Knee joint infections with Staphylococcus aureus and Micrococcus species

Area of Science:

• Orthopedics
• Infectious Diseases
• Microbiology

Background:

• Understanding factors influencing joint infection susceptibility is crucial for preventing and treating orthopedic infections.
• Staphylococcus aureus and Micrococcus species are common bacteria implicated in joint infections.

Purpose of the Study:

• To investigate the infectivity of Staphylococcus aureus and Micrococcus species in rabbit knees.
• To evaluate the impact of antibiotics, stainless-steel particles, autologous blood, and steroids on joint infection development and persistence.

Main Methods:

• Rabbit knees were injected with varying bacterial concentrations (Staphylococcus aureus, Micrococcus species).
• The effects of pre-injection antibiotics (methicillin, cephacetrile, clindamycin), stainless-steel particles, autologous blood, and steroids (systemic and intraarticular) on infection were assessed.

Main Results:

• Staphylococcus aureus caused progressive infection in 50% of knees, whereas Micrococcus species resulted in transient colonization.
• Antibiotics administered before bacterial injection provided protection against infection.
• Stainless-steel particles did not increase susceptibility but prolonged existing Micrococcus infections and prevented Staphylococcus aureus infection during bacteremia.
• Steroids decreased resistance to Micrococcus infection and exacerbated infection-related destruction.

Conclusions:

• Staphylococcus aureus is more virulent than Micrococcus species in inducing rabbit knee infections.
• Antibiotics are effective in preventing Staphylococcus aureus knee infections, while steroids impair the host's defense mechanisms against Micrococcus species.