In vitro biofilm formation by Staphylococcus aureus dependent on the culture medium

BACKGROUND AND OBJECTIVES: Bacterial biofilms are clusters of bacteria that attach to surfaces or to each other or are immersed in a self-produced matrix. The matrix is composed of extracellular polymeric substances (EPS) and its formation depends on the availability of nutrients, synthesis, and secretion of extracellular substances. In general, biofilm formation has been challenging in the field of medicine. Biofilms increase antibiotic resistance in such a way that the dense extracellular matrix and the outer layer of the cell protect the entire biofilm community and increase resistance to detergents and antibiotics and interfere with antibiotic therapy. Many bacterial pathogens are able to form biofilms in a wide range of clinical contexts, one of the most important bacteria in this context is Staphylococcus aureus, which is an opportunistic pathogen implicated as the most common agent of skin and soft tissue infections. It has the ability to adhere to and form a biofilm on tissues or medical indwelling devices. This study aimed to investigate biofilm formation by S. aureus ATCC۸۷۵: in two media, Brain Heart Infusion (BHI) broth and Muller Hinton broth. MATERIALS AND METHODSThe conditions for both cultural media were considered the same. In this method, the bacterium with ۵.۷ McFarland's concentration was poured into a microplate containing the mentioned and incubated for ۴۶ hours in an incubator at ۵۹  C. After the incubation period, the medium was removed and the wells were rinsed using distilled water. In the next step, the wells were stained with ۵.۱% crystal violet for ۴۵ min and washed using distilled water. Finally, the dye was solubilized using a ۵۵۳ acetic acid solution, and biofilm formation was quantified at ۷۷۵ nm wavelength. RESULTS AND DISCUSSION: The results showed that S. aureus ATCC۸۷۵: formed a stronger biofilm in the Muller Hintonbroth medium while the biofilm formation in BHI broth was negative. CONCLUSION: According our results the Muller Hinton broth medium is strongly recommended to use for S. aureus ATCC۸۷۵: biofilm formation, however, the BHI broth is not appropriate.