Lower Respiratory Tract Infections

Question 1

Lower respiratory Tract infections:

Acute (5)/Chronic (3) LRTI.

Answer 1

Acute LRTI:

• Pneumonia
• Bronchitis
• Bronchiolitis
• Legionnaires disease
• Whooping cough

Chronic LRTI:

• Tuberculosis
• Aspergillosis
• Cystic fibrosis

Question 2

Pneumonia: The basics
Definition?
Acquired?
How many people die PA?
presentation AT, T?
importance of identification?

Answer 2

• An acute LRTI associated with recent developed radiological signs, infection of the lungs due to bacteria, virus or fungi.
• May be acquired in the community (CAP) or hospital (HAP); associated risk factors.
• Approximately 30,000 die PA in UK.
• May present Atypically or Typically
• May be caused by several organisms therefore accurate identification is essential to ensure appropriate treatment.

Question 3

Classification of pneumonia:

Answer 3

• Community acquired pneumonia (CAP)
• Hospital acquired pneumonia (HAP)
• Aspiration pneumonia
• Recurrent pneumonia

Question 4

Community Acquired pneumonia:
- Approx. percentage of cases per year?

• when is it seen?
• The stats: How many diagnosed at GP?
• how many admitted to hospital?
• how many die?
• how does age affect?

Answer 4

• Every year 0.5% to 1% of uk adults will have CAP (~320,000 - 640,000 people)
• Mainly seasonal.
• CAP is diagnosed in 5 -12% of patients presenting to their GP.
• 22- 42% admitted to hospital.
• 5 - 14% die in hospital
• 50& of death occur in patients over 84 years or more.

Question 5

Typical pneumonia: signs and symptoms:

Answer 5

Predominately respiratory: most commonly in elderly, may occur spontaneously in young adults.

Signs:

• cough
• cyanosis
• Tachypnoea
• Tachycardia

Symptoms:

• Fever
• Muscle aches
• shakes/rigor
• dsypnoea
• sputum production (rust coloured)

Question 6

Micro-organisms most commonly associated with Typical pneumonia CAP:

• Common (1 + characteristic)
• Uncommon (3)

Answer 6

Most common bacteria:
- Streptococcus pneumoniae (diplococcus gram +ve)

Less common:

• Haemophilus influenzae
• Staphylococcus aureus (CF)
• Pseudomonas aeruginosa (CF)

Question 7

Atypical pneumonia: signs and symptoms:

Answer 7

Predominately not respiratory. -common in very young and very old.
- S.pneumoniae not recovered from culture.

Signs:

• Rash
• Cyanosis
• Tachypnoea
• Tachycardia
• Dry cough

Symptoms:

• Headache
• Confusion
• Diarrhoea
• Incontinence
• No sputum

Question 8

Micro-organisms associated with atypical CAP:
- Most common (1)

• Less common (3)
• Don’t forget the viruses

Answer 8

Most common:
- Mycoplasma pneumoniae

Less common:

• Legionella pneumophilia (legionnaires disease)
• Chlamydophila psittaci (Psittacosis) (birds)
• Chlamydophila pneumonia

Viruses:

• Influenza A/B
• Rhinovirus
• Covid-19

Question 9

Radiological differences between atypical and typical pneumonia:

• Typical
• Atypical

Answer 9

• Typical: Widespread consolidation

- Atypical: Patchy consolidation

Question 10

Organisms that cause CAP and associated risk factors:

Answer 10

Risk Factor:
- Elderly/young, S.pneumoniae, M. pneumoniae, presents typical and atypical.

Smokers/travelers abroad, L.pnemoniae, present atypically.

Alcoholic/vagrants: S.pneumonia

Contact with animals/bird: Cl. psittaci, present atypical.

Question 11

Hospital Acquired pneumonia: Stats:

Answer 11

• 3rd most common hospital acquired infection (Nosocomial) (23% HAI)
• Patient may present with typical/atypical symptoms as described previously.

Question 12

Risk factors for HAP include: (3)

Answer 12

• Ventilation support: Klebsiella pneumoniae, Pseudomonas aeruginosa. (hospital flora): VAP ~48hrs or more following incubation.
• Immunosupression: organ transplants - aspergillus fumigatus
• immobility and vomiting: Aspiration pneumonia - oral bacteria e.g. viridians streptococci and anaerobic bacteria.

Question 13

Treatment of pneumonia:

• Uncomplicated CAP?
• Severe CAP of unknown aetiology?
• Atypical Pneumonia (CAP/HAP)
• HAP?

Answer 13

• Uncomplicated CAP: Amoxicillin or erythromycin, moxifloxacin is used now the other two show resistance.
• Sever CAP of unknown aetiology: Cefuroxime and erythromycin
• Atypical pneumonia: Erythromycin
• HAP: Cefotaxime +/- Gentamycin.

Question 14

Streptococcus pneumonia mechanism of pathogenicity:

• Most common where? CAP/HAP?
• Capsule?
• avoiding host defense?
• how many types of capsular.
• ~how many serotypes cause serious disease?
• Vaccine?

Answer 14

• S.pneumoniae: most common cause of CAP
• Capsule (A major virulence factor) (Polysaccharide)
• Antiphagocytic (evasion)
• 92 different capsular types; serotypes differ virulence.

90% pneumonia are caused by about 23 serotypes (used to develop vaccine PPSV23; Pneumococcal pneumoniae vaccine 23).

Question 15

Mechanism of pathogenicity:

• Adhesion protein?
• Protection proteins? avoiding host defense. (2)
• Toxin released proteins (2)?

Answer 15

• CbpA: a major pneumoccocal adhesion protein (adhesin). The adhesion interacts with carbohydrates on pulmonary epithelial surface.
• PspA (protective antigen): inhibits complement-mediated opsonizations.
• IgA1 protease: Cleaves IgA1 the principle immunoglobulin isotype for the respiratory tract.
• Autolysin: (LytA, LytB, LytC): breaks peptide cross linking in cell wall peptidoglycan releasing cell wall components; massive inflammation and pneumolysin release.
• Pneumolysin: Toxin released during autolysis: inhibits neutrophil chemotaxis, phagocytosis, lymphocyte proliferation and immunoglobulin synthesis. `

Question 16

Laboratory investigation:
Specimen? 
Non-culture techniques?
Safety? 
Identification?

Answer 16

Sample: early morning Sputum.

• Non-culture: Microscopy, gram-stain, lateral flow.
• Culture: - Sputum & Sputolysin (N-acetylcysteine)
  - Blood Agar: 37, 5%CO2, 24hrs + optochin disc
  - Chocolate Agar: 37, 5% CO2 24hrs).

Safety consideration:

• S.pneumonia: cat 2
• Sputum sample: cat 3; class one safety cabinet.

Identification:
- Basic: Colonial appearance: S.pneumonia grows as an alpha hemolytic.
- Gram positive diplococci.
Full: optochin sensitivity differentiates S. pneumonia from normal oral streps.

Question 17

S. pneumonia:
Antigen detection urine?

Sensitivity testing and resistance?

Vaccination?

Answer 17

Antigen detection utilizes urine sample.

• Non-culture technique: Immunochromographic assay/lateral flow assay.
• Sample = urine
• Rabbit anti-strep pneumoniae bound to nitrocellulose membrane.
• urine is added.
• 86% sensitivity, 94% specificity.
• Diagnosis if positive: however negative does not rule out infection.

Sensitivity testing/treatment and prevention:
- S. pneumoniae is susceptible to penicillin and almost all antibiotics.

• Penicillin resistance S. pneumoniae (DRSP) now widespread. eg. tetracycline, macrolides, trimethoprim-sulfamethoxazole. - 25% multi-drug resistance.
• Fluoroquinolones remain active: moxifloxacin

Vaccines:
- 23 valent pneumococcal polysaccharide vaccine (PPSV23).

• childhood vaccines: Pneumococcal conjugated vaccine (PCV13).