Bacterial Skin Infections II

Question 1

What is the presentation of osteomyelitis?

Answer 1

Local: gradual onset bone pain/tenderness/warmth, erythema, edema

Systemic: absent unless concurrent bacteremia or other SSTI

Question 2

How do we diagnose Osteomyelitis?

Answer 2

Clinical signs/symptoms
Bone biopsy
Imaging - plain radiograph or MRI

Question 3

What would you treat osteomyelitis with?

Answer 3

Antibiotics

Question 4

What is the most common cause of Osteomyelitis?

Answer 4

S. aureus

Question 5

What does osteomyelitis caused by Pseudomonas aeruginosa present as?

Answer 5

Moist wounds - puncture wound with wet shoes/socks, diabetic foot

Question 6

_________ is a new onset of a painful erythematous/edematous joint, limited range of motion, purulent material obtained on aspiration. Fever in most patients. Usually in a single large joint.

Answer 6

Septic arthritis

Question 7

How do you diagnose septic arthritis?

Answer 7

Signs and symptoms
Culture (90%) of synovial fluid and gram stain (60-80%)

Question 8

What is the most common cause of Septic Arthritis?

Answer 8

S. aureus

Question 9

What is the second most common cause of Septic Arthritis?

Answer 9

Streptococci

Question 10

What bacteria causes septic arthritis in healthy young adults that are sexually active?

Answer 10

Neisseria gonorrhoeae

Question 11

What are the 3 types of necrotizing soft tissue infections?

Answer 11

1. Necrotizing fasciitis - muscle fascia and subcutaneous fat
2. Necrotizing myositis - skeletal muscle
3. Necrotizing cellulitis - rapid spreading necrotizing infection of dermis

Question 12

________ is a rapidly spreading acute infection of muscle fascia. Also called streptococcal gangrene

Answer 12

Necrotizing Fasciitis

Question 13

What is the presentation of necrotizing fasciitis? x3

Answer 13

1. Early - no skin involvement
2. Fever that escalates, severe pain inconsistent with skin findings
3. Progressing cellulitis –> blisters –> gangrene inches per hour

Question 14

What bacteria cause necrotizing fasciitis?

Answer 14

S. pyogenes > C. perfringens

Question 15

How do you treat necrotizing fasciitis?

Answer 15

Hospitalize
Surgical debridement or amputation
Antibiotics
Skin graft

Question 16

What are the characteristics of Clostridium perfringens?

Answer 16

Gram + rods
Non-motile
Multiple rapidly
Anaerobic
Beta-hemolytic
Spore forming

Question 17

What diseases does C. perfringens cause?

Answer 17

Cellulitis
Gas Gangrene
Clostridial food poisoning

Question 18

What is the virulence factor of C. perfringens? What is its function?

Answer 18

alpha-toxin

Important in skin/soft tissue infections
Phospholipase - disrupts cell membranes
Mediates massive lysis, hemolysis, and tissue destruction

Question 19

Traumatic and surgical wounds, delay between injury and surgery, and devitalized, decreased blood flow in tissue (anaerobic environment) and contamination of wound with spore/vegetative bacteria are all risk factors for ________

Answer 19

Gas gangrene/ Clostridial myonecrosis

Question 20

________ presents with fever and excruciating pain at affected site. Rapid development of foul smelling wound containing a thin serosanguineous discharge and gas bubbles. Rapid spread and several inches per hour.

Answer 20

Gas gangrene

Question 21

Gas gangrene will show evidence of _________ (gas in tissues). Will see low opacity pockets on X-ray and crackles felt/heard with palpating near the wound.

Answer 21

Crepitus

Question 22

What are the characteristics of Pseudomonas aeruginosa?

Answer 22

Gram -
aerobic
motile rod
Oxidase +
Blue/Green colonies

Question 23

What are the virulence factors of P. aeruginosa?

Answer 23

1. Exotoxin A
2. Multi-Drug Resistance

Question 24

What does exotoxin A (ExoA) of P. aeruginosa do?

Answer 24

AB toxin
Inactivates EF-2 via ADP-ribosylation
Blocks protein synthesis = cell death

Question 25

What skin and soft tissue infections does P. aeruginosa cause?

Answer 25

1. Burn wounds 2. Folliculitis 3. Cellulitis, osteomyelitis, osteochondritis of foot (after penetrating injury, moist environment like sweaty shoes or socks)

Question 26

Bacteremia caused by P. aeruginosa occurs primarily in ______. Can lead to ______

Answer 26

patients with neuropenia and Extensive burns Ecythma gangrenosum

Question 27

_______ is a cutaneous manifestation of bacteremia. Involves one or more painless erythematous or purpuric macules that rapidly become painful, develop into pustules or bullae, then into gangrenous ulcers or eschars.

Answer 27

Ecthyma gangrenosum

Question 28

What are the risk factors with burn wound infections?

Answer 28

Increase in wound surface area lead to increased likelihood of infection

Question 29

What bacteria cause burn wound infections?

Answer 29

P. aeruginosa , S. aureus