L8 Infections in Skin, Joints and Bones

Question 1

What does SSSI stand for?

Answer 1

Skin-skin structure infections

Question 2

Main organism causing infections

Answer 2

Staphylococcus aureus

Streptococcus pyogenes

Question 3

S. aureus characteristics

Answer 3

Gram-positive coccus (clusters)
Catalase positive
33 different virulence factors

Question 4

S. pyogenes characteristics

Answer 4

Gram-positive coccus (chains)
Catalase negative
Lancefield group A strep

Question 5

Skin inhospitable environemnt

Answer 5

• Dry
• Constant shedding
• Low pH
• Sebaceous secretion
• Competitive with resident microbiota

Question 6

Types of skin infections resulting from trauma

Answer 6

Accidental e.g. scrapes and cuts

Deliberate e.g. survey

Question 7

What can skin infections result from?

Answer 7

Haematogenous colonisation

Question 8

Folliculitis

Answer 8

Superficial infection of hair follicle
S. aureus
Hot tub folliculitis = pseudomonas aeruginosa

Question 9

Furuncle

Answer 9

Deep version of folliculitis

Still involves a single follicle

Question 10

Carbuncle

Answer 10

Collection of furuncles
Extend into subcutaneous fat
Drain fluid prior to antibiotic treatment

Question 11

Impetigo

Answer 11

Superficial skin infection
Highly infectious
Group A streptococci s. aureus
Disrupts corneal layer of skin

Question 12

SSSS (Staphylococci scalded skin syndrome)

Answer 12

S. aureus
Exfoliative exotoxin 
Children under 6 mainly 
Risk of secondary skin infection 
Increased mortality in adults

Question 13

Erysipelas

Answer 13

Superficial form of cellulitis
Distinct areas between inflamed and non-inflamed areas
Group A streptococci

Question 14

Cellulitis

Answer 14

Unable to distinguish as much between inflamed and non-inflamed areas
Group A streptococci
Lead to sepsis and septic shock

Question 15

Surgical wound infection

Answer 15

S. aureus = antibiotic prophylaxis frequently employed

Question 16

Necrotising fascilitis

Answer 16

Uncommon and severe
Superficial and deep (affect any body site)
Start with group A strep
 - Cellulitis
 - Impaired blood flow (necrosis)
 - Anaerobe involvement 
 - Rapid tissue destruction

Question 17

Gangrene

Answer 17

Deep tissue infection
Clostridium spp.
Arises in areas of poor blood flow
Gas gangrene = C. perfingens

Question 18

Anthrax

Answer 18

Bacillus anthracis
Gram positive sporing bacillus
Found in animals etc
Cutaneous Anthrax = skin lesions (black ‘eschar’

Question 19

Rickettsial infection

Answer 19

Rickettsia spp. (obligate intracellular)

Transmitted by fleas etc

Question 20

Cat and dog bites

Answer 20

Pasturella multocida infection

Capnocytophaga canimorus

Question 21

Rat bites

Answer 21

Spirillum minus

Streptobacillus moniliformis

Question 22

Human bites

Answer 22

Oral commensal microbiota

Eikenella corrodens

Question 23

Lyme disease

Answer 23

Borellia burgdorferi
Transmitted to humans by lxodes tick
Lead to fever, muscle pain, headache

Question 24

Osteomyelitis

Answer 24

Infection of bone

Pain and swelling around affected area

Question 25

Arthritis

Answer 25

Swollen and painful joints

Caused by immunological reaction (reactive rheumatoid) or infection (septic arthritis)