The effect of antibiotic prophylaxis and topical antiseptics on the bacterial flora of the skin after cardiac surgery.

A controlled trial of antibiotic prophylaxis in cardiac surgery compared a two-dose regimen of teicoplanin with a longer conventional course of flucloxacillin and tobramycin. In 12 patients the susceptibility of the bacterial skin flora of four different sites to each of the three antibiotics was determined and the results are reported here. Less than 1% of the Gram-positive colonies showed reduced sensitivity to teicoplanin (MIC greater than or equal to 4 mg l-1). Before operation, 99% inhibition of Gram-positive growth was achieved at 26 (54%) of 48 sites by 1 mg l-1 of flucloxacillin and 13 (27%) sites by 2 mg l-1 tobramycin. By the 7th day after operation there was a significant reduction in the number of sites showing similar sensitivity to flucloxacillin [16 (33%) sites, P less than 0.05]. The use of teicoplanin was not associated with the emergence of Gram-negative skin flora but tobramycin promoted acquisition of aminoglycoside-resistant strains.