Question

When a patient undergoes a total joint replacement or fracture fixation procedure, the implanted material can provide a surface for bacterial colonization. When an implant becomes infected, how would the patient’s body react to the infection?

a. (5 points total) Explain the immune cell response to the bacterial colonization.

b. (5 points total) Explain all the potential consequences of the immune cell response in (a) on the implant material.

Answer 1

A) The implant after placement gets infected during the peri operative period or during hospitalization. The immune response of the body gets activated immediately if a bacterial invasion occurs.The common bacteria that infect the implants are Staphylococcus Epidermis, Staphylococcus Aureus, E.Coli, Pseudomonas Aeruginosa.

• If the immune system of the body is strong then the implant gets covered with the host protein layer, cytokines and the bacteria fails to infect the implant and to colonize. If the immune system is poor then the virulence of the bacteria and its toxins will damage the cell functions.
• These bacteria are removed by the process of phagocytosis. The major phagocyte cells are neutrophils and macrophages.
• The macrophages comes to the implant site within minute or hour to initiate the inflammatory process and foreign body response.
• Once the bacteria is engulfed by phagocyte, its trapped in an intracellular vesicle called phagosome. which subsequently fuse with another vesicle called lysosomes to form phagolysosome.
• The bacteria is killed by the digest enzymes or following a respiratory burst to destroy the phagocytosed microbe.

B) Consequences of immune cell response on Implants:

• This can result in biodegradation of the implant. The macrophages during its foreign body reactions, release mediators of degradation i.e oxygen free radicals, degradative enzymes and acid in between the cellular membrane and the implant that result in the biodegradation of the implant.
• Following to the phagocytic reactions of macrophages, the implant surface exhibit reduced bactericidal capability.
• Based on the surface chemistry of the implant, the implant material can facilitate apoptosis (programed cell death) leaving the macrophages incapable of attacking the foreign organisms that may be adherent to the implant.
• The biodegradation of the implant with result in implant failure.
• A new implantation may be needed. The failed implant needs to be removed, as it may result in system infections leading to multi organ failure.