EFFECT OF CHLORHEXIDINE ON A CHLORHEXIDINE-SENSITIVE AND A CHLORHEXIDINE-RESISTANT STRAIN OF PROVIDENCIA-STUARTII

The sensitivity and resistance of three strains of Prouidencia stuarrii to various antibacterial agents, and especially to chlorhexidine, are described. Prooidencia stuartii Pv 2 was the most sensitive, and Pv 67 the most resistant, to chlorhexidine and to polymyxin B. These two strains took up approximately equal amounts of chlorhexidine from solution, but the biguanide had a considerably greater effect on the electrophoretic mobility of cells of strain Pv 2. Greater inner membrane damage (determined by the leakage of K + and of pentoses) occurred with Pv 2. Chlorhexidine at 20 pg/ml achieved a 2-log reduction and 50 pg/ml a >7-log reduction in viable numbers in strain Pv 2 over a 120 min contact period at 20°C. In contrast, these concentrations induced © 1985 Oxford University Press. All rights reserved.