from Renmin Hospital of Wuhan University. Methods qnr gene was detected by PCR in non-duplicate E.coli (n=129), E.cloacae (n=10) and K.pneumoniae (n=29) isolates.PCR technique was used to amplify the gene encoding type I integrons.Kirby-Bauer disk diffusion method was used to test the in vitro suscepti- bility of the isolates to 16 antimicrobial agents.ESBLs were investigated according to phenotypie screening and confirmatory test recom- mended by NCCLS.MIC values of ciprofloxacin were determined for qnr gene positive strains.Results qnr gene were identified in 6 clinical isolates including 5 strains of E.coli and I E.cloacae, qnr gene was not found in K.pneumoniae isolates.The 6 qnr-positive clinical iso- lates were positive for type I integrons.All the 6 strains were susceptible to imipenem but resistant to many other drugs tested.Only 2 of the E.coli isolates were susceptible to ciprofloxacin.Conclusions In Hubei Province, the prevalence of qnr is confirmed.The serious situa- tion of multidrug-resistance in clinical isolates with qnr gene requires careful monitoring of qnr-carrying isolates.
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Aim To identify the extended-spectrum ?-lactamases(ESBLs) gene in Klebsiellae pneumoniae isolates with qnr gene.Methods Antimicrobial agents susceptibilities were determined with standard agar dilution procedure on Mueller-Hintonagar and 3 isolates with qnr gene were confirmed as ESBLs producing strains by NCCLS Confirmatory Test.The partial blagene of ESBLs producing isolates were detected by PCR using universal primers for TEM,SHV,CTX-M-1group,CTX-M-2 group,CTX-M-13group,OXA-1group,OXA-2 group,OXA-10 group,PER-1 and VEB-1,respectively.At the same time,Class 1 integrase gene was also detected by PCR.The entire blaCTX-M-13group,blaTEM,blaOXA-1group were amplified by PCR using the primers outside the Open Reading Frame(ORF) of these ?-lactamases.The PCR products were also directly sequenced and analyzed;the clinical isolates of ESBLs producers were detected by PFGE. Results 3 Klebsiellae pneumoniae isolates with qnr gene were ESBLs producers and they produced CTX-M-14 ESBLs and TEM-1 ?-lactamases.1 isolate simultaneously produced OXA-1?-lactamases,and 3 isolates carried class 1 integron.Besides quinolones,ESBL producers were also resistant to most ?-lactams,and PFGE patterns of two isolates were same.Conclusion 3 Klebsiellae pneumoniae isolates with qnr gene produced CTX-M-14 ESBLs,which caused their multi-resistance,and clone spread was found in them.More attention should be paid to detect those strains.