Effect of the source of Mueller-Hinton agar and resistance frequency on the detection of methicillin-resistant Staphylococcus aureus.

摘要: Inconsistencies in the results of disk diffusion tests oxacillin against Staphylococcus aureus that occurred when using commercially prepared Mueller-Hinton agar from different sources led us to evaluate ability media detect resistance oxacillin, methicillin, and nafcillin S. aureus. five manufacturers was our laboratory used for standard dilution tests. Ten oxacillin-resistant isolates, which three were definitive-resistant seven occult-resistant, examined. All strains resistant all antimicrobial agents on four out agars. The occult-resistant consistently detected as only one With slight differences, more readily by initially incubated at 30 degrees C, extended incubation improved detection. frequency within a population cells low compared with definitively cells. heterogeneity colony morphology apparent growth rates contributed problem detecting some isolates. Definitive-resistant isolates characterized very high stable resistance. Occult-resistant lower resistance, although true may be difficult ascertain because rates. Images