Comparative Analysis of Potential Determinants of Resistance to Aminoglycosides in Burkholderia pseudomallei Strains with Different Level of Sensitivity to Gentamicin

The aim of the study was to identify and compare potential determinants of aminoglycoside resistance in gentamicin susceptible Burkholderia pseudomallei strains. Materials and methods . A bioinformatics analysis of whole genome shotgun sequences of three B. pseudomallei strains having different levels of sensitivity to gentamicin was carried out. Results and discussion . B. pseudomallei is intrinsically resistant to aminoglycosides. Such strains, as a rule, are not taken into account in the classical scheme of isolation and identification. At the same time, there were no significant differences in the clinical manifestations of melioidosis during infection with gentamicin-resistant and sensitive strains. In B. pseudomallei strains of different sequence types (ST70, ST948, and ST1566), point missense mutations were found in the genes of three efflux pumps of the RND family: AmrAB-OprA, BpeAB-OprB, BpeEF-OprC, and one with unknown functions, as well as in the gene aminoglycoside-6’-N-acetyltransferase AAC(6’)-III. All three strains had amino acid substitutions in the AmrA periplasmic linker: ARG160SER, Arg116Gln and Gly237Arg, Thr317Lys, respectively. In moderately sensitive strains (ST948 and ST1566), an identical Val222Met substitution was found in the repressor of the AmrAB-OprA operon, AmrR. It is likely that the intermediate level of sensitivity to gentamicin in the studied strains is mediated by the constitutive expression of the AmrAB-OprA operon, which partially compensates for the structural defects. It is also possible that a dinucleotide deletion in the AAC (6’)-III aminoglycoside-6’-N-acetyltransferase gene, as well as detected mutations in the homologues of the periplasmic linker (BPSL2234) of an uncharacterized efflux operon of the RND family, are involved in the loss of resistance to gentamicin.