The use of drip flow and rotating disk reactors for Staphylococcus aureus biofilm analysis

Most microbes in nature are thought to exist as surface-associated communities in biofilms.(1) Bacterial biofilms are encased within a matrix and attached to a surface.(2) Biofilm formation and development are commonly studied in the laboratory using batch systems such as microtiter plates or flow systems, such as flow-cells. These methodologies are useful for screening mutant and chemical libraries (microtiter plates)(3) or growing biofilms for visualization (flow cells)(4). Here we present detailed protocols for growing Staphylococcus aureus in two additional types of flow system biofilms: the drip flow biofilm reactor and the rotating disk biofilm reactor. Drip flow biofilm reactors are designed for the study of biofilms grown under low shear conditions.(5) The drip flow reactor consists of four parallel test channels, each capable of holding one standard glass microscope slide sized coupon, or a length of catheter or stint. The drip flow reactor is ideal for microsensor monitoring, general biofilm studies, biofilm cryosectioning samples, high biomass production, medical material evaluations, and indwelling medical device testing.(6,7,8,9) The rotating disk reactor consists of a teflon disk containing recesses for removable coupons.(10) The removable coupons can by made from any machinable material. The bottom of the rotating disk contains a bar magnet to allow disk rotation to create liquid surface shear across surface-flush coupons. The entire disk containing 18 coupons is placed in a 1000 mL glass side-arm reactor vessel. A liquid growth media is circulated through the vessel while the disk is rotated by a magnetic stirrer. The coupons are removed from the reactor vessel and then scraped to collect the biofilm sample for further study or microscopy imaging. Rotating disc reactors are designed for laboratory evaluations of biocide efficacy, biofilm removal, and performance of anti-fouling materials.(9,11,12,13).