Investigation of Micrococcaceae in a department of cardiac surgery. Biochemical characterization and sensitivity patterns of strains isolated from patients, staff, and air.

A total of 965 strains of Micrococcaceae isolated from 200 patients, personnel, and air in a department of cardiac surgery were classified by means of Baird-Parker's scheme. The majority of strains were identified as Staphylococcus epidermidis (S. epidermidis) biotype 1, but S. epidermidis biotype 4 accounted for c. 25% of isolates from patients post-operatively. Pre-operative isolates were generally sensitive to most antibiotics tested while post-operative strains of coagulase-negative Micrococcaceae from patients and isolates from personnel and air were frequently multiply-resistant. Strains of Staphylococcus aureus (S. aureus) were sensitive or resistant only to penicillin. More patients were colonized with coagulase-negative Micrococcaceae after operation than at admission to the hospital (p less than 0.001), while the frequency of S. aureus carriers was the same before and after operation and equal to the frequency found earlier. The frequency of S. aureus carriers among the personnel, however, was lower than reported earlier (10%). Multiply-resistant strains of S. epidermidis seem to have replaced resistant strains of S. aureus as the predominant hospital saprophyte among Micrococcaceae.