3 - Micro: Infections Flashcards
Define osteomyelitis
inflammation of bone due to an infection
acute: develops over several weeks
chronic: evolves over months to years
What are the Hematogenous sources of osteomyelitis?
Staph Aureus
What are the Contiguous sources of osteomyelitis?
e. g. puncture wounds, foot ulcur
- polymicrobial: gram + cocci, gram - rods, anaerobes
What are the traumatic sources of osteomyelitis?
surgery or fracture
S. aureus
What is the most common cause of osteomyelitis?
S. aureus in any of the source scenerios (hematoginous, contigious, traumatic)
What is the most important part of treatment for osteomyelitis?
DRAINAGE
debridement
long term IV (nafcillin/oxacillin) or vanco for (MRSA)
Describe the lab tests and characteristics of S. Aureus
Gram Positive
Grape-like Clusters
Catalase +
Coagulase +
Opportunistic infection, commonly nosocomial (post-surgery)
What is the mechanism of resistance of MRSA
MRSA contains the mecA gene that codes PBP2a which does not allow methicillin to bind to the cell wall.
Describe the bug that is a common cause of osteomyelitis in puncture wounds.
Pseudomonas Aruginosa
- gram negative rod
- Green/Blue on culture
- Characteristic grape-like odor
- Highly antibiotic resistant
Most important virulence factor of pseudomonas aruginosa?
Alginate capsule biofilm that allows it to be transferred by inanimate objects (puntcture!!)
What is a common cause of osteomyelitis in sickle cell children?
Salmonella
Describe the formation of osteomyelitis in TB patients.
If untreated TB can spread to the spinal column (Pott Disease), can develop bone infection aka duhhhh
Describe reactive arthritis
autoimmune condition due to an infection in a different location of the body (e.g. GI infection, STD)
Display a classic triad of symptoms: “cant see, cant pee, can’t bend my knee”
Describe the bugs involved with GI infections that can lead to reactive arthritis?
Campylobacter, Salmonella, Shigella, Yersinia
STD - Chlamydia
What is the factor commonly associated with reactive arthritis?
HLA-B27
Describe septic arthritis
inflammation due to infection of the joint (suppurative, purulent, infectious)
20,000 cases/year - gonococcal, nongonococcal
What is the most important dx tool for septic arthritis?
**Patient history, most commonly seen with knee joint infection
Joint fluid - gram stain, culture
CBC - increased neutrophils
ESR/CRP -
Imaging Techniques
Describe the gonococcal sources of septic arthritis.
Neisseria Gonorrheae
Fastidious gram - diplococci
Grows on Thayer-Martin Chocolate agar*
Virulence - PILI for attachment, antigenic variation, and LOS
Describe the suspected causes of septic arthritis with history of poly vs monoarticular joint pain.
Poly - think gonorrhea
Mono - think joint replacement infection
Describe gonococcemia, include why it is more common in women
Fever and migratory joint pain, pustular rash, due to untreated gonococcal infection.
More common in women because they tend to be asymptomatic
Describe the common causes of nongonococcal septic arthritis
S.Aureus - primary cause of prosthetic joint infections in SHORT TERM (3mos)
Borellia Burgdorferi – lyme disease caused
Also Streptococcus and Pseudomonas (IV drugs)
Describe the course of treatment for septic arthritis
Drainage of infected joint
IV antibiotics for several weeks
Prosthetic - surgery to replace joint
