Bacillus Strains Associated to Homoscleromorpha Sponges are Highly Active Against Multidrug Resistant Bacteria

Abstract

The search for new, powerful antimicrobials is essential to respond to the current worldwidespread of antibiotic-resistant pathogens. Sponge-associated bacteria have great potential for production of antimicrobials against resistant and multidrug resistant (MDR) pathogenic bacteria, but only few species of the Class Homoscleromorpha have been screened for these activities so far.The aim of this study was to isolate andidentify sponge-associated bacteria active againstantibiotic-resistant pathogensfrom sponges of classes Homoscleromorpha and Demospongiae.Byemploying five different growth conditions, atotal of 239 colony-forming units were isolated and remainedviable. Among these, 17 (7.1%) isolates presented antimicrobial activity against pathogenic and (multi)drug resistant bacteria including vancomycin-resistant Enterococcus faecalis, Escherichia coli, Citrobacter freundii, Klebsiella penumoniae, Staphylococcus spp. and Streptococcus spp. Bioactive bacteria belonging to genera Bacillus and Vibrio were identified at species level and the DNA fingerprint patterns showed that strains of the same genus were not clonally related. The most active strains belong to genus Bacillus and were isolated from Oscarella sp., Plakina cyanorosea and Chondrilla caribensis. Our results show for the first time that sponge-associated strains of Bacillus pumilus and Bacillus muralis have high anti-MDR activity, and that the Homoscleromorpha may be a better source of such anti-MDR active bacteria than the Demospongiae. These results suggest that marine bacteria associated to homoscleromorph sponges maybe an interesting source of new antimicrobialsubstanceswith biotechnological potentialto treat infections caused by antibiotic-resistant bacteria.