3 - Micro: Infections

Question 1

Define osteomyelitis

Answer 1

inflammation of bone due to an infection

acute: develops over several weeks
chronic: evolves over months to years

Question 2

What are the Hematogenous sources of osteomyelitis?

Answer 2

Staph Aureus

Question 3

What are the Contiguous sources of osteomyelitis?

Answer 3

e. g. puncture wounds, foot ulcur

- polymicrobial: gram + cocci, gram - rods, anaerobes

Question 4

What are the traumatic sources of osteomyelitis?

Answer 4

surgery or fracture

S. aureus

Question 5

What is the most common cause of osteomyelitis?

Answer 5

S. aureus in any of the source scenerios (hematoginous, contigious, traumatic)

Question 6

What is the most important part of treatment for osteomyelitis?

Answer 6

DRAINAGE
debridement
long term IV (nafcillin/oxacillin) or vanco for (MRSA)

Question 7

Describe the lab tests and characteristics of S. Aureus

Answer 7

Gram Positive
Grape-like Clusters
Catalase +
Coagulase +

Opportunistic infection, commonly nosocomial (post-surgery)

Question 8

What is the mechanism of resistance of MRSA

Answer 8

MRSA contains the mecA gene that codes PBP2a which does not allow methicillin to bind to the cell wall.

Question 9

Describe the bug that is a common cause of osteomyelitis in puncture wounds.

Answer 9

Pseudomonas Aruginosa

• gram negative rod
• Green/Blue on culture
• Characteristic grape-like odor
• Highly antibiotic resistant

Question 10

Most important virulence factor of pseudomonas aruginosa?

Answer 10

Alginate capsule biofilm that allows it to be transferred by inanimate objects (puntcture!!)

Question 11

What is a common cause of osteomyelitis in sickle cell children?

Answer 11

Salmonella

Question 12

Describe the formation of osteomyelitis in TB patients.

Answer 12

If untreated TB can spread to the spinal column (Pott Disease), can develop bone infection aka duhhhh

Question 13

Describe reactive arthritis

Answer 13

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”

Question 14

Describe the bugs involved with GI infections that can lead to reactive arthritis?

Answer 14

Campylobacter, Salmonella, Shigella, Yersinia

STD - Chlamydia

Question 15

What is the factor commonly associated with reactive arthritis?

Answer 15

HLA-B27

Question 16

Describe septic arthritis

Answer 16

inflammation due to infection of the joint (suppurative, purulent, infectious)

20,000 cases/year - gonococcal, nongonococcal

Question 17

What is the most important dx tool for septic arthritis?

Answer 17

**Patient history, most commonly seen with knee joint infection

Joint fluid - gram stain, culture
CBC - increased neutrophils
ESR/CRP -

Imaging Techniques

Question 18

Describe the gonococcal sources of septic arthritis.

Answer 18

Neisseria Gonorrheae
Fastidious gram - diplococci
Grows on Thayer-Martin Chocolate agar*
Virulence - PILI for attachment, antigenic variation, and LOS

Question 19

Describe the suspected causes of septic arthritis with history of poly vs monoarticular joint pain.

Answer 19

Poly - think gonorrhea

Mono - think joint replacement infection

Question 20

Describe gonococcemia, include why it is more common in women

Answer 20

Fever and migratory joint pain, pustular rash, due to untreated gonococcal infection.

More common in women because they tend to be asymptomatic

Question 21

Describe the common causes of nongonococcal septic arthritis

Answer 21

S.Aureus - primary cause of prosthetic joint infections in SHORT TERM (3mos)

Borellia Burgdorferi – lyme disease caused

Also Streptococcus and Pseudomonas (IV drugs)

Question 22

Describe the course of treatment for septic arthritis

Answer 22

Drainage of infected joint
IV antibiotics for several weeks
Prosthetic - surgery to replace joint