A methicillin-resistant strain of Staphylococcus aureus (MRSA, phage type 84/85) was introduced into City of Memphis Hospital by a burn patient who had recently been treated for MRSA bacteremia in another institution 500 miles distant. Despite prompt recognition of the problem and institution of isolation procedures, six other patients developed secondary colonization during the ensuing six months, and five of these experienced clinically significant infections with MRSA. Three of the patients originally infected with MRSA, as well as two additional patients, subsequently developed colonization with staphylococcal strains of phage type 84/85 that were resistant to both methicillin and gentamicin (MRGRSA). Spread of the staphylococcal strains was most likely accomplished primarily via passive transfer from person to person. The hydrotherapy unit, which became contaminated with both MRSA and MRGRSA, may have played a secondary role. As illustrated by this outbreak, patients carrying potentially dangerous bacterial strains should be identified and informed of the problems posed by such carriage. It may be imprudent to admit such patients to hospitals that are free of the potential pathogen.
The outbreak described here exemplifies a number of potential problems associated with control of nosocomial staphylococcal infections: (a) interhospital spread of methicillin-resistant strains; (b) secondary patient-to-patient intrahospital spread; and (c) emergence of even more resistant strains, possibly associated with selective pressures exerted by widespread use of broad-spectrum antimicrobial agents.