Mycological study on prevalence and molecular diversity within airborne Cladosporium cladosporioides complex in Cairo, Egypt

Abstract

Outdoor airborne spores in Cairo, Egypt, are dominated by Cladosporium species, ecologically significant fungi that considerably influence ecosystem dynamics and public health. Therefore, understanding their molecular diversity and seasonal behavior is essential for assessing allergy risks and environmental quality. This study investigates the seasonal variation and molecular genotyping of airborne Cladosporium species in Cairo, Egypt. Airborne fungi were collected across four metropolitan districts in Cairo throughout all four seasons using passive settling plates, and isolates were identified through combined macroscopic, microscopic, and molecular approaches, including ITS-PCR/RFLP, Microsatellite Primed-PCR (MP-PCR), and Universally Primed PCR (UP-PCR). Based on macroscopic and microscopic investigation as well as molecular typing, Cladosporium accounted for 21.3% of the total mycobiota. Five Cladosporium species were identified: C. cladosporioides complex (30; 33.3%), C. herbarum (24; 26.6%), C. sphaerospermum (18; 20%), C. macrocarpum (9; 10%), and C. oxysporum (9; 10%). Seasonal variation analysis revealed significantly higher abundances in the summer and autumn. Molecular characterization was conducted using Internal Transcribed Spacer-PCR (ITS-PCR) combined with restriction fragment length polymorphism (RFLP) using MspI and CfoI restriction enzymes; Microsatellite Primed-PCR (MP-PCR) employing (AG)₈C and (AGG)₅ primers; and Universal Primed PCR (UP-PCR) using the L45 primer. ITS-RFLP analysis of 30 C. cladosporioides complex strains—the most abundant—identified 8 unique genotypes with MspI and 5 with CfoI. In addition, MP-PCR of the C. cladosporioides complex revealed substantial intraspecific diversity, detecting 17, and 10 genotypes with the respective primers—(AG)₈C and (AGG)₅ primers—supporting a clear climatic distribution pattern. UP‑PCR with L45 primer further revealed high molecular diversity among C. cladosporioides complex isolates from Cairo, identifying 18 genotypes with seasonal clustering. These findings highlight dynamic population structure and cryptic diversity of airborne Cladosporium in Cairo, Egypt, emphasizing their importance for aerobiological monitoring and allergen risk assessment. Understanding the ecological drivers, allergenic potential, and public health implications of these common urban fungi is made possible by the integration of morphological and molecular data, which reveals a complex population structure made up of both season-specific variants and persistent genotypes.