ABSTRACT
Objective To investigate the class I integrons and their gene cassettes of imipenem-resistant Pseudomonas aeruginosa (IRPA) , and to analyze the correlation between integrons and drug resistance. Methods PCR was used to determine the presence of integrase genes and class I integrons. The variable regions were detected by sequencing. Resistance genes of integron gene cassettes including metal-β-lactamases, aminoglycoside modifying enzymes (AMEs), 16SrRNA methylating enzyme and the OprD2 genes were detected by PCR. The VITEK-2 automated system was used to determine the antibiotic susceptibility of integron-positive IRPA strains. Results The positive rates of integrase genes and class I integrons were 23.3%(20/86)and 8.14%(7/86) , and five kinds of gene cassettes were detected in 86 IRPA strains. The class I integrons-positive bacterial strains exhibited different resistant patterns to 12 antibiotics with large number of resistance genes. Conclusion The class I integrons and their gene cassettes are associated with multiple drug resistance of IRPA.
ABSTRACT
Objective Since integrons play an important role in the spread of antibiotic resistance genes in bacteria,the characterization of a new resistance gene cassette in class 1 integron positive strains of E.coli was analyzed. Methods The presence and genetic content of class 1 integron were examined by PCR and sequencing.The sequence was analyzed by using some bioinformatics softwares.Results 5 class 1 integron positive strains were amplified by primers of in-F and in-B which were set for amplifying the region of antibiotics resistance genes.Among the 5 strains,an amplicon of 1009 bp was yielded.Sequencing analysis revealed that amplicon of 1009 bp harbored a 780 bp ORF.Further analysis with bioinformatics software showed that it was 99.6% and 99.5% identical to the known aadA23 and aadA21 cassette,and was just 66.4% identical to the known aadA5 cassette.It was conferring resistant to spectinomycin and streptomycin,and was given a new name aadA23b.Conclusions Multi-drug resistance genes has been proved changeable in E.coli clinical strains.The result not only stressed the need for continuing surveillance of antibiotic resistance in the molecular level,but also the need caring for genetic variation of drug resistance gene cassettes.