Molecular Characterisation of Virulence Factors in Cryptococcus spp. Isolated from Humans, Pigeons, and Eucalyptus Sources

This study aimed to isolate and identify Cryptococcus species from three distinct sources: sputum samples of pigeon fanciers, dried pigeon droppings, and eucalyptus tree leaves. A total of 150 specimens were collected over a two-month period, comprising 50 samples each from human sputum, pigeon droppings collected across various areas of Baghdad, and eucalyptus leaves obtained from the Baghdad College of Veterinary Medicine. All samples were cultured on Sabouraud dextrose agar supplemented with chloramphenicol and incubated at 25°C for 2–3 days. From the initial cultures, 20 isolates presumptively identified as Cryptococcus spp. were obtained: 6 isolates (12%) from human sputum, 9 isolates (18%) from pigeon droppings, and 5 isolates (10%) from eucalyptus leaves, giving an overall recovery rate of 13.3%. Molecular identification using PCR was employed to detect two key virulence genes: CAP64 (associated with capsule formation) and LAC1 (involved in melanin production). These genes were detected in 13 out of 14 confirmed Cryptococcus isolates (92.85%). Specifically, 75% of C. neoformans isolates from human samples carried these genes, while the C. albidus isolate lacked them. All Cryptococcus isolates from pigeon droppings and eucalyptus leaves tested positive for both virulence genes (100%).