Micro - Respiratory Tract Infections

Question 1

Define pneumonia and what are the S/S

Answer 1

Inflammation of the lung alveoli

fever, cough, SOB, pleuritic chest pain

Question 2

What is the difference between upper and lower respiratory tract infection

Answer 2

URTI = sinusitis, tonsilitis
LRTI = bronchitis, pneumonia, empyema, bronchiectasis, lung abscess

Question 3

What are the risk factors for pneumonia

Answer 3

Poor swallow (CVA, muscle weakness, alcohol)
Abnormal ciliary function (smoking, viral infection, Kartagener’s)
Abnormal mucous (cystic fibrosis)
Dilated airways: bronchiectasis
Defects in host immunity: HIV, immunosuppression

Question 4

What is the difference between community and hospital acquired pneumonia

Answer 4

Community acquired (85%): usually pathogen is not identified
- Typical: Strep. pneumoniae (gram +ve), H. influenzae, Moraxella catarrhalis, staphylococcus aureus, klebsiella pneumoniae
- Atypical: legionella, mycoplasma, coxiella burnetii, chlamydia psittaci

Hospital acquired (15%): after 48hrs of hospital admission
- Enterobacteriaciae (e.g. E. coli, Klebsiella), pseudomonas, H. influenzae, staph aureus, acinetobacter baumanii, fungi (Candida)

Question 5

What is the difference between typical and atypical infection

Answer 5

Typical = classic signs and symptoms, classic CXR changes (i.e. consolidation), respond to penicillin Abx

Atypical = no / atypical signs and symptoms, not in-keeping with CXR, don’t respond to penicillin Abx (no cell wall). May have extra-pulmonary features, e.g. hepatitis, hyponatraemia

Question 6

How does causative organism of pneumonia change with age

Answer 6

0-1 months: E. coli, GBS, Listeria monocytogenes
1-6 months: Chlamydia trachomatis, S. aureus, RSV
6 months-5years: mycoplasma pneumoniae, influenzae
16-30 years: m. pneumoniae, Strep. pneumoniae

Question 7

What are the signs and symptoms of pneumonia

Answer 7

Symptoms: SOB, cough + sputum, fever, rigors, pleuritic chest pain, malaise, N&V
Signs: pyrexia, tachycardia, tachypnoea, cyanosis, bronchial breathing, crackles, dullness to percussion

Question 8

What are the key features of strep. pneumoniae infection

Answer 8

Most common (30-50%)
Gram +ve diplococci
Alpha-haemolytic (green tinge) and optochin sensitive
Rust-coloured sputum
Lobar on CXR

Question 9

What are the key features of H. influenzae infection

Answer 9

Gram -ve cocco-bacilli (stain on chocolate agar)
Associated with smoking or pre-existing lung disease e.g. COPD
May produce beta-lactamase

Question 10

What are the key features of moraxella catarrhalis infection

Answer 10

Gram -ve cocci
Associated with smoking

Question 11

What are the key features of staph aureus pneumonia

Answer 11

Gram +ve cocci (Grape bunch clusters)
Associated with recent viral infection (influenza)
CXR: cavitating lesions

Question 12

What are the key features of Klebsiella pneumoniae pneumonia

Answer 12

Gram -ve rods, enterbacter
Seen in alcoholics and the elderly
Causes haemoptysis

Question 13

What are the key features of legionella pneumonia

Answer 13

Associated with travel, air conditioning, water towers
Buffered charcoal yeast extract
Causes hyponatraemia and hepatitis (Deranged LFTs), confusion, diarrhoea, abdo pain

Question 14

What are the key features of chlamydia psittaci (psittacosis) pneumonia

Answer 14

Exposure to birds (parrots)
Causes splenomegaly, rash, haemolytic anaemia
Identified on serology

Question 15

What are the key features of mycoplasma pneumonia

Answer 15

Seen in uni students/boarding schools
Causes erythema multiforme
Barking cough (dry) with normal CXR
Cold agglutinins

Question 16

What are the key features of coxiella burnetii (Q fever) infection

Answer 16

Exposure to farm animals (aerosol or milk)
Causes hepatitis
Identified on serology

Question 17

What are the key features of TB pneumonia

Answer 17

Presents with prolonged prodrome, fevers, weight loss, haemoptysis
CXR: upper lobe cavitation
Auramine stain and a Ziehl-Neelsen stain → Acid fast bacilli (red rods)
Cavitating caseating granuloma

Question 18

What are the key features of pneumocystis jirovecii (including treatment)

Answer 18

Protozoa
CXR: bilateral infiltrative change
Detected by immunofluorescence or silver stain
Walk test (attaching an oxygen saturation probe and asking the patient to walk) will show desaturation on exertion
Presents with: dry cough, weight loss, SOB, malaise
Treatment/prophylaxis: co-trimoxazole (septrin)

Question 19

What can aspergillus fumigatus infection cause

Answer 19

Allergic bronchopulmonary aspergillosis: chronic wheeze, eosinophilia, bronchiectasis
Aspergilloma: fungal ball → haemoptysis
Invasive aspergillosis: seen in immunocompromised patients (treat with amphotericin B)

Question 20

Which respiratory tract infections are more common in the immunosuppressed

Answer 20

HIV: PCP, TB, cryptococcus neoformans
Splenectomy: encapsulated organisms (NHS)
Cystic fibrosis: Pseudomonas aeruginosa, Burkholderia cepacia
Neutropenia: Aspergillus → amphotericin B

Question 21

What investigations should be done for pneumonia

Answer 21

Urinary antigens (legionella, strep. pneumoniae)
Sputum culture
Bronchial/broncho-alveolar lavage (esp. for HAP)

FBC, U&Es, CRP, blood cultures, serology (Chlamydia, legionella, coxiella), immunofluorescence (PCP)

CXR

Note: serology is only useful if paired (one unwell, one getting better)

Question 22

How do you assess severity and necessity for admission in pneumonia

Answer 22

CURB-65
Confusion
Urea >7
Resp rate >30
BP <90
>65

1 → community treatment
2 → admit
3 → treat as severe infection

Question 23

What is the management for typical CAP

Answer 23

Mild (CURB 0-1): amoxicillin
Moderate (CURB 2): amoxicillin + clarithromycin
Severe: Admit + Co-amoxiclav + clarithromycin

Penicillin allergy: cefuroxime + clarithromycin

Question 24

What is the management for atypical CAP

Answer 24

Cell-wall active antibiotics (e.g. penicillins) do NOT work → so need agents that work on protein synthesis

Clarithromycin/erythromycin
Doxycycline

Question 25

What is the management for HAP

Answer 25

First line: Ciprofloxacin ± vancocmycin
Second line/severe: tazocin (piptazobactam) + vancomycin

Question 26

What is the management for aspiration pneumonia

Answer 26

Tazocin + metronidazole

Question 27

What antibiotics are indicated for MRSA and pseudomonas

Answer 27

MRSA: Vancomycin
Pseudomonas: Piptazobactam OR ciprofloxacin ± gentamicin

Question 28

What is bronchitis and what are the causes

Answer 28

Inflammation of medium-sized airways
Viruses (most common), strep. pneumoniae, H. influenzae, moraxella catarrhalis

Question 29

What should be considered if there is failure to improve after antibiotics for pneumonia

Answer 29

Empyema/abscess
Proximal obstruction (tumour)
Resistant organisms (travel hx)
Not receiving/absorbing antibiotics
Immunosuppression
Other diagnosis (lung cancer, cryptogenic organising pneumonia