[Application of a micromethod to the study of the bactericidal activity of 2 antiseptics based on chlorhexidine gluconate].

Minimal bactericidal concentrations (MBCs) of two antiseptics containing chlorhexidine digluconate (5% for the A solution, 1.5% for the B solution) were determined using a microdilution method. This method is a miniaturization of the Afnor T 72150 standard for antiseptics and disinfectants. 133 hospital isolates were studied, including 68 Enterobacteriaceae, 11 Acinetobacter, 18 Pseudomonas, 1 Achromobacter, 23 Staphylococcus, and 12 S. faecalis. Each microplate was seeded with eleven of these strains and one reference strain (E. coli CIP 54127, P. aeruginosa CIP A22, S. aureus CIP 53154, and S. faecium CIP 5855). Ten microliter of a standardized inoculum (2 to 3 10(8) bacteria/ml) were added to 90 microliters of a solution containing the antiseptic. Each antiseptic was tested in various concentrations (1.95 to 125 mg/l for A and 1.17 to 75 mg/l for B). After five minutes contact at 21 degrees C, 1.5 microliter from each well was seeded on a neutralizing agar plate (letheen agar + 3% tween 80 + 0.3% lecithin + 3% saponin + 0.1% histidine). The neutralizing effectiveness of this plate on the antiseptics in the concentrations used had been ascertained previously. The Afnor T 72150 standard was established for each reference strain. MBCs 90 (in mg/l) found were as follows: 31.2 (A) and 18.8 (B) for Enterobacteriaceae, 15.6 (A) and 9.4 (B) for Acinetobacter, 31.2 (A) and 18.8 (B) for Pseudomonas, 62.5 (A) and 37.7 (B) for Staphylococcus and 125 (A) and 37.5 (B) for S. faecalis.(ABSTRACT TRUNCATED AT 250 WORDS)