Research Of The Mechanism Of Integrons Mediated Multi-drug Resistance In Clinical Isolates Of Klebsiella Pneumoniae

Objective: Our study aimed to investigate the distribution of integrons in clinical isolates of Klebsiella pneumoniae and explore the molecular mechanism of integron-mediated multiple-drug resistance in K.pneumoniae.Methods: Class 1,2,and 3 integrase genes were detected by polymerase chain reaction(PCR)among 178 K.pneumoniae clinical isolates.Antibiotic susceptibility was examined by disk-diffusion method.Conjugation experiments were conducted to evaluate the horizontal-transfer capability,and multilocus sequence typing(MLST)assays were conducted to explore the genetic relationships among the isolates.Highly virulent serotypes were identified by PCR from the 44 integron-positive isolates with variable regions.Results: intI1 and intI2 were detected in 60.1% and 1.7% of isolates,respectively,intI3 were not detected in all 178 isolates.The positive rate of variable was 39.6%.88.6%(39/44)of the integrons were located in conjugative plasmids among the isolates containing variable regions;Dihydrofolate reductase(dfr A)and aminoglycoside adenyltransferase(aad)were found to be the most common gene cassettes combination in class 1 and 2 integrons.These gene cassettes encoded resistance to trimethoprim and aminoglycosides respectively.Moreover,the relevance between integron carriage and antibiotic resistance was most significant for aminoglycosides,phenicols,and fluoroquinolones.Among the isolates with variable regions,9 were classified as highly virulent serotypes(k1,k2,k20,and k54).In addition,MLST analysis detected 13 sequence types(STs),with the predominant ones being ST11 and ST15.The e BURST analysis revalued the existence of 11 singleton STs and one group,which is comprised of ST11 and ST437.Conclusions: The wide diversity of detected integrons suggested that the horizontal transfer by mobile genetic elements played a major role in the distribution of antimicrobial resistance genes,thereby indicating the urgent need to use effective means of avoiding the spread of drug-resistant bacteria.