Microbiology Flashcards
What are the most common pathogens in MSK infections?
Staphylococcus Aureus
Staphylococcus Epidermidis
Streptococcus Pyogenes
Gram -ves
Anaerobes
What are the most commonly used antibiotics in MSK infections?
Flucloxacillin
Vancomycin
Doxycycline
Clindamycin
Metronidazole
Cotrimoxazole
Describe gram +ve organisms
Thicker cell wall
Thicker peptidoglycan component
Seen as violet or blue
Describe gram -ve organisms
Thinner cell wall
High content in lipopolysaccharide
Seen as pink in dye
Describe staphylococcus species
Gram +ve cocci in clusters
Aerobic and facultatively anaerobic
Describe Staphylococcus aureus
common human pathogen which causes wound, skin, bone and joint infections.
Some strains produce toxins.
What toxins can staphylococcus aureus produce?
Enterotoxin - food poisoning
SSSST - Staphylococcal scalded skin syndrome toxin
PVL - Panton valentine leukocidin
What antibiotic is used for staphylococcus aureus?
Flucloxacillin except in resistant strains
How can staphylococcus aureus be differentiated from other types of staph?
Produces enzymes, including coagulase, enzyme that clots plasma.
What is osteomyelitis?
Inflammation of the bone and medullary cavity, usually located in one of the long bones.
How does osteomyelitis occur?
Blood flow is slowed and turbulent, predisposing to bacterial seeding. In addition, lining cells have little or no phagocytic activity. Abscess may form.
The abscess is limited by growth plate, spreads transversely along Volkmann canals and elevates periosteum.
As the abscess spreads segments of the devitalised bone remains within it. Occasionally abscess is walled off by fibrosis and bone sclerosis to form Brodie’s abscess.
Infectious process may erode periosteum and form sinus through soft tissues and skin to drain externally.
How is osteomyelitis diagnosed?
Gold standard is a bone biopsy for a sample
How is osteomyelitis treated?
Debridement and antimicrobials
