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MI: Infection CPC Flashcards

1
Q

Describe the typical clinical findings in Pneumocystis jirovecii pneumonia.

A

Widespread, bilateral ground-glass shadowing with reduced exercise tolerance and low saturations.

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2
Q

How is PCP treated?

A

Co-trimoxazole

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3
Q

Which investigation can be used to confirm a diagnosis of PCP?

A

Bronchoalveolar lavage cytology

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4
Q

Which stain is used to identify PCP?

A

Silver stain (Grocott-Gomori stain)

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5
Q

List some causes of immunodeficiency.

A
  • Inherited
  • Immunosuppressive therapy
  • Chemotherapy
  • Radiotherapy
  • HIV
  • Chronic illness
  • Malnutrition
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6
Q

Which organisms do the following defects make you susceptible to?

  1. T cell defect
  2. B cell defect
  3. Neutrophil defect
  4. Complement defect
A

T cell defect:

  • Sepsis
  • CMV, EBV, VZV
  • Candida, PCP
  • Usually aggressive opportunistic infections

B cell defect:

  • Streptococcus, Staphylococcus, Haemophilus
  • Giardia
  • Usually recurrent sinopulmonary infections

Neutrophil defect

  • Staphyloccocus, Pseudomonas
  • Candida, nocardia, aspergillus

Complement defect

  • Neisseria
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7
Q

What is Cryptococcus?

A

Yeast that causes fungal meningoencephalitis

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8
Q

What is Actinomyces and what does it cause?

A

Gram-positive rod that causes lung abscesses in immunocompromised patients (particularly alcoholics)

NOTE: it’s closely associated with Nocardia

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9
Q

What are the issues with investigatin and managing suspected Actinomyces infection?

A

Slow-growing (so difficult to culture) and difficult to treat

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10
Q

Describe the histological features of Actinomyces.

A

Basophilic sulfur granules

Gram-positive rods that branch as they grow

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11
Q

Why is it difficult to treat infected prosthetic materials?

A

Pathogens form biofilms which are difficult to penetrate with antibiotics

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12
Q

What are the general management principles of treating infected prosthetic material?

A
  • Antibiotic treatment alone is not curative in most cases
  • Removal of prosthesis and adequate debridement is the most important part of treatment

NOTE: treatment failure can occur without resistance

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13
Q

Which bacteria are all stool samples tested for?

A
  • Salmonella
  • Shigella
  • E. coli O157
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14
Q

Which other bacterium will be tested for in stool stamples from patients > 65 years?

A

C. difficile

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15
Q

What are the steps in the management of a patient with C. difficile infection?

A
  • Isolate in a single room
  • Assess severity
  • Stop offending antibiotics if possible
  • Wash hands with soap and water after each patient contact and use gloves and aprons
  • Commence C. difficile care pathway, fluid balance chart and Bristol stool chart
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16
Q

List some indicators of severe disease in people with C. difficile infection.

A
  • High temperature
  • High heart rate
  • High WCC
  • Rising creatinine
  • Clinical or radiological signs of severe colitis
  • Failure to respond to therapy at 72 hours
17
Q

Why is diarrhoea not a marker of severe infection?

A

Very severe C. difficile infection may cause an ileus which prevents stool output and leads to megacolon

18
Q

How is non-severe C. difficile disease treated?

A
  • Metronidazole 400 mg TDS for 10-14 days
  • If intolerant or not responding at 72 hours, change to vancomycin 125 mg QDS for 10-14 days
19
Q

How is severe C. difficile disease treated?

A
  • Vancomycin 125 mg QDS for 14 days
  • Consider adding metronidazole 500 mg IV TDS
20
Q

What are some features of particularly severe C. difficile disease that warrants surgical assessment?

A

Colonic dilatation or ileus/vomiting

21
Q

Which C. difficile ribotype caused a severe outbreak in June 2005?

A

Ribotype 027

22
Q

List some risk factors for C. difficile infection.

A
  • Antibiotic use (also PPIs, cytotoxic drugs, non-surgical procedures (e.g. NG tubes))
  • 65+ years
  • Duration of hospital stay
  • Severe underlying disease
23
Q

How do PPIs increase risk of C. difficile infection?

A

They raise the pH of the stomach so more C. difficile flora can survive in the stomach

24
Q

Describe the typical presentation of C. difficile infection.

A

Abrupt onset with explosive watery and foul-smelling diarrhoea

25
Q

What are the actions of the two toxins produced by C. difficile?

A
  • One damages the epithelial cells (cytotoxin) resulting in neutrophilic infiltration of the tissues
  • The other disrupts tight junctions leading to loss of fluid into the bowel

NOTE: high WCC and low CRP is a common feature in C. difficile colitis

26
Q

How can C. difficile infection be prevented?

A
  • Cleanliness and hygiene (isolation, hand hygiene, personal protective measures)
  • Restrictive approach to antibiotic use (narrow-spectrum where possible)

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