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. 1990 Sep;34(9):1777–1779. doi: 10.1128/aac.34.9.1777

Insertional inactivation of the mec gene in a transposon mutant of a methicillin-resistant clinical isolate of Staphylococcus aureus.

P Matthews 1, A Tomasz 1
PMCID: PMC171923  PMID: 2178337

Abstract

All clinical strains of methicillin-resistant Staphylococcus aureus (MRSA) examined so far contain the mec gene and its product, the penicillin-binding protein (PBP) 2A. Yet the same strains show tremendous variation in the phenotypic expression of antibiotic resistance (MIC), which is under the control of a set of additional, auxiliary genes. Thus, the quantitative contribution of the mec gene to the resistance phenotype of MRSA is not known, and no mutants with the lesion located within the mec gene have been described. We subjected a highly resistant MRSA strain to transposon mutagenesis with the erythromycin resistance transposon Tn551, and a mutant expressing greatly decreased methicillin resistance (RUSA4) was selected to characterize the transposon insertion site. The results indicate that the Tn551 insertion site in mutant RUSA4 is between base pairs 1000 and 1400 of the sequence encoding PBP 2A. Thus, the uniform and greater than 200-fold drop in the methicillin MIC (4 micrograms/ml) for this mutant relative to that for the parent strain (MIC greater than or equal to 800 micrograms/ml) must be related to the inactivation of the PBP 2A gene. The results provide the first unequivocal evidence for the importance of PBP 2A as a quantitative contributor to the MIC for MRSA.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

  1. Berger-Bächi B., Barberis-Maino L., Strässle A., Kayser F. H. FemA, a host-mediated factor essential for methicillin resistance in Staphylococcus aureus: molecular cloning and characterization. Mol Gen Genet. 1989 Oct;219(1-2):263–269. doi: 10.1007/BF00261186. [DOI] [PubMed] [Google Scholar]
  2. Berger-Bächi B. Insertional inactivation of staphylococcal methicillin resistance by Tn551. J Bacteriol. 1983 Apr;154(1):479–487. doi: 10.1128/jb.154.1.479-487.1983. [DOI] [PMC free article] [PubMed] [Google Scholar]
  3. Berger-Bächi B., Strässle A., Kayser F. H. Characterization of an isogenic set of methicillin-resistant and susceptible mutants of Staphylococcus aureus. Eur J Clin Microbiol. 1986 Dec;5(6):697–701. doi: 10.1007/BF02013308. [DOI] [PubMed] [Google Scholar]
  4. Hartman B. J., Tomasz A. Expression of methicillin resistance in heterogeneous strains of Staphylococcus aureus. Antimicrob Agents Chemother. 1986 Jan;29(1):85–92. doi: 10.1128/aac.29.1.85. [DOI] [PMC free article] [PubMed] [Google Scholar]
  5. Inglis B., Matthews P. R., Stewart P. R. The expression in Staphylococcus aureus of cloned DNA encoding methicillin resistance. J Gen Microbiol. 1988 Jun;134(6):1465–1469. doi: 10.1099/00221287-134-6-1465. [DOI] [PubMed] [Google Scholar]
  6. Jordens J. Z., Hall L. M. Characterisation of methicillin-resistant Staphylococcus aureus isolates by restriction endonuclease digestion of chromosomal DNA. J Med Microbiol. 1988 Oct;27(2):117–123. doi: 10.1099/00222615-27-2-117. [DOI] [PubMed] [Google Scholar]
  7. Kornblum J., Hartman B. J., Novick R. P., Tomasz A. Conversion of a homogeneously methicillin-resistant strain of Staphylococcus aureus to heterogeneous resistance by Tn551-mediated insertional inactivation. Eur J Clin Microbiol. 1986 Dec;5(6):714–718. doi: 10.1007/BF02013311. [DOI] [PubMed] [Google Scholar]
  8. Matsuhashi M., Song M. D., Ishino F., Wachi M., Doi M., Inoue M., Ubukata K., Yamashita N., Konno M. Molecular cloning of the gene of a penicillin-binding protein supposed to cause high resistance to beta-lactam antibiotics in Staphylococcus aureus. J Bacteriol. 1986 Sep;167(3):975–980. doi: 10.1128/jb.167.3.975-980.1986. [DOI] [PMC free article] [PubMed] [Google Scholar]
  9. Matthews P. R., Reed K. C., Stewart P. R. The cloning of chromosomal DNA associated with methicillin and other resistances in Staphylococcus aureus. J Gen Microbiol. 1987 Jul;133(7):1919–1929. doi: 10.1099/00221287-133-7-1919. [DOI] [PubMed] [Google Scholar]
  10. Murakami K., Tomasz A. Involvement of multiple genetic determinants in high-level methicillin resistance in Staphylococcus aureus. J Bacteriol. 1989 Feb;171(2):874–879. doi: 10.1128/jb.171.2.874-879.1989. [DOI] [PMC free article] [PubMed] [Google Scholar]
  11. Perkins J. B., Youngman P. J. A physical and functional analysis of Tn917, a Streptococcus transposon in the Tn3 family that functions in Bacillus. Plasmid. 1984 Sep;12(2):119–138. doi: 10.1016/0147-619x(84)90058-1. [DOI] [PubMed] [Google Scholar]
  12. Song M. D., Wachi M., Doi M., Ishino F., Matsuhashi M. Evolution of an inducible penicillin-target protein in methicillin-resistant Staphylococcus aureus by gene fusion. FEBS Lett. 1987 Aug 31;221(1):167–171. doi: 10.1016/0014-5793(87)80373-3. [DOI] [PubMed] [Google Scholar]
  13. Tomasz A., Drugeon H. B., de Lencastre H. M., Jabes D., McDougall L., Bille J. New mechanism for methicillin resistance in Staphylococcus aureus: clinical isolates that lack the PBP 2a gene and contain normal penicillin-binding proteins with modified penicillin-binding capacity. Antimicrob Agents Chemother. 1989 Nov;33(11):1869–1874. doi: 10.1128/aac.33.11.1869. [DOI] [PMC free article] [PubMed] [Google Scholar]
  14. Tonin E., Tomasz A. Beta-lactam-specific resistant mutants of Staphylococcus aureus. Antimicrob Agents Chemother. 1986 Oct;30(4):577–583. doi: 10.1128/aac.30.4.577. [DOI] [PMC free article] [PubMed] [Google Scholar]

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