[21] In vitro methods to study staphylococcal biofilm formation

This chapter discusses the in vitro methods to study Staphylococcal biofilm formation. Chronic nosocomial infections by gram-positive bacteria have become more prevalent with the increased use of prosthetic biomedical implants. Two of the most commonly isolated organisms associated with biomedical implant infections are Staphylococcus epidermidis, a member of the normal skin microbiota, and Staphylococcus aureus, a resident of aural and nasal cavities in a large proportion of healthy individuals. Staphylococci opportunistically colonize intravenous catheters, artificial heart valves, replacement hip joints, and many other prosthetic devices. Chronic infection of a prosthetic implant can serve as a septic focus that can lead to osteomyelitis, acute sepsis, and death, particularly in immunocompromised patients. Cells within a biofilm are less sensitive to antibiotic agents, host immune defenses, and therefore are difficult to treat clinically. Often, the only means of eliminating the infection is to remove the prosthetic implant. A number of methods have been developed that are useful for the in vitro cultivation of staphylococcal biofilms. These methods enable in identifying and studying the molecular mechanisms that leads to biofilm formation. Syngeneic mutant strains for genes important for the formation or maintenance of a biofilm in vitro can then be constructed and tested in animal models for in vivo virulence and biofilm formation.