English
Community-Acquired Pneumonia in Adults
Synopsis
Key Points
- Community-acquired pneumonia is an acute infection of the pulmonary parenchyma that is not acquired in a hospital or other health care facility (patient neither hospitalized nor residing in a long-term care facility for at least 14 days before the onset of symptoms)
- History and physical examination suggest diagnosis, which is confirmed with chest radiography
- Testing for the causative agent (eg, blood and sputum cultures) is not necessary for patients able to be treated as outpatients unless it is likely that treatment or isolation procedures would change based on a suspected unusual pathogen
- When infection with SARS-CoV-2 is suspected or probable, confirm the diagnosis. CDC and WHO recommend polymerase chain reaction as the standard for diagnosis; antigen testing is also widely available
- Select site of care decisions (eg, outpatient, general hospital ward, ICU) on pneumonia severity level, Pneumonia Severity Index score, and CURB-65r1 score. Do not allow these scoring systems to supersede clinical judgment
- Select empiric antibiotic therapy based on the site of care and likely pathogen. Initiate treatment promptly once diagnosis of pneumonia appears likely
- Patients able to be treated as outpatients with no significant risk of drug-resistant Streptococcus pneumoniae should receive first line therapy with a macrolide or second line therapy with doxycycline
- Treat hospitalized (general ward) patients with no significant risk of drug-resistant Streptococcus pneumoniae empirically with respiratory quinolone monotherapy; alternatives include a β-lactam plus a macrolide or a β-lactam plus doxycycline
- First line treatment for patients in ICU is usually a combination therapy of β-lactam plus either azithromycin or a respiratory quinolone
- Additional coverage is required in patients with suspected community-acquired MRSA or Pseudomonas species infections
- Treat all hospitalized patients who test positive for influenza with oseltamivir, regardless of the duration of illness
- Treatment of COVID-19 pneumonia includes infection control measures, routine supportive care, and medications that include antiviral, monoclonal antibody, immunomodulator, and corticosteroid drugs
- Pneumococcal vaccination is indicated in patients aged 65 years or older and aged 19 to 64 years with certain underlying medical conditions or other risk factors;r2influenza vaccination is recommended for all persons aged 6 months or olderr3
- CDC recommends vaccination against COVID-19 for all persons 5 years and older r4
Urgent Action
Pitfalls
- Lack of response to initial therapy may suggest unusual pathogens (eg, Legionella species, fungi, viruses), nosocomial infection, or an infectious complication (eg, empyema, postobstructive pneumonia, abscess)
- False-negative chest radiograph findings may occur, especially in a dehydrated patient; the diagnosis should then primarily depend on history and physical examination findings
- False-negative respiratory sample cultures can occur if obtained after antibiotic therapy has been started r7
Terminology
Clinical Clarification
- Community-acquired pneumonia in adults is acute infection of the pulmonary parenchyma that is not acquired in a hospital or other health care facility (patient neither hospitalized nor residing in a long-term care facility for at least 14 days before the onset of symptoms) r5
Classification
- By cause r8
- Typical
- Classically caused by Streptococcus pneumoniae, but other pyogenic organisms may cause a similar presentation
- Characterized both by cough that produces purulent sputum and by lobar consolidation
- Atypical
- Caused by Mycoplasma pneumoniae, Chlamydia pneumoniae, Legionella species, and respiratory viruses
- Characterized by dry cough and patchy infiltrates
- Typical
- By severity level (and site of care) r6
- Determined by severity of illness scores in combination with clinical judgment and an assessment of the patient’s social support
- Pneumonia that can be managed in an outpatient setting
- Pneumonia that should be managed with inpatient admission (general ward)
- Pneumonia that is severe and should be managed in the ICU
- Severe community-acquired pneumonia (either major criteria or 3 or more minor criteria) r6
- Major criteria
- Need for mechanical ventilation
- Septic shock with need for vasopressors
- Minor criteria
- Respiratory rate of 30 breaths per minute or more
- Ratio of arterial partial pressure of oxygen (PaO₂) to fraction of inspired oxygen (FiO₂) 250 or less
- Multilobar disease
- Leukopenia (leukocyte count less than 4000 cells/μL)
- Uremia (BUN level of 20 mg/dL or higher)
- Confusion or disorientation
- Hypothermia (core temperature lower than 36 °C)
- Thrombocytopenia (platelet count less than 100,000 cells/μL)
- Hypotension requiring aggressive fluid resuscitation
- Major criteria
- Determined by severity of illness scores in combination with clinical judgment and an assessment of the patient’s social support
Diagnosis
Clinical Presentation
History
Physical examination
- General
- Altered mental status may occur with severe pneumonia, especially in older patients c14c15
- Fever (typically over 38.1 °C) c16
- In COVID-19 pneumonia, while fever is typical, it may be low-grade or absent, even in hospitalized patients (especially if vaccinated) r9
- Signs of respiratory distress
- Tachycardia occurs with fever and with severe disease c20
- Other symptoms that may suggest COVID-19 infection:
- Upper respiratory tract symptoms (eg, rhinorrhea, sneezing, sore throat) may be present in up to 20% of symptomatic infections r10
- Alteration in smell and/or taste is less common but highly suggestive r11
- Gastrointestinal symptoms (eg, abdominal pain, nausea, vomiting, diarrhea) are present in 10% to 20% of symptomatic infections r9r10
- Pulmonary
Causes and Risk Factors
Causes
Risk factors and/or associations
Other risk factors/associations
- Hospitalization and treatment with parenteral antibiotics in the preceding 90 days c45
- MRSA, Pseudomonas aeruginosa, resistant gram-negative bacilli
- Documented history of infection with these organisms
- Previously regarded as health care–associated pneumonia, infection due to these bacteria is now considered within the spectrum of community-acquired pneumonia r6
- MRSA, Pseudomonas aeruginosa, resistant gram-negative bacilli
- Chronic obstructive pulmonary disease c46
- Streptococcus pneumoniae
- Haemophilus influenzae
- Moraxella (Branhamella) catarrhalis
- Legionella species
- Bronchiectasis c47
- Pseudomonasaeruginosa
- Burkholderia cepacia
- Staphylococcus aureus
- Cystic fibrosis c48
- Pseudomonas aeruginosa
- Most common organism in adults
- Pseudomonas aeruginosa
- Diabetes c49
- Staphylococcus aureus
- Gram-negative organisms
- Renal disease c50
- Streptococcus pneumoniae
- Early-stage HIV c51
- Streptococcus pneumoniae
- Haemophilus influenzae
- Mycobacterium tuberculosis
- Late-stage HIV
- Pneumocystisjiroveci
- Cryptococcus species
- Histoplasma species
- Medical conditions that result in aspiration of nasopharyngeal secretions, food, liquids, or gastric contents c52
- Alcohol use disorder c53
- Streptococcus pneumoniae
- Klebsiella pneumoniae
- Anaerobic bacteria
- Asplenia c54c55
- Encapsulated organisms
- Streptococcus pneumoniae
- Haemophilus influenzae
- Encapsulated organisms
- Sickle cell disease c56
- Streptococcus pneumonia
- Haemophilus influenzae
- Poor dental hygiene c57
- Anaerobic bacteria
- Smoking c58
- Streptococcus pneumonia
- Haemophilus influenzae
- Moraxella (Branhamella) catarrhalis
- Legionella species
- Travel history c59
- Exposure to animals c62
- Specific comorbid conditions that have been associated with increased risk for severe COVID-19 infection include the following (based on systematic review or meta-analysis): r16
- Chronic kidney disease
- Chronic liver disease
- Chronic lung disease
- Tuberculosis
- Diabetes mellitus, type 1 and type 2
- Malignancy
- Pregnancy and recent pregnancy
- Obesity (BMI of 30 kg/m² or higher)
- Serious cardiac conditions (eg, heart failure, coronary artery disease, cardiomyopathy)
- Smoking, current and former
- Cerebrovascular disease
- Mental health disorders (mood disorders and schizophrenia spectrum disorders)
Diagnostic Procedures
Primary diagnostic tools
- History and physical examination alone may be sufficient to suggest the diagnosis r13c69
- Chest radiography or other chest imaging demonstrating an infiltrate confirms the diagnosis r13
- Testing to identify a causative agent is not routine for outpatients, except in certain circumstances r13
- Testing to identify a causative agent (eg, polymerase chain reaction, blood cultures, sputum testing, pleural fluid testing, antigen testing, and/or cultures for fungi and tuberculosis, depending on history and clinical findings) is indicated if: r13
- Infection with SARS-CoV-2 is suspected or probable
- Severe pneumonia
- Pleural effusion and/or a cavitary infiltrate
- Specific comorbidities (eg, alcohol use disorder, liver disease, leukopenia, chronic lung disease, asplenia)
- Identification of a suspected pathogen would significantly alter antibiotic choice
- Failure of outpatient treatment
- Epidemiologic considerations (eg, outbreaks of public health importance)
- Pulse oximetry assesses hypoxemia r13c70
- Other laboratory tests—including blood gases, CBC, C-reactive protein, and blood chemistries (including lactate)—may be useful in both determining degree of severity at presentation and managing hospitalized patients r13
- Serum procalcitonin has been used to discriminate between infectious and noninfectious causes of pneumonia and between bacterial and viral causes. However, current guidelines do not recommend its use either to determine need for antibacterial therapy or to determine when to discontinue antibiotics r6r19
Laboratory
- Blood gas tests are not routine but they are indicated when there is respiratory distress and/or suspicion of carbon dioxide retention c71c72
- PaO₂ or FiO₂ ratio less than 250 suggests the need for ICU admission and/or mechanical ventilation r20
- CBC will reveal leukocytosis in most cases of community-acquired pneumonia c73
- Serum chemistry testing is indicated for hospitalized patients receiving IV fluids and to monitor renal function and glucose levels in patients with severe pneumonia. BUN level can be used as a criterion to determine a CURB-65 score, and lactate levelr22 can be used to identify and manage sepsis r21c74
- C-reactive protein c75
- C-reactive protein level greater than 30 mg/L, in addition to suggestive symptoms and signs, implies diagnosis of pneumonia r19
- Etiologic testing
- Blood cultures are indicated for patients with: r6
- Severe community-acquired pneumonia (patients admitted to ICU) c76
- Patients being empirically treated for MRSA or Pseudomonas aeruginosa (or other resistant gram-negative bacilli)
- Patients previously infected with MRSA or Pseudomonas aeruginosa (or other resistant gram-negative bacilli), especially those with history of respiratory tract infection
- Patients who were hospitalized and received parenteral antibiotics, whether during the hospitalization event or not, in the last 90 days
- Sputum Gram stain and culture are indicated for: r6
- All ICU patients (severe) c77c78
- Use an endotracheal specimen in intubated patients
- Patients being empirically treated for MRSA or Pseudomonas aeruginosa (or other resistant gram-negative bacilli)
- Patients previously infected with MRSA or Pseudomonas aeruginosa (or other resistant gram-negative bacilli), especially those with prior respiratory tract infection
- Patients who were hospitalized and received parenteral antibiotics, whether during the hospitalization event or not, within the last 90 days
- All ICU patients (severe) c77c78
- Blood cultures are indicated for patients with: r6
- Pathogen-specific tests
- SARS-CoV-2 polymerase chain reaction or antigen test c79
- In general, polymerase chain reaction is more sensitive than antigen testing, although specificity is nearly equivalent r23
- A negative antigen test result may warrant retesting (preferably within 2 days) with polymerase chain reaction if there is a high suspicion for infection based on clinical or epidemiologic indicators
- Nasopharyngeal, deep nasal (midturbinate), anterior nare, oropharyngeal, or saliva specimens may be submitted for polymerase chain reaction testing; nasopharyngeal wash (or aspirate) or nasal aspirate specimens (using 1-1.5 mL of nonbacteriostatic saline) are also acceptable r24
- Bronchoalveolar lavage or tracheal aspirate are suitable lower respiratory tract specimens for polymerase chain reaction testing. A deep cough sputum specimen is also acceptable (sputum induction not advised) r24
- Antigen tests are validated only for use on certain specimens; check manufacturer's specifications
- In general, polymerase chain reaction is more sensitive than antigen testing, although specificity is nearly equivalent r23
- Legionella urinary antigen test
- Pneumococcal urinary antigen test (for diagnosis of Streptococcus pneumoniae)
- Influenza test r6
- Obtain nasal swab samples to test for influenza in patients with suspected viral pneumonia r25c82c83
- Testing for influenza with a rapid influenza molecular assay (ie, influenza nucleic acid amplification test) is preferred over a rapid influenza diagnostic test (ie, antigen test) r6
- Standard polymerase chain reaction may be used if rapid molecular test is not available. It detects influenza A and B viruses on sputum and endotracheal or bronchoalveolar lavage specimens and confirms positive nasal swab rapid test result in nonepidemic settings r26c84c85
- Fungal culture and tuberculosis testing
- Indicated for patients with:
- Cavitary infiltrate on chest radiograph r13c86c87
- Persistent cough associated with weight loss, weakness, or night sweats r25c88c89
- Presence of risk factors for tuberculosis (eg, older adults, those who traveled to or reside in tuberculosis-endemic regions, those with low socioeconomic status) r25c90c91c92c93c94c95
- Indicated for patients with:
- Serology and/or polymerase chain reaction test may be indicated to confirm the diagnosis of pathogens such as Chlamydia, Legionella, or Mycoplasma pneumoniaer25c96c97c98c99c100c101
- SARS-CoV-2 polymerase chain reaction or antigen test c79
Imaging
- Chest radiography r13c102
- Routine investigation for evaluation of pneumonia in adults
- Results may be negative, especially with dehydration
- Lung infiltrate is the hallmark finding
- May demonstrate alveolar filling with inflammatory exudate or interstitial thickening
- Pleural effusion may be present
- With COVID-19, usually shows bilateral involvement, varying from consolidation in more severely ill patients to ground-glass opacities in less severe cases
- Lung ultrasonography r27r28c103
- CT r29c104
- More sensitive than plain radiographs for detecting pneumonia
- Consider if clinical suspicion for pneumonia remains high despite negative chest radiography findings
- Better at visualizing upper lobes and lingula, necrotizing infection, multilobar disease, interstitial infiltrates due to atypical pathogens, empyema, and pleural involvement
- Useful for excluding tuberculosis or lung cancer
- Can help differentiate COVID-19 pneumonia from other viral pneumonias r14
Procedures
Diagnostic thoracentesis r13c105
General explanation
- Insertion of a small-gauge needle between the ribs, through the thorax, and into the pleural space to access pleural fluid for diagnostic purposes
- Procedure can be performed with or without ultrasonographic guidance
Indication
- Pleural effusions greater than 5 cm high on a lateral view chest radiograph c106
Contraindications
- No absolute contraindications
- Relative
- Uncorrected coagulopathy
- Small effusion with secure clinical diagnosis
- Mechanically ventilated patient
- Perform bilateral thoracentesis only after ensuring absence of pneumothorax in the first side
Complications r31
- Pain at puncture site
- Bleeding (eg, hematoma, hemothorax, hemoperitoneum)
- Pneumothorax
- Re-expansion pulmonary edema
- Infection (eg, empyema, soft tissue infection)
- Spleen or liver puncture
- Vasovagal events
- Retained intrapleural catheter fragments
Interpretation of results
- Pleural fluid analysis
- Obtain pH, glucose, Gram stain, and aerobic and anaerobic cultures r32
- Parapneumonic effusion and empyema are exudative
- Protein level higher than 3 g/dL
- Ratio of pleural fluid protein to serum protein greater than 0.5
- Lactate dehydrogenase level higher than 200 units/L
- Ratio of pleural fluid lactate dehydrogenase to serum lactate dehydrogenase higher than 0.6
- Glucose level lower than 60 mg/mL
- pH is generally low
- WBC count may exceed 50,000 cells/mm³ with neutrophils predominating
- Parapneumonic effusion and empyema are exudative
- Fluid can be saved for further analysis based on initial results
- Other pleural fluid testing (eg, cytology) based on clinical suspicion
- Obtain pH, glucose, Gram stain, and aerobic and anaerobic cultures r32
Differential Diagnosis
Most common
- Bronchitis c107d1
- Presents with fever, malaise, productive cough, hoarseness, chest pain, and muscle pain
- Differentiated by chest radiography and physical examination
- No radiographic evidence of pulmonary pathology
- Signs of consolidation (eg, rales, egophony, fremitus) indicative of pneumonia will be absent
- Seasonal influenza c108d2
- Sudden onset of high fever with chills, myalgia, or malaise
- Dry cough, sneezing, sore throat, nasal discharge, and substernal soreness
- History of contact with an infected person
- Viral infection present in the winter season
- Differentiated by history and laboratory testing
- Antigen detection test using nasopharyngeal secretion will help in detecting type A and type B viral antigens
- Asthma d3
- Patient may present with recurrent attacks of dyspnea with wheezing or accessory muscle use c109
- Differentiated by history (absence of fever), chest radiography, spirometry/pulmonary function testing, and response to bronchodilators
- Chronic obstructive pulmonary disease c110d4
- Patients present with dyspnea, pursed lip breathing, or use of accessory muscles for breathing
- Other features include chronic productive cough, cyanosis, tachycardia, and tachypnea
- Differentiated by history, chest radiography, and spirometry/pulmonary function testing
- Spirometry shows abnormal diffusing capacity, fixed reduction in FEV1, and increased total lung capacity and/or residual volume in patients with chronic obstructive pulmonary disease
- Chest radiography shows hyperinflation with flattened diaphragm, tenting of the diaphragm at the rib, and increased retrosternal chest space in patients with chronic obstructive pulmonary disease
- Congestive heart failure d5
- Characterized by: c111
- Dyspnea
- Fatigue
- Exercise intolerance
- Fluid retention
- Differentiated by:
- Chest radiography showing:
- Pulmonary edema
- Pleural effusion
- Pulmonary venous congestion
- Chamber dilation
- Kerley B lines
- Cardiomegaly
- Echocardiography showing abnormalities with cardiac structure and function
- Chest radiography showing:
- Characterized by: c111
- Pneumothorax
- Sudden onset of breathlessness and chest pain c112
- Differentiated by history, physical examination, and chest radiography
- Chest radiography will reveal air in the pleural space
- Pulmonary embolism d6
- Blocking of pulmonary artery by thrombus
- Patients present with dyspnea and pleuritic chest pain but usually do not have a fever or cough productive of purulent sputum c113
- Calf tenderness and swelling may be present if embolism was caused by deep venous thrombosis
- Differentiated by history, physical examination, and imaging
- Chest CT shows filling defects in the pulmonary arteries
- Tuberculosis d7
- Patients present with weight loss, night sweats, and cough c114
- Travel to or residence in a tuberculosis-infected endemic area or advanced age (born early 20th century during worldwide endemicity)
- Differentiated by history, laboratory testing, and imaging
- Positive tuberculin test result
- Chest radiography findings of reactivation disease (usually in older patients) showing upper-lobe predominance or cavity, and/or granuloma formation
- Chest radiography of primary tuberculous pneumonia (usually in in younger patients) showing hilar adenopathy, and/or pleural effusion (sometimes massive)
Treatment
Goals
- Eradicate infection
- Relieve symptoms and provide supportive care as needed
- Prevent disease progression and complications
Disposition
Admission criteria
Use severity of illness scores in combination with clinical judgment to determine if the patient can be safely managed as an outpatient or should be managed as an inpatient. The 2019 guidelines recommend Pneumonia Severity Index preferentially over the CURB-65 criteria r6
- Pneumonia Severity Index r33
- Uses a point system of several variables including patient age, vital signs, mental status, and the presence of comorbid conditions (eg, neoplastic disease, liver disease, chronic heart failure, cerebrovascular disease, renal disease)
- Classifies patients into a mortality risk level
- Class I and II patients (fewer than 70 points) may be treated as outpatients
- Class III patients should be treated in an observation unit or briefly hospitalized (71-90 points)
- Class IV (91-130 points) and V (greater than 130 points) should be treated as inpatients
- CURB-65 criteria r1
- Patients receive 1 point for each of the following indicators:
- Confusion (compared to baseline)
- BUN greater than 20 mg/dL
- Respiratory rate greater than or equal to 30 breaths per minute
- Systolic blood pressure less than 90 mm Hg or diastolic blood pressure of 60 mm Hg or less
- Age 65 years or older
- Inpatient admission is recommended for patients with a score of 2 or more
- Most patients with a score of 1 can be managed as outpatients; consider overnight observation for some patients
- Patients receive 1 point for each of the following indicators:
- Studies of specific biomarkers used to identify high-risk patients have not proven more accurate than these scoring systems r34
For COVID-19 pneumonia:
- Nonsevere pneumonia: admission criteria include radiographic evidence of pneumonia, progressive clinical illness, risk factors for severe disease, and inadequate care at home. CDC provides further guidance r35
- More severe/critical respiratory tract disease requires ICU admission r36
- Implement standard, contact, and (at least) droplet precautions as soon as the diagnosis is suspected; airborne precautions are recommended r37
Consider inpatient admission for patients otherwise meeting criteria for outpatient treatment but who are unable to safely and reliably take medication orally or who have insufficient personal support r25
Criteria for ICU admission
- Recommended with either major criteria or 3 or more minor criteria (severe community-acquired pneumonia) r6
- Major criteria
- Need for mechanical ventilation
- Septic shock with need for vasopressors
- Minor criteria
- Respiratory rate of 30 breaths per minute or more
- Ratio of arterial PaO₂ to fraction of inspired oxygen (FiO₂) of 250 or less
- Multilobar disease
- Leukopenia (leukocyte count less than 4000 cells/μL)
- Uremia (BUN level of 20 mg/dL or higher)
- Confusion or disorientation
- Hypothermia (core temperature lower than 36 °C)
- Thrombocytopenia (platelet count fewer than 100,000 cells/μL)
- Hypotension requiring aggressive fluid resuscitation
- Major criteria
- Pneumonia prognostic prediction tools have also been used in practice to determine level of in-hospital care; ICU is appropriate in the following patients: r29
- Pneumonia severity index: class V (greater than 130 points)
- CURB-65r1 score of 4 or 5
- For severe COVID-19 pneumonia
- Admit patients with severe/critical respiratory tract disease to an intensive care environment r36
- Tachypnea (respiratory rate greater than 30 breaths or less than 10 breaths per minute), severe respiratory distress, inadequate oxygenation (eg, SpO₂ less than 92%)
- Presence of severe complications (eg, septic shock, acute respiratory distress syndrome)
- Admit patients with severe/critical respiratory tract disease to an intensive care environment r36
Recommendations for specialist referral
- Refer to pulmonologist for:
- Respiratory failure requiring noninvasive and positive pressure ventilation or intubation and mechanical ventilation
- Worsening hypoxemia
- Pleural effusion requiring chest tube drainage
- Nonresolving pneumonia (characterized by persistent fever and absence of clinical improvement)
- Bronchoscopic sampling, if necessary
- Refer to infectious disease specialist for assistance with identification of causative agent and antibiotic management of severe pneumonia or pneumonia that does not respond to empiric antibiotics
Treatment Options
Determine the optimal care setting using severity of illness scores and clinical judgment r6
For COVID-19 pneumonia: d8
- Until a diagnosis of COVID-19 is confirmed by polymerase chain reaction or antigen test, administer appropriate antimicrobial therapy for other viral pathogens (eg, influenza virus) or bacterial pathogens in accordance with the severity of clinical disease, site of acquisition (hospital or community), epidemiologic risk factors, and local antimicrobial susceptibility patterns r18
- WHOr18, NIHr38, and Surviving Sepsis Campaignr39 provide specific guidance for oxygenation, ventilation, and fluid management in COVID-19
- Current standard treatment options include infection control measures, routine supportive care, and medications including antiviral, monoclonal antibody, immunomodulator, and corticosteroid drugs d8
- Antivirals and monoclonal antibodies directed at viral components are most effective when used early in the course of infection (to prevent cell entry and viral replication); antiinflammatory drugs (eg, dexamethasone) and immunomodulators are of most benefit during the hyperinflammatory response in later phases of severe disease
- At present, in the absence of a standard indication for it, published guidelines do not recommend therapeutic anticoagulation but do suggest or recommend use of usual prophylactic regimens in any hospitalized patient with COVID-19, including pregnant patients r18r38r39r40r41r42
For non-COVID-19 pneumonias: begin empiric therapy based on treatment setting; in patients admitted to the hospital, give first antimicrobial dose before patient leaves emergency department
- Outpatient treatment
- First line therapy for patients without comorbidities or risk factors for antibiotic-resistant pathogens includes amoxicillin or doxycycline or a macrolide (only in areas with pneumococcal resistance to macrolides less than 25%) r6
- For outpatient adults with the following comorbidities, antibiotic options include combination therapy or monotherapy r6
- Consider administering treatment (eg, oseltamivir) to patients with positive test results for influenza, independent of duration of illness before diagnosis r6
- General ward inpatient treatment (nonsevere community-acquired pneumonia without risk factors for MRSA, Pseudomonas aeruginosa, or resistant gram-negative bacilli) r6
- Monotherapy with an appropriate respiratory fluoroquinolone, orr6r43
- A β-lactam plus a macrolide may be used r6r43
- Doxycycline may be used in place of a macrolide r6
- A systematic review showed either monotherapy with a respiratory quinolone or combination therapy with a β-lactam plus a macrolide to be superior to β-lactam monotherapy in patients requiring hospitalization r44
- Administer treatment (eg, oseltamivir) to patients with positive test results for influenza, independent of duration of illness before diagnosis; because patients with influenza often have concurrent bacterial infection, administer recommended antibacterial antibiotics, pending culture results r6
- 2019 guidelines recommend clinicians only cover empirically for MRSA or Pseudomonas aeruginosa in adults with community-acquired pneumonia if locally validated risk factors for either pathogen are present. Infectious Diseases Society of America guidelines do not recommend empiric coverage (pending culture results) for these organisms based on individual risk factors in patients with nonsevere pneumonia r6
- ICU inpatient treatment (severe community-acquired pneumonia without risk factors for MRSA or Pseudomonas aeruginosa) r6
- β-lactam plus a macrolide r6
- Alternatively, a β-lactam plus a respiratory fluoroquinolone may be used r6
- Administer treatment (eg, oseltamivir) to patients with positive test results for influenza, independent of duration of illness before diagnosis; because concurrent bacterial infection is common with influenza, administer recommended antibacterial antibiotics, pending culture results r6
- 2019 American Thoracic Society and Infectious Diseases Society of America guidelines recommend clinicians only cover empirically for MRSA or Pseudomonas aeruginosa in adults with community-acquired pneumonia if locally validated risk factors for either pathogen are present. In the absence of these, clinicians may treat patients with severe pneumonia empirically for these pathogens when there is a history of recent (90 days) hospitalization and parenteral antibiotic treatment or documented past infection with these pathogens. De-escalate antibiotics if indicated by culture results r6
General considerations
- 2019 guidelines recommend that duration of antibiotic therapy be guided by a validated measure of clinical stability. Continue antibiotic therapy until the patient achieves stability and for no fewer than a total of 5 days r6
- Indicators of clinical stability: r45
- Temperature of 37.8 °C or lower
- Heart rate of 100 beats per minute or fewer
- Respiratory rate of 24 breaths per minute or fewer
- Systolic blood pressure of 90 mm Hg or higher
- Arterial oxygen saturation of 90% or higher or PO₂ of 60 mm Hg or higher on room air
- Ability to maintain oral intake
- Normal mental status
- Indicators of clinical stability: r45
- Most patients will achieve clinical stability within the first 48 to 72 hours; thus, a total duration of therapy of 5 days should be appropriate for most patients r6
- 2019 guidelines suggest duration of therapy for community-acquired pneumonia due to suspected or proven MRSA orPseudomonas aeruginosa should be 7 days r6
- Other pathogens or clinical circumstances may require a longer duration:
- Initial therapy is not effective against identified pathogen r6
- Staphylococcus aureus lobar pneumonia (2 weeks) r29
- Staphylococcus aureus bacteremia (4 weeks, IV) r29
- Mycoplasma pneumoniae or Chlamydia pneumoniae (10-14 days) r29
- Legionella (14-21 days) r29
- Complications caused by extrapulmonary infections (eg, meningitis, endocarditis) r6
- If there is no improvement within 72 hours of initiation of the empiric treatment, there may be drug resistance, an unsuspected pathogen, or unrecognized complications (eg, endobronchial obstruction, empyema)
- When culture and antibiotic susceptibility results are available, adjust antibiotics to specific, narrow-spectrum therapy r6
- Treatment can be switched from IV to oral once hemodynamic stability and clinical improvement are seen r6
- Use of adjunctive corticosteroids remains controversial and clinical studies have produced conflicting reports. They may be considered in some cases of severe pneumonia, particularly with septic shock r6r29r43
- 2019 Infectious Diseases Society of America guidelines recommend not routinely using corticosteroids in adults with nonsevere community-acquired pneumonia and suggest not routinely using corticosteroids in adults with severe community-acquired pneumonia or severe influenza pneumonia r6
- 2019 Infectious Diseases Society of America guidelines endorse the Surviving Sepsis Campaign recommendationsr46 on the use of steroids in patients with septic shock refractory to adequate fluid resuscitation and vasopressor support r6
Drug therapy
- Antibiotics r12
- Macrolides c115
- First line therapy for outpatient treatment; used in combination with other antibiotics in the inpatient setting
- Azithromycin c116
- Azithromycin Oral tablet; Outpatient Adults: 500 mg PO on day 1, followed by 250 mg PO once daily for at least 5 days.
- Azithromycin Oral tablet; Hospitalized Adults: 500 mg PO once daily for at least 5 days.
- Azithromycin Solution for injection; Adults: 500 mg IV once daily for at least 5 days.
- Clarithromycin c117
- Clarithromycin Oral tablet; Adults: 500 mg PO every 12 hours for at least 5 days.
- Tetracyclines c118
- Acceptable alternative to macrolides
- Doxycycline c119
- Doxycycline Hyclate Oral tablet; Adults: 100 mg PO every 12 hours for at least 5 days.
- Doxycycline Hyclate Solution for injection; Adults: 100 mg IV every 12 hours for at least 5 days.
- Quinolones c120
- Respiratory quinolones (ie, gemifloxacin, moxifloxacin, levofloxacin, delafloxacin) are first line outpatient therapy for patients with community-acquired pneumonia who are at risk for multidrug-resistant Streptococcus pneumoniae
- Gemifloxacin c121
- Gemifloxacin Oral tablet; Adults: 320 mg PO once daily for at least 5 days.
- Moxifloxacin c122
- Moxifloxacin Hydrochloride Oral tablet; Adults: 400 mg PO once daily for at least 5 days.
- Moxifloxacin Hydrochloride Solution for injection; Adults: 400 mg IV once daily for at least 5 days.
- Levofloxacin c123c124
- Levofloxacin Oral tablet; Adults: 750 mg PO every 24 hours for at least 5 days.
- Levofloxacin Solution for injection; Adults: 750 mg IV every 24 hours for at least 5 days.
- Delafloxacin c125
- Delafloxacin Oral tablet; Adults: 450 mg PO every 12 hours for 5 to 10 days.
- Delafloxacin Solution for injection; Adults: 300 mg IV every 12 hours for 5 to 10 days.
- Penicillins c126c127
- Frequently used in combination regimens in both outpatient and inpatient settings
- Amoxicillin c128c129
- Amoxicillin Trihydrate Oral tablet; Adults: 1 g PO every 8 hours for at least 5 days.
- Amoxicillin-clavulanate c130c131
- Amoxicillin Trihydrate, Clavulanate Potassium Oral tablet; Adults: 875 mg amoxicillin with 125 mg clavulanate PO every 12 hours or 500 mg amoxicillin with 125 mg clavulanate PO every 8 hours for at least 5 days.
- Amoxicillin Trihydrate, Clavulanate Potassium Oral tablet, extended-release; Adults: 2,000 mg amoxicillin with 125 mg clavulanate PO every 12 hours for at least 5 days.
- Ampicillin-sulbactam c132c133
- Ampicillin Sodium, Sulbactam Sodium Solution for injection; Adults: 1.5 g (1 g ampicillin and 0.5 g sulbactam) or 3 g (2 g ampicillin and 1 g sulbactam) IV every 6 hours for at least 5 days.
- Piperacillin-tazobactam c134c135
- Piperacillin Sodium, Tazobactam Sodium Solution for injection; Adults: 4.5 g (4 g piperacillin and 0.5 g tazobactam) IV every 6 hours for at least 7 days.
- Cephalosporins c136c137
- Frequently used in combination regimens in both outpatient and inpatient settings
- Cefuroxime c138c139
- Cefuroxime Axetil Oral tablet; Adults: 500 mg PO every 12 hours for at least 5 days.
- Cefpodoxime c140c141
- Cefpodoxime Proxetil Oral tablet; Adults: 200 mg PO every 12 hours for at least 5 days.
- Ceftriaxone c142c143
- Ceftriaxone Sodium Solution for injection; Adults: 1 to 2 g IV every 24 hours for at least 5 days.
- Cefotaxime c144c145
- Cefotaxime Sodium Solution for injection; Adults: 1 to 2 g IV every 8 hours for at least 5 days.
- Ceftaroline c146
- Ceftaroline fosamil Solution for injection; Adults: 600 mg IV every 12 hours for at least 5 days.
- Cefepime c147c148
- Cefepime Hydrochloride Solution for injection; Adults: 2 g IV every 8 hours for at least 7 days.
- Ceftazidime c149
- Ceftazidime Sodium Solution for injection; Adults: 2 g IV every 8 hours for at least 7 days.
- Carbapenems c150c151
- Used in combination regimens in the inpatient and ICU settings to manage seriously ill patients with community-acquired pneumonia; imipenem-cilastatin and meropenem also provide coverage for suspected Pseudomonas infection
- Imipenem-cilastatin c152c153
- Imipenem, Cilastatin Sodium Solution for injection; Adults: 500 mg IV every 6 hours for at least 7 days.
- Meropenem c154c155
- Meropenem Solution for injection; Adults: 1 g IV every 8 hours for at least 7 days.
- Monobactams c156c157
- Glycopeptides c160c161
- Used for the treatment of MRSA and penicillin-resistant pneumococci
- Vancomycin c162c163
- Vancomycin Hydrochloride Solution for injection; Adults: 20 to 35 mg/kg/dose (Max: 3,000 mg/dose) IV loading dose, followed by 15 to 20 mg/kg/dose IV every 8 to 12 hours for at least 7 days; adjust dose based on target PK/PD parameter. Consider loading dose in critically ill patients.
- Oxazolidinones c164c165
- Used for the treatment of infections due to aerobic gram-positive bacteria, including MRSA and penicillin-resistant pneumococci
- Linezolid c166c167
- Linezolid Oral tablet; Adults: 600 mg PO every 12 hours for at least 7 days.
- Linezolid Solution for injection; Adults: 600 mg IV every 12 hours for at least 7 days.
- Pleuromutilin c168
- Macrolides c115
- Antiviral agents r12r48c170
- Antiviral agents are recommended for patients with confirmed or suspected influenza who have severe, complicated, or progressive illness; who are hospitalized; or who are at high risk for complications, regardless of the time since symptom onset. Can be considered for previously healthy, symptomatic outpatients not at high risk for influenza complications if initiated within 48 hours of onset of symptoms c171c172
- Neuraminidase inhibitors c173
- Polymerase acidic endonuclease inhibitor
Nondrug and supportive care
Supplemental oxygen or mechanical ventilation r50
- May be required in patients with severe pneumonia or underlying cardiopulmonary disease c178c179c180
- Maintain oxygen saturation within 94% to 98% in patients with hypoxemia r43
Respiratory therapy c181
- Postural drainage facilitated by chest percussion may be helpful in patients who have difficulty mobilizing respiratory secretions c182c183
Breathing exercises c184
- Strengthen the chest wall muscles; beneficial particularly to sedentary patients
- Help patients mobilize secretions to improve expectoration
Venous thromboembolism prophylaxis r43c185
- Low-molecular-weight heparin is recommended in patients at high risk
- Early ambulation is recommended
- Advise patients to quit smoking, using counseling and pharmacologic approaches recommended in tobacco cessation guidelines and reviews r51r52d9
Procedures
Therapeutic thoracentesis c187
- Drainage of pleural fluid for therapeutic (versus diagnostic) purposes
- Relieves dyspnea caused by a large parapneumonic effusion
- Evacuation of purulent fluid is essential for treatment of empyema
- Parapneumonic pleural effusion r13
- Fluid more than 5 cm high on the lateral view of an upright chest radiograph or more than 10 mm of fluid on a lateral decubitus view
- Pleural fluid drainage by chest tube is recommended in cases of empyema r53
- Pleural fluid pH is less than 7.28
- Pleural fluid glucose level is less than 40 mg/dL
- Ratio of pleural fluid to serum glucose is less than 0.5
- Pleural fluid lactate dehydrogenase level is greater than 1000 units/L
- No absolute contraindications
- Relative
- Uncorrected coagulopathy
- Mechanically ventilated patient
- Perform bilateral thoracentesis only after ensuring absence of pneumothorax in the first side
- Pain at puncture site
- Bleeding (eg, hematoma, hemothorax, hemoperitoneum)
- Pneumothorax
- Re-expansion pulmonary edema
- Infection (eg, empyema, soft tissue infection)
- Spleen or liver puncture
- Vasovagal events
- Retained intrapleural catheter fragments
Comorbidities
- Patients with comorbid disorders such as neoplastic disease, liver disease, congestive heart failure, cerebrovascular disease, or renal disease are likely to require hospital admission and IV antibiotics, at least initially c188c189c190c191c192
- Immunocompromised patients c193
- Prone to multiorganism pneumonia, including unusual pathogens such as cytomegalovirus, Pneumocystis jiroveci, and fungal infection
- Microbiologic diagnosis may require bronchoscopy with biopsy, immunohistology, and quantitative molecular assays
- Begin empiric therapy as soon as possible based on epidemiologic history, sputum Gram stain, previous courses of antimicrobial agents, and historical microbiologic data
- Pneumonia caused by SARS-CoV-2 is a prominent feature of COVID-19; clinicians must consider whether treatment for additional potential causes of community-acquired pneumonia is appropriate r15c194
Special populations
- Older patients
- Classic signs and symptoms may be absent or altered in older patients
- Presentation may include nonspecific symptoms such as confusion r25
- May recover more slowly compared with younger patients
- Aspiration is an important risk factor for community-acquired pneumonia in older patients
- Classic signs and symptoms may be absent or altered in older patients
- Pregnant patients
- Prone to preterm labor and delivery
- Prone to pulmonary edema
- Acidosis and hypoxic state are poorly tolerated by the fetus
- High risk for severe influenza
- Treat with pregnancy-safe antibiotics
- Azithromycin or erythromycin with or without ceftriaxone, depending on severity of illness; antiviral neuraminidase inhibitor for influenza
- Antibiotics to be avoided in pregnancy include doxycycline, fluoroquinolones, and clarithromycin
- Lefamulin may cause fetal harm when administered during pregnancy; effective contraception use is recommended for patients of reproductive potential
Monitoring
- 2019 guidelines recommend against routinely obtaining follow-up chest imaging in adults with community-acquired pneumonia whose symptoms have resolved within 5 to 7 days r6
- In hospitalized patients with confirmed COVID-19, repeated testing may be done to document clearance of virus, defined as 2 consecutive negative results on polymerase chain reaction at least 24 hours apart r37
Complications and Prognosis
Complications
- Reduction in breathing capacity requiring mechanical ventilation c195c196
- Empyema or lung abscess secondary to inadequately treated pleural effusion c197
- Systemic complications (eg, sepsis, meningitis, bacteremia, endocarditis) c198c199c200c201
- Pneumonia may recur in recently treated patients, particularly in high-risk groups (eg, older patients, patients who smoke, patients who have alcohol use disorder, immunosuppressed patients, patients with bronchopulmonary anatomic abnormalities) c202c203c204c205c206
Prognosis
- Outcomes are improved through early diagnosis and timely administration of antibiotics r7r54
- Treatment within 4 to 6 hours of hospital arrival reduces mortality
- Patients with a CURB-65r1 score of 0 to 1 or a Pneumonia Severity Index risk class of I and II are at low risk of mortality. Mortality rate is higher in patients with higher scores or risk class
- Infections due to Staphylococcusaureus or gram-negative bacilli and aspiration pneumonia are associated with high mortality rates for all populations
- Incorrect diagnosis, comorbidities, inappropriate medication dose or route of administration, presence of an unusual or unanticipated pathogen, adverse drug reactions, or complications negatively impact prognosis
- With COVID-19 pneumonia, patients who require hospital admission often require prolonged inpatient stay (more than 20 days) and experience significant deconditioning. Infection fatality ratio (proportion of deaths among all who are infected, including confirmed cases, undiagnosed cases, and unreported cases) varies across global locations but has been estimated as 0.15% r9r10r55
Screening and Prevention
Prevention
- Tobacco use
- Immunization d10
- Pneumococcal vaccine c208
- In the United States, 2 formulations have historically been available: PCV13 and PPSV23; in 2021, 20-valent pneumococcal conjugate vaccine (PCV20) and 15-valent pneumococcal conjugate vaccine (PCV15) were licensed by the FDA for adults aged 18 years or older r2
- Advisory Committee on Immunization Practices recommends PCV15 or PCV20 for adults who have not received pneumococcal conjugate vaccine, are aged 65 years or older, or are aged 19 to 64 years with certain underlying conditions r2
- Adults aged 65 years or older who have not previously received pneumococcal conjugate vaccine or whose earlier vaccination history is unknown should receive 1 dose of pneumococcal conjugate vaccine (either PCV20 or PCV15) r2
- Adults aged 19 to 64 years with certain underlying medical conditions or other risk factors who have not previously received pneumococcal conjugate vaccine or whose earlier vaccination history is unknown should receive 1 dose of pneumococcal conjugate vaccine (either PCV20 or PCV15) r2
- For both age groups, if PCV15 is used, it should be followed by a dose of PPSV23 at least 1 year later (a minimum interval of 8 weeks can be considered for adults who have an immunocompromising condition, cochlear implant, or cerebrospinal fluid leak) r2
- For adults who have previously received only PPSV23, pneumococcal conjugate vaccine (either PCV20 or PCV15) may be administered at least 1 year after their last PPSV23 dose r2
- When PCV15 is used in those with a history of receiving PPSV23, it does not need to be followed by another dose of PPSV23 r2
- Benefits of providing PCV15 or PCV20 to adults who have received PCV13 only or both PCV13 and PPSV23 have not been evaluated; in such cases, the previously recommended PPSV23 series should be completed r2
- Advisory Committee on Immunization Practices considers the following to be underlying medical conditions or risk factors for adults in the 19- to 64-year age group: r2
- Alcoholism; chronic heart, liver, or lung disease; chronic renal failure; cigarette smoking; cochlear implant; congenital or acquired asplenia; cerebrospinal fluid leak; diabetes mellitus; generalized malignancy; HIV; Hodgkin disease; immunodeficiency; iatrogenic immunosuppression; leukemia, lymphoma, or multiple myeloma; nephrotic syndrome; solid organ transplant; sickle cell disease; or other hemoglobinopathies r2
- Yearly influenza vaccination is recommended for all persons 6 months of age and older r3c209
- CDC recommends vaccination against COVID-19 for all persons 5 years of age and older r4
- Pneumococcal vaccine c208
- Dental hygiene
- Lack of good dental hygiene is a risk factor for community-acquired pneumonia; periodic dental hygiene checks are recommended c210
