L12. Lower Respiratory Tract Infections

Question 1

What are the 6 major syndromes that occur in the lower respiratory tract?

Answer 1

1. Acute Bronchitis
2. Acute Exacerbations of Chronic Bronchitis
3. Bronchiolitis
4. Pneumonia
5. Lung Abscess
6. Empyema

Question 2

What is the most common pathogenesis of acute bronchitis?

Answer 2

Usually an URT that has spread down the epithelia causing infection of the bronchi.
Thus is often starts with rhinitis, sore throat, hoarseness and then bronchitis.

Question 3

What is meant by acute exacerbation of chronic bronchitis? How are they caused?

Answer 3

Chronic Bronchitis leaves the LRT relatively damaged and susceptible to secondary bacterial infection. The acute exacerbations cause small bouts of fever, productive sputum (purulent and blood stained)

Question 4

What is the most common example of chronic bronchitis?

Answer 4

Chronic Obstruction Pulmonary Disease

Question 5

What are the usual causative pathogens causing acute exacerbations of chronic bronchitis?

Answer 5

Usually by non-pathogenic pathogens
Pneumoccoi (less virulent)
H.influenzae (non-typable)

Question 6

What is the major pathogenic cause of Bronchiolitis?

Answer 6

RSV

Question 7

Why is bronchiolitis more common in infants?

Answer 7

It is believed that children acquire preformed antibodies from their mothers. However in infancy, the immune system isn’t matured enough to form a matured response.

Question 8

What are the three types of pneumonia?

Answer 8

1. Typical (lobar)
2. Atypical (diffuse)
3. Other

Question 9

What are the major pathogenic organisms that cause acute bacterial pneumonia?

Answer 9

Pneumococci (80% community acquired)
H.influenzae
Staphylcocci
Klebsiella
Legionella
TB
Chlamyophilia

Question 10

What is the pathogenesis of acute pneumonia?

Answer 10

Aspiration of microbiota into the alveoli where they replicate and cause inflammation

Question 11

What are the characteristics of typical pneumonia? What is another name for it?

Answer 11

Lobar Pneumonia

Restricted to one lobe of the lung with subsequent inflammation in only that area (spreading)

Question 12

What is special about the Chlaymidiophilia pneumoniae bacteria?

Answer 12

Have specific life cycles
Replicating form intracellularly forming inclusion bodies until their burst out and kill the cell in the process
Non-replicating form during extracellular (infectious) form

Question 13

What are the major pathogenic causes of atypical pneumonia?

Answer 13

Mycoplasma
Chlamydia
M.catarrhalis
influenza
RSV
adenovirus

Question 14

What is the pathogenesis (and symptoms) of atypical pneumonia?

Answer 14

Gradual development with cough (less productive, less purulent) with dramatic change in CXR - interstitial tissue inflammation

Question 15

What are special about mycoplasma bacteria?

Answer 15

have no cell wall (no fixed shapes or sizes) and are important pathogens

Question 16

What bacteria aspirated in the birthing process is the causative organism to atypical pneumonia?

Answer 16

Chlamydia

Question 17

Another group of pathogens [3] cause other types of pneumonia. What are they?

Answer 17

FUNGI

Histoplasma, Aspergillus, Pneumocystis

Question 18

How are lung abscesses formed?

Answer 18

Often are remnants that persist after pneumonia is resolved.

Question 19

What causative organisms lead to lung abscess formation?

Answer 19

Caused by mixed anaerobes including as well as staphylcoccus and Klebsiella

Question 20

Why is empyema?

Answer 20

Collection of pus in the pleural cavity

Question 21

What is the major pathogenic cause of empyema?

Answer 21

Complication of penumonia
penetrating chest trauma
Eosophageal rupture
Inoculation of the pleural cavity after thoracentesis or chest tube placement

Question 22

What 4 factors must be considered when clinically diagnosing patients with LRTIs

Answer 22

1. Community vs. hospital acquired
2. Severity index
3. Underlying illnesses
4. Other risk factors (occupation, travel, homelessness)

Question 23

What types and considerations should be made when deciding what kind of sample should be taken for a lab diagnosis of LRTI?

Answer 23

1. Properly collect a sputum sample from deep chest
2. Transtracheal aspirate (not widely used in Aus.)
3. Aspiration: trachemostomy, endotracehal tube via endoscope
4. Pleural tap
5. Lung Biopsy (needle or open)
6. Blood culture and serology

Question 24

What are we looking for (and not looking for) when looking at gram stains of sputum collections?

Answer 24

Looking for pus: neutrophils and inflammatory cells.
Not looking for squamous epithelium: suggests contamination with mouth (URT microbiota)
Gram positive cocci: pneumococcus in atypical pneumonia

Question 25

For what bacteria is it important to do serological diagnoses for? Why is this?

Answer 25

Mycoplasma pneumoniae Legionella pneumophilia Chamydiophilia and Chlamydia Coxiella burneti They are difficult to culture

Question 26

Why are mouth/throat swabs often useless in diagnosing bacterial pneumonia?

Answer 26

Because mouth swabs test for URT bacteria. It is often the URT microbiota that is the causative organism of the LRT and thus you are unable to decipher which one is the cause.

Question 27

Are mouth/throat swabs relevant to diagnosing viral LRT?

Answer 27

Yes because viruses rarely colonise the RT. Eg. RSV found in the throat is often a good indication of primary infection and is indicative of possible bronchiolitis in the LRT.

Question 28

What is the process of specific antigen detection in aspirate and/or serological tests?

Answer 28

Draw blood from the patient or draw fluid and direct immunofluorescence: Antigen detection is run against common viruses (the most common circulating viruses of the time)

Question 29

What circumstances would it be important to make a specific diagnosis? [3]

Answer 29

1. Helps prescribe appropriate antibiotics (whether to even use them) 2. "Must Know" infections: outbreaks, public health issues, bioterrorism 3. "Should Know" infections: for antibiotic resistant bacteria and Gram Negative Rods (inherently resistant)

Question 30

What is the current gold-standard treatment for pneumonia?

Answer 30

Penicillin G/amoxicillin + Doxycycline/macrolide Penicillin: pneumococcus (most common cause) Tetracycline: Other causes that are normally penicillin resistant

Question 31

Treatment for pneumonia is modified once a specific diagnosis is made (if it is made). What impacts on what changes are made?

Answer 31

Based in the severity of the pneumonia Specific risk factors The specific causative agent (resistance)

Question 32

In meningitis, penicillin and tetracyclines are antagonistic drugs. Why is this not the case for pneumonia treatment?

Answer 32

This is because treatment for meningitis requires the drugs to cross the blood brain barrier. And penicillin only does so in small amounts (not enough to counter the bactericidal effects of tetracycline) In pneumonia, there is no limit on penicillin accessing the target (lungs) and hence there is no antagonism.

Question 33

What vaccines are available for the prevention of pneumonia? [3]

Answer 33

1. Influenza Vaccines 2. Pneumococcal vaccines 3. Specialised (for people more likely to be in contact with causative organisms)