Community-acquired Pneumonia

Question 1

Where does pneumonia occur?

Answer 1

Lower respiratory tract infection of lung parenchyma

Proliferation of microbial pathogens in the alveolar level

Question 2

What is the most common type of pneumonia?

Answer 2

Bacterial

Less common: viral, fungal

Question 3

How does pneumonia enter the lower respiratory tract?

Answer 3

1. Aspiration of oropharyngeal secretions
2. Inhalation of aerosols: aerosolized droplets
3. Hematogenous spreading: bacteremia from extra-pulmonary source

Question 4

What are signs and symptoms of pneumonia?

Answer 4

1. Respiratory: cough, chest pain, SOB, hypoxia
2. Systemic: fever >38C, chills, tachypnea RR >24bpm, tachycardia HR >90bpm, hypotension SBP <100
3. Lab: leukocytosis - elevated WBC
4. Elderly: fatigue, anorexia, nausea, changes in mental status

Question 5

How might you detect pneumonia in a physical examination?

Answer 5

1. Diminished breath sounds

2. Inspiratory crackles during lung expansion

Question 6

Radiographic findings that assist in diagnosing pneumonia

Answer 6

Look for infiltrates or dense consolidations

1. Chest x-ray (CXR): more common bc cheaper and more available
2. CT scan: reserved for immunocompromised people or not responding to normal therapy

Question 7

What kind of culture should be used to diagnose pneumonia?

Answer 7

1. Sputum: low yield due to frequent contamination from oropharyngeal secretions
   - Quality: >10 neutrophils and <25 epithelial cells per LPF
2. Lower respiratory tract: preferred but invasive (bronchoalveolar lavage BAL)
   - Use only if pt is not responding or they’re very ill in ICU bc sedation is required
3. Blood culture: rule out bacteremia bc it crosses over easily

Question 8

What kind of diagnostic tests are not routinely used for diagnosis?

Answer 8

1. Laboratory findings (CRP, procalcitonin): non-specific
2. Urinary antigen tests: indicate exposure but remain positive for days to weeks despite abx tx
   - for Streptococcus pneumoniae, Legionella pneumophilia (serogroup 1 only)

Question 9

When is the onset of CAP and nosocomial pneumonia?

Answer 9

CAP: <48h post-admission

HAP/NAP: >48h post-admission or post-mechanical ventilation

Question 10

What are the risk factors for CAP?

Answer 10

1. Age >65y/o
2. Previous hospitalization for CAP
3. Smoking
4. Underlying conditions: COPD, DM, HF, cancer, immunosuppression

Question 11

How can we prevent CAP?

Answer 11

1. Smoking cessation
2. Prevent postviral infections: immunization
   - pneumococcal: PCV10/13 or PPSV23
   - influenza

Question 12

Why is Burkholderia pseudomallei a concern?

Answer 12

Gram-negative bacilli that causes melioidosis: group of infections including severe pneumonia
Prevalence in SG is 3rd highest in the world

Question 13

What are the criteria for risk stratification?

Answer 13

1. Pneumonia Severity Index (PSI): 20 variables, 5 mortality risk classes
2. CURB-65 Score: more common in clinical, only 5 variables & 3 mortality risk classes
3. IDSA-ATS criteria for severe CAP: >1 major or >3 minor criteria

Question 14

What are the major criteria under IDSA/ATS criteria?

Answer 14

1. Mechanical ventilation

2. Septic shock requiring vasoactive medications: to support BP in hypotension

Question 15

What are the minor criteria under IDSA/ATS criteria?

Answer 15

1. RR >30bpm
2. PaO2/FiO2 <250 (measure hypoxia)
3. Multilobar infiltrates
4. Confusion/disorientation
5. Uremia (urea >7 mmol/L)
6. Leukopenia (WBC <4 x 10^9/L)
7. Hypothermia (temp <36C)
8. Hypotension req aggressive fluid resuscitation

Question 16

What is the treatment duration for pneumonia?

Answer 16

At least 5 days with clinical stability (usually within 48-72h)
- Afebrile, maintain oral intake
- Normal vitals, O2 saturation and mental status
Exception:
- MRSA or Pseudomonas: 7 days
- Burkholderia pseudomallei: 3-6 months

Question 17

Standard regimen for healthy outpatient

Answer 17

1. PO Amoxicillin 1g TDS OR
2. PO Levofloxacin 750 OD/moxifloxacin
   - restrict to penicillin allergies

Question 18

Who is the population that is not considered generally healthy outpatient?

Answer 18

1. Chronic disease: heart, lung, liver, renal
2. Diabetes mellitus
3. Malignancies
4. Alcoholism
5. Asplenia

Question 19

Why is ciprofloxacin not used?

Answer 19

Poor activity against Streptococcus pneumoniae

Question 20

Why do we reserve respiratory fluoroquinolones for patients with penicillin allergy?

Answer 20

1. Increased adverse effects (e.g. tendonitis, tendon rupture, neuropathy, QTc prolongation, CNS disturbances, hypoglycemia)
2. Collateral damage/resistance with overuse
3. Preserve Gram-negative activity: levo/cipro only PO options for Pseudomonas
4. Delay TB diagnosis due to partial treatment

Question 21

Standard regimen for outpatients who have other conditions

Answer 21

1. PO Amoxicillin/clavulanate 625mg TDS or 2g BD OR PO cefuroxime 500mg BD (coverage for B-lactamase producing H. influenzae)
   w/ PO clarithromycin 500mg BD/azithromycin 500mg OD or PO doxycycline 100mg BD (atypical coverage)
2. PO levofloxacin 750mg OD/moxifloxacin

Question 22

Why is erythromycin not used?

Answer 22

It is an older macrolide that causes more GIT side effects

Question 23

Standard regimen for non-severe inpatient

Answer 23

1. IV Amoxicillin/clavulanate 1.2g q8h or IV ceftriaxone 1-2g q24h
   + PO clarithromycin 500mg BD/azithromycin 500mg OD or PO doxycycline 100mg BD
2. IV levofloxacin 750mg q24h/moxifloxacin

Question 24

Why is IV ceftriaxone preferred over IV cefuroxime?

Answer 24

Ceftriaxone has more experience and clinical data for inpatient CAP treatment than cefuroxime

Question 25

What are the organisms to cover for outpatient and non-severe inpatient pneumonia?

Answer 25

``` Streptococcus pneumoniae Haemophilus influenzae Atypicals (Chlamydophila pneumoniae, Mycoplasma pneumoniae) - not needed for healthy outpatient - Legionella pneumophilia for inpatient ```

Question 26

Organisms to cover for severe inpatient pneumonia

Answer 26

``` Streptococcus pneumoniae Haemophilus influenzae Atypicals Gram-negative bacilli (Klebsiella pneumoniae, Burkholderia pseudomallei) Staphylococcus aureus ```

Question 27

Standard regimen for severe inpatient pneumonia

Answer 27

1. IV Amoxicillin/clavulanate 1.2g q8h + IV ceftazidime 2g q8h + PO/IV clarithromycin 500mg BD/q12h/azithromycin 500mg OD/q24h OR PO/IV doxycycline 100mg BD 2. IV levofloxacin 750mg q8h/moxifloxacin + IV ceftazidime 2g q8h

Question 28

Should we give ceftazidime if inpatient w/ severe pneumonia has a penicillin allergy?

Answer 28

depends on severity of allergy 1. If can tolerate 3rd gen cephalosporin (low chance of cross-reactivity) then add ceftazidime 2. Omit if reaction is severe e.g. anaphylaxis, and give only respiratory fluoroquinolone - Monitor closely and use cultures to direct antibiotics therapy

Question 29

What are the indications for anaerobic coverage?

Answer 29

Either lung abscess (pus collection) OR empyema (pus/abscess in pleural space)

Question 30

What are the likely anaerobes in pneumonia?

Answer 30

Oropharyngeal space anaerobes: Bacteroides fragilis, Prevotella spp., Porphyromonas spp., Fusobacterium spp.

Question 31

Drugs for anaerobic coverage

Answer 31

Add IV/PO clindamycin or metronidazole | Not required if regimen contains amoxicillin/clavulanate or moxifloxacin

Question 32

What are the indications for MRSA coverage and Pseudomonas coverage?

Answer 32

- Prior respiratory isolation in last 1 year - Severe CAP only: hospitalization and IV antibiotics treatment in the past 90 days (+ locally validated risk factors) * 2nd point does not apply for Pseudomonas bc ceftazidime also covers Pseudomonas for severe CAP

Question 33

MRSA Coverage

Answer 33

IV vancomycin OR IV/PO linezolid Do not use daptomycin as it is inactivated in the lung surfactant

Question 34

How to modify regimen for Pseudomonal coverage?

Answer 34

Change to anti-pseudomonal B-lactam: IV piperacillin/tazobactam, IV ceftazidime, IV cefepime, IV meropenem Choose IV/PO levofloxacin over moxifloxacin

Question 35

Monitoring for efficacy of therapy

Answer 35

1. Clinical improvement in 48-72h: decrease in signs and symptoms - Elderly or multiple comorbidities may take longer 2. Do not escalate abx in 1st 72h unless culture-directed or significant clinical deterioration 3. Repeat radiological tests only for clinical deterioration to look for missed complications - Radiological improvement lags behind clinical, takes 4-6weeks for resolution

Question 36

Monitoring for safety of therapy

Answer 36

1. Adverse effects of abx (side effects and allergy) | 2. Renal function for dose adjustment

Question 37

When should we step down from IV to PO abx?

Answer 37

1. hemodynamically stable 2. clinically improved/improving 3. afebrile >24h 4. normally functioning GIT 5. can ingest PO medications

Question 38

Benefits of PO step-down therapy

Answer 38

1. pt comfort and mobility 2. less phlebitis & risk of nosocomial bacteremia 3. less preparation and administration time 4. less costs 5. facilitates discharge

Question 39

How to step down to PO therapy if there are no positive cultures?

Answer 39

Use same abx or abx from the same class - B-lactams: change to PO amox/clav or PO cefuroxime MRSA/Pseudomonas: stop empiric therapy in 48h if no culture + patient is improving Burkholderia: if no culture just remove ceftazidime