Cloning and characterization of the fmt gene which affects the methicillin resistance level and autolysis in the presence of triton X-100 in methicillin-resistant Staphylococcus aureus

Antimicrob Agents Chemother. 1997 Nov;41(11):2355-61. doi: 10.1128/AAC.41.11.2355.


In methicillin-resistant Staphylococcus aureus (MRSA) strains, Triton X-100 reduced the oxacillin resistance level, although the degree of reduction varied from strain to strain. To study the responses of MRSA strains to Triton X-100, we isolated a Tn551 insertion mutant of the COL strain that became more susceptible to oxacillin in the presence of 0.02% Triton X-100. The Tn551 insertion of the mutant was transduced back to the parent strain, other MRSA strains (strains KSA8 and NCTC 10443), and methicillin-susceptible strain RN450. All transductants of MRSA strains had reduced levels of resistance to oxacillin in the presence of 0.02% Triton X-100, while those of RN450 did not. Tn551 mutants of KSA8 and NCTC 10443 also had reduced levels of resistance in the absence of 0.02% Triton X-100. The autolysis rates of the transductants in the presence of 0.02% Triton X-100 were significantly increased. Amino acid analysis of peptidoglycan and testing of heat-inactivated cells for their susceptibilities to several bacteriolytic enzymes showed that there were no significant differences between the parents and the respective Tn551 mutants. The Tn551 insertion site mapped at a location different from the previously identified fem and llm sites. Cloning and sequencing showed that Tn551 had inserted at the C-terminal region of a novel gene designated fmt. The putative Fmt protein showed a hydropathy pattern similar to that of S. aureus penicillin-binding proteins and contained two of the three conserved motifs shared by penicillin-binding proteins and beta-lactamases, suggesting that fmt may be involved in cell wall synthesis.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacteriolysis / genetics
  • Cloning, Molecular
  • Excipients / pharmacology
  • Hydroxymethyl and Formyl Transferases / genetics*
  • Hydroxymethyl and Formyl Transferases / pharmacology
  • Methicillin Resistance / genetics*
  • Microbial Sensitivity Tests
  • Molecular Sequence Data
  • Octoxynol / pharmacology
  • Oxacillin / pharmacology*
  • Penicillins / pharmacology*
  • Staphylococcus aureus / drug effects*
  • Staphylococcus aureus / genetics


  • Excipients
  • Penicillins
  • Octoxynol
  • Hydroxymethyl and Formyl Transferases
  • methionyl-tRNA formyltransferase
  • Oxacillin

Associated data

  • GENBANK/AB009635