期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2022
卷号：119
期号：38
DOI：10.1073/pnas.2203593119
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Significance
Carbapenem-resistant
Klebsiella pneumoniae represents an urgent threat to human health. Together with carbapenemase-mediated hydrolysis, mutations in the outer membrane porin OmpK36 have evolved to limit carbapenem influx. Analysis of the
ompK36 gene from high-risk
K. pneumoniae sequence types revealed the repeated emergence of an identical 5′ synonymous mutation. Whilst synonymous mutations are usually considered silent, we show that it reduces OmpK36 translation by inducing the formation of a messenger RNA secondary structure that obstructs the ribosomal binding site. While OmpK36 depletion attenuates virulence in a mouse lung infection model, it tips the balance towards antibiotic therapy failure. These results show mechanistically how the de novo emergence of a synonymous mutation contributes to last line antimicrobial resistance.
Outer membrane porins in Gram-negative bacteria facilitate antibiotic influx. In
Klebsiella pneumoniae, modifications in the porin OmpK36 are implicated in increasing resistance to carbapenems. An analysis of large
K. pneumoniae genome collections, encompassing major healthcare-associated clones, revealed the recurrent emergence of a synonymous cytosine-to-thymine transition at position 25 (25c > t) in
ompK36. We show that the 25c > t transition increases carbapenem resistance through depletion of OmpK36 from the outer membrane. The mutation attenuates
K. pneumoniae in a murine pneumonia model, which accounts for its limited clonal expansion observed by phylogenetic analysis. However, in the context of carbapenem treatment, the 25c > t transition tips the balance toward treatment failure, thus accounting for its recurrent emergence. Mechanistically, the 25c > t transition mediates an intramolecular messenger RNA (mRNA) interaction between a uracil encoded by 25t and the first adenine within the Shine–Dalgarno sequence. This specific interaction leads to the formation of an RNA stem structure, which obscures the ribosomal binding site thus disrupting translation. While mutations reducing OmpK36 expression via transcriptional silencing are known, we uniquely demonstrate the repeated selection of a synonymous
ompK36 mutation mediating translational suppression in response to antibiotic pressure.
