The femA gene encodes a protein precursor which plays a role in peptidoglycan biosynthesis in Staphylococcus aureus and is also considered as a factor influencing the level of methicillin resistance. A femA homologous gene was recently characterized in S. epidermidis, entailing the possibility of femA phylogenetic conservation in staphylococcal species. Accordingly, we assessed the presence of femA homologous genes in S. hominis and S. saprophyticus. Strategy for identification relied upon alignment of S. aureus and D.<space>epidermidis femA sequences and upon identification of potentially conserved regions. Amplifications of portions of the femA genes were performed under permissive annealing conditions, by using several sets of primers designed to match the consensus regions. DNA sequencing of overlapping PCR fragments led to the characterization of the entire femA genes of S. hominis and S. saprophyticus, and provided more precise information on the femA start codon for all five species. The genomic organization of all these femA genes appeared highly conserved, with alternance of homologous and variable regions. On this basis, a consensus sequence of the femA gene was defined and interspecies variations were exploited to design strategies for staphylococci species-specific identification, including multiplex PCR amplification and a reverse hybridization assay.
Caracterisation moleculaire du gene femA de Staphylococcus hominis et S. saprophyticus, et distinction des especes staphylococciques fondee sur femA. Le gene femA code une proteine precurseur active dans la synthese du peptidoglycane chez Staphylococcus aureus et est aussi considere comme un facteur influencant le niveau de resistance a la methicilline. Un gene homologue a ete recemment caracterise chez S. epidermidis, entrainant la possibilite que le gene femA soit conserve chez les differentes especes de staphylocoques. Nous avons pu effectivement demontrer la presence de genes homologues chez S. hominis et S. saprophyticus. La strategie ayant amene ces identifications reposait sur l'alignement des sequences femA de S. aureus et S.<space>epidermidis, qui a mis en evidence la presence de regions conservees. En utilisant plusieurs paires d'amorces correspondant a ces regions conservees, des portions partiellement redondantes du gene femA ont ete amplifiees, puis sequencees, ce qui a permis de caracteriser l'integralite des genes femA de S. hominis et S. saprophyticus. L'organisation des genes femA apparait hautement conservee<space>: des sequences homologues alternent avec des sequences specifiques d'especes. Une sequence de ce gene, consensus pour tous les staphylocoques, a ete definie et les variations entre especes ont ete exploitees pour mettre au point deux strategies permettant l'identification des staphylocoques au niveau de l'espece<space>: une amplification par PCR en multiplex et un test d'hybridation inverse.