Molecular characterization of integrons in clinical isolates of betalactamase-producingEscherichia coliandKlebsiella pneumoniaein Iran

Abstract

Integrons are considered to play a significant role in the evolution and spread of antibiotic resistance genes. A total of 349 clinical isolates of Escherichia coli and Klebsiella pneumoniae were investigated for molecular characterization of integrons and betalactamases. Antimicrobial susceptibility testing was also performed as the Clinical and Laboratory Standards Institute (CLSI) guidelines. The frequency of extended spectrum betalactamases (ESBL) or metallo-betalactamases (MBL)-producing isolates, patient demographics, and the susceptibility to various antimicrobial agents were described. BlaCTX-M was the most frequently detected betalactamase in all isolates. Moreover, MBL producing K. pneumoniae carried blaIMP and blaVIM at 100 and 41·6%, respectively but no MBL-positive E. coli was detected. Class 1 integrons were more frequent among E. coli and K. pneumoniae isolates in comparison with class 2 integrons and the frequency of intI2 in K. pneumoniae was significantly higher than E. coli isolates. Five different resistance gene arrays were identified among class 1 integrons. Dihydrofolate reductase (dfrA) and aminoglycoside adenyltransferase (aad) gene cassettes were found to be predominant in the class 1 integrons. These results indicate that class 1 integrons are widespread among ESBL-producing isolates of K. pneumoniae and E. coli and appropriate surveillance and control measures are essential to prevent further dissemination of these elements among Enterobacteriaceae in our country.

Occurrence and characterization of class 1 integrons in Escherichia coli from healthy individuals and those with urinary infection

“…Sequencing analysis of the cassette arrays revealed a predominance of the dfrA17 and dfrA17-aadA5 arrays in this population. This finding agrees with those of previous studies reporting a strong association between class 1 integrons and the dfrA and aadA cassettes [15,33]. Indeed, the dfrA17 and aadA5 cassettes were formerly found in a class 1 integron of an E. coli isolated in 1998 from the urinary tract of an Australian patient [34].…”

“…More than 130 gene cassettes encoding resistance to all classes of antibiotics and more than 60 gene cassettes of unknown function have been described in mobile integrons [13]. In Enterobacteriaceae, most gene cassettes associated with class 1 integrons encode resistance to streptomycin (aadA) and trimethoprim (dfrA) [14][15][16].…”

Detection of Integrons and Staphylococcal Cassette Chromosome mec Types in Clinical Methicillin-resistant Coagulase Negative Staphylococci Strains

“…In our study, the class 1 integron containing the aadA1 gene was similar to that found in gram-negative bacteria [33]. Therefore, the transfer of resistance genes that may occur between ram-positive and gram-negative organisms could lead to the construction of diverse resistance to the usual antibiotics [34].…”

Prevalence of Acquired Carbapenemase Genes in Klebsiella Pneumoniae by Multiplex PCR in Isfahan

“…in 2015 in Zanjan, Iran, metallo-b-lactamase producing K. pneumoniae strains carried bla IMP and bla VIM were found in 100% and 41·6%, respectively. [21]…”