February 8th 2017

Extracted compound shows potent antibacterial activity against MRSA bacteria.

A compound extracted from the deep-water marine sponge has demonstrated substantial antibacterial activity against superbug methicillin-resistantStaphylococcus aureus(MRSA), according to a study published inMarineDrugs.

The CDC estimates more than 80,000 invasive MRSA infections and 11,285 related deaths occur each year. MRSA bacteria is resistant to all beta-lactam antibiotics such as methicillin, penicillin, oxacillin, and amoxicillin.

The deep-water sponge—–which resides near the Bahamas––is of the genus Spongosorites and has been a “source of a number of biologically active bis-indole alkaloids that are reported to have a variety of activities including antibacterial, antiviral, antifungal, antiplasmodial, cytotoxic, as well as anti-inflammatory activities,” said lead author Amy Wright, PhD.

Over the past decade, the investigators have developed a library of materials called the FAU Harbor Branch-enriched fraction library, which are tested against various diseases. Once an activity is observed, the investigators use bioassay-directed fractionation to purify the bioactive natural products. According to the authors, the structures of the new compounds are determined through spectroscopic means with an emphasis on the use of nuclear magnetic resonance spectroscopy.

Using this approach, the investigators can then define how the compounds work through a wide array of methods, such as small molecule immunochemical chromatography.

For the study, investigators screened fractions from the FAU Harbor Branch-enriched fraction library in a number of assays, including growth inhibition of the bacteria MRSA. They then collaborated to test the growth inhibition of the causative agent for tuberculosis and the parasite Plasmodium falciparum, which is one of the many causes of malaria, according to the study.

The highly enriched fraction containing the new compound­­—–which the investigators named dragmacidin G––showed activity in all 3 assays. It was then further purified to obtain pure dragmacidin G, which enabled its structure elucidation and biological testing.

“We found substantial antibacterial activity for dragmacidin G,” Wright said. “It is greater than 10-fold more potent than other members of the bis-indole alkaloids while retaining selectivity towards bacterial over mammalian cells.”

Based on the preliminary findings, the investigators plan to conduct additional studies.

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