Mycopathogia 112: 119-124, 1990. 9 1989 Kluwer Academic Publishers. Printed in Belgium. Oral yeasts in patients with cancer of the mouth, before and during radiotherapy Claudete R. Paula, 1 Maria Carmeli C. Sampaio, 2 Esther G. Birman 2 & Antonio M. Siqueira 3 Institute of Biomedical Science, Department of Microbiology, USP ; 2 School of Dentristry, Department of Stomatology, USP; 3Fundation of Teaching and Technology of Alfenas, MG Received 25 August 1989; accepted in revised form 27 March 1990 Abstract The yeasts of patients with oral cancer has been studied before and during Xr-therapy. Gram and PAS smears revealed an increase of yeast-like structures, during treatment, from 56~o to 66~o of the cases. Before radiotherapy oral yeasts were isolated from 56~o of the patients with cancer represented by Candida albicans (3070); C. tropicalis (12~o); C. glabrata and C. krusei (470), besides six other different species (2 ~o). During radiotherapy yeasts were isolated in 72 ~o of the cases, as follow: C. albicans (36 7o); C. tropicalis (16~o); Rhodotorula rubra (6~o); C. kefyr; C. krusei and Pichia farinosa (4~o), besides other nine species (2 ~ C. albicans serotype A represented 93 ~o of the isolated samples, before treatment and 88,8 70 during Xr-therapy. Introduction The oral cavity presents, normally, a high inci- dence of yeasts, specially C. albicans, which are present as commensal or saprophitic micro- organism. Its pathogenicity depends on many fac- tors which predispose the host to candidosis [18, 22]. Publications concerning the frequency of iso- lation of yeasts, specially C. albicans, from the oral cavities of normal individuals abound in the literature but they relate a great disparity of fre- quencies [22]. Studies reported to date have concentrated on the prevalence of C. albicans whilst little or no information is available about other Candida spp. or other types of yeasts [21, 22]. C. albicans strains have been shown to be divisible into two serotypes, A and B. The serotype A has been more frequently isolated than B, and few reports have been traced on the distribution of these sero- types in the oral flora [19]. Head and neck radiation often causes painful and debilitating mucositis which is, usually, asso- ciated to xerostomy and candidosis, described mainly as pseudo-membranous type [28]. Few studies are known about the association of oral yeasts, oral cancer, and radiotherapy although it is well established the relation of malignant dis- eases and patients submitted to X-irradiation with oral infections, predominantly of yeasts etiology. No reports have been traced on the dis- tribution of C. albicans serotypes in these cases [6, 28]. The aim of this investigation was to determine the oral yeast flora present in patients with oral cancer, before and during radiotherapy. In addi- tion, the distribution of C. albicans serotypes was also investigated.