section name header

Basic Information ⬇

AUTHOR: Jorge Mercado, MD

Definition

Pneumonia is defined as inflammation of the pulmonary parenchyma caused by an infectious agent (in this case, bacteria). It can be further categorized as community-acquired or health care-associated. The definition of community-acquired pneumonia (CAP), traditionally referred to alveolar infection that develops in the outpatient setting or within 48 hr of admission, now includes patients previously categorized as having health care-associated pneumonia (HCAP) since the microbiology and treatment is similar. Hospital-acquired pneumonia (HAP) is pneumonia occurring ≥48 h after hospital admission and not incubating at the time of admission.1

Synonyms

Community-acquired pneumonia

CAP

Health care-associated pneumonia

Hospital-acquired pneumonia

ICD-10CM CODES
J15.9Unspecified bacterial pneumonia
J13Pneumonia due to Streptococcus pneumoniae
J15.1Pneumonia due to Pseudomonas
J15.20Pneumonia due to staphylococcus, unspecified
J15.0Pneumonia due to Klebsiella pneumoniae
J14Pneumonia due to Haemophilus influenzae
J15.211Pneumonia due to methicillin-susceptible Staphylococcus aureus
J15.212Pneumonia due to methicillin-resistant Staphylococcus aureus
J15.6Pneumonia due to other aerobic gram-negative bacteria
J15.7Pneumonia due to Mycoplasma pneumoniae
Epidemiology & Demographics

  • The annual incidence of pneumonia in the U.S. is 24.8 cases per 10,000 adults, with the highest rates among adults between 65 to 79 yr of age (63 cases per 10,000 adults) and those >80 yr old (164.3 cases per 10,000 adults). Health care expenditures for CAP exceed $10 billion annually.
  • Hospitalization rate for pneumonia is 15% to 20%. Incidence is highest among the oldest adults.
  • In 2017, the tenth leading cause of mortality in the U.S. reported by the National Center for Health Statistics was influenza and pneumonia together. Deaths per 100,000 population: 15.1.
  • Globally, Streptococcus pneumoniae (pneumococcus) is the most common pathogen causing community-acquired pneumonia.
Physical Findings & Clinical Presentation

  • Fever, tachypnea, chills, tachycardia, cough, and sometimes pleuritic chest pain (especially if a pleural effusion is present)
  • Presentation varies with the cause of pneumonia, the patient’s age, and the clinical situation:
    1. Patients with streptococcal pneumonia usually present with high fever, chills, atypical chest pain, cough, and copious production of rusty-appearing purulent sputum. Pleurisy in the setting of parapneumonic effusions can also occur. Potential complications include bacteremia, empyema, and distant infections (e.g., meningitis).
    2. Mycoplasma pneumoniae: Insidious onset; headache; dry, paroxysmal cough that is worse at night; myalgias; malaise; sore throat; extrapulmonary manifestations (e.g., erythema multiforme, aseptic meningitis, urticaria, erythema nodosum) may be present. (See chapter on “Mycoplasma Pneumonia.”)
    3. Chlamydia pneumoniae: Persistent, nonproductive cough, low-grade fever, headache, sore throat.
    4. Legionella pneumophila: High fever, mild cough, mental status change, myalgias, diarrhea, respiratory failure. (See chapter on “Legionnaires Disease.”)
    5. MRSA pneumonia: Often preceded by influenza, may present with shock and respiratory failure.
    6. Elderly or immunocompromised hosts with pneumonia may initially present with only minimal symptoms (e.g., low-grade fever, confusion); respiratory and nonrespiratory symptoms are less commonly reported by older patients with pneumonia.
  • In general, auscultation of lungs in patients with pneumonia reveals crackles/rhonchi and diminished breath sounds. Egophany may also be present.
  • Dullness on percussion or decreased fremitus may be an indication that a pleural effusion is present.
Etiology2

  • Table 1 summarizes common pathogens causing CAP
  • Streptococcus pneumoniae (5% to 15% of hospitalized CAP cases): Incidence has been declining due to widespread use of pneumococcal vaccination and reduced rate of cigarette smoking
  • Haemophilus influenzae (3% to 10% of CAP cases)
  • L. pneumophila (1% to 5% of adult pneumonias) (2% to 8% of CAP cases)
  • Klebsiella pneumoniae, Pseudomonas aeruginosa, Escherichia coli
  • Staphylococcus aureus (3% to 5% of CAP cases)
  • Atypical organisms such as Mycoplasma pneumoniae, Chlamydia pneumoniae, and Legionella pneumophila implicated in up to 40% of cases of CAP
  • Gram-negative organisms cause >80% of nosocomial pneumonias
  • Predisposing factors (Table 2 and Table 3):
    1. Influenza infection is one of the important predisposing factors to S. pneumoniae and S. aureus pneumonia
    2. Chronic obstructive pulmonary disease: H. influenzae, S. pneumoniae, Legionella, Moraxella catarrhalis
    3. Seizures: Aspiration pneumonia
    4. Compromised hosts: Legionella, gram-negative organisms
    5. Alcoholism: K. pneumoniae, S. pneumoniae, H. influenzae
    6. HIV: S. pneumoniae
    7. IV drug addicts with right-sided bacterial endocarditis: S. aureus
    8. Older patient with comorbid diseases: C. pneumoniae

TABLE 2 Risk Factors for Developing Severe Community-Acquired Pneumonia

Advanced age
Comorbid illness (e.g., chronic respiratory illness, cardiovascular disease, diabetes mellitus, neurologic illness, renal insufficiency, malignancy)
Cigarette smoking
Alcohol abuse
Absence of antibiotic therapy before hospitalization
Failure to contain infection to its initial site of entry
Immune suppression
Genetic polymorphisms in the immune response

From Vincent JL et al: Textbook of critical care, ed 7, Philadelphia, 2017, Elsevier.

TABLE 3 Clinical Associations With Specific Pathogens

ConditionCommonly Encountered Pathogens
AlcoholismStreptococcus pneumoniae (including penicillin-resistant), anaerobes, gram-negative bacilli (possibly Klebsiella pneumoniae), tuberculosis
Chronic obstructive pulmonary disease/current or former smokerS. pneumoniae, Haemophilus influenzae, Moraxella catarrhalis
Residence in nursing homeS. pneumoniae, gram-negative bacilli, H. influenzae, Staphylococcus aureus, Chlamydophila pneumoniae; consider M. tuberculosis. Consider anaerobes, but these are less common
Poor dental hygieneAnaerobes
Bat exposureHistoplasma capsulatum
Bird exposureChlamydophila psittaci, Cryptococcus neoformans, H. capsulatum
Rabbit exposureFrancisella tularensis
Travel to southwestern United StatesCoccidioidomycosis; hantavirus in selected areas
Exposure to farm animals or parturient catsCoxiella burnetii (Q fever)
Postinfluenza pneumoniaS. pneumoniae, S. aureus (including the community-acquired strain of methicillin-resistant S. aureus), H. influenzae
Structural disease of the lung (e.g., bronchiectasis, cystic fibrosis)Pseudomonas aeruginosa, Pseudomonas cepacia, or S. aureus
Sickle cell disease, aspleniaPneumococcus, H. influenzae
Suspected bioterrorismAnthrax, tularemia, plague
Travel to AsiaSevere acute respiratory syndrome, tuberculosis, melioidosis

From Vincent JL et al: Textbook of critical care, ed 7, Philadelphia, 2017, Elsevier.

TABLE 1 Common Pathogens Causing Community-Acquired Pneumonia

Inpatient, With No Cardiopulmonary Disease or Modifying Factors
Streptococcus pneumoniae, Haemophilus influenzae, Mycoplasma pneumoniae, Chlamydophila pneumoniae, mixed infection (bacteria plus atypical pathogen), viruses (including influenza), Legionella spp., and others (Mycobacterium tuberculosis, endemic fungi, Pneumocystis jirovecii)
Inpatient, With Cardiopulmonary Disease and/or Modifying Factors
All of the above, but drug-resistant S. pneumoniae (DRSP) and enteric gram-negative organisms are more of a concern
Severe Community-Acquired Pneumonia, With No Risks for Pseudomonas Aeruginosa
S. pneumoniae (including DRSP), Legionella spp., H. influenzae, enteric gram-negative bacilli, Staphylococcus aureus (including methicillin-resistant S. aureus), M. pneumoniae, respiratory viruses (including influenza), others (C. pneumoniae, M. tuberculosis, endemic fungi)
Severe CAP, With Risks for P. Aeruginosa
All of the pathogens above plus P. aeruginosa

From Vincent JL et al: Textbook of critical care, ed 7, Philadelphia, 2017, Elsevier.

Diagnosis ⬆ ⬇

Differential Diagnosis

  • Viral pneumonias (see chapter on “Viral Pneumonia”)
  • Aspiration pneumonia (see chapter on “Aspiration Pneumonia”)
  • Exacerbation of chronic bronchitis
  • Pulmonary embolism or infarction (see chapter on “Pulmonary Embolism”)
  • Lung neoplasm
  • Bronchiolitis
  • Sarcoidosis (see chapter on “Sarcoidosis”)
  • Hypersensitivity pneumonitis (see chapter on “Hypersensitivity Pneumonitis”)
  • Pulmonary edema
  • Drug-induced lung injury
  • Fungal pneumonias
  • Parasitic pneumonias
  • Atypical pneumonia
  • Tuberculosis
  • Cryptogenic organizing pneumonia
Workup

Diagnostic testing for CAP is summarized in Table 4. Useful tools for assessing severity of illness are the CURB-65 (see “Disposition”) and Pneumonia Severity Index (Fig. 1 and Box 1). Poor prognostic indicators are hypotension (SBP <90 or DBP <60), respiratory rate >30/min, fever (>40° C; 104° F), or hypothermia (<35° C; 95° F). None of these indices is as valuable as clinical judgment.3

BOX 1 Severe Pneumonia: Diagnostic Criteria∗

Major Criteria

Invasive mechanical ventilation

Use of vasopressors to maintain blood pressure

Minor Criteria

Respiratory rate ≥30 breaths/min

Multilobar infiltrates

New-onset confusion/disorientation

Uremia (BUN >20 mg/dl)

Leukopenia (WBC count <4000 cells/μL)

PaO2/FIO2 ratio ≥250

Thrombocytopenia (platelet count <100,000 cells/μL)

Hypothermia (core temperature <36° C; 96.8° F)

Hypotension requiring aggressive fluid resuscitation

From Parrillo JE, Dellinger RP: Critical care medicine: principles of diagnosis and management in the adult, ed 4, Philadelphia, 2014, Saunders.

TABLE 4 Diagnostic Testing for Community-Acquired Pneumonia

TestSensitivitySpecificityComment
Chest radiograph65%-85%85%-95%Computed tomography is more sensitive to infiltrates. Recommended for all patients.
Computed tomographyGold standardNot infection specificShould not be performed routinely but helpful to identify cavitation and loculated pleural fluid. Recommended in the evaluation of nonresponding patients.
Blood cultures10%-20%High when positiveUsually shows pneumococcus (in 50%-80% of positive samples) and defines antibiotic susceptibility. Recommended in patients with severe CAP, particularly if not on antibiotic therapy at the time of testing.
Sputum Gram stain40%-100% depending on criteria0%-100% depending on criteriaCan correlate with sputum culture to define predominant organism and can be used to identify unsuspected pathogens. Recommended if sputum culture is obtained. May not be able to narrow empiric therapy choices.
Sputum cultureUse if suspect drug-resistant or unusual pathogen, but a positive result cannot differentiate colonization from infection. Obtain via tracheal aspirate in all intubated patients.
Oximetry or arterial blood gasDefine both severity of infection and need for oxygen; if hypercarbia is suspected, a blood gas sample is needed. Recommended in severe community-acquired pneumonia.
Serologic testing for Legionella, Chlamydophila pneumoniae, Mycobacterium pneumoniae, virusesAccurate, but usually requires acute and convalescent titers collected 4 to 6 wk apart. Not routinely recommended.
Legionella urinary antigen50%-80%Specific to serogroup 1, but the best acute diagnostic test for Legionella.
Pneumococcal urinary antigen70%-100%80%False positives if recent pneumococcal infection. Can increase sensitivity with concentrated urine.
Serum procalcitoninNot a routine test, but if performed, should be measured with the highly sensitive Kryptor assay. May help guide duration of therapy and need for ICU admission.

From Vincent JL et al: Textbook of critical care, ed 7, Philadelphia, 2017, Elsevier.

Figure 1 The pneumonia severity index.

!!flowchart!!

BP, Blood pressure; O2, oxygen; PO2, partial pressure of oxygen.

From Sellke FW et al: Sabiston & Spencer surgery of the chest, ed 9, Philadelphia, 2016, Elsevier.

Laboratory Tests

  • Complete blood count with differential; white blood cell count is elevated, usually with left shift or the presence of bandemia
  • Sputum culture should be obtained, ideally prior to initiation of antibiotics, in hospitalized patients or if drug-resistant or unusual pathogen is suspected
  • Blood cultures (hospitalized patients only): Positive in approximately 20% of cases of pneumococcal pneumonia
  • Pneumococcal urinary antigen test can be used to detect the C-polysaccharide antigen of S. pneumoniae (70% sensitivity). It is a useful tool in the treatment of hospitalized adult patients with CAP4
  • When suspecting Legionella, a respiratory specimen culture on special media and/or a urinary antigen should be requested
  • Serologic testing for HIV in selected patients
  • Serum electrolytes (hyponatremia in suspected Legionella pneumonia), BUN, creatinine
  • Nasopharyngeal swab for rapid and PCR testing for influenza
  • Serum procalcitonin level: Often used to distinguish pneumonia from heart failure in patients presenting to the emergency department with acute dyspnea. The procalcitonin level is significantly higher in patients with pneumonia than in those without. However, serum procalcitonin should not be used to determine initiation or duration of antibiotic therapy in patients with radiographically confirmed CAP unless antibiotic therapy is being extended beyond 5 to 7 days. Recent trials regarding procalcitonin-guided use of antibiotics for lower respiratory tract infections did not result in less use of antibiotics than did usual care among patients with suspected lower respiratory tract infection5
  • Pulse oximetry or arterial blood gases: Hypoxemia with partial pressure of oxygen <60 mm Hg while the patient is breathing room air, a standard criterion for hospital admission
  • Table 5 summarizes recommended microbiologic evaluation in patients with community acquired pneumonia
  • Fig. 2 illustrates an algorithm for the diagnosis and treatment of nosocomial pneumonia
  • Ventilator-associated pneumonia: Table 6 and Fig. E3 summarizes a proposed strategy for managing antimicrobial therapy in patients with ventilator-associated pneumonia

TABLE 6 Proposed Strategy for Managing Antimicrobial Therapy in Patients With Ventilator-Associated Pneumonia

Proposed StrategyRationale
Step 1: Start therapy using broad-spectrum antibioticsDue to the emergence of multiresistant GNB, such as P. aeruginosa and ESBL-producing GNB, and the increasing role of MRSA, empirical treatment with broad-spectrum antibiotics is justified in most patients with a clinical suspicion of VAP.
Step 2: Stop therapy if the diagnosis of infection becomes unlikelyThe goal is to ensure that ICU patients with true bacterial infection receive immediate appropriate treatment. However, this can result in more patients receiving antimicrobial therapy than necessary because clinical signs of infection are nonspecific.
Step 3: Use narrower spectrum antibiotics once the etiologic agent is identifiedFor many patients with VAP, including those with late-onset infection, therapy can be narrowed once the results of respiratory tract and blood cultures are available, either because an anticipated organism (e.g., P. aeruginosa and Acinetobacter spp or MRSA) was not recovered, or because the organism isolated is sensitive to a more narrow-spectrum antibiotic than used in the initial regimen.
Step 4: Use pharmacokinetic-pharmacodynamic data to optimize treatmentClinical and bacteriologic outcomes can be improved by optimizing the therapeutic regimen according to pharmacokinetic and pharmacodynamic properties of the agents selected for treatment.
Step 5: Switch to monotherapy on days 3 to 5There are no clinical benefits to using a regimen combining two antibiotics for more than days 3 to 5, provided that initial therapy was appropriate, the clinical course appears favorable, and microbiologic data do not point to a very difficult-to-treat microorganism.
Step 6: Shorten the duration of therapyReducing duration of therapy in patients with VAP has led to good outcomes with less antibiotic use. Prolonged therapy leads to colonization with antibiotic-resistant bacteria, which may precede a recurrent episode of VAP.

ESBL, Extended-spectrum β-lactamase; GNB, gram-negative bacteria; ICU, intensive care unit; MRSA, methicillin-resistant Staphylococcus aureus; VAP, ventilator-associated pneumonia.

From Broaddus VC et al: Murray & Nadel’s textbook of respiratory medicine, ed 7, Philadelphia, 2022, Elsevier.

Figure 2 A suggested algorithm for the diagnosis and treatment of nosocomial pneumonia.

!!flowchart!!

From Parrillo JE, Dellinger RP: Critical care medicine, principles of diagnosis and management in the adult, ed 4, Philadelphia, 2014, Elsevier.

TABLE 5 Recommended Microbiologic Evaluation in Patients With Community-Acquired Pneumonia

Patients Who do not Require Hospitalization
None∗
Patients Who Require Hospitalization
Two sets of blood cultures (obtained prior to antibiotics) in selected patients
Gram stain and culture of a valid sputum sample in selected patients
Urinary antigen test for detection of Legionella pneumophila (in endemic areas or during outbreaks)
Stain for acid-fast bacilli and culture of sputum (if tuberculosis is suggested by clinical history or radiologic findings)
Fungal stain and culture of sputum, and fungal serologies (if infection by an endemic fungus is suggested by the clinical history or radiologic findings)
Sputum examination for Pneumocystis jirovecii (if suggested by clinical history, HIV infection, or radiologic findings)
Nucleic acid amplification tests for Mycoplasma pneumoniae, Chlamydophila pneumoniae, Chlamydophila psittaci, Coxiella burnetii, Legionella species, respiratory viruses (in endemic areas or during outbreaks) and other agents (e.g., Streptococcus pneumoniae) if available
Culture and microscopic evaluation of pleural fluid (if significant fluid is present)
Additional Tests for Patients Who Require Treatment in an ICU
Gram stain and culture of endotracheal aspirate or bronchoscopically obtained specimens using a protected specimen brush or BAL

BAL, Bronchoalveolar lavage; ICU, intensive care unit.

∗Gram stain and culture should be strongly considered in patients with risk factors for infection by an antimicrobial-resistant organism or unusual pathogen.

From Broaddus VC et al: Murray & Nadel’s textbook of respiratory medicine, ed 7, Philadelphia, 2022, Elsevier.

Figure E3 The invasive diagnostic strategy.

!!flowchart!!

Diagnostic and therapeutic strategy applied to patients with a clinical suspicion of ventilator-associated pneumonia (VAP) managed according to the invasive strategy. ATS, American Thoracic Society; BAL, bronchoalveolar lavage; IDSA, Infectious Diseases Society of America; PSB, protected specimen brush.

From Broaddus VC et al: Murray & Nadel’s textbook of respiratory medicine, ed 7, Philadelphia, 2022, Elsevier.

Imaging Studies

Chest x-ray (PA and lateral) (Fig. 4): Findings vary with the stage and type of pneumonia and the hydration of the patient:

  • Classically, pneumococcal pneumonia presents with a segmental lobe infiltrate (Fig. E5).
  • Diffuse infiltrates on chest x-ray can be seen with L. pneumophila (Fig. 6), M. pneumoniae, viral pneumonias, P. jirovecii (carinii), miliary tuberculosis, aspiration, aspergillosis.
  • An initial chest x-ray is also useful to rule out the presence of complications (pneumothorax, empyema, abscesses).

Figure 6 Chest radiograph of a patient with extensive gram-negative pneumonia.

Note the patchy infiltrates throughout both lungs, which are more prominent on the right.

From Weinberger SE: Principles of pulmonary medicine, ed 7, Philadelphia, 2019, Elsevier.

Figure 4 Posteroanterior (A) and Lateral (B) Chest Radiographs Show Lobar Pneumonia (Probably Caused by Streptococcus Pneumoniae) Affecting the Right Middle Lobe

In (A) the arrow points to a minor fissure, which defines the upper border of the middle lobe. In (B) the long arrow points to a minor fissure, and the short arrow points to a major fissure.

From Weinberger SE: Principles of pulmonary medicine, ed 7, Philadelphia, 2019, Elsevier.

Figure E5 A, Pneumococcal Pneumonia, Right Middle Lobe

B, Gram-Positive Diplococci (Sputum).

From Ryan ET et al: Hunter’s tropical medicine and emerging infectious diseases, ed 10, Philadelphia, 2019, Elsevier.

∗According to ATS/IDSA 2007 guidelines.

Treatment ⬆ ⬇

Nonpharmacologic Therapy

  • Avoidance of tobacco use
  • Oxygen to maintain partial oxygen pressure in arterial blood >60 mm Hg or oxygen saturation >88% in COPD patients and >92% in non-COPD patients
  • IV hydration, correction of dehydration
  • Assisted ventilation in patients with significant respiratory failure
Acute General Rx

  • Antibiotic therapy should be based on clinical, radiographic, and laboratory evaluation.6-8 Empiric therapy regimens for community-acquired pneumonia are summarized in Tables 7 and 8.
  • Macrolides (azithromycin or clarithromycin) or doxycycline can be used for empiric outpatient treatment of CAP as long as the patient has not received antibiotics within the past 3 mo and does not reside in a community in which the prevalence of macrolide resistance is high.9 Updated guidelines from the American Thoracic Society and Infectious Diseases Society of America have added amoxicillin as a first-line agent for healthy adult outpatients with CAP.10 The treatment of choice in suspected Legionella pneumonia is either a quinolone (e.g., moxifloxacin) or a macrolide (e.g., azithromycin) antibiotic. A beta-lactam antibiotic is usually added to macrolides.
  • In the hospital setting, patients not requiring ICU care can be treated empirically with a second- or third-generation cephalosporin (ceftriaxone, cefotaxime, or cefuroxime) plus a macrolide (azithromycin or clarithromycin) or doxycycline. An antipseudomonal quinolone (levofloxacin or moxifloxacin) can be substituted in place of the macrolide or doxycycline.11
  • Empiric therapy in ICU patients: IV beta-lactam (ceftriaxone, cefotaxime, ampicillin-sulbactam) plus an IV quinolone (levofloxacin, moxifloxacin) or IV azithromycin.
  • In hospitalized patients at risk for P. aeruginosa infection, empiric treatment should consist of an antipseudomonal beta-lactam (meropenem, doripenem, imipenem, or piperacillin-tazobactam) with or without a second antipseudomonal agent such as an aminoglycoside or an antipseudomonal quinolone.
  • In patients with suspected methicillin-resistant S. aureus,vancomycin or linezolid is effective.
  • Corticosteroids: Clinical trials evaluating adjunctive use of corticosteroids in severe CAP have produced mixed results. There is no evidence that adjunctive use of corticosteroids improves outcomes in mild to moderate CAP. Guidelines advise against adjunctive treatment of CAP with corticosteroids except in patients with septic shock that is refractory to fluid resuscitation and vasopressor support.12,13
  • Duration of antibiotic treatment ranges from 5 to 14 days. Trials have shown that in adults hospitalized with CAP, stopping antibiotic treatment after 5 days in clinically stable patients is reasonable and noninferior to usual care.8,14 Hematogenous Staphylococcus infection, abscesses, and cavitary lesions might require prolonged antibiotic therapy, sometimes until radiologic resolution is documented.

TABLE 7 Guidelines for Empirical Oral Outpatient Treatment of Immunocompetent Adults With Community-Acquired Pneumonia

ATS/IDSA
No modifying factorsa: Amoxicillin,b doxycycline or advanced macrolide if S. pneumoniae macrolide resistance <25%c,d
Comorbiditiesa: Beta-lactam,e macrolidef or doxycycline,d or fluoroquinoloneg alone
BTS
Primary: Amoxicillin
Alternatives: Clarithromycin or doxycycline
ERs/ESCMID
Amoxicillin or doxycycline with macrolide as alternative if low levels of resistance
DRSPTWG
Primary: Amoxicillin, amoxicillin-clavulanate, cefuroxime, doxycycline, macrolide (if low rate of resistance)
Alternative: Fluoroquinoloneh

ATS/IDSA, American Thoracic Society/Infectious Diseases Society of America; BTS, British Thoracic Society; DRSPTWG, Drug-Resistant Streptococcus pneumoniae Therapeutic Working Group; ERS/ESCMID, European Respiratory Society and European Society for Clinical Microbiology and Infectious Diseases.

a American Thoracic Society/Infectious Disease Society of America comorbidities (modifying factors) include chronic heart, lung, liver or kidney disease; diabetes; asplenia; alcoholism; and malignancy.

b Amoxicillin 1 g q8h, doxycycline 100 mg q12h, azithromycin 500 mg on first day then 250 mg/day, clarithromycin 500 mg q8h, or clarithromycin extended release 1000 mg/day.

c Advanced macrolides are azithromycin and clarithromycin.

d Second-choice agent.

e Amoxicillin-clavulanate (500 mg amoxicillin plus 125 mg clavulanate q8h, 875 mg amoxicillin plus 125 mg clavulanate q12h or 2 g amoxicillin plus 125 mg clavulanic acid q12h), cefpodoxime, cefprozil, or cefuroxime.

f Because of increasing macrolide resistance, erythromycin cannot be relied upon to ensure coverage of beta-lactamase-producing Haemophilus influenzae. A combination of a beta-lactam/beta-lactamase inhibitor is preferred.

g Antipneumococcal fluoroquinolones include levofloxacin, and moxifloxacin.

h Levofloxacin or moxifloxacin.

From Broaddus VC et al: Murray & Nadel’s textbook of respiratory medicine, ed 7, Philadelphia, 2022, Elsevier.

TABLE 8 Guidelines for Empirical Parenteral Inpatient Treatment of Immunocompetent Adults With Community-Acquired Pneumonia

Mild to Moderate Disease
ATS/IDSA
  • Primary:c Ampicillin and sulbactam, cefotaxime, ceftriaxone, or ceftaroline with azithromycin or clarithromycin
  • Alternative: Fluoroquinolonea alone or, if history of prior respiratory isolation of MRSAd or Pseudomonas aeruginosa,e treatment to cover these agents
BTS
  • Mild: Oral amoxicillin. Alternatives parenteral amoxicillin or benzylpenicillin or clarithromycin
  • Moderate: Oral amoxicillin and clarithromycin (can consider clarithromycin monotherapy if prior therapy with amoxicillin)
  • Alternative if unable to take oral medication: Parenteral amoxicillin or benzylpenicillin plus clarithromycin (if intolerant of penicillin but able to take a cephalosporin parenteral second- or third-generation cephalosporin plus clarithromycin)
  • Alternative: If unable to take penicillin or macrolide,b oral doxycycline, or if not able to take any of these, a respiratory fluoroquinolonea
ERS/ESCMID
  • Aminopenicillin, aminopenicillin with beta-lactamase inhibitor, penicillin, cefotaxime, ceftriaxone with or without macrolideb
  • Respiratory fluoroquinolone alonea
DRSPTWG
  • Primary: Cefuroxime, cefotaxime, ceftriaxone, or ampicillin-sulbactam; macrolideb
  • Alternative: Fluoroquinolonea
Severe Disease
ATS/IDSA
  • Primaryc: Ampicillin and sulbactam, cefotaxime, ceftriaxone, or ceftaroline with azithromycin or clarithromycin
  • Alternative: Broad-spectrum β-lactam as for primary with fluoroquinolonea or, if history of prior respiratory isolation or prior hospitalization with parenteral antimicrobials within 90 days in setting of locally validated risk factors for MRSAd or P. aeruginosa,e treatment to cover these agents
BTS
  • Primary: Amoxicillin/clavulanate (or if penicillin intolerant cefuroxime, cefotaxime, or ceftriaxone) plus macrolideb
ERS/ESCMID
  • Cefotaxime or ceftriaxone plus macrolide or respiratory fluoroquinolone
  • Alternative: Respiratory fluoroquinolone alone if no sepsis
DRSPTWG
  • Primary: Ceftriaxone or cefotaxime, macrolide;b or ceftriaxone or cefotaxime, fluoroquinolonea
  • Alternative (with caution): Fluoroquinolonea

ATS/IDSA, American Thoracic Society/Infectious Diseases Society of America; BTS, British Thoracic Society; DRSPTWG, Drug-Resistant Streptococcus pneumoniae Therapeutic Working Group; ERS/ESCMID, European Respiratory Society and European Society for Clinical Microbiology and Infectious Diseases.

a Antipneumococcal fluoroquinolones include levofloxacin 750 mg/day and moxifloxacin 400 mg/day.

b Advanced macrolides are azithromycin and clarithromycin.

c Ampicillin and sulbactam 1.5-3 g q6h, cefotaxime 1-2 g q8h, ceftriaxone 1-2 g/day, or ceftaroline 600 mg q12h and azithromycin 500 mg/day or 500 mg on day 1 and 250 mg once a day thereafter for mild disease or clarithromycin 500 mg bid.

d Antistaphylococcal treatments include vancomycin (15 mg/kg q12h, adjust based on levels) or linezolid (600 mg q12h).

e Antipseudomonal β-lactams include piperacillin-tazobactam (4.5 g q6h), cefepime (2 g q8h), ceftazidime (2 g q8h), imipenem (500 mg q6h), meropenem (1 g q8h), or aztreonam (2 g q8h).

f If ceftazidime used should be combined with penicillin to ensure coverage of pneumococci per ERS/ESCMID guideline.

g Recommendation to double cover P. aeruginosa with both a β-lactam and either ciprofloxacin or an aminoglycoside per ERS/ESCMID guideline.

From Broaddus VC et al: Murray & Nadel’s textbook of respiratory medicine, ed 7, Philadelphia, 2022, Elsevier.

Chronic Rx

Parapneumonic effusion and empyema can be managed with chest tube placement for drainage. (See chapters on “Pleural Effusion” and “Empyema.”)

Disposition

Risk factors for a poor outcome from CAP are summarized in Table 9. Indications for hospital admission are:

  • Hypoxemia (oxygen saturation <90% while patient is breathing room air)
  • Hemodynamic instability
  • Inability to tolerate medications
  • Active coexisting condition requiring hospitalization. A criterion often used to determine hospital admission is known as the “CURB-65”:Confusion, BUN >19.6 mg/dl, Respiratory rate >30 breaths/min, systolic BP <90 mg Hg, and diastolic BP ≤60 mm Hg, age ≥65. Patients are generally admitted to the hospital if they fulfill two or more criteria and to the ICU if they have three or more criteria.15

TABLE 9 Risk Factors for a Poor Outcome From Community-Acquired Pneumonia

Patient-Related Factors
Male sex
Absence of pleuritic chest pain
Nonclassic clinical presentation
Neoplastic illness
Neurologic illness
Age >65 yr old
Family history of severe pneumonia or death from sepsis
Abnormal Physical Findings
Respiratory rate >30 breaths/min on admission
Systolic (<90 mm Hg) or diastolic (<60 mm Hg) hypotension
Tachycardia (>125 beats/min)
High fever (>40° C; 104° F) or afebrile
Confusion
Laboratory Abnormalities
Blood urea nitrogen >19.6 mg/dl
Leukocytosis or leukopenia (<4000/mm3)
Multilobar radiographic abnormalities
Rapidly progressive radiographic abnormalities during therapy
Bacteremia
Hyponatremia (<130 mmol/L)
Multiple organ failure
Respiratory failure
Hypoalbuminemia
Thrombocytopenia (<100,000/mm3) or thrombocytosis (>400,000/mm3)
Arterial pH <7.35
Pleural effusion
Pathogen-Related Factors
High-risk organisms
Type III pneumococcus, Staphylococcus aureus, gram-negative bacilli (including Pseudomonas aeruginosa), aspiration organisms, severe acute respiratory syndrome
Possibly high levels of penicillin resistance (minimal inhibitory concentration of at least 4 mg/L) in pneumococcus
Therapy-Related Factors
Delay in initial antibiotic therapy (more than 4 h)
Initial therapy with inappropriate antibiotic therapy
Failure to have a clinical response to empiric therapy within 72 h

From Vincent JL et al: Textbook of critical care, ed 7, Philadelphia, 2017, Elsevier.

Pearls & Considerations ⬆ ⬇

Comments

  • “Recurrent pneumonia”: Table 10 summarizes the differential diagnosis of recurrent pneumonia.
  • Causes of slowly resolving or nonresolving pneumonia:
    1. Difficult to treat infections: Viral pneumonia, Legionella, pneumococci or staphylococci with impaired host response, tuberculosis, atypical mycobacteria, nocardia, or fungi
    2. Neoplasm: Lung, lymphoma, metastasis
    3. Congestive heart failure
    4. Pulmonary embolism
    5. Immunologic or idiopathic: Cryptogenic organizing pneumonia, eosinophilic pneumonia, granulomatosis with polyangiitis
    6. Drug toxicity (e.g., amiodarone, methotrexate)
  • Repeat imaging: If patients with pneumonia are not improving, repeat thoracic imaging should be done promptly. In those with complete clinical recovery, it is reasonable to wait 6 to 8 wk before repeating the imaging study to document clearing of the infiltrate. However, the latest guidelines (2019 ATS/IDSA) do not recommend follow-up imaging.10

TABLE 10 Differential Diagnosis of Recurrent Pneumonia

Hereditary Disorders
Cystic fibrosis
Sickle cell disease
Disorders of Immunity
Aids
Bruton agammaglobulinemia
Complement deficiency
Selective IgG subclass deficiencies
Common variable immunodeficiency syndrome
Severe combined immunodeficiency syndrome
Disorders of Leukocytes
Chronic granulomatous disease
Hyperimmunoglobulin E syndrome (Job syndrome)
Leukocyte adhesion defect
Disorders of Cilia
Primary ciliary dyskinesia
Kartagener syndrome
Anatomic Disorders
Sequestration
Lobar emphysema
Foreign body
Tracheoesophageal fistula (H type)
Congenital pulmonary airway malformation (cystic adenomatoid malformation)
Gastroesophageal reflux
Bronchiectasis
Aspiration (oropharyngeal incoordination)
Noninfectious Mimics of Pneumonia
Autoimmune diseases (e.g., granulomatosis with polyangiitis)
Hypersensitivity pneumonitis

From Marcdante KJ et al: Nelson essentials of pediatrics, ed 9, Philadelphia, 2023, Elsevier.

Patients may be eligible for lung cancer screening, which should be performed as clinically indicated.

  • Prevention: Four pneumococcal vaccines are currently available: The 23-valent pneumococcal polysaccharides vaccine (PPSV23), the pneumococcal conjugated vaccine (PCV13), a new 15 valent PVC (PVC-15), and a 20-valent PVC-20 (Prevnar). The Centers for Disease Control and Prevention (CDC) recommends giving the PCV13 to all children. PPSV20 is recommended as a single dose for all adults >65 yr and any other individual with risk factors (including smoking; alcoholism; diabetes mellitus; or chronic heart, lung, or liver disease). It is administered as a single dose. Eligible adults who have received only PPSV23 may receive either PVC-20 or PVC-15 1yr later. Eligible adults who have received PVC-13 alone should receive a chaser dose of PPSV23 at 1 year later. During the influenza season, patients should also receive influenza vaccination.
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