The gastrointestinal tract of poultry is inhabited by a diverse community of bacteria, fungi, protozoa and viruses. The aim of the study was to determine the influence of early antimicrobial treatment on the fungal microflora of the gastrointestinal tract of turkeys and analyze candidiasis occurrence in later age of the birds from treated flocks. The samples were collected from the oral cavity, crop and cloaca of turkey poults treated at first week of life with one of the following treatments: amoxicillin; amoxicillin and clavulanic acid; enrofloxacin; florfenicol; lincomycin and spectinomycin; amoxicillin and colistin; amoxicillin, clavulanic acid, and colistin; enrofloxacin and colistin. Sampling was again carried out during the 5^th week of the turkey’s life. The most common isolated fungal were Candida and Trichosporon. Treatment with amoxicillin or amoxicillin and clavulanic acid provided the highest number of positive samples, while treatment with enrofloxacin provided the lowest number of positive samples. The inclusion of colistin in the treatment regimen resulted in a reduction of the number of positive fungal samples. Clinical candidiasis was not observed in any of the examined birds. The experiments demonstrated that early antimicrobial treatment in poultry can predispose to fungal colonization and that beta-lactams have the highest influence on gastrointestinal colonization by fungi.

Key words: Antimicrobial agent, Fungal infestation, Gastrointestinal tract, Turkeys