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review micro > MI: Respiratory Tract Infections > Flashcards

MI: Respiratory Tract Infections Flashcards

1
Q

List some ways in which the body can be compromised, thereby increasing the risk of respiratory tract infection.

A
  • Poor swallow (aspiration)
  • Abnormal ciliary function (e.g. smoking)
  • Abnormal mucus (e.g. CF)
  • Dilated airways (e.g. bronchiectasis)
  • Defect in host immunity
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2
Q

What type of bacterium is Streptococcus pneumoniae?

A
  • Gram-positive cocci in chains
  • Alpha-haemolytic and optochin-sensitive
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3
Q

What is optochin used for?

A

Used to differentiate S. pneumoniae from other alpha-haemolytic streptocci

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4
Q

Epidemiology of S. Pneumoniae infection in CAP

A

20-50% of CAP
Almost always penicillin sensitive

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5
Q

What is pneumonia and what are its presenting symptoms

A

Inflammation of alveoli due to infection
Presentation:
- Fever
- Cough
- SoB
- Pleuritic chest pain

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6
Q

Why is no microbiological identification of the pathogen made in the most cases of CAP?

A

Difficult to obtain a good sputum sample and early treatment is usually initiated with empirical antibiotics

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7
Q

List the main organisms that cause CAP.

A
  • VIRUSES
  • Streptococcus pneumoniae
  • Haemophilus influenzae
  • Mycoplasma pneumoniae
  • Moraxella catarrhalis
  • Staph aureus
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8
Q

List the most prevalent pathogens causing CAP in the following age groups:

  • 0-1 months
  • 1-6 months
  • 6 months - 5 years
  • 16 - 30 years
A

0 - 1 months:

  • Escherichia coli
  • Group B Streptococcus
  • Listeria monocytogenes

1-6 months:

  • Chlamydia trachomatis
  • Staphylococcus auerus
  • RSV

6 months - 5 years:

  • Mycoplasma pnaeumoniae
  • Influenza

16-30 years:

  • Mycoplasma pneumoniae
  • Streptococcus pneumoniae
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9
Q

List the causes of CAP that fall into the following two categories:

  • Typical
  • Atypical
A

Typical (85%):

  • Streptococcus pnaeumoniae - lobar
  • Haemophilus influenzae - bronchopneumonia

Atypical:

  • Legionella - Summer/ Water exposure
  • Mycoplasma - barking cough, normal CXR
  • Coxiella burnetii (Q fever) - farm animals, hepatitis
  • Chlamydia psittaci - Exposure to birds, splenomegaly, rash, haemolytic anaemia
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10
Q

What investigations would you consider in pneumonia

A

FBC, U&E, CRP

Blood culture, sputum culture

ABG

CXR

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11
Q

What is the CURB-65 score? How is it interpreted?

A
  • Confusion
  • Urea > 7 mmol/L
  • Respiratory rate > 30/min
  • BP < 90 systolic, < 60 diastolic

Score of 2 = consider hospital admission
Score of more than 2 = severe pneumonia that may need ITU admission

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12
Q

What is bronchitis and in which group of people does it most likely occur

A

Inflammation of bronchi and medium-sized airways
Mainly affects smokers

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13
Q

Outline the presentation of bronchitis.

A
  • Cough
  • Fever
  • Increased sputum production
  • Increased SOB
  • CXR often normal
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14
Q

Which organisms cause bronchitis?

A
  • Viruses
  • Streptococcus pneumoniae
  • Haemophilus influenzae
  • Moraxella catarrhalis
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15
Q

How is bronchitis managed

A
  • Smoking cessation
  • Bronchodilators
  • Physiotherapy
  • +/- Antibiotics
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16
Q

List some bacterial causes of cavitating lung lesions.

A
  • Staphylococcus aureus
  • Klebsiella pneumoniae
  • TB
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17
Q

What type of bacteria is H. influenzae and what kind of agar is it cultured on

A
  • Gram negative coccobacillus
  • Cultured on chocolate agar

More common with preexisting lung disease

15-35% CAP

May produce beta-lactamase

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18
Q

How is Legionella spread and what abnormal symptoms can it present with?

A

Inhalation of infected water droplets

Can present with confusion, abdominal pain and diarrhoea

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19
Q

What electrolyte derangement commonly occurs with Legionella pneumonia

A

Hyponatraemia (can cause neurological symptoms like confusion or drowsiness)

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20
Q

What would you see on FBC in Legionella infection?

A

Lymphopaenia

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21
Q

How does Legionella pneumonia appear on CXR

A

Bilateral interstitial shadowing

22
Q

What medium is Legionella grown on?

A

Buffered charcoal yeast extract

23
Q

How is Legionella pneumoniae diagnosed and treated

A

Diagnosed by urine antigen detection
Treated with macrolides

24
Q

What is a feature of bacteria that cause atypical pneumonia and how does it affect treatment?

A

They have NO cell wall
Therefore not susceptable to cell wall targetting antibiotics e.g. penicillins

25
Q

List four atypical organisms.

A
  • Mycoplasma pneumoniae
  • Legionella pneumophilia
  • Chlamydia psittaci
  • Coxiella burnetii
26
Q

Which type of antibiotics do work on atypical bacteria?

A

Antibiotics that interfere with protein synthesis (macrolides, tetracyclines)

27
Q

How is Coxiella burnetii spread and treated

A

Spread by domestic/farm animals and transmitted by infected aerosol or milk
Treated with macrolides

28
Q

How is Chlamydia psittaci spread and treated

A

Spread from birds by inhalation

Treated with macrolides

29
Q

Which investigation is used for Coxiella and Chlamydia psittaci?

A

Serology

NOTE: serology looks at the development of antibodies after an infection. Therefore it requires paired samples (usually collected on presentation and then 10-14 days later)

It is useful for investigating bacteria that are difficult to culture.

30
Q

What is an empyema?

A

Collection of pus within the pleural cavity

31
Q

List some reasons for failure to respond to treatment.

A
  • Empyema/abscess
  • Proximal obstruction (e.g. tumour)
  • Resistant organisms
  • Not absorbing antibiotics
  • Immunosuppression
  • Alternative diagnosis (e.g. lung cancer)
32
Q

What is the classical CXR feature of TB?

A

Upper lobe cavitation

33
Q

What clues in history might point you towards TB?

A
  • Ethnicity/recent travel to endemic regions
  • Prolonged course
  • Fevers
  • Weight loss
  • Haemoptysis
34
Q

How is TB diagnosed?

A

Primary latent TB: TST, IGRA
Active (primary or secondary) TB: PCR, sputum culture, CXR

35
Q

Which types of staining are used when investigating TB?

A
  • Auramine stain
  • Ziehl-Neelsen stain

NOTE: they are red rods

36
Q

Define hospital-acquired pneumonia.

A

A pneumonia that presents > 48 hours after hospital admission

37
Q

List some organisms that cause HAP.

A
  • Enterobacteriaciae 31% (MOST COMMON - e.g. E. coli, K. pneumoniae)
  • Staphylococcus aureus 19%
  • Pseudomonas 17%
  • Haemophilus influenzae
  • Acinetobacter baumanii
  • Fungi (e.g. Candida)
38
Q

Classical PCP CXR presentation

A

Bilateral consolidation “Bats wing”

39
Q

Describe the typical presentation of Pneumocystic jirovecii pneumonia.

A
  • Dry cough
  • Weight loss
  • SOB
  • Malaise
  • Walk test - desaturation on exertion
40
Q

How is PCP diagnosed?

A
  • Blood PCR (early detection in HIV patients)
  • Sputum staining with silver-based stains
  • Bronchoalveolar lavage and immunofluorescence
41
Q

What is the treatment for PCP?

A

Co-trimoxazole (septrin)

42
Q

What are the main features of allergic bronchopulmonary aspergillosis?

A
  • Chronic wheeze
  • Eosinophilia
  • Bronchiectasis
43
Q

What is an aspergilloma?

A
  • Fungal ball often forming within a pre-existing cavity
  • May cause haemoptysis
44
Q

Who is affected by invasive aspergillosis and how is it treated?

A

Affects immunocomprimised individuals

Treated with amphotericin B

45
Q

Flowering spores?

A

Aspergillus

46
Q

Which organisms cause pneumonia in the following subgroups of patients:

  • HIV
  • Neutropenia
  • Bone marrow transplant
  • Splenectomy
A
  • HIV: PCP, TB, Atypical mycobacteria
  • Neutropaenia: Fungal (e.g. Aspergillus)
  • Bone marrow transplant: CMV
  • Splenectomy: Encapsulated organisms (e.g. Streptococcus pnaeumoniae, Haemophilus influenzae)
47
Q

What is the emprical treatment for mild-to-moderate CAP?

A

Amoxicillin

(macrolide if penicillin allergic)

48
Q

What is the emprical treatment for moderate-to-severe CAP?

A

Co-amoxiclav AND clarithromycin

49
Q

What are the 1st and 2nd line treatment options for HAP?

A

Check local guidelines
Mild = co-amoxiclav
Severe = tazocin
(glycopeptides if MRSA)

50
Q

Which antibiotics are used to treat HAP caused by:

  • MRSA
  • Pseudomonas
A
  • MRSA - Vancomycin
  • Pseudomonas - Tazocin OR ciprofloxain +/- gentamicin
51
Q

How can pneumonia be prevented

A

Vaccinations
Smoking advice

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