76 - LRT Infections Flashcards
Frequent aetiological agents of acute bronchitis
Viral URTI
Frequent aetiological agent of acute exacerbation of chronic bronchitis
Usually pneumococci and/or H influenzae
Symptoms of acute exacerbation of chronic bronchitis/COPD
Sputum becomes more purulent, bloody
Less-virulent H influenzae and S pneumoniae
Higher-numbered pneumococci, unserotyped H influenzae
Frequent aetiological agent of bronchiolitis
RSV (particularly common under one year)
Effect of RSV on adults
Acute bronchitis symptoms, which can last a few weeks
Why does RSV cause bronchiolitis in under-ones?
Babies still have antibodies against RSV from mother.
Antibodies form immune complexes with virus.
Cā activation, etc, which causes more-severe inflammation than in older children without maternal antibodies
Effect of bronciholitis on ventilation
Gas is trapped in bronchioles.
On inspiration, bronchioles are opened.
On expiration, bronchioles collapse (no cartilage), trapping air. This manifests as a long expiratory wheeze.
Types of pneumonia
1
2
3
1) Acute bacterial
2) Typical pneumonia
3) Atypical pneumonia
Acute bacterial pneumonia common aetiological agents 1 2 3 4 5 6 7
Pneumococci (~80% of non-nosocomial cases. ~50% of nosocomial cases)
H influenzae
Staph (nosocomial)
Klebsiella (nosocomial)
Legionella (often immunocompromised, EG older)
TB
Chlamydophila
Chlamydophila pneumoniae, psittacae
Intracellular bacteria, same family as Chlamydia trachomatis.
Have replicative and infective forms.
Chlamidophila species that can cause pneumonia
Chlamydophila pneumoniae and psittacae
C psittacae vector
Birds.
Live harmlessly in birds, unless bird is stressed (EG: when captured).
Typical pneumonia
Sudden onset, sputum is purulent and bloody.
Restricted to one lobe
Atypical pneumonia
Chronic
Sputum not bloody, purulent.
Not restricted to one lung section, diffuse through lungs.
Bacterial cause of atypical pneumonia
Mycoplasma pneumonia
Causes of atypical pneumonia 1 2 3 4 5 6
Mycoplasma Chlamydia M. catarrhalis (can also cause otitis media) Influenza RSV Adenovirus
Chlamydia that can cause pneumonia in babies (particularly first month of life)
Chlamydia trachomatis
How do infants get C trachomatis pneumonia?
From infected mother.
Where does inflammation from typical pneumonia tend to be?
Alveoli
Where does inflammation from atypical pneumonia tend to be?
Interstitial tissue
Examples of fungal causes of pneumonia
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2
3
Histoplasma
Aspergillius
Pneumocystis
Bacteria which can cause lung abscesses
Mixed anaerobes.
Empyema
Pus in the pleural space
Aetiological agent of empyema
S aureus, as a secondary infection from pneumonia
Why make a specific diagnosis of pneumonia?
1
2
1) Appropriate antibiotic prescribing
2) Notifiable pathogens
Examples of notifiable pathogen-caused pneumonias 1 2 3 4 5
SARS, MERS Influenza (H5N1) Legionella spp Bioterrorism agents (anthrax, yersinia) Community-acquired MRSA
Ways to specifically diagnose pneumonia
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2
3
Clinical
Radiological
Lab
Clinical considerations of pneumonia 1 2 3 4 5 6
1) Community- or hospital-acquired
2) Severity index (becoming less used)
3) Underlying illness: COPD, ADIS, cystic fibrosis
4) Occupation (contact with animals, air quality, air conditioning)
5) Travel
6) Homelessness
Bacteirum that can be in potting mix for gardening
Legionella longbeachii
Bacterium that can be from animal furs
Bacillus anthraxis
Infection particularly associated with homelessness in Melbourne
Tuberculosis
Types of specimens for pneumonia diagnosis 1 2 3 4 5 6 7
1) Properly collected sputum
2) Transtracheal aspirate
3) Aspiration via tracheostomy, endotracheal tube
4) Aspiration via bronchoscope
5) Pleural tap (if effusion)
6) Lung biopsy (by needle or open)
7) Blood for culture and serology
Properly collected sputum
Coughed from lungs, observed by a clinician.
NOT spit - same organisms are in saliva that can cause pneumonia
Culture diagnosis of pneumonia 1 2 3 4
1) Look for purulent part of sample.
2) Plate purulent sample, gram stain.
3) Look for polymorphonuclear cells (must be present).
4) Look for buccal bacteria, as this indicates contamination.
Ways to collect sputum with less contamination than coughing
Transtracheal tube, tracheostomy, endotracheal tube, aspiration via bronchoscope
How to take a sample with a bronchoscope
Inject a small amount of saline, take sample
Use of a pleural tap
If pleural space is purulent, probably the same agent that caused pneumonia
Lung biopsy by needle
1
2
3
1) Relatively non-invasive, performed by a radiologist.
2) Radiologist locates area of interest, inserts needle between ribs to site of inflammation.
3) Perform in unresolved pneumonia, not in standard pneumonia
Is blood cultured from a pneumonia patient often positive for pneumonia-causing organism?
No
Transtracheal tube
Anaesthatise patient with a local.
Insert needle into cricothyroid space, insert into lungs.
When is serological diagnosis of pneumonia useful?
When bacterium is hard to grow.
Examples of bacteria that are diagnosed with serological techniques for pneumonia 1 2 3 4
1) Mycoplasma pneumonie
2) Legionella pneumophila
3) Chlamydophila, Chlamydia
4) Coxiella burnetii
Cause of typhus fever
Ricketsia prowazechii (spread by insects)
What do you look for in a serological test?
Specific IgM, rising titre
Which aetiological agents for pneumonia are tested for with antigen detection?
Common viruses (RSV, influenza, parainfluenza, etc), Bordatella, Legionella pneumophila type 1
How is the sample for antigen detection taken?
Tube inserted into nose, fluid form nose taken
When is an URT swab useful for diagnosing LRT infection?
When it is a viral infection. Bacteria living in URT can cause LRTI, but viruses do not live here normally
Best-guess antibiotics prescribed for community acquired pneumonia
Pen G/Amoxycillin + doxycycline/macrolide
Pen G for pneumococcus.
Tetracyclines and macrolides are effective for less-common bacteria (EG: mycoplasma are resistant to Pen G, as have no cell wall)
Why is using penicillin and tetracyclines together unusual?
When treating meningitis, are antagonistic
When do you modify best-guess antibiotic prescription
If severe, if there are specific risk factors, if you known the causative organism
Examples of vaccines for pneumonia
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2
3
1) Influenza vaccine
2) Pneumococcal vaccines (23-valent polysaccharide, 13-valent conjugate)
3) Coxiella (Q fever)
