Biofilm formation plays a critical role in antimicrobial resistance in  Staphylococcus aureus . In a new study, the researchers investigated the potential of crude extracts of 79 Micronesian marine microorganisms to inhibit  S. aureus  biofilm formation. The results showed that an extract of  Streptomyces  sp. MC025 inhibited  Staphylococcus aureus biofilm formation.

The emerging rate of antibiotic resistance is a huge threat to public health. In particular, Staphylococcus aureus is a major pathogen that frequently causes infections in the patients in the hospital and is well-known with a high rate of antibiotic resistance such as methicillin-resistant S. aureus (MRSA).

It is necessary to discover a new drug that can control the infection of S. aureus and MRSA . It is known that S. aureus produces biofilms with extracellular polymeric substances and universally attaches to the surface of organs and tissues. The polymeric biofilms function as a barrier to interfere with the diffusion of antibiotics and protect pathogens against antibiotics.

Furthermore, subinhibitory concentrations of several antibiotics often increase biofilm formation. Therefore, inhibition of biofilm formation of S. aureus is thought as a strategy to control infection of S. aureus without an additional increase in antibiotic resistance. Currently, there are several ways to inhibit microbial biofilm formation.

In the study, the antibiotic activities of the extracts of 79 cultured bacterial strains were isolated from Micronesian marine organisms were evaluated, and a series of bipyridine compounds were purified from the bioactive extract of Streptomyces sp. MC025 by bioactivity-guided isolation.

The antibiofilm activities of the isolated compounds were evaluated by biofilm formation assays in 96-well microtiter plates, and confocal microscopy, in order to identify biofilm inhibitors targeting S. aureus strains including methicillin-resistant S. aureus (MRSA).

Bioactivity-guided isolation led to the i solation of a series of 2,2'-bipyridines: collismycin B, collismycin C, SF2738 D, SF2738 F, pyrisulfoxin A, and pyrisulfoxin B. Among these bipyridines, collismycin C was found to be the most effective inhibitor of biofilm formation by methicillin-sensitive  S. aureus  and methicillin-resistant  S. aureus  (MRSA).

The compound inhibited MRSA biofilm formation by more than 90% at a concentration of 50 μg / mL. The antibiofilm activity of collismycin C was speculated to be related to iron acquisition and the presence and position of the hydroxyl group of 2,2'-bipyridines.