Purpose. Ctn[15–34], a carboxyl-terminal fragment of crotalicidin (a cathelicidin from the venom gland of a South American rattlesnake), has shown antifungal activity against clinical and standard strains of Candida species. The aim of the present work was to investigate the underlying mechanisms of the candidicidal activity of Ctn[15–34].
Methodology. The time-kill profile and drug synergism were evaluated by means of a microdilution assay and multi-parametric flow cytometry. The presumptive interaction of Ctn[15–34] with lipid membranes was estimated in vitro with a lipid-mimic compound, the chromogenic substance 4-nitro-3-(octanoyloxy)benzoic acid (4N3OBA).
Results/Key findings. The absorbance increment (at 425 nm) indicated a concentration- and time-dependent in-solution association between Ctn[15–34] and 4N3OBA. The interaction of Ctn[15-34] with Candida cells was confirmed by flow cytometric measurements with the 5(6)-carboxyfluorescein-labelled peptide (CF-Ctn[15–34]). Analysis of the killing time of Candida exposed to Ctn[15–34] and amphotericin B (AMB) showed that both the peptide and polyene drug reduce the number of c.f.u. but in mechanistically different ways. The Ctn[15–34] peptide alone caused yeast cell membrane disruption, which was confirmed by lactate dehydrogenase leakage and biomarkers of cell death mediated by necrosis.
Conclusion. Overall, Ctn[15–34] displays a synergistic antifungal activity with AMB, an effect that can be further developed into a multi-target therapeutic option with other antimycotics currently in use.
Complicated skin and soft tissue infections constitute a heterogeneous group of severe disorders, with surgical site infections being the most common hospital-acquired ones. The aim of our study was to investigate the synergistic and bactericidal activities of antimicrobial combinations of fosfomycin with rifampicin and tigecycline against Enterococcus faecalis, Enterococcus faecium and methicillin-resistant Staphylococcus aureus (MRSA) clinical isolates, and also to evaluate their in vivo effects in a mouse wound infection model. In in vitro studies, the combinations of fosfomycin with rifampicin and tigecycline were both synergistic. These synergies were confirmed in in vivo studies: the drug combinations showed the highest antimicrobial effects compared to monotherapy. In conclusion, the efficacy of fosfomycin combinations, also confirmed in our in vivo model, may suggest new directions in the treatment of infected skin and a possible alternative way to control bacterial skin infection.