Antibacterial activity of the skin secretions of Hydromantes sarrabusensis, (Amphibia, Plethodontidae)

The multidrug resistance (MDR) represents a serious problem in the successful of therapy relating infectious diseases in humans and animals. It occurs when an infectious agent resulted not sensitive at different antimicrobial drugs (i.e. antibiotics), for this reason in the last years the researchers are trying to discover new formulates. Recent studies are focusing on different properties of skin amphibian secretion and some identified compounds are considered promising candidates for the future antimicrobial therapy. In the present work, we have investigated the antimicrobial profile of cutaneous secretion produced by Hydromantes sarrabusensis, a plethodontid salamander, endemic to a small area of south-eastern Sardinia. We have addressed the in vitro response of cutaneous swabs obtained from this species. Each sample was suspended in saline solution 0.9% and 0.1 mL was used in a Kirby-Bauer antimicrobial susceptibility testing with a set of human’s Gram positive and Gram negative pathogens, such as Escherichia coli, Staphylococcus aureus, Candida albicans, Pseudomonas aeruginosa, Streptococcus intermedius and Streptococcus pyogenes. Within 23 samples analysed (8 males, 7 females and 8 juveniles), 6 from males and 3 from juveniles showed a great antimicrobial profile against Gram positive bacteria, with inhibition diameter from 11 to 23 mm. These results appear encouraging, especially considering the dramatic emergence of these diseases due to Gram positive cocci such as S. aureus methicillin resistant strains, responsible for several difficult-to-treat infections in humans. In this context, our preliminary study could be a novel way to improve knowledge on amphibian physiology and for new antimicrobial drugs.