The role of oxidative stress response in modulating fluconazole resistance in cryptococcus clinical isolates

Abstract

Introduction Fluconazole-resistant Cryptococcus neoformans has emerged as a significant public health concern, complicating the management and treatment of cryptococcal infections. Resistance to fluconazole is associated with increased rates of treatment failure, relapse, and mortality. Resistant strains have been reported globally, with varying prevalence rates. Objectives This study aimed to asses the role of oxidative stress resistance in modulating fluconazole resistance using cryptococcal isolates. Methods A laboratory-based experimental study was conducted at the Makerere University Microbiology Laboratory. Twenty Cryptococcus species isolates were analysed for tolerance to hydrogen peroxide (H2O2) and fluconazole resistance. Minimum inhibitory concentrations (MICs) were determined before and after oxidative stress exposure. Data were analyzed using STATA to calculate the proportion of H2O2- and fluconazole-resistant isolates. Fluconazole resistant Cryptococcus neoformans has emerged as a significant public health concern, posing challenges in the management and treatment of Cryptococcal infections. This abstract provides a comprehensive overview of the epidemiology, mechanism of resistance, clinical implications and therapeutic strategies associated with fluconazole resistant Cryptococcus neoformans. fluconazole resistant Cryptococcus neoformans strains have been reported worldwide, with varying prevalence rates. The clinical implications of fluconazole resistance include increased rates of treatment failure, relapse and mortality. To address the challenges due to fluconazole resistance, alternative treatment approaches have been explored. combination therapy, employing multiple antifungal agents with different mechanisms of action. This study determined the resistance pattern of Cryptococcus isolates with and without external oxidative stress. In a laboratory-based experiment study, we analysed 20 Cryptococcus species isolates at the Makerere University Microbiology laboratory. We determined their tolerance levels to hydrogen peroxide and assessed for their resistance partners before and after exposure to hydrogen peroxide. Data was analysed to determine the proportion of H2O2 and fluconazole resistant isolates were calculated using STATA. At lower doses of H2O2, most isolates-maintained growth although there was a heterogeneity response at higher concentrations. The MIC values for C. gattii were higher in stressed compared with non-stressed conditions. While in C. neoformans, there was a heterogenous response to Fluconazole post-oxidative stress exposure. We observed that oxidative stress sensitizes cryptococcus isolates to fluconazole though there were a number of isolates that remined resistant after exposure. This study demonstrates that the resistance patterns of Cryptococcus isolates are oxidative stress dependant and heterogenous in nature. The results highlight the heterogenous resistance nature of Cryptococcus isolates underpinning the need for cases to case analysis of resistance profiles.

Results • At lower H2O2 concentrations, most isolates-maintained growth, though responses varied at higher doses. C. gattii showed increased MICs under oxidative stress compared to non-stressed conditions. C. neoformans exhibited a heterogeneous response to fluconazole following H2O2 exposure. Oxidative stress sensitized some isolates to fluconazole, although several remained resistant. At lower H2O2 concentrations, most isolates-maintained growth, though responses varied at higher doses. • C. gattii showed increased MICs under oxidative stress compared to non-stressed conditions. • C. neoformans exhibited a heterogeneous response to fluconazole following H2O2 exposure. • Oxidative stress sensitized some isolates to fluconazole, although several remained resistant. Recommendations Routine resistance profiling should be incorporated into clinical management of cryptococcal infections. Combination antifungal therapy using agents with diverse mechanisms of action should be considered for resistant cases. Further research is needed to understand the molecular basis of oxidative stress-induced sensitivity and resistance. Conclusion Resistance patterns in Cryptococcus isolates are influenced by oxidative stress and are highly heterogeneous. These findings highlight the complexity of antifungal resistance and the need for individualized resistance profiling.