Module 4.1 - Lower Respiratory Tract Pathogens

Question 1

What is the lower respiratory tract?

Answer 1

Lower respiratory tract = below the larynx

Question 2

What are the signs and symptoms of a lower respiratory tract infection?

Answer 2

An acute illness (present for 21 days or less) usually has cough as the main symptom with at least one other lower respiratory tract symptom: sputum production, dyspnea, wheeze or chest discomfort/pain

Question 3

What is acute bronchitis?

Answer 3

An acute illness that occurs in a patient without chronic lung disease

Question 4

What are the signs and symptoms of acute bronchitis?

Answer 4

• A cough may be non-productive with symptom similar to a lower respiratory tract infection: sputum production, dyspnea, wheeze or chest discomfort/pain
• Bacteria are an uncommon cause accounting for only 6%.
• Viruses associated with bronchitis include Influenza A & B, parainfluenza, coronavirus types 1 to 3, rhinoviruses, respiratory syncytial virus and human metapneumovirus

Question 5

What are some respiratory manifestations of influenza?

Answer 5

It is an acute illness with a cough and at least one of the following symptoms:

• sputum production
• wheeze
• chest discomfort/pain
• fever > 4 days
• dyspnea/tachypnea without obvious cause

Question 6

What are some considerations to take in mind for older adults with lower respiratory tract infections?

Answer 6

• Comorbid conditions such as HF, COPD, DM, altered mental status, dementia, dysphagia and cancer increase the mortality of community-acquired pneumonia
• Consider the altered immunological status in the elderly
• Long term care residents may require broader spectrum antibiotic coverage
• More than 50% of all cases of pneumonia occur in patients > 65 years of age.
• Streptococcus pneumonia remains the dominant etiology of lower respiratory tract infections but may be polymicrobial
• When choosing antibiotic therapy, resistance patterns in the community and in long term care facilities need to be reviewed

Question 7

What are the differential diagnoses for patients with lower respiratory tract infections?

Answer 7

• Pneumonia
• Post nasal drip syndrome
• GERD
• Asthma
• Ace inhibitor use
• HF
• Pulmonary embolism (PE)
• Lung cancer

Question 8

What should you suspect in patients who have difficulty swallowing and show signs of an acute lower respiratory tract infection?

Answer 8

Aspiration

A CXR may be indicated to rule out this finding

Question 9

How do you distinguish between a respiratory infection and an exacerbation of heart failure?

Answer 9

Obtain a BNP, the BNP if elevated will point more towards a cardiac cause.

Question 10

In general describe the antibiotic approach to treating lower respiratory tract infections

Answer 10

• Milder LRTI requires only narrow spectrum antimicrobials if any
• Severe LRTI requires a combination of antimicrobials while cultures are pending
• When culture data becomes available, review present therapy and change if necessary – choose the narrowest spectrum drug that is effective
• Avoid antibiotic overuse – antimicrobial agents are generally reserved for cases in which a specific pathogen is suspected or diagnosed in patients who are at high risk for complications or when treatment might limit the spread of a contagious illness.
• Beta-lactams is the primary mechanism of resistance among H. influenzae and is a well-known predictor of treatment failure in community acquired respiratory tract infections. This can be overcome with the use of B-lactamase-stable cephalosporins in part. Close attention to culture sensitivities is key; input from Infectious Disease specialists may be indicated.
• Macrolide antibiotics such as Biaxin, Zithromax Dificid and Erythromycin inhibit the growth of bacteria. They are often prescribed for atypical pathogens in the outpatient setting.
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Question 11

For viral Acute tracheobronchitis, what is the recommended treatment?

Answer 11

No antibiotic therapy indicated for viral infections

Question 12

With acute tracheobronchitis caused by mycoplasma pneumoniae & chlamydia pneumoniae, what is the recommended treatment?

Answer 12

• Doxycycline
• Macrolides (note risk of QT segment prolongation and torsade de points including azithromycin

Question 13

In an acute bacterial exacerbation of COPD caused by Streptococcus pneumoniae, what is the recommended antibiotics to prescribe for treatment?

Answer 13

Consider:

• Amoxicillin - 1g PO q8h x5 days
• Trimethoprim-sulfamethoxazole
• Doxycycline - 100mg PO q12h x5 days
• second-generation cephalosporin

Question 14

In an acute bacterial exacerbation of COPD caused by Haemophilus** **pneumoniae, what is the recommended antibiotics to prescribe for treatment?

Answer 14

Consider:

• Amoxicillin - 1g PO q8h x5 days (PREFERRED Tx)
• Azithromycin - 500mg PO x1, then 250mg PO daily x4 days

Question 15

What is the recommended course of treatment for Influenza H & B?

Answer 15

• Zanamivir (Relenza) 10 mg (two inhalations BID) or Oseltamivir (Tamiflu) 75 mg BID x 5 days.
• Ideally should be initiated within 48 hours of onset of symptoms

Question 16

What are the 7 typical bacterial pathogens causing community-acquired pneumonia (85% of cases)?

Answer 16

1. Streptococcus pneumoniae
2. Penicillin sensitive S. pneumoniae
3. Penicillin resistant S. pneumoniae
4. Haemophilus influenzae
5. Ampicillin sensitive H. influenzae
6. Ampicillin resistant H. influenzae
7. Moraxella catarrhalis (all strains penicillin resistant)

Question 17

What are the 3 atypical respiratory pathogens causing community-acquired pneumonia (15% of cases)?

Answer 17

1. Legionella species
2. Mycoplasma species
3. Chlamydia pneumoniae

Question 18

How should empiric antibiotic coverage for community acquired pneumonia be approached?

Answer 18

• If a patient has received an antibiotic within the previous 3 months, macrolide monotherapy is not recommended.
  
  • Treatment failures can lead to drug resistance.
  • Strep pneumonia is increasingly more resistant likely due to treatment failure with macrolides.
• Guidelines suggest treating both atypical pathogens and pneumococcus with macrolides or doxycycline when antibiotic resistance is not anticipated.
• Patients with major comorbidities, a history of recent antibiotic use, and areas with of doxycycline resistant Strep pneumonia (most of United States), combination therapy with a beta-lactam plus either a macrolide or doxycycline or monotherapy with a respiratory fluoroquinolone (levaquin) is suggested.
• Most outpatients can be treated with a 5 day course of antibiotics. If patients who have not responded to therapy after 48-72 hours, they should be closely re-evaluated.