Incidence and etiology of biofilm-associated infections on medical devices
The adherence of microorganisms on the surface of MDs is considered an essential step in the infectious pathogenic mechanism (Katsikogianni and Missirlis, 2004), and the proper management of this phenomenon represents a constant concern of the medical community.
An implanted bone replacement device may damage surrounding tissues, thus creating favorable conditions for microbial biofilm formation and therefore infections, especially when the host’s immune system is compromised (Campoccia et al., 2006). Infections associated with orthopedic implants are numerous, with higher rates of morbidity and mortality, and cause devastating complications, while treatment is expensive. The possibility of infection of the bone implant increases by 5-40% in the case of a further surgery. In general, about 5% of orthopedic implants are infected (Trampuz and Widmer, 2006).
The organisms responsible for infections associated with orthopedic implants are often opportunistic infections, and 16% of these infections are polymicrobial. S. epidermidis and S. aureus are the main etiologic agents of orthopedic infections, followed by Staphylococcus hominis, Staphylococcus haemolyticus, Pseudomonas aeruginosa, and Enterococcus faecalis (Campoccia et al., 2006).
Infections associated with orthopedic implants can be classified depending on the postimplantation time when they occur in: (1) early infections that occur 3 months after the operation, produced by microorganisms with the high virulence (e.g., S. aureus); (2) late infections that occur between 3 and 24 months from the surgery, caused by microorganisms with reduced virulence (e.g., coagulase-negative staphylococci, Propionibacterium acnes); (3) secondary infections that occur 24 months after surgery and which are complications of adjacent infections (respiratory, dental, skin, and urinary) (Trampuz and Widmer, 2006).
Hip replacement-associated infections require greater attention due to the severe complications that can occur. Hip replacement implant usage has grown in the last decade as a requirement to improve the quality of life. However, the implantation is also associated with undesirable effects caused by microbial adherence to the surface of the prosthesis. Microorganisms may originate either from direct contamination of the prosthesis, either from contaminated wound or from adjacent infections. The rate of infection is 1.5-2.5% of the total number of interventions, and the mortality 2.5%. Patients with advanced age, presenting other diseases (heart disease, diabetes, cancer, rheumatoid arthritis) have an increased risk of acquiring infections associated with hip prosthesis implantation. A 9.5% incidence of infection has been reported in patients over 80 years. The infections are difficult to treat, sometimes requiring the removal of the prosthesis, thus being responsible for the implant failure. Staphylococci are the commonly found microorganisms in hip prostheses-associated infections (Guggenbichler et al., 2011).