The in vitro activity of caspofungin and micafungin was determined with and without farnesol in RPMI-1640 against Candida parapsilosis biofilms. Drug interactions were examined using the XTT colorimetric assay-based broth microdilution checkerboard method. Drug-drug interactions were assessed utilizing a fractional inhibitory concentration index (

Secondary fungal infections may complicate the clinical course of patients affected by viral respiratory diseases, especially those admitted to intensive care unit. Hospitalized COVID-19 patients are at increased risk of fungal co-infections exacerbating the prognosis of disease due to misdiagnosis that often result in treatment failure and high mortality rate. COVID-19-associated fungal infections caused by predominantly Aspergillus and Candida species, and fungi of the order Mucorales have been reported from several countries to become significant challenge for healthcare system. Early diagnosis and adequate antifungal therapy is essential to improve clinical outcomes, however, drug resistance shows a rising trend highlighting the need for alternative therapeutic agents. The purpose of this review is to summarize the current knowledge on COVID-19-associated mycoses, treatment strategies and the most recent advancements in antifungal drug development focusing on peptides with antifungal activity.

Killing rates (K) of 1-32 mg ml "1 caspofungin were determined in RPMI-1640 and in 50 % serum using time-kill methodology against three Candida krusei (MICs of all three isolates 0.25 mg mlin RPMI-1640 and 2 mg ml "1 in serum) and three Candida inconspicua clinical isolates (MIC ranges 0.06-0.12 mg ml "1 in RPMI-1640 and 0.25-0.5 mg ml "1 in serum), against C. krusei ATCC 6258 and against one C. krusei isolate that was resistant to echinocandins (MIC 8 mg mlin RPMI-1640 and 32 mg ml "1 in serum). In RPMI-1640, the highest mean K values were observed at 4 ("1.05 h "1) and 16 ("0.27 h "1 ) mg ml "1 caspofungin for C. krusei and C.inconspicua clinical isolates, respectively. In 50 % serum, mean K value ranges at 1-32 and 4-32 mg ml "1 concentrations for C. inconspicua and C. krusei were "1.12 to "1.44 and "0.42 to, respectively. While K values against C. krusei in RPMI-1640 and 50 % serum were comparable, serum significantly increased the killing rate against C. inconspicua (P,0.0003 for all tested concentrations). In a neutropenic murine model, daily caspofungin at 1, 2, 3, 5 and 15 mg kg "1 significantly decreased the fungal tissue burden of C. inconspicua in the kidneys (P,0.05-0.001). Against C. krusei, doses of 3, 5 and 15 mg kg "1 caspofungin were effective (P,0.05-0.01). All effective doses were comparably efficacious for both species. Only the highest 15 mg kg "1 caspofungin dose was effective even against the echinocandin-resistant C.krusei isolate. In 50 % serum, killing was concentration independent at effective concentrations (¢4 and ¢1 mg ml "1 for C. krusei and C. inconspicua, respectively), suggesting that the efficacy of dose escalation is questionable. These in vitro results were also supported by the murine model.

Farnesol is a quorum-sensing molecule that inhibits biofilm formation in Candida albicans. Previous in vitro data suggest that, in combination with certain antifungals, farnesol may have an adjuvant anti-biofilm agent. However, the in vivo efficacy of farnesol is very questionable. Therefore, the in vitro and in vivo activity of fluconazole combined with farnesol was evaluated against C. albicans biofilms using fractional inhibitory concentration index (FICI) determination, time-kill experiments and a murine vulvovaginitis model. The median biofilm MICs of fluconazole-sensitive C. albicans isolates ranged between 4 -> 512 mg/L and 150-300 μM for fluconazole and farnesol, respectively. These values were 512 -> 512 mg/L and > 300 μM for fluconazole-resistant clinical isolates. Farnesol decreased the median MICs of fluconazole by 2-64-fold for biofilms. Based on FICI, synergistic interaction was observed only in the case of the sessile SC5314 reference strain (FICIs: 0.16-0.27). In time-kill studies, only the 512 mg/L fluconazole and 512 mg/L fluconazole + 75 μM farnesol reduced biofilm mass significantly at each time point in the case of all isolates. The combination reduced the metabolic activity of biofilms for all isolates in a concentration- and time-dependent manner. Our findings revealed that farnesol alone was not protective in a murine vulvovaginitis model. Farnesol was not beneficial in combination with fluconazole for fluconazole-susceptible isolates, but partially increased fluconazole activity against one fluconazole-resistant isolate, but not the other one.

Monkeypox is an emerging zoonotic disease with a growing prevalence outside of its endemic area, posing a significant threat to public health. Despite the epidemiological and field investigations of monkeypox, little is known about its maintenance in natural reservoirs, biological implications or disease management. African rodents are considered possible reservoirs, although many mammalian species have been naturally infected with the monkeypox virus (MPXV). The involvement of domestic livestock and pets in spillover events cannot be ruled out, which may facilitate secondary virus transmission to humans. Investigation of MPXV infection in putative reservoir species and non-human primates experimentally uncovered novel findings relevant to the course of pathogenesis, virulence factors and transmission of MPXV that provided valuable information for designing appropriate prevention measures and effective vaccines.