Antibiotic-resistant bacteria inhibited by extracts and fractions from Brazilian marine sponges

Abstract

The growing number of bacterial strains resistant to conventional antibiotics has become a serious medical problem in recent years. Marine sponges are a rich source of bioactive compounds, and many species can be useful for the development of new antimicrobial drugs. This study reports the in vitro screening of marine sponges in the search for novel substances against antibiotic-resistant bacteria. Sponge extracts were tested against 44 bacterial strains, including fourteen antibiotic-resistant strains. Ten out of the twelve sponge species studied showed activity in one or more of the bioassays. Aqueous extracts of Cinachyrella sp. and Petromica citrina showed a large action spectrum over resistant-bacteria such as Staphylococcus aureus, coagulase-negative staphylococci and Enterococcus faecalis. Aqueous extract of P. citrina was fractioned and aqueous fraction showed a greatest inhibitory activity on Staphylococcus strains. In addition, this fraction demonstrated a bactericidal effect on exponentially growing S. aureus cells at the MIC (16 μg/mL). The mechanism of action of bioactive fraction is still unclear, but we showed that it affect protein biosynthesis of Staphylococcus. Our results demonstrated for the first time that P. citrina is a potential source of new drugs for the treatment of infections by antibiotic-resistant bacteria.