[Resistance to linezolid in Staphylococcus aureus before its release]

Resistance to antibiotics is a global problem in geriatric centres.

The aim of this study was to determine the frequency of the resistance to linezolid in Staphylococcus aureus strains before its release in a geriatric centre.

From 03-01-01 to 03-04-30 linezolid was included in the panel of antibiotics tested in S. aureus strains. The susceptibilities were estimated by the disk diffusion test in routine clinical microbiology practice.

A total of 213 strains of S. aureus was analysed. All of them were susceptible to the following antibiotics: linezolid, cotrimoxazol, fosfomycin, and glycopeptides. The meticillin-resistant S. aureus (MRSA) represented 67.1% (60.3-73.3) strains. The resistance to pefloxacin, tobramycin and erythromycin concerned 92.3% (86.3-95.9), 73.4% (65.3-80.3) and 31.5% (24.1-39.8) of MRSA strains respectively. The MRSA strains were less resistant to the following antimicrobial drugs: gentamicin 7.0% (3.6-12.8), fusidic acid 2.1% (0.5-6.5) and rifampicin 1.4% (0.2-5.5). The resistance concerning at the same time gentamicin, pefloxacin and fucidic acid represented 2.1% (0.5-6.5) of SARM strains, rifampicin was not interested.

Linezolid was effective in vitro in S. aureus strains regardless their susceptibilities in meticillin. According to its effectiveness in vivo, linezolid may be of use for the treatment of infections due to MRSA. However, there has been two reports of resistance of MRSA in clinical infections. The use of linezolid has to follow the instructions and it should be carefully monitored.