Bactericidal activities upon gram-negative bacilli of various disinfectants (phenol, cresol soap, iodophor, benzethonium chloride, chlorhexidine, glutaraldehyde, alkil di (amino ethyl) glycin and triclosan) were examined by a method similar to that for determining the phenol index for the purpose of evaluating fundamentally the effect of disinfectants. The results may be summarized as follows:
On the disinfectants tested, those showing bactericidal effects at the concentration routinely used and upon exposure for one minute or shorter were phenol, cresol soap, iodophor and glutaraldehyde.
Chlorhexidine and benzethonium chloride showed ver y inconsistent bactericidal effects o n gramnegative bacilli by short-time exposure. Many strains were not killed by these agents at concentrations routinely used.
The bactericidal effect of chlorhexidine was enhanced when used in the presence of ethanol.
Addition of blood serum, affecting most largely the effect of iodophor, markedly lowered the bactericidal effect.
