MALDI-TOF MS characterisation, genetic diversity and antifungal susceptibility of Trichosporon species from Iranian clinical samples.

BACKGROUND: Trichosporonosis is an emerging fungal infection caused by Trichosporon species, a genus of yeast-like fungi, which are frequently encountered in human infections ranging from mild cutaneous lesions to fungemia in immunocompromised patients. The incidence of trichosporonosis has increased in recent years, owing to higher numbers of individuals at risk for this infection. Although amphotericin B, posaconazole and isavuconazole are generally effective against Trichosporon species, some isolates may have variable susceptibility to these antifungals. OBJECTIVES: Herein, we evaluated the species distribution, genetic diversity and antifungal susceptibility profiles of Trichosporon isolates in Iran. METHODS: The yeasts were identified by matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF MS). Phylogenetic analysis was performed based on amplified fragment length polymorphism (AFLP). The in vitro susceptibilities of eight antifungal agents were analysed using the Clinical and Laboratory Standards Institute broth microdilution methods. RESULTS: The isolates belonged to the species T asahii (n = 20), T japonicum (n = 4) and T faecale (n = 3). A dendrogram of the AFLP analysis demonstrated that T asahii and non-asahii Trichosporon strains (T japonicum and T faecale) are phylogenetically distinct. While voriconazole was the most active agent (GM MIC = 0.075 µg/ml), high fluconazole MICs (8 µg/ml) were observed for a quarter of Trichosporon isolates. The GM MIC value of amphotericin B for T asahii and non-asahii Trichosporon species was 0.9 µg/ml. CONCLUSIONS: The distribution and antifungal susceptibility patterns of the identified Trichosporon species could inform therapeutic choices for treating these emerging life-threatening fungi.

Use of cell surface protein typing for genotyping of azole-resistant and -susceptible Aspergillus fumigatus isolates in Iran.

Aspergillus fumigatus is the leading cause of mortality in severely immunocompromised individuals. Understanding pathogen dispersion and relatedness is essential for determining the epidemiology of nosocomial infections. Therefore, the aim of this study was to investigate the diversity and putative origins of clinical and environmental azole-susceptible and -resistant A. fumigatus isolates from Iran. In all, 79 isolates, including 64 azole-susceptible and 15 -resistant isolates, were genotyped using the cell surface protein (CSP) gene. Seven distinct repeat types (r01, r02, r03, r04, r05, r06 and r07) and 11 different CSP variants (t01, t02, t03, t04A, t06A, t06B, t08, t10, t18A, t18B and t22) were observed. Interestingly, t06B, t18A and t18B were exclusively present in azole-resistant isolates. The Simpson's index of diversity (D) was calculated at 0.78. Resistant isolates were genetically less diverse than azole-susceptible isolates. However, azole-resistant A. fumigatus without TR34 /L98H were more diverse than with TR34 /L98H. The limited CSP type diversity of the TR34 /L98H isolates versus azole-susceptible isolates suggests that repeated independent emergence of the TR34 /L98H mechanism is unlikely. It has been suggested that CSP types might have a common ancestor that developed locally and subsequently migrated worldwide.