Geographical distribution of Cryptococcus neoformans in Iran, pathogenic factors, and antifungal susceptibility profile.

Background: Approximately 70 species of Cryptococcus have been identified, some of which are human and animal pathogens, while others are environmental saprophytes. Cryptococcus neoformans is one of the most important pathogenic species, and pigeon droppings serve as the most important ecological niche. This study aimed to investigate the frequency of C. neoformans in pigeon droppings from various Iranian provinces, as well as assess the pathogenic factors and antifungal susceptibility of the isolates.

Methods: 428 pigeon droppings samples were collected from 10 Iranian provinces and cultured on Niger seed agar. DNAs were extracted, and CNLAC1 (Outer and Inner) and STR1 primers were used for the detection of species and varieties of C. neoformans, respectively. Virulence factors were also identified using specific culture media under appropriate conditions. Antifungal susceptibility testing was conducted against 8 antifungals using CLSI guidelines.

Results: Out of the 428 examined samples, 37 (8.6%) were positive for C. neoformans. All isolates exhibited capsule production and dark brown pigmentation as key pathogenic factors. Urease and catalase activities were present in all isolates. Based on the established ECVs guidelines, all isolates displayed wild-type phenotypes against voriconazole and 5-flucytosine. While 100% isolates were non-wild type against amphotericin B.

Conclusions: The frequency of C. neoformans was 8.6% in Iranian cities, with a high (31.5%) frequency in Kermanshah and a low (3.1%) frequency in Fars province. All isolates showed sensitivity to voriconazole and 5-flucytosine. Additionally, pathogenic factors were present in all strains to varying degrees.