Chlorhexidine digluconate induces mitotic recombination in diploid cells of Aspergillus nidulans

Chlorhexidine digluconate (1,1'-hexamethylene-bis[(5-p-clorophenyl)-biguanide]) is a bisbiguanidine antiseptic, used to decrease plaque formation and to control periodontal diseases. The determination of the frequency of mitotic crossing-over constitutes a very important method for detecting carcinogenic agents. OBJECTIVE: The recombinogenic potential of chlorhexidine digluconate was evaluated on Aspergillus nidulans by the production of cells homozygous for the following nutritional markers: riboA1, pabaA124, biA1, methA17 and pyroA4. METHOD: A. nidulans was exposed to three concentrations of chlorhexidine digluconate (1, 5, and 10 mu M). RESULTS: Inhibition of colony development, conidiophore morphological alteration (cytotoxic effect), and the recombinogenic effect, indicated by homozygotization index (HI) values higher than 2.0, were observed for all concentrations of chlorhexidine digluconate. A homozygous pyro+//pyro+ diploid strain and a diploid homozygous for the recessive w gene were isolated from UT448//A757 diploid treated with chlorhexidine digluconate, emphasazing its recombinogenic potential. CONCLUSION: Although, beneficial effects of chlorhexidine, as an antiseptic agent, are reported in the literature, our results revealed that chlorhexidine digluconate, at less levels lowered those used clinically, caused toxic and recombinogenic effects on diploid A. nidulans strain.