Detection of high levels of resistance to linezolid and vancomycin in Staphylococcus aureus

Both methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-sensitive S. aureus (MSSA) are rapidly overcoming the current array of drugs. One hundred and fifty isolates from a hospital were studied for resistance towards linezolid and vancomycin. Fifty-four (36.0 %) isolates were MRSA. Both MRSA and MSSA showed high resistance towards linezolid when using the disc diffusion method, with the figures being 48.1 and 29.2 %, respectively. The figures for the E-test were 46.3 and 27.0 %, respectively. The vancomycin resistance was remarkable in MRSA (14.8 %), but relatively low in MSSA (3.1 %). The E-test results were 13.0 and 4.16 %, respectively. The cfr gene was detected in 78 % of linezolid-resistant isolates and the vanA operon was detected in 74 % of vancomycin-resistant isolates. This level of resistance against linezolid and vancomycin is unprecedented. These results are alarming and highlight the threat of non-treatable S. aureus strains.