High-level mupirocin resistance among Spanish methicillin-resistant Staphylococcus aureus

Twelve strains of methicillin-resistant Staphylococcus aureus with high-lev el resistance to mupirocin were studied. The MIC of methicillin was 16 to 1 28 mg/l and the MIC of mupirocin greater than or equal to 512 mg/l. All of the isolates carried a plasmid of about 30 MDa, and one strain lost resista nce to mupirocin when the plasmid was cured. Three different resistance pat terns were found: six strains were resistant to ciprofloxacin, kanamycin, a nd 10 mg/l of cadmium sulfate; two strains were resistant to these agents a s well as to gentamicin, erythromycin, clindamycin, mercury chloride, and e thidium bromide; and four strains were resistant to the previously named ag ents as well as to rifampicin and tetracycline. The use of this valuable to pical antibiotic, especially in long-term-care facilities, should be monito red to avoid dissemination of resistance.