Oral transmission of Candida albicans between partners in HIV-infected couples could contribute to dissemination of fluconazole-resistant isolates

Background: Fluconazole resistance has emerged among Candida albicans isolates and has been associated with the prolonged or repeated use of the drug. This study was designed to discover whether transmission of oral isolates could occur between sexual partners and thereby explain fluconazole resistance in patients never treated with the drug. Materials and methods: The oral flora of 10 HIV-infected couples (five heterosexual and five homosexual) were studied. In vitro susceptibility testing and genotyping (restriction fragment length polymorphism with EcoRI and HinfI) were used to delineate strain relatedness for 230 clones (five clones per sample, one to four samples per patient). Results: The genetic diversity of the clones with one DNA subtype was specific to a given patient or a given couple, except in one case in which unrelated patients shared clones of the same genotype. The persistence of clones between partners was stable over time in six out of 10 couples and only transient in one couple. Fluconazole resistance in isolates from patients who had never been treated with azoles was associated in three patients with the first episode of oropharyngeal candidiasis and treatment failure. Conclusion: The observation that couples tended to share genetically indistinguishable clones was highly suggestive of transmission between partners. This phenomenon may, in part, explain the pathogenesis of oropharyngeal candidiasis and the increased frequency of fluconazole resistance both in vitro and in vivo.