Review of the Microbial Spectrum of Mixed Respiratory Fungal Infections

BACKGROUND: This review examines the increasing clinical challenge of mixed respiratory fungal infections (MRFIs), emphasizing interkingdom interactions and their impact on disease progression and patient outcomes. MAIN BODY: We critically analyze current literature on the clinical implications, risk factors, and diagnostic complexities of MRFIs, with a primary focus on fungal-bacterial, fungal-viral, and fungal-parasitic co-infections. Fungal-bacterial co-infections, often involving Candida spp. and Pseudomonas aeruginosa, significantly worsen disease severity. Fungal-viral co-infections, particularly in COVID-19 patients with Candida albicans and Aspergillus fumigatus, represent a major threat. While rare, fungal-parasitic co-infections pose risks for immunocompromised individuals. The review highlights diagnostic difficulties due to non-specific symptoms and the vital need to distinguish colonization from true infection. It also explores the complex symbiotic, synergistic, and antagonistic relationships between fungi and other microorganisms, alongside the immune-modulating role of commensal fungi. CONCLUSION: Ultimately, this review seeks to enhance understanding of MRFIs to improve diagnostic and therapeutic strategies and patient care.