Community Acquired Pneumonia

Jump to: navigation, search

Author / Curator: Justin Berk, MD

Faculty Advisor: TBD

Learning Objectives

  1. Define what pneumonia is and the different types of pneumonia.
  2. Know the three most common causes of community acquired pneumonia (CAP).
  3. Know the most common antibiotic regiments for CAP.
  4. Understand the different risk stratification calculators available to providers and when to refer to the inpatient setting.

Teaching Points

  1. Pneumonia is responsible for 16% of all deaths of children and is the most common cause of death from infectious diseases in adults.[1] [2]
  2. The new expanded CURB-65 is a potentially more accurate PNA severity score. [3]
  3. A "blooming" pneumonia - One study examining the effect of dehydration on x-ray findings revealed that patients with clinical signs of dehydration developed worsening chest x-ray findings over a several day period as their volume status was corrected. [4]
  4. There seems to be beneficial in treating severe CAP with steroids [5] [6] [7]. This is not the case in pediatric patients [8] unless the patient is undergoing treatment for asthma-related wheezing as well. [9]
  5. Oseltamivir in adults with influenza accelerates time to clinical symptom alleviation, reduces the risk of lower respiratory tract complications and admittance to a hospital, but increases the occurrence of nausea and vomiting. [10]
  6. Honey has been shown to improve cough symptoms in children, but should not be given to kids under the age of 1 due to cross contamination with botulism toxin. [11]


  • Pneumonia is defined as infection of the lungs.
  • Pneumonia is the most common infectious cause of death in the United States and 8th most common cause of death. [1]
  • Community-acquired-pneumonia (CAP) represents the 5th most common diagnosis of patients presenting in an outpatient setting with complaints of a cough.
  • It is the 2nd most common cause of hospitalization in children 1-17 years old in the United States.
  • Complications include: parapneumonic effusion, empyema, bacterial superinfection


The most commonly identified bacterial etiologies of CAP are: Streptococcus pneumoniae, Haemophilus influenzae, Mycoplasma pneumoniae, Chlamydophila pneumoniae, Staphylococcus aureus, and Moraxella catarrhalis [12]


IDSA Diagnostic Criteria for CAP [13] are:

  • CXR findings of new infiltrate AND
  • At least 2 of: fever, cough, chest pain, or dyspnea

The diagnosis of HCAP is made if:

  • hospitalized in an acute care hospital for two or more days within 90 days of the infection; OR
  • resides in a nursing home or long-term care facility; OR
  • received recent intravenous antibiotic therapy, chemotherapy, or wound care within the past 30 days of the current infection; OR
  • attended a hospital or hemodialysis clinic. [14]

Signs and Symptoms

Elderly patients may present with less pronounced symptoms (i.e. no fever, mild cough). [15]

Differential Diagnosis

DDx: HCAP, CHF, TB, ILD, Bronchitis, Aspiration pneumonitis, pertussis, structural lung disease, PE, malignancy

Risk factors for TB: time spent in an endemic region, homelessness, exposure to others with TB, recent incarceration.

Note: Empiric treatment of CAP with quinolones can delay diagnosis of tuberculosis, as these drugs have anti-mycobacterial activity. [16]

Physical Exam

Likelihood ratios for findings on history, exam, and laboratory studies can be found here but are generally unimpressive. [17]

There is significant inter-observer disagreement in the physical exam findings of CAP and physical examination is not sufficiently accurate to diagnose or exclude PNA [18] [19] [20].

Pediatric Correlate: In febrile infants < age 2, the LACK OF tachypnea is associated with a 97% negative predictive value (i.e. no tachypnea suggests no pneumonia). [21]

Work-up (Evidence-based labs and imaging)


Blood Cx: Blood cultures are rarely helpful in the ambulatory setting and are not recommended for the outpatient management of CAP. The IDSA/ATS guidelines state that blood cultures are found to be positive in 5-14% of patients admitted to the hospital.

Sputum Cx: The utility of sputum gram staining has been studied and debated for decades. Multiple prospective studies have produced disparate results regarding the test's sensitivity and ability to alter management in CAP. Sputum gram stain for S. pneumonia has estimated sensitivity between 50 and 60% and specificity of greater than 80%. [22]

Urine: The urine Legionella antigen assay tests for L. pneumophila serogroup 1 and can detect up to 70% of cases. [23] Urine s. pneumo antigen test has a reported sensitivity of 70-90% and a specificity of approximately 99%. This test has been used predominantly in hospitalized patients. [24]

HIV screening should be performed for any patient between the ages of 13-75 in a medical setting presenting with CAP though this is often not done. [25] A diagnosis of bacterial pneumonia may be a predictive factor of HIV with a calculated OR of 47.7 [26] and has been shown to be a significant predictor for undocumented HIV. [27]

Pediatric Correlation: Urine S. pnuemo antigen not as helpful in pediatric population [28] It has good sensitivity (100%) and (although limited specificity, 56%) in children with suspected pneumococcal disease. [29]


Images of PNA on CXR

Pediatric Correlate: JAMA Pediatrics video on point-of-care ultrasound for diagnosis of PNA in children and young adults:


When to Admit / Risk Stratification

Several risk stratification tools exist including Pneumonia Severity Index (PSI) and CURB-65 [30] An elevated respiratory rate, systolic blood pressure below 90 mmHg and pulse greater than 125 beats/minute are all signs concerning for poor outcome. [31] CURB-65: Confusion; Uremia (BUN>20); RR>30; BP<90 systolic (or 60 diastolic); Age>65: Admit if 2 or more present.


IDSA Treatment Recommendations: [32]

Patient Context First-line treatment
Healthy Macrolide or Doxycycline
Healthy with ABX in last 30 days Fluoroquinolone OR (Beta-lactam + Macrolide)
Significant co-morbidities (CHF, immunosupression, asplenia, CAD, DM Fluoroquinolone OR (Beta-lactam + Macrolide)
Suspected aspiration Augmentin OR clindamycin
Bacterial Superinfection Beta-lactam OR fluorquinolone

Treatment Duration

IDSA/ATS guidelines recommend a minimum of five days of antibiotic treatment for uncomplicated CAP. Patients should be afebrile for 48-72 hours with resolution or marked improvement in symptoms prior to antibiotic discontinuation. [33]

Trial Summaries

CAP-START - In hospitalized patients with CAP, beta-lactam monotherapy was found to be non-inferior to beta-lactam + azithromycin or fluoroquinolone monotherapy. (CAP-START trial) [34] Similar findings have been found in children. [35]

FLORALI - In severe CAP with hypoxemic respiratory failure, high-flow nasal canula appears superior to NRB face-make and BiPap (WJC:FLORALI Trial) [36]

Ongoing controversies / New updates

In pediatrics, there is not good evidence for the treatment of Mycoplasma pneumonia. [37] [38]

Teaching Resources


  1. 1.0 1.1 Wunderink & Waterer: Clinical practice. Community-acquired pneumonia. N. Engl. J. Med. 2014;370:543-51.
  2. Pneumonia. Facesheet. WHO Sept 2016:
  3. Liu et al.: Expanded CURB-65: a new score system predicts severity of community-acquired pneumonia with superior efficiency. Sci Rep 2016;6:22911.
  4. Hash et al.: The relationship between volume status, hydration, and radiographic findings in the diagnosis of community-acquired pneumonia. J Fam Pract 2000;49:833-7.
  5. Siemieniuk et al.: Corticosteroid Therapy for Patients Hospitalized With Community-Acquired Pneumonia: A Systematic Review and Meta-analysis. Ann. Intern. Med. 2015;163:519-28.
  6. Torres et al.: Effect of corticosteroids on treatment failure among hospitalized patients with severe community-acquired pneumonia and high inflammatory response: a randomized clinical trial. JAMA 2015;313:677-86.
  7. Blum et al.: Adjunct prednisone therapy for patients with community-acquired pneumonia: a multicentre, double-blind, randomised, placebo-controlled trial. Lancet 2015;385:1511-8.
  8. Ambroggio et al.: Adjunct Systemic Corticosteroid Therapy in Children With Community-Acquired Pneumonia in the Outpatient Setting. J Pediatric Infect Dis Soc 2015;4:21-7.
  9. Weiss et al.: Adjunct corticosteroids in children hospitalized with community-acquired pneumonia. Pediatrics 2011;127:e255-63.
  10. Dobson et al.: Oseltamivir treatment for influenza in adults: a meta-analysis of randomised controlled trials. Lancet 2015;385:1729-1737.
  12. File &: Community-acquired pneumonia. Lancet 2003;362:1991-2001.
  13. Infectious Diseases Society of America: Guidelines for the management of adults with hospital-acquired, ventilator-associated, and healthcare-associated pneumonia. Am. J. Respir. Crit. Care Med. 2005;171:388-416.
  14. Infectious Diseases Society of America: Guidelines for the management of adults with hospital-acquired, ventilator-associated, and healthcare-associated pneumonia. Am. J. Respir. Crit. Care Med. 2005;171:388-416.
  15. Metlay et al.: Influence of age on symptoms at presentation in patients with community-acquired pneumonia. Arch. Intern. Med. 1997;157:1453-9..
  16. Dooley et al.: Empiric treatment of community-acquired pneumonia with fluoroquinolones, and delays in the treatment of tuberculosis. Clin. Infect. Dis. 2002;34:1607-12.
  17. Metlay & Fine: Testing strategies in the initial management of patients with community-acquired pneumonia. Ann. Intern. Med. 2003;138:109-18.
  18. Wipf et al.: Diagnosing pneumonia by physical examination: relevant or relic?. Arch. Intern. Med. 1999;159:1082-7.
  19. Rosh & Newman: Evidence-based emergency medicine/rational clinical examination abstract. Diagnosing pneumonia by medical history and physical examination. Ann Emerg Med 2005;46:465-7.
  20. Metlay et al.: Does this patient have community-acquired pneumonia? Diagnosing pneumonia by history and physical examination. JAMA 1997;278:1440-5.
  21. Taylor et al.: Establishing clinically relevant standards for tachypnea in febrile children younger than 2 years. Arch Pediatr Adolesc Med 1995;149:283-7.
  22. Gleckman et al.: Sputum gram stain assessment in community-acquired bacteremic pneumonia. J. Clin. Microbiol. 1988;26:846-9.
  23. Mandell et al.: Update of practice guidelines for the management of community-acquired pneumonia in immunocompetent adults. Clin. Infect. Dis. 2003;37:1405-33.
  24. Pesola &: The urinary antigen test for the diagnosis of pneumococcal pneumonia. Chest 2001;119:9-11.
  25. Clifton et al.: Suboptimal HIV Testing Among Patients Admitted With Pneumonia: A Missed Opportunity. AIDS Educ Prev 2017;29:377-388.
  26. Damery et al.: Assessing the predictive value of HIV indicator conditions in general practice: a case-control study using the THIN database. Br J Gen Pract 2013;63:e370-7.
  27. Owens et al.: Prevalence of HIV infection among inpatients and outpatients in Department of Veterans Affairs health care systems: implications for screening programs for HIV. Am J Public Health 2007;97:2173-8.
  28. Neuman & Harper: Evaluation of a rapid urine antigen assay for the detection of invasive pneumococcal disease in children. Pediatrics 2003;112:1279-82.
  29. Elemraid et al.: A case-control study to assess the urinary pneumococcal antigen test in childhood pneumonia. Clin Pediatr (Phila) 2014;53:286-8.
  30. Lim et al.: Defining community acquired pneumonia severity on presentation to hospital: an international derivation and validation study. Thorax 2003;58:377-82.
  31. Marras et al.: Applying a prediction rule to identify low-risk patients with community-acquired pneumonia. Chest 2000;118:1339-43.
  32. Segreti et al.: Principles of antibiotic treatment of community-acquired pneumonia in the outpatient setting. Am. J. Med. 2005;118 Suppl 7A:21S-28S.
  33. Uranga et al.: Duration of Antibiotic Treatment in Community-Acquired Pneumonia: A Multicenter Randomized Clinical Trial. JAMA Intern Med 2016;176:1257-65.
  34. Postma et al.: Antibiotic treatment strategies for community-acquired pneumonia in adults. N. Engl. J. Med. 2015;372:1312-23.
  35. Williams et al.: Effectiveness of β-Lactam Monotherapy vs Macrolide Combination Therapy for Children Hospitalized With Pneumonia. JAMA Pediatr 2017;:.
  36. Frat et al.: High-flow oxygen through nasal cannula in acute hypoxemic respiratory failure. N. Engl. J. Med. 2015;372:2185-96.
  37. Biondi et al.: Treatment of mycoplasma pneumonia: a systematic review. Pediatrics 2014;133:1081-90.
  38. Gardiner et al.: Antibiotics for community-acquired lower respiratory tract infections secondary to Mycoplasma pneumoniae in children. Cochrane Database Syst Rev 2015;1:CD004875.
The content on or accessible through ClinicWiki is for informational purposes only. ClinicWiki is not a substitute for professional advice or expert medical services from a qualified healthcare provider.