MSKS Immunology Lecture 1_Microbio of MSKS Flashcards
What are the 8 infections of the MSKS
¡ Osteomyelitis ¡ Endocarditis, myocarditis, pericarditis ¡ Infectious myositis ¡ Septic arthritis, viral arthritis ¡ Myonecrosis gangrene
What are the risk factors for osteomyelitis?
§ Diabetes § Kidney failure § Smoking, IV drug use § Pressure ulcers § Traumatic wounds, joint replacement, fixation devices
What are the 6 main infections that cause osteomyelitis?
¡ Staphylococcus aureus ¡ TB – Pott Disease ¡ Salmonella – sickle cell ¡ Staph epidermidis - prosthetics ¡ Pasteurella multocida – cat and dog bites ¡ Gonorrhea
Reminder card: what is the hemolysis patteren for Beta, alpha and gamma hemolysis?
Bacteria is cultured on a blood agar plate. full lysis is beta hemolysis, partial lysis is alpha hemolysis (looks green), and very little hemolysis is gamma hemolysis
What are the most common characterisitics of staph A
1) cocci
2) “cluster of graps”
3) Gram Positive
4) Catalase Positive
5) beta-hemolytic
6) coagulase postive
What does coagulase do?
Coagulase helps to convert fibrinogen to fibrin resulting in a clot
What does Protein A do?
binds host antibodies to prevent antibody-mediated
clearance of the bacteria
What does catalyase do?
it breaks H2O2 into H2O and O2
What are the 5 main virulent enzymens made by Staph A. and what do they do?
1) Coagulase - converts fibrinogen in to fibrin leading to clot formation
2) hyaluronidase - hydrolysis hyaluronic acid in connective tissue leading to degradation of the ECM allowing proliferation of Staph A.
3) fibrinolysin - disolves clots (opposite of coagulase)
4) Lipases - hydrolyzes lipids which can kill cells as the cell membran is degraded
5) Nuclease - hydrolyzes DNA
What are the 4 main toxins produced by Staph A?
¡ Cytotoxins ¡ Exfoliative toxins - Scalded skin syndrome ¡ Enterotoxins – Food poisoning ¡ Toxic Shock Syndrome Toxin –TSST
Of Endocarditis, myocarditis, pericarditis which is most common and why?
Endocarditis because it is in direct contact with the blood.
What is the main cause of myonecrosis gangrene?
Clostridium perfringens
What is the Pathogenesis of Clostridium perfringens?
- Multiply subcutaneously
- Anaerobic cellulitis
- Invasion of muscle
- Gas production, necrosis
- If toxin escapes into blood, leads rapidly to death by hemolysis and renal failure
What is the shape of Clostridium perfringens
It is a gram possitive rod
What is a common treatment of Clostridium perfringens?
Hyperbaric chamber therapy is often helpful because Clostridium perfringens is a strict anarob
