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Media type:
E-Article
Title:
High-Level β-Lactam Resistance and Cell Wall Synthesis Catalyzed by the mecA Homologue of Staphylococcus sciuri Introduced into Staphylococcus aureus
Contributor:
Severin, Anatoly;
Wu, Shang Wei;
Tabei, Keiko;
Tomasz, Alexander
Published:
American Society for Microbiology, 2005
Published in:
Journal of Bacteriology, 187 (2005) 19, Seite 6651-6658
Description:
<jats:title>ABSTRACT</jats:title>
<jats:p>
A close homologue of
<jats:italic>mecA</jats:italic>
, the determinant of broad-spectrum β-lactam resistance in
<jats:italic>Staphylococcus aureus</jats:italic>
was recently identified as a native gene in the animal commensal species
<jats:italic>Staphylococcus sciuri</jats:italic>
. Introduction of the
<jats:italic>mecA</jats:italic>
homologue from a methicillin-resistant strain of
<jats:italic>S. sciuri</jats:italic>
into a susceptible strain of
<jats:italic>S. aureus</jats:italic>
caused an increase in drug resistance and allowed continued growth and cell wall synthesis of the bacteria in the presence of high concentrations of antibiotic. We determined the muropeptide composition of the
<jats:italic>S. sciuri</jats:italic>
cell wall by using a combination of high-performance liquid chromatography, mass spectrometric analysis, and Edman degradation. Several major differences between the cell walls of
<jats:italic>S. aureus</jats:italic>
and
<jats:italic>S. sciuri</jats:italic>
were noted. The pentapeptide branches in
<jats:italic>S. sciuri</jats:italic>
were composed of one alanine and four glycine residues in contrast to the pentaglycine units in
<jats:italic>S. aureus</jats:italic>
. The
<jats:italic>S. sciuri</jats:italic>
wall but not the wall of
<jats:italic>S. aureus</jats:italic>
contained tri- and tetrapeptide units, suggesting the presence of
<jats:sc>dd</jats:sc>
- and
<jats:sc>ld</jats:sc>
-carboxypeptidase activity. Most interestingly,
<jats:italic>S. aureus</jats:italic>
carrying the
<jats:italic>S. sciuri mecA</jats:italic>
and growing in methicillin-containing medium produced a cell wall typical of
<jats:italic>S. aureus</jats:italic>
and not
<jats:italic>S. sciuri</jats:italic>
, in spite of the fact that wall synthesis under these conditions had an absolute dependence on the heterologous
<jats:italic>S. sciuri</jats:italic>
gene product. The protein product of the
<jats:italic>S. sciuri mecA</jats:italic>
can efficiently participate in cell wall biosynthesis and build a cell wall using the cell wall precursors characteristic of the
<jats:italic>S. aureus</jats:italic>
host.
</jats:p>