Journal
MICROBIAL PATHOGENESIS
Volume 142, Issue -, Pages -Publisher
ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD
DOI: 10.1016/j.micpath.2020.104058
Keywords
Colistin resistance; A. baumannii; pmrB mutations
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Funding
- Department of Health Sciences, Magna Graecia University of Catanzaro
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Colistin resistance among extensively-resistant Acinetobacter baumannii isolates is a serious health-care problem. Alterations in PmrA-PmrB two-component system have been associated with resistance to colistin. We investigated three pairs of colistin-susceptible and colistin-resistant A. baumannii, sequentially isolated from three patients before and after colistin treatment, respectively. The pmrA and pmrB genes were sequenced by Sanger method. Amino acidic positions and their effect on protein were predicted by InterPro and PROVEAN tools. Expression of pmrA, pmrB and pmrC genes was assessed by semi-quantitative reverse transcription-PCR (qRT-PCR). We found three different nonsynonymous substitutions P233T, E301G and L168K in pmrB coding region, each one in a different colistin resistance strain. The E301G and L168K substitutions represent novel mutations in pmrB, not previously described. Relative expression of pmrA, pmrB and pmrC mRNA increased in all colistin resistant strains. In our study, pmrB substitutions were associated with pmrC over-expression and colistin resistance. Further studies are necessary to understand their impact on modification of lipid A components.
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