ID: community-acquired pneumonia

healthcare-associated pneumonia

• since guidelines have been released, several studies have evaluated these criteria

  • no clear benefit in patient outcome

  • poorly predicted patients with multi drug resistant (MDR) pathogens

• resulted in 15 years of antibiotic over-prescribing

• despite recommendations to abandon this definition, it’s still often used to justify broad therapy

pathophysiology of pneumonia

1. microbes invade the airway

   • through inhalation, aspiration, or even contamination from food

2. host defenses are overcome

   • impaired mucociliary clearance

   • overwhelmed or absent macrophages

3. bacterial proliferation and inflammation

   • bacteria invade alveoli

   • macrophages recruit neutrophils and produce cytokines

   • the immune system is ‘ramped up’

signs and symptoms of pneumonia

• new or worsening sputum production

• new or worsening cough

• increased respiratory rate

• pleuritic chest pain

• leukocytosis or leukopenia

• fever/hypothermia

• asculatory changes, such as crackles or rales

• decreases in oxygenation

diagnosis of pneumonia

• chest x-ray (CXR) is essential

  • however, it doesn’t differentiate between viruses and bacteria

• infiltrate/consolidation on CXR may represent pneumonia

  • doesn’t differentiate between bacteria and viral

  • CXR is also not specific to pneumonia

  • if a CXR clears up overnight → rule out pneumonia

• for patients that are hospitalized with a negative CXR but positive clinical symptoms, it’s reasonable to re-image in 24-48 hours

sputum analysis

• in the majority of patients, cultures are conducted based on expectorated sputum (“gunk” in the lungs)

  • 40-60% of patients will not produce sputum

  • 40-60% of those that can → poor samples

• a “good” sample requires identification of polymorphonuclear leukocytes (PMNs) and lack of epithelial cells in sputum culture

  • > 25 PMNs and < 10 epithelial cells

    • indicated spit and not “gunk”

  • PMNs indicates inflammation, and thus infection

• cultures are recommended in patients with:

  • severe disease (eg. ICU)

  • receiving MRSA/P. aeruginosa coverage

procalcitonin test (PCT)

• normally produced in thyroidal C-cell

• upregulated production in adipocytes response to bacterial infection

  • a lab test indicative of infection, but anything that has a strong inflammatory response could lead to a false positive

• the most commonly used cutoff is 0.25 ng/mL

  • > 0.25 → antibiotic therapy is encouraged

• typically peaks within 24 hours of infection onset

  • initial elevations may be observed with viral infections, though this is typically followed by a rapid decrease

• plays an unclear role in the treatment of CAP

  • may not be elevated in patients with atypical bacteria

• NOT recommended as a guide for initiating antibiotics in patients with radiographically confirmed pneumonia and clinical signs/symptoms

pneumonia severity index (PSI)

• determines the treatment setting based on demographics, co-morbidities, phsyical exam, labs, etc

  • replaced the CURB-65 tool

• criteria:

  • respiratory rate ≥ 30 bpm

  • SBP < 90 mmHg

  • temp ≥ 40 or < 35 ºC

  • tachycardia ≥ 125 bpm

  • arterial pH < 7.35

  • BUN ≥ 30 mg/dL

  • sodium < 130 mmol/L

  • glucose ≥ 250 mg/dL

  • Hct < 30%

  • pO2 < 60 mmHg

PSI risk class 1

• < 50 points

• outpatient setting

PSI risk class 2

• 51-70 points

• outpatient setting

PSI risk class 3

• 71-90 points

• outpatient or brief inpatient setting

PSI risk class 4

• 91-130 points

• inpatient setting

PSI risk class 5

• > 130 points

• inpatient setting

CURB-65 criteria

• confusion

• uremia (BUN > 20 mg/dL)

• RR > 30 bpm)

• BP < 90/60

• age > 65

CURB-65 score 0-1

• outpatient setting

CURB-65 score 3

• inpatient → floor setting

CURB-65 score ≥ 3

• inpatient → ICU setting

IDSA severity criteria

• determines whether a not a patient should be admitted to the ICU for their pneumona infection

  • in combination with clinical judgement, should be used to determine inpatient setting of care (ICU vs non-ICU)

  • comprised of values that are readily available for patients being admitted

• patient must meet 1 major criteria OR 3 minor criteria in order for ICU admission

IDSA severe pneumonia: minor criteria

• need 3:

  • RR ≥ 30 bpm

  • PaO2/FiO2 ≤ 250

  • multilobal infiltrates

  • confusion

  • BUN ≥ 20 mg/dL (uremia)

  • leukopenia due to infection → WBC < 4×10³

  • thrombocytopenia → platelets < 100×10³

  • hypothermia (< 36ºC)

  • hypotension requiring aggressive fluid resuscitation

IDSA severe pneumonia: major criteria

• need 1:

  • mechanical ventilation

  • septic shock (requires vasopressors)

bacteria that can cause CAP

• Streptococcus pneumoniae → most common

• Haemophilus influenzae

• Mycoplasma pneumoniae

• Clamydophilia pneumoniae

• Legionella pneumophila

• S. aureus (rare, may have risk factors for infection)

• rarely other gram-negative bacilli

etiology of CAP

• often no pathogen is identified (up to 62%)

• viral pathogens account for 24% of identified pathogens

• bacterial pathogens account for 14% of CAP infections

  • normally, treat as bacterial infection

  • viral infections → tend to not have to treat

risk factors for MRSA and P. aeruginosa

• overall, CAP caused by these pathogens is rare

• prevalence of these pathogens should be locally evaluated

• most consistent factors:

  • previous infection with MRSA or P. aeruginosa, especially respiratory infections

  • hospitalization WITH receipt of intravenous antibiotics witihn 90 days

MRSA in the community

• often severe production of Panton Valentin Leukocidin plays a role in cavitary pneumonia

• still, very uncommon

first-line agents for outpatients (otherwise healthy)

• options:

  • amoxicillin

  • doxycycline

alternative agents for outpatients (otherwise healthy)

• options:

  • azithromycin

  • clarithromycin

  • if local S. pneumoniae resistance is < 25%

first-line agents for outpatients WITH co-morbidities

• options:

  • amoxicillin/clauvanate

  • cefpodoxime

  • cefuroxime

• PLUS

  • azithromycin

  • doxycycline

• so for example, a regimen would look like cefpodoxime + cefuroxime

• these regimens are used because these patients are at higher risk for resistant organisms

alternative agents for outpatients WITH co-morbidities

• options

  • levofloxacin

  • moxifloxacin

  • remember, ciprofloxacin is NOT a respiratory antibitotic

fluoroquinolones and macrolides

• remember, these agents can cause QTc prolongation, and as such, should be used with caution and avoided if possible

  • in patients with contraindications to these agents, doxycycline can be used alternatively

first-line agents for non-ICU inpatients with NO MRSA/P. aeruginosa risk factors

• options:

  • IV ß-lactam + azithromycin

alternative agents for non-ICU inpatients with NO MRSA/P. aeruginosa risk factors

• options:

  • levofloxacin

  • moxifloxacin

  • IV ß-lactam + doxycycline

first-line agents for non-ICU inpatients with recent antibiotic exposure

• options:

  • IV ß-lactam + azithromycin

first-line agents for non-ICU inpatients with recent MRSA infection

• options:

  • add MRSA coverage to CAP regimen

first-line agents for non-ICU inpatients with recent P. aeruginosa infection

• options:

  • change IV ß-lactam to anti-pseudomonal IV ß-lactam (cefepime)

IV ß-lactams

• options:

  • ceftriaxone

  • ceftaroline

  • cefotaxime

  • ampicillin-sulbactam

first-line agents for ICU inpatients with NO MRSA/P. aeruginosa risk factors

• options:

  • IV ß-lactam + azithromycin

alternative agents for ICU inpatients with NO MRSA/P. aeruginosa risk factors

• options:

  • IV ß-lactam + levofloxacin OR moxifloxacin

first-line agents for ICU inpatients with MRSA/P. aeruginosa risk factors

• options:

  • vancomycin + anti-pseudomonal ß-lactam

  • linezolid + anti-pseudomonal ß-lactam

MRSA coverage

• patients receiving MRSA/P. aeruginosa coverage can be safely de-escalated at 48 hours if cultures are not positive for that organism

• additionally, MRSA therapy can be discontinued with negative MSRA nasal PCR

MRSA nasal PCR

• detects nasal colonization of S. aureus

• it’s an excellent negative predictor of MSRA pneumonia

  • negative result = unlikely MRSA infection and can safely discontinue MRSA therapy

• however, it’s a poor positive predictor

  • positive result = idk bruh

  • no need to escalate therapy, can just continue

additional diagnostic testing

• pneumococcal urinary antigen test generally is not recommended

  • only in patient with severe pneumonia (ie. in the ICU)

• Legionella urinary antigen test is generally not recommended either, except:

  • patients with severe (ICU) pneumonia

  • indicated by epidemiologic factors such as local outbreak or recent travel

  • most patients coming from the community won’t have this, but if it’s becoming more prevalent in a nursing home population, there’s an issue

pneumococcal urinary antigen test

• detects portion of the cell wall of bacteria

• high specificity (>94%) with varied sensitivity (>65%)

  • predictive values increase with bacteremia

Legionella urinary antigen test

• a specific antigen immunoassay

• only detects serotype 1 (most common serotype)

• upp to 99% specificity

• may persist following adequate treatment (weeks to months)

Legionella pneumophilia infection

• increasing in prevalence in recent years

• generally results from environmental exposures (eg. contaminated water systems)

• may be associated with:

  • muscle aches

  • non-productive cough

  • rapid progression

  • high fevers

• CXR typically shows patchy infiltrates or nodular infiltrates

• frequently, these patients have a severe presentation

aspiration pneumonia/pneomonitis

• the entry of something other than air into the lungs, eg spit or even food

• occurs more commonly in elderly and patients admitted from nursing homes/long-term care facilities

• difficult to distinguish between pneumonia and pneumonitis

  • inflammation without infection

• treatment does NOT require additional anaerobic coverage beyond a typical CAP regimen

  • mouth anaerobes are typically gram-positive and respond to ß-lactams

treatment duration

• generally, 5-7 days is appropriate (unless there’s resistance, or slow to improve)

  • patient should be afebrile for 48-72 hours prior to discontinuation of antibiotics

  • FQs and macrolides should NOT exceed 5 days of treatment!

  • new data suggests that treatment as short as 3 days may be appropriate for some patients

• HAP/VAP guidelines recommend no more than 7 days unless patients are not responding to treatment

3-day treatment

• suitable for patients that are not critically ill, immunocompetent, and clinically stable after 3 days of ß-lactam treatment

• key exclusions:

  • aspiration pneumonia

  • legionellosis

  • atypical pathogens

  • lung abscess

  • massive pleural effusion

directed therapy

• often, no pathogen is identified, and empiric therapy is continued for the duration

  • culturing is not super helpful most of the time → just continue with empiric therapy

• this type of treatment approach is based on susceptabilities, when available

• for Legionella: lexofloxacin or azithromycin

recently approved drugs for CAP

• lefamulin

• omadacycline

• delafloxacin

  • these agents appear to be effective for PORT class 4

  • has a potential role for patients with allergies/intolerance to other agents

  • have high rates of susceptibility for common CAP pathogens

  • much more expensive