Epidemiologic Study of a Hospital Outbreak of Micrococcic Infections

A case of severe mastitis appeared in a nursery where no mastitis, pyoderma, pneumonia, or micrococcic sepsis had been seen for two years. In the following 10 weeks, 25 cases of mastitis and 10 cases of severe dermatitis were observed. The causative organism, a strain of M. pyogenes aureus, was identified by phage typing and by reactions to antibiotics. Its source could not be determined. It infected hospital personnel as well as patients. Asymptomatic carriers were found. A striking difference was noted between housekeeping personnel on wards (5.3% carrier rate) and those assigned to other areas (no carriers). The initial strain was resistant to penicillin, streptomycin, and streptomycin but not to erythromycin; later a second strain was found, resistant also to erythromycin though identical in phage type. Control measures stopped the epidemic, and all carriers have been treated and cleared.