Skin and Soft Tissue Infections

Question 1

What is gas gangrene and what bacteria causes it?

Answer 1

Bacterial infection by CLOSTRIDIUM PERFRINGENS bacteria.

Medical emergency, caused by gunshot wound

Question 2

What is impetigo and what bacteria causes it?

Answer 2

Superficial infection of epidermis

• -> golden crusts
• -> S.aureus

Question 3

What is cellulitis?

Answer 3

Tender red swollen painful skin, down to fascia

Question 4

What is necrotising fascitis?

Answer 4

Severely painful erythematous infection of the skin

Leads to compartment syndrome and subsequent muscle necrosis.

Fever, sepsis and CREPITUS on examination

Medical emergency –> radical debridement.

Question 5

What organism causes nec fac, and what demographics?

Answer 5

Nec fac 1 - E.coli and anaerobes (elderly, diabetics)

Nec fac 2 - S.pyogenes (all ages)

Question 6

What organism causes cellulitis?

Answer 6

S.pyogenes, staph.aureus

Question 7

What is septic arthritis?

Answer 7

Inflammation of a joint due to bacterial infection.

Symptoms include severe pain, swelling, redness and heat in affected joints. These symptoms tend to develop quickly over a few hours or days.
You may also have difficulty moving the affected joint, and some people have a high temperature (fever).

Question 8

What organisms cause septic arthritis?

Answer 8

Staph.aureus most common in adults

Neisseria gonorrhoea most common in young, sexually active adults

E.coli in the elderly, IVDU and seriously ill patients

Question 9

What organisms cause osteomyelitis?

Answer 9

Staph.aureus (95%)

Salmonella spp.

Question 10

How can osteomyelitis occur?

Answer 10

• Haematogenous or contiguous (surrounding soft tissue) from a pre-existing infection
• Trauma
• IVDU
• Iatrogenically (intra-operative or device-related)
• Injury to bone (fracture)
• Pre-existing health condition, such as diabetes, poor circulation, which means the bone does not get a steady blood supply, so infection-fighting white blood cells cannot reach the site of injury

Question 11

Why is osteomyelitis difficult to treat?

Answer 11

Once staph.aureus has been remodelled into the hydroxyapatite, creating necrotic sections of bone (aka. sequestrum), it is very difficult to target with antibiotics (3 months min treatment, or surgical debridement)

Question 12

How long is the antibiotic course for osteomyelitis, and which antibiotic should be used, if the pathogen hasn’t been remodelled into the bone?

Answer 12

6 weeks, Flucloxacillin

Question 13

In which case is osteomyelitis a medical emergency?

Answer 13

In the spine - if it compresses spinal nerves it will rapidly cause subsequent neurological complications

Question 14

What happens if a biomedical device (e.g.. a prosthetic limb) becomes infected?

Answer 14

1. Remove device
2. Treat patient with antibiotics for 3 months
3. Put in new prosthetic limb

Question 15

What are the symptoms of acute osteomyelitis?

Answer 15

The symptoms of acute osteomyelitis include:

• Fever >38C
• Bone pain, which can often be severe
• Swelling, redness and warmth at the site of the infection
• Acute onset malaise
• Tenderness
• Restricted range of mvmt
• Lymphadenopathy

Question 16

What are the symptoms of chronic osteomyelitis

Answer 16

• Insidious onset of malaise and fever
• Persistent localised bone pain of insidious onset
• Night sweats

Question 17

Why should you ask about past history of UTI in a patient with suspected osteomyelitis?

Answer 17

Bacteria from the bladder could migrate to the lumbar spine via the venous plexus in the pelvis

Question 18

Which narrow-spectrum beta-lactam is most commonly used in the treatment of skin and soft tissue infections?

Answer 18

Flucloxacillin (NB doesn’t work against MRSA)

Question 19

What is erysipelas?

Answer 19

Superficial cellulitis of the dermis, often associated with group A strep