‘Methicillin resistant’ Staphylococcus aureus infections during 1978–79: clinical and bacteriologic observations

Eighty Staphylococcus aureus strains were isolated from various clinical sources during 1978–79. Amongst them 67·5% were found resistant to methicillin (M-R). No low level resistant mutants were isolated, but 14·2% were characterized as ‘heterogenous mutants’ and the remaining 53·3% as ‘high resistant mutants’. M-R strains were mostly resistant to cephalothin (67·5% VS 55%), 3l·2% to clindamycin and 5% to gentamicin, the latter strains being sensitive only to cotrimoxazole and rifampicin. In a limited epidemiological study of the medical service personnel no M-R were identified. Twenty-eight M-R strains were phage untypable. M-R strains were equally distributed amongst out- and in-patients, while prior exposure to a β-lactam antibiotic and resistance to methicillin coincided in 25% of the patients. ‘Heterogenous resistant mutants’ to methicillin and cephalothin proved to be virulent and implicated in serious life-threatening infections. Methicillin and analogues should not now be the antibiotic of choice in Greece when a Staphylococcus aureus infection is suspected.