Lecture 20: Lower resp. tract infection; Pneumonia

Question 1

What is the most common serious bacterial infection?

Answer 1

Pneumonia

Question 2

Pneumonia is hard to distinguish from RSV, rhinovirus, covid etc withoverlapping symptoms. So what is the greatest indicator of pneumonia?

Answer 2

Fever + Cough.

Distinguishes bronchitis form pneumonia

Question 3

What symptoms are seen in pneumonia of the elderly?

Answer 3

Increased RR
Crackles
Consolidation
Fevers/chills
Non-pulmonary i.e dilirium or falls or lack of appetite

Question 4

What might indicate consolidation on CXR?

Answer 4

Lower lobes sitting on diaphragm when they full with pus the diaphragm cant be distinguished

Question 5

What are the risk factors for pneumonia?

Answer 5

• <2yrs or >65yrs
• Chronic lung disease (interferes with innate immune system)
• Smoking
• Immune dysfunction

Question 6

What are the innate immune properties of the resp. tract?

Answer 6

Ciliated epithelium
Nasal turbinates
Nasal secretions
Saliva
Epiglottis
Goblet cells
Airway liquid
PAMS
Alveolar fluid
Neutrophils

Question 7

What are the two top agents causing pneumonia?

Answer 7

1. S. pneumoniae
2. Heamophilus influenza

BUT depends on study…

Question 8

How prevelent is streptococcus pneumoniae?

Answer 8

alpha heamolytic streptococcus viridans group.

Transiently colonizes lung when aspirated can cause pneumonia

5-10% adults, 20-40% of children.
- Prevalence of colonization increases in winter in adults, persists for few weeks

Question 9

What gives pneumococcal virulence?

Answer 9

Pneumococcal surface protein A (PSPA): Binds to epithelial cells and also prevent deposition of C3b

PSPC: Prevents activation of complement cascade

Pili: Contribute to colonization and cytokine production (TNFa) during invasion

Polysaccharide capsule: Prevents phagocytosis and complement deposition

Pneumolysin: (toxin) lyses neutrophils and epithelial cells

Choline binding protein: Binds to Ig receptor on epithelial cells - allows transport into cell

Question 10

What are the investigations for a suspected pneumonia?

Answer 10

• CXR is primary investigation
• Sputum culture (often contaminated)
• Nasopharyngeal swab (Viral PCR)
• Blood cultures
• Urine ICT(proteins shedded from blood into urine, but low conc. therefore low sensitivity)
• Serology
• CT chest/ bronchoscopy

Question 11

Whats the role of antibiotics and pneumonia?

Answer 11

• Antibiotics required, reduces duration of illness and risk of death
• Beware of penicillin resistance
• Oral vs IV dosing (esp. if meningitis develop)
• Penicillin resistance associated with resistance to others.

Question 12

What can we target in bacteria that are distinguished from humans?

Answer 12

Bacterial ribosomes, are sufficiently diff to human, so they can be targeted

i. e
- 50S transpeptidation (Macrolides)
- 50S peptidyl transferase
- 30S initiation (Aminoglycosides)
- 30S tRNA binding (Tetracyclines)

Question 13

How do macrolides function?

Answer 13

• Broad spectrum
• Limited activity against gram negative
• Active against streptococci, staphylococci and other cause of pneumonia
• Treatment of chlamydia

Question 14

Whats the adverse effects of macrolide antimicrobials?

Answer 14

• GI tract upset
• Sudden death (Long QT)
• Drug-drug interactions

Question 15

Whats the empiric treatment of pneumonia?

Answer 15

Based on severity and setting generally 5 days of treatment required

• Mild -> Severe

Question 16

What causes bronchitis?

Answer 16

It is a viral illness

Adenovirus and influenza is most common

Question 17

Do antibiotics help with bronchitis?

Answer 17

• Randomised placebo-controlled trails have NOT demonstrated a benefit

Treatment for cough: NSAIDs, Sedating antihistamines