CFR gene mediated linezolid resistance in staphylococcal isolates

Linezolid is one of the most potent antibacterial agents against gram positive organisms especially used in the treatment of skin and soft tissue infections and hospital acquired pneumonias. Recently resistant isolates to this drug are increasingly observed in many parts of the world but resistance is still rare in India. We have encountered two such resistant isolates from a tissue specimen culture. The isolates were identified as S. Aureus and S. Epidermidis by phenotypic tests. Both the isolates were resistant to linezolid by disc diffusion method. When the minimum inhibitory concentration (MIC) was determined by E- strip method, MIC for S.aureus was 32μg/ml and that of S.epidermidis was >256μg/ml. cfr gene was detected in both the isolates by PCR. Both the isolates were sensitive to Tigecycline, Vancomycin, Cotrimoxazole and Levofloxacin with variable resistance to other antibiotics. This is a first case report of cfr gene mediated linezolid resistance in our country.