The intrinsic resistome of Klebsiella pneumoniae

Alejandra Bernardini, Trinidad Cuesta, Anna Tomás, José A Bengoechea, José L Martínez, María B Sánchez

Molecular epidemiology studies aiming at understanding the acquisition of resistance by clinical isolates of Klebsiella pneumoniae are regularly published; however, information on the genes that contribute to its characteristic phenotype of susceptibility to antibiotics (intrinsic resistome) is scarce. To fill this gap, a K. pneumoniae transposon mutants' library was screened and 171 mutants presenting changes in their susceptibility to antibiotics were selected. The transposon insertion site was determined in 75 of them. Twenty-seven mutants, for which insertion points had been previously identified, were included in the analysis. One hundred and two mutants were selected for further studies. In 70 of them the transposon was inserted in a gene with a known function, while in 19 the insertion occurred in genes encoding proteins with unknown functions and 13 insertions occurred in intergenic regions. Eighty-seven of the insertions were localized in the chromosome, with 15 insertions located in the two plasmids carried by this strain. Whereas some of the mutated genes are already known to be involved in antibiotic resistance (ampG, acrB, tolC), several of them are involved in regular processes of bacterial physiology, including K. pneumoniae virulence. Together with results published for other organisms, our results support that determinants involved in basic processes of the bacterial physiology may contribute to antibiotic resistance. Our findings also indicate that, besides acquired resistance genes, plasmids may harbour other genes belonging to their backbone that can also be involved in resistance.