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Musculoskeletal > Microbiology > Flashcards

Microbiology Flashcards

1
Q

G + vs G -

A

One of the differences between G+ and G- is the cell wall of the bacteria, G+ has a thicker wall and its peptidoglycan component is thicker, G- has a high content of Lipopolysaccharide.

The G+ in violet or blue (as it retains both the crystal violet and safranin) while G -
bacteria when washed with alcohol lose the Crystal violet and retain the safranin (pink)
This is crucial to make a treatment decision

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2
Q
A
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3
Q

About Staph. aureus?

A

-G+
-one type of staphylococci
-Cluster (Staph)
-Only Coagulation positive (which appears gold)(wound, skin infection)–>distinguish it from other staph species
-Aerobic but facultatively anaerobic (grows best aerobically (in the air), but also grows anaerobically)
-Antibiotic (i.e. flucloxacillin)
-Two main strains:
MRSA (resistance strain)
MSSA

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4
Q

List some clinical presentations of acute bone and joint infections

A

Temperature
Pain, redness, swelling
Reduced mobility

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5
Q

Define SIRS

A 
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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6
Q

What is septic arthritis? How can it be introduced?

A

Infection of the joint space

Blood spread, direct innoculation or from infected bone

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7
Q

What are the main organisms that cause septic arthritis?

A

Staph. aureus

Streptococci

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8
Q

List diagnostic investigations for septic arthritis

A

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

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9
Q

What is the main empirical treatment for septic arthritis?

empirical treatment given based on experience and experiments

A

Flucloxacillin (Staph. aureus)

N.B. high-dose IV to maximise uptake

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10
Q

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

A

Ceftriaxone for H. influenzae/Kingella cover

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11
Q

How long does antibiotic treatment for septic arthritis usually last?

A

2-4 weeks

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12
Q

What is osteomyelitis?

A

Inflammation of bone + their medullary cavity

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13
Q

Classification of osteomyletitis?

A

Acute vs chronic (time)
Contiguous vs haematogenous (spread)
Host Status: Presence of vascular insufficiency, host susceptibility

The left description is contiguous The top right description is haematogenous (the blood flow is slow in terminal branches in the metaphyseal, so the bacteria has a high chance to start the infection)
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14
Q

Which organisms cause chronic osteomyelitis?

A

Mycoplasma
Pseudomonas
Salmonella
Brucella (goat’s milk)

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15
Q

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

A

4-8 weeks duration of antibiotic treatment

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16
Q

Which organisms cause type 1 necrotising fasciitis?

A

Mixed anaerobes and other bacteria

17
Q

Which organism causes type 2 necrotising fasciitis?

A

Group A Strep. (flesh-eating bacteria)

18
Q

List the mainstay treatment for necrotising fasciitis

A

Surgical debridement

Pencillin + clindamycin

19
Q

What is gas gangrene?

A

Spores forming in tissue, causing accumulation of gas bubbles

20
Q

What is tetanus?

A

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

21
Q

When is vancomycin used empirically instead of flucloxacillin?

A

If MRSA, diptherioids, or penicillin-allergic

22
Q

Why is clindamicin useful?

A

Antitoxin properties - effective against PVL, group A Strep.

23
Q

Why do bacteria in biofilms pose a problem?

A

Resistant to immune system and antibiotics

24
Q

Why are superficial wound swabs a waste of time?

A

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

25
Q

Coagulate- positive?

A

Coagulase is an enzyme which converts fibrinogen into fibrin resulting in clotting; an enzyme that clots the plasma.

Musculoskeletal (9 decks)

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