Abstract
Phyllomedusa azurea is a frog species well distributed geographically in South America, including Brazilian biomes as Pantanal and Cerrado. Compared with other anurans from the Phyllomedusinae family, there are few reports on the bioactive potential of skin-derived molecules from this species. In this perspective, the aim of the present study was to evaluate the in vitro antibacterial activity of skin secretion of P. azurea by detection of Minimum Inhibitory Concentration (MIC) of the growth of bacterial indicator strains and to determine if occurs a changing in the bacterial cell envelope permeability. The MIC determination was carried out by the microdilution plate method. The absorbance was measured and analyzed statistically using the t-test to compare two groups (0.05 % of significance). The impact of the crude extract on cell envelope permeability of Staphylococcus aureus ATCC 25923 was conducted by the crystal violet assay, and the absorbance was measured spectrophotometry followed by the calculation of the crystal violet uptake percentage. The specific MIC for S. aureus ATCC 25923 and Escherichia coli ATCC 25922 was 31.25 µg/mL, while for Bacillus subtilis ATCC 6633 was 125 µg/mL and Pseudomonas aeruginosa ATCC 27853 was 250 µg/mL. The treatment with crescent concentrations of frog skin secretion increased the crystal violet uptake by S. aureus ATCC 25923 cells, suggesting an action on the cell plasma membrane. The results demonstrated that the skin secretion of P. azurea presents antibacterial activity and merit further investigations to characterize the bioactive molecules.
Highlights
Phyllomedusa (Anura: Hylidae) is a frog genus, composed by 32 species and presents unique characteristics that differentiate it from other frogs, like green color in the dorsal body region, pupils located in the vertical fends, slow locomotion and arboreal life style (Caramaschi & Cruz, 2002; Frost, 2017)
The skin secretion of frogs from the family Phyllomedusinae consists in an abounding source of antimicrobial peptides (AMPs), from the dermaseptin and phylloseptin families (Brand et al, 2013)
According to Calderon et al (2011), the compounds from these two families encountered in the skin secretion of P. azurea have lytic activity against Gram-positive bacteria (Corynebacterium glutamicum, Enterococcus faecalis, Klebsiella pneumoniae, Micrococcus luteus, Nocardia spp., Nocardia brasiliensis, S. aureus, Streptococcus agalactiae, Streptococcus dysgalactiae), Gram-negative bacteria (Acholeplasma laidlawii, Acinetobacter calcoaceticus, E. coli, Neisseria gonorrhoeae, P. aeruginosa), fungus
Summary
Phyllomedusa (Anura: Hylidae) is a frog genus, composed by 32 species and presents unique characteristics that differentiate it from other frogs, like green color in the dorsal body region, pupils located in the vertical fends, slow locomotion and arboreal life style (Caramaschi & Cruz, 2002; Frost, 2017). The last work involving the evaluation of bioactivity of peptides extracted from P. azurea was from Kückelhaus et al (2009) where the authors confirmed activity against Plasmodium falciparum and Leishmania amazonensis of a synthetic amidated-phylloseptin-1 with low toxicity against human macrophages, opening up this molecule as a candidate for the treatment of these tropical protozoal diseases In this context, our goal was to investigate the antimicrobial activity of the skin secretion of P. azurea from Brazilian Cerrado by determination of the minimum inhibitory concentration (MIC) against different reference bacterial strains and to evaluate of its capacity in affecting the bacterial cellular envelop permeability
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