Impact of mecA promoter mutations on mecA expression and β-lactam resistance levels
| Autor: | Nadine McCallum, Brigitte Berger-Bächi, Miriam Ender |
|---|---|
| Rok vydání: | 2008 |
| Předmět: |
DNA
Bacterial Microbiology (medical) Staphylococcus aureus Molecular Sequence Data Mutant Repressor Microbial Sensitivity Tests Biology beta-Lactams Microbiology beta-Lactam Resistance Plasmid Bacterial Proteins Transcription (biology) polycyclic compounds Humans Penicillin-Binding Proteins Point Mutation Promoter Regions Genetic Substance Abuse Intravenous Gene Genetics Base Sequence SCCmec Point mutation Sequence Analysis DNA General Medicine Staphylococcal Infections biochemical phenomena metabolism and nutrition bacterial infections and mycoses Anti-Bacterial Agents Ribosomal binding site Infectious Diseases Sequence Alignment Switzerland |
| Zdroj: | International Journal of Medical Microbiology. 298:607-617 |
| ISSN: | 1438-4221 |
| DOI: | 10.1016/j.ijmm.2008.01.015 |
| Popis: | The reason for the extremely low-level oxacillin resistance in a so-called 'drug clone', a methicillin-resistant Staphylococcus aureus circulating among injection drug users in Zurich, Switzerland, could be traced back to the mecA promoter sequence and particularly to the strain's genetic background. Sequencing of its mec complex identified a point mutation (TATACT to TATATT), creating a perfect palindrome in the -10 region of the mecA promoter/operator region containing the binding sites for the mecA repressors MecI and BlaI. Two strains with vastly different beta-lactam resistance phenotypes, the low-level resistant drug clone type strain CHE482 and the highly homogeneously resistant strain COLn, were cured of their SCCmec elements and subsequently transformed with plasmids containing mecA under the control of either the wild-type or mutant promoter. Expression studies showed that this mutation had significant effects on both mecA transcription and corresponding PBP2a production, but only small effects on beta-lactam resistance levels within a given genetic background. A further mutation in the mecA ribosomal binding site (GGAGG to GGAGT), common to SCCmec type IV strains, was found to have no discernable effect on mecA transcription and PBP2a content, and only minimal effects on beta-lactam resistance. Factors associated with the genetic backgrounds into which these differently controlled mecA genes were introduced had a much higher impact on beta-lactam resistance levels than the rates of mecA transcription. The tight repression of mecA expression in this drug clone in the absence of beta-lactams could contribute to the apparent fitness of this fast growing strain. |
| Databáze: | OpenAIRE |
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