Cryptococcus neoformans is a human-pathogenic yeast responsible for pneumonia and meningitis, mainly in patients immunocompromised. Infections caused by C. neoformans are a global health concern. Synthetic antimicrobial peptides (SAMPs) have emerged as alternative molecules to cope with fungal infections, including C. neoformans. Here, eight SAMPs were tested regarding their antifungal potential against C. neoformans and had their mechanisms of action elucidated by fluorescence and scanning electron microscopies. Five SAMPs showed an inhibitory effect (MIC50) on C. neoformans growth at low concentrations. Fluorescence microscope (FM) revealed that SAMPs induced 6-kDa pores in the C. neoformans membrane. Inhibitory assays in the presence of ergosterol revealed that some peptides lost their activity, suggesting interaction with it. Furthermore, FM analysis revealed that SAMPs induced caspase 3/7-mediated apoptosis and DNA degradation in C. neoformans cells. Scanning Electron Microscopy (SEM) analysis revealed that peptides induced many morphological alterations such as cell membrane, wall damage, and loss of internal content on C. neoformans cells. Our results strongly suggest synthetic peptides are potential alternative molecules to control C. neoformans growth and treat the cryptococcal infection.

Cryptococcus neoformans is a multidrug-resistant pathogen responsible for infections in immunocompromised patients. Here, itraconazole (ITR), a commercial antifungal drug with low effectiveness against C. neoformans, was combined with different synthetic antimicrobial peptides (SAMPs), Mo-CBP3-PepII, RcAlb-PepII, RcAlb-PepIII, PepGAT, and PepKAA. The Mo-CBP3-PepII was designed based on the sequence of MoCBP3, purified from Moringa oleifera seeds. RcAlb-PepII and RcAlb-PepIII were designed using Rc-2S-Alb, purified from Ricinus communis seed cakes. The putative sequence of a chitinase from Arabidopsis thaliana was used to design PepGAT and PepKAA. All SAMPs have a positive liquid charge and a hydrophobic potential ranging from 41–65%. The mechanisms of action responsible for the combined effect were evaluated for the best combinations using fluorescence microscopy (FM). The synthetic peptides enhanced the activity of ITR by 10-fold against C. neoformans. Our results demonstrated that the combinations could induce pore formation in the membrane and the overaccumulation of ROS on C. neoformans cells. Our findings indicate that our peptides successfully potentialize the activity of ITR against C. neoformans. Therefore, synthetic peptides are potential molecules to assist antifungal agents in treating Cryptococcal infections.

Antimicrobial drugs are becoming ineffective given the resistance acquired by microorganisms. As such, it is imperative to seek new antimicrobial molecules that could provide a basis for the development of new drugs. Therefore, this work aimed to evaluate the antimicrobial potential and the mechanisms of action of the essential oil extracted from leaves of Croton blanchetianus (named CbEO) on different fungi and bacteria of clinical importance in both planktonic and biofilm lifestyles. GC-MS/MS analysis revealed the presence of twenty-two different compounds in the CbEO, which were identified using the Kovats retention index. Among these, the most abundant were amorphene (20.03%), spathulenol (5%), bicyclogermacrene (1.49%), caryophyllene oxide (4.55%), and eucalyptol (5.62%). CbOE (50 µg mL−1) barely inhibited the growth of Bacillus subtilis (23%), Pseudomonas aeruginosa (27%), and Salmonella enterica (28%), and no inhibition was obtained against Enterobacter aerogenes and Klebsiella pneumoniae. Additionally, no activity against bacterial biofilm was detected. In contrast, CbEO was active against Candida species. C. albicans and C. parapsilosis were inhibited by 78 and 75%, respectively. The antibiofilm potential also was favorable against C. albicans and C. parapsilosis, inhibiting 44 and 74% of biofilm formation and reducing around 41 and 27% of the preformed biofilm, respectively. CbOE caused membrane damage and pore formation, overproduction of ROS, and apoptosis on C. albicans and C. parapsilosis cells, as well as not inducing hemolysis in human red cells. The results obtained in this work raise the possibility of using the essential oil of C. blanchetianus leaves as an alternative to fight infections caused by C. albicans and C. parapsilosis.

In this study, the chemical composition of the essential oil (EO) extracted from Croton blanchetianus Baill leaves was identified, and antimicrobial and antibiofilm activities against Staphylococcus aureus, Staphylococcus epidermidis, and Escherichia coli strains were determined. Moreover, the effects of EO in combination with ampicillin and tetracycline were investigated. Thirty‐four components, mainly mono‐and sesquiterpenes that represented 94.05 % of the chemical composition, were identified in the EO. The EO showed bacteriostatic and bactericidal activities against all strains tested. Furthermore, the EO showed a synergistic effect with ampicillin and tetracycline. EO significantly inhibited biofilm formation and reduced the number of viable cells in biofilms. The EO may be a promising natural product for preventing bacterial biofilm infections.

Aims This study aimed to evaluate the antifungal and antibiofilm effects of essential oil (EO) from leaves of Lippia gracilis and its major constituents, thymol and carvacrol, against phytopathogenic fungi. Methods and Results The leaves of L. gracilis were hydrodistilled to obtain the EO and the chemical composition was determined by GC/MS analysis. The antifungal activity of EO of L. gracilis was evaluated on the vegetative and mycelial growth of Colletotrichum gloeosporioides, Colletotrichum lindemuthianum, Fusarium oxysporum and Fusarium solani. In addition, the ability of the oil to inhibit fungal biofilm formation was assessed by total biomass quantification using crystal violet staining, analysis of metabolic activity, and scanning electron microscopy (SEM). Moreover the antifungal and antibiofilm activities of the monoterpenes, thymol and carvacrol, present in EO of L. gracilis were evaluated against F. oxysporum. The analysis of the chemical composition of EO extracted from L. gracilis, revealed the presence of monoterpenes (94·13%), which included carvacrol (48·57%) and thymol (7·78%), and 4 sesquiterpenes (3·74%). In general, EO showed significant antifungal activity and inhibited the formation of fungal biofilms. Furthermore, thymol and carvacrol showed significant antifungal and antibiofilm activities against F. oxysporum. SEM images showed structural changes in fungal morphology upon treatment with EO of L. gracilis. Conclusion The results presented in this study showed promising antifungal and antibiofilm effects of EO of L. gracilis and its major components, carvacrol and thymol. Significance and Impact of the Study These findings indicate that the EO extracted from L. gracilis, and the monoterpenes, carvacrol and thymol have a great potential as antifungal and antibiofilm agents. Furthermore, this is the first report of the antibiofilm activity of the EO of L. gracilis and its major components against phytopathogenic fungi.