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Objective To analyze the distribution of class 1,2 and 3 integrons and their gene cassettes,and to explore its relationship with drug resistance in Shigella.Methods Antimicrobial susceptibility was detected by minimal inhibitory concentration (MIC) method.All the genes of integrons and gene cassettes were amplified by polymerase chain reaction (PCR).The amplicons were identified by amplified fragment length polymorphism (AFLP) and sequencing.Results Fifty seven multi-drug resistant strains were identified from a total of 62 Shigella strains (91.9％).Among multi drug resistant strains,52 strains carried integrons of class 1 (91.2 ％) and 55 strains carried integrons of class 2 (96.5％).Only 2 strains carried class 1 integrons alone,5 strains carried class 2 integrons alone and 50 strains had both class 1 and class 2 integrons.Class 3 integrons were not detected.The gene cassettes of typical class 1 integrons,dfrV and dfrA17-aadA5,were detected in 6 strains and 2 strains,respectively.Atypical class 1 integrons with gene cassettes blaOxA30 aadA1 were detected in 44 strains.The typical and atypical class 1 integrons coexisted in 6 Shigella flexneri strains.Gene cassettes for class 2 integrons were dfrA1 sat1-aadA1.Conclusions The multi-drug resistant Shigella strains are widely distributed in Ji'nan,and the atypical class 1 integrons and class 2 integrons are common in these strains.Coexistence of the two integrons is observed in some of the strains.
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Objective To discuss the characteristics of extended-spectrum beta-lactamases(ESBLs)-producing Shigella and the relation between them and drug-resistance plasmid. Methods The suspicious ESBLs-producing isolates were screened by K-B disc diffusion method, and the ESBLs-producing strains were confirmed by confirmatory test recommended by the National Committee for Clinical Laboratory Standards. Furthermore, the partial blageneof these isolates were detected by PCR using universal primers for TEM, SHV, CTX-M-1 group, CTX-M-2 group and CTX-M-9 group, respectively. The entire blaCTX-M-9 and blaTEM were amplified by PCR using the primers outside the open reading frame (ORF) of these β-1actamases and products were directly sequenced. The conjugation experiment was performed to determine whether the resistance was transferable. Minimal inhibitory concentration (MIC) was detected with double agar dilution method. Results Of the 275 isolates, 12 strains were identified as ESBLs producers. Among them, 8 strains were CTX-M-14 carriers and 4 strains were CTX-M-3 carriers. All ESBLs-producing isolates are positive for plasmid conjugative transfer test. The transconjugants are only resistance to betalactams. Conclusions High resistance to beta-laetams in Shigella is caused by production of ESBLs in the local area. The ESBLs-produeing isolates can transfer the drug resistance through lateral transfer of plasmid.
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Objective To investigate the status of extended-spectrum β-lactamases (ESBLs) production by Escherichia coli and Klebsiella pheumoniae, analyze the characteristics of drug resistance of Escherichia coli and Klebsiella pheumoniae in our hospital from Jan 1998 to Dec 2006, in order to provide a guidance to clinical rational use of antibiotics.Methods Disc diffusion test (K-B method) was used to study the drug resistance of E. coli and K.pheumoniae isolates, and ESBLs-producing strains were identified with screening test and confirmatory test. WHONET5.4 software was apllied to performing data analysis.Results In 947 strains of E. coli, 311 strains (32.8%) were detected to produce ESBLs;in 293 strains of K.pheumoniae, 69 ESBLs-producing strains (23.5%) were detected. The resistance rate of ESBLs-producing strains was significantly higher than that of ESBLs non-producing ones (P<0.05), and but ESBLs-producing strains displayed multi-resistant.Conclusion The positive rate of ESBLs producing strains is higher in our hospital. Drug resistance monitoring should be strenghed to rationally use antibacterials and to prevent increase, prevalence and outbreak of ESBLs producing strains.
