Microbiology and Infections Flashcards by Kerry Hendrie

List some clinical presentations of acute bone and joint infections

Temperature
Pain, redness, swelling
Reduced mobility

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Define SIRS

2+ of
Temp less than 36 or more than 38
Heart rate more than 90
Resp rate more than 20
PaCO2 less than 4.3kPa
WBC more than 12k or less than 4k

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What is septic arthritis? How can it be introduced?

Infection of the joint space

Blood spread, direct innoculation or from infected bone

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What are the main organisms that cause septic arthritis?

Staph. aureus

Streptococci

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List diagnostic investigations for septic arthritis

Blood culture if pyrexial
Blood tests
Joint fluid aspirate for microscopy/culture
USS, XR, CT bone

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What is the main empirical treatment for septic arthritis?

Flucloxacillin (Staph. aureus)

N.B. high-dose IV to maximise uptake

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If there is a child under 5yrs old with septic arthritis, which antibiotic should be added and why?

Ceftriaxone for H. influenzae/Kingella cover

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How long does antibiotic treatment for septic arthritis usually last?

2-4 weeks

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Which organisms cause chronic osteomyelitis?

Mycoplasma
Pseudomonas
Salmonella
Brucella (goat’s milk)

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Treatment and diagnosis of osteomyelitis is similar to septic arthritis. What is the key difference in terms of treatment length?

4-8 weeks duration of antibiotic treatment

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Which organisms cause type 1 necrotising fasciitis?

Mixed anaerobes and other bacteria

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Which organism causes type 2 necrotising fasciitis?

Group A Strep. (flesh-eating bacteria)

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List the mainstay treatment for necrotising fasciitis

Surgical debridement

Pencillin + clindamycin

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What is gas gangrene?

Spores forming in tissue, causing accumulation of gas bubbles

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What is tetanus?

Neurotoxin produced by Clostridium tetani prevents release of neurotransmitters, causing locked jaw/spastic paralysis

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When is vancomycin used empirically instead of flucloxacillin?

If MRSA, diptherioids, or penicillin-allergic

Why is clindamicin useful?

Antitoxin properties - effective against PVL, group A Strep.

Why do bacteria in biofilms pose a problem?

Resistant to immune system and antibiotics

Why are superficial wound swabs a waste of time?

Reflect skin flora rather than deep infection (coag neg Staph. are part of flora)

What is the main treatment for osteomyelitis?

Debridement/ drainage
Biopsy
Antimicrobials (IV)

What is the main treatment for diabetic foot ulcer?

Debridement

Flucloxicillin

What are the two main classifications of osteomyelitis

Acute/chronic

Haematogenous (in blood)/ contiguous (adjacent to infection source)

How is osteomyelitis typically investigated?

Imaging - XR/CT/MRI
Biopsy
Wound swab
Blood culture

What is the main management of prosthetic joint infection?

Remove prosthesis
6 week therapy
Re-implant after antibiotics

What are the main signs of septic arthiritis?

Sever pain Red, hot, swollen Reduced movement

When does chronic osteomyelitis usually develop?

After untreated acute osteomyelitis

What is the classical clinical sign of necrotizing fasciitis?

Crepitus

What is the main treatment for cellulitis?

Flucloxicillin and benzylpenicllin

What investigations are used in prosthetic joint infection?

CRP Joint aspiration Technetium bone scan XR

What is osteomyelitis?

Infection of bone, including its marrow

What are the main mechanisms by which bone can become infected?

Penetrating trauma/surgeryHaematogenous spread

What is a sequestrum?

Dead segment of bone

What is the significance clinically of sequestrums?

Once one develops, antibiotics will not cure infection

Why do kids tend to get acute osteomyelitis more than adults?

Metaphyses have poor/slow blood flow which enables bacteria to accummulate easier

Which organism is the commonest cause of bone infections?

Staph. aureus

Chronic osteomyelitis cannot be treated by antibiotics alone. True/False?

True | Surgical debridement also usually required

Which group of people are particularly at risk of osteomyelitis of the spine?

IV drug users Diabetics Immunocompromised

List clinical features of osteomyelitis of spine

Constant insidious back pain Paraspinal muscle spasm Spinal tenderness Systemic upset