Drug resistance studies with topical antiseptics.

Species of Proteus, Serratia, and Pseudomonas became resistant to chlorhexidine after five to eight transfers in vitro. Cross-resistance to benzalkonium chloride also was detected. Resistance to povidone-iodine was not encountered. Chlorhexidine resistance was stable after drug-free transfers of Serratia and Pseudomonas but was transitory for Proteus.