SALT TOLERANCE OF EMRSA-16 AND ITS EFFECT ON THE SENSITIVITY OF SCREENING CULTURES

The salt (NaCl) tolerance of methicillin-resistant Staphylococcus aure us (EMRSA)-16 was compared with 18 other MRSA isolates by an agar inco rporation technique. The NaCl minimum inhibitory concentration (MIC) o f EMRSA-16 was 7% which compared with an MIC(50) of 7%, MIC(90) of 10% , range (55-105%) for the other isolates. Study of the growth kinetics in broth containing NaCl at concentrations up to 10% indicated comple te inhibition of growth by 7 and 10% NaCl and partial inhibition by 5% . Addition of EMRSA-16 at inocula of less than or equal to 1 cfu/mL in to salt broths revealed lower than expected EMRSA recovery from broths containing 5, 7.5 and 10% NaCl. Two and a half per cent NaCl broths w ere not inhibitory. Selective broth containing 2.5% NaCl should be con sidered for use when screening for EMRSA-16.