Biofilm is one virulence factor of bacteria. It contributes not only to bacterial adherence to many kinds of infection-establishing surfaces, but also to bacterial resistance against antimicrobial agents and antiseptic agents. Thus, inhibitors of bacterial biofilm formation should be useful in the prevention of infections. We found that a culture of Streptomyces sp. strain MC11024 showed inhibitory activity on biofilm formation by Staphylococcus aureus and isolated streptorubin B as an inhibitor of this formation in S. aureus. The biofilm formation of methicillin resistant S. aureus (MRSA) N315 was reduced to less than 30% at 1 µg/mL of streptorubin B, and at this concentration cell growth was not affected. Our study suggests that streptorubin B has the potential to be a leading compound of anti-infectious agents of S. aureus.
Key words biofilm; inhibitor; Staphylococcus aureus; Streptomyces; prodigiosinPathogenic bacteria produce many kinds of virulence factors and cause human infectious diseases. Among them, adherence factors are important for establishing infections.
1,2)Such factors also confer adhering and staying on every surface including medical devices. One of such factors, biofilm, is a relatively flexible and sticky structure.3) Once bacteria form biofilm on the surface of medical devices set in the human body, it is difficult to remove the biofilm. It is also known that biofilm prevents the penetration of antibacterial drugs and helps bacteria escape from host immune systems.
4)Some infections correlate with biofilm formation at the clinical site.
5)Biofilm formation by bacteria starts with the production of adhering factors. Bacterial cells attach to many kinds of surfaces via electrical charge and specific interactions. After that, bacteria develop biofilm by producing high viscosity extracellular matrix including polysaccharides, proteins, DNA and so on. After the biofilm has been developed, part of the bacteria in the biofilm releases some proteases, detaching them from the biofilm, and the small block of biofilm containing bacteria moves to other places. 6) While bacteria attach to surfaces and mature biofilm, they also release many virulence factors.
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