The reliability of methicillin sensitivity tests on four culture media

Open Access
Publisher Website
Google Scholar
Abstract
The influence of culture medium, incubation temperature, and antibiotic content on the reliability of methicillin disc-sensitivity tests on strains of Staphylococcus aureus was evaluated. Tests were performed with an inoculum giving semiconfluent growth of colonies on four media, with 5-μg and 10-μg methicillin discs at incubation temperatures of 30, 35, and 37°C. With Sensitest agar and Mueller-Hinton agar at 35°C or below, methicillin resistance was reliably detected. On DST agar and Wellcotest agar discrimination between sensitive and resistant strains was possible only at 30°C. On Wellcotest agar and DST agar it was not possible to detect methicillin resistance in one resistant strain at any temperature. For sensitive and resistant strains, the use of a 5-μg disc allowed greater differentiation than the 10-μg disc.