Bactericidal Effects of Disinfectants on Clinical Isolates from the Hospital. (Report 4).

At our hospital, we have been conducting experiments on the time course of bactericidal effectiveness of disinfectants against clinically isolated bacterial strains. In the present study, we investigated the following commonly used disinfectants; chlorhexidine gluconate (CHG), benzalkonium chloride (BAC), povidone iodine (PVP-I) and alkyl diaminoethylglycine hydrochloride (ADG). The results showed that PVP-I exhibited the greatest bactericidal effect among these disinfectants with a bactericidal time of within 20 seconds for both gram-positive and gramnegative bacteria. CHG, BAC and ADG appeared to have a relatively delayed bactericidal time against gram-positive bacteria and 7 of 9 strains tended to show resistance to these disinfectants. These findings point to the need to add ethanol in order to ensure the effectiveness of disinfec tion when using these agents. Furthermore, these disinfectants showed only poor bactericidal effectiveness at low concentrations against gram-negative bacteria, thus indicating that caution is needed when determining the appropriate concentration levels. Moreover, since our results for BAC and PVP-I differ from those described in our previous reports, extreme care is thus called for when determining the concentration levels and exposure times due to intrinsic bacterial factors and the time course of bactericidal effectiveness.