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Pneumonia, Bacterial
Rahele Lameh, MD
image BASICS
Bacterial pneumonia is an infection of the pulmonary parenchyma by a bacterial organism.
Bacterial pneumonia can be classified as the following:
  • Community-acquired pneumonia (CAP): lower respiratory tract infection not acquired in a hospital, long-term care facility, or during other recent contact with the health care system
  • Medical care-associated pneumonia
    • Hospital-acquired pneumonia (HAP): pneumonia within ≥48 hours after admission and did not appear to be incubating at time of admission
    • Ventilator-associated pneumonia (VAP): Pneumonia that develops >48 to 72 hours after endotracheal intubation.
    • Health care-associated pneumonia (HCAP): Pneumonia that occurs in a nonhospitalized patient with extensive health care contact, such as the following:
      • IV therapy/wound care within past 30 days
      • Residing in a nursing home/long-term care
      • Hospitalization in an acute care hospital for ≥2 days within the past 90 days
      • Visited a hospital/hemodialysis clinic within the past 30 days (1,2)
  • Influenza and pneumonia are the 8th leading cause of death in the United States, with about 53,692 deaths in 2010.
  • In 2006, 55,477 people died of pneumonia (3).
  • HAP is the leading cause of death among hospitalacquired infections and is the primary cause of death in the ICU.
  • Rates of infection are three times higher in African Americans than in whites and are 5 to 10 times higher in Native American adults and 10 times higher in Native American children (2).
  • Mortality rate in children is approximately 1.6 million a year (4). Hospitalization rate for children with CAP is still highest among the very young ages (<18 months). Respiratory viruses are the most commonly detected causes of pneumonia (5).
  • CAP: 5 to 11 cases/1,000 persons with increased incidence occurring in the winter months.
  • HAP: 5 to 10 cases/1,000 admissions; incidence increase 6- to 20-fold in ventilated patients (6)[A].
  • Adults, CAP
    • Typical (85%): Streptococcus pneumoniae, Haemophilus influenzae, Staphylococcus aureus, group A Streptococcus, Moraxella catarrhalis
    • Atypical (15%): Legionella sp., Mycoplasma pneumoniae, Chlamydophila pneumoniae
  • Adults, HCAP/HAP/VAP
    • Aerobic gram-negative bacilli: Pseudomonas aeruginosa, Escherichia coli, Klebsiella pneumoniae, and Acinetobacter sp.
    • Gram-positive cocci: Streptococcus sp. and S. aureus (including MRSA)
  • Children
    • Birth to 20 days: E. coli, group B Streptococci, Listeria monocytogenes
    • 3 weeks to 3 months: Chlamydia trachomatis, S. pneumoniae
    • 4 months to 18 years
      • Typical: S. pneumoniae
      • Atypical: C. pneumoniae, M. pneumoniae
  • Age >65 years
  • HIV/immunocompromised
  • Recent antibiotic therapy/resistance to antibiotics
  • Asthma, CAD, COPD, chronic renal failure, CHF, diabetes, liver disease, VAP, HAP, HCAP
  • Hospitalization for ≥2 days during past 90 days
  • Severe illness
  • Antibiotic therapy in the past 6 months
  • Poor functional status as defined by activities of daily living score
  • Immunosuppression (including steroid users)
  • All children 2 to 59 months of age should be routinely vaccinated with pneumococcal conjugate (PCV13); given at 2, 4, and 6 months of age; a fourth dose at 12 to 15 months of age. PCV13 is also FDA approved for those >50 years of age.
  • For adults aged 65 years or older who have not received any penumonia vaccination, ACIP currently recommends PCV13 followed by pneumococcal polysaccharide (PPSV23) with 6 to 12 months interval. If they received PPSV23 vaccine before age 65 years, they should receive another dose of the vaccine at age 65 years or later if at least 5 years have passed since their previous dose.
  • PPSV23 is also indicated at age 19 to 64 years who are immunocompromised, including asthma and cigarette smokers. A second dose of PPSV23 is recommended 5 years after the first dose for persons aged 19 to 64 years with functional or anatomic asplenia and for persons with immunocompromising conditions. ACIP does not recommend multiple revaccinations due to uncertainty about safety and benefit of revaccination.
  • Annual influenza vaccine is recommended according to current guidelines.
  • Fever, chills, rigors, malaise, fatigue
  • Dyspnea
  • Cough, with/without sputum
  • Pleuritic chest pain
  • Myalgias
  • GI symptoms
Geriatric Considerations
Older adults with pneumonia often present with weakness, mental status change, or history of falls.
  • Fever >100.4°F (38°C), tachypnea, tachycardia
  • Rales, rhonchi, egophony, increased fremitus, bronchial breath sounds, dullness to percussion, asymmetric breath sounds, abdominal tenderness
Bronchitis, asthma exacerbation, pulmonary edema, lung cancer, pulmonary tuberculosis, pneumonitis
Initial Tests (lab, imaging)
  • Routine laboratory testing to establish an etiology in outpatients with CAP is usually unnecessary.
  • For hospitalized patients with CAP, a CBC, sputum Gram stain, and two sets of blood cultures
  • More extensive diagnostic testing in patients with CAP is recommended if:
    • Blood cultures: ICU admission, cavitary infiltrates, leukopenia, alcohol abuse, severe liver disease, asplenia, positive pneumococcal urine antigen test (UAT), pleural effusion
    • Sputum Gram stain and cultures: ICU admission, failure of outpatient treatment, cavitary infiltrates, alcohol abuse, severe COPD/structural lung disease, positive Legionella UAT, positive pneumococcal UAT, pleural effusion
    • Legionella UAT: ICU admission, failure of outpatient treatment, alcohol abuse, travel in past 2 weeks, pleural effusion
    • Pneumococcal UAT: ICU admission, failure of outpatient treatment, leukopenia, alcohol abuse, severe liver disease, asplenia, pleural effusion
  • A chest x-ray (CXR) is indicated when pneumonia is suspected or with an acute respiratory infection and
    • Vital signs: temperature >100°F (37.8°C); heart rate (HR) >100 beats/min; respiratory rate (RR) >20 breaths/min
    • At least two of the following clinical findings: decreased breath sounds, rales, no asthma
  • Early in disease course, CXR may be negative.
  • Evidence of necrotizing/cavitary pneumonia should raise suspicion for MRSA pneumonia, especially with history of prior MRSA skin lesions.
Diagnostic Procedures/Other
  • For VAP/HAP: By bronchoscopic or nonbronchoscopic means, obtain a lower respiratory tract sample for culture prior to initiation/change of therapy. Serial evaluations may be needed (6)[A].
  • Safe cessation of antibiotics can be done from a good quality negative sputum culture.
First Line
  • Adults
    • CAP, outpatient
      • No significant differences in efficacy between antibiotic option in adults (7)[A]
      • Previously healthy, no antibiotics in past 3 months
        • Azithromycin 500 mg PO 1 time, then 250 mg PO daily for 4 days; clarithromycin 500 mg PO BID for 10 days; erythromycin 500 mg PO BID for 10 days, or
        • Doxycycline 100 mg PO BID for 10 days
      • Comorbid conditions, immunosuppressed, antibiotic use in past 3 months
        • Levofloxacin 750 mg PO daily for 5 days; moxifloxacin 400 mg PO daily for 10 days; or
        • Amoxicillin 1 g PO TID; amoxicillin-clavulanate 2 g PO BID + macrolide
        • Treatment may be stopped if
          • Afebrile for >48 hours
          • Supplemental oxygen no longer needed
          • P.811

          • No more than one of the following:
            • A. HR >100 beats/min
            • B. RR >24 breaths/min
            • C. Systolic BP ≤90 mm Hg
    • CAP, inpatient (non-ICU)
      • IV antibiotics initially, then switch to oral after clinical improvement
      • Cefotaxime; ceftriaxone; ampicillin-sulbactam + macrolide (clarithromycin; erythromycin) for 14 days or
      • Moxifloxacin; levofloxacin for 14 days
      • If Pseudomonas is a consideration.
        • Piperacillin-tazobactam; cefepime; imipenem; meropenem + levofloxacin or
        • Piperacillin-tazobactam; cefepime; imipenem; meropenem + aminoglycoside and azithromycin or
        • Piperacillin-tazobactam; cefepime; imipenem; meropenem + aminoglycoside + levofloxacin
      • If MRSA is a consideration.
        • Add vancomycin or linezolid.
      • Use IV antibiotics.
      • Early onset (<5 days) and no risk factors for multidrug-resistant pathogens
        • Ceftriaxone; ampicillin-sulbactam; ertapenem or
        • Levofloxacin; moxifloxacin
      • Late onset (≥5 days) or risk factors for multidrug-resistant pathogens (antibiotic therapy in preceding 90 days; high frequency of antibiotic resistance in community/hospital; immunosuppressive disease/therapy; risk factors for HCAP)
        • MRSA coverage: linezolid or vancomycin + &bgr;-lactam cefepime; ceftazidime; imipenem; meropenem; piperacillin-tazobactam + either fluoroquinolone (levofloxacin) or aminoglycoside (amikacin; gentamicin; tobramycin) (level II)
        • Short-course versus prolonged-course antibiotic therapy for HAP in critically ill adults is only as effective and reduced recurrence of VAP-associated multidrug resistance (8).
        • Drug-resistant S. pneumoniae should be treated with high-dose amoxicillin, amoxicillin/clavulanate, cefpodoxime with a macrolide, or a respiratory fluoroquinolone.
    • Adult IV antibiotic doses
      • &bgr;-Lactams (ampicillin-sulbactam 3 g q6h; aztreonam 2 g q6h; cefepime 1 to 2 g q8-12h; cefotaxime 1 g q6-8h; ceftazidime 2 g q8h; ceftriaxone 1 g daily; imipenem 500 mg q6h; meropenem 1 g IV q8h)
      • Aminoglycosides (amikacin 20 mg/kg daily; gentamicin 7 mg/kg daily; tobramycin 7 mg/kg daily)
      • Fluoroquinolones (levofloxacin 750 mg daily; moxifloxacin 400 mg daily)
      • Macrolides (azithromycin 500 mg daily; clarithromycin 500 mg daily; erythromycin 500 to 1,000 mg q6h)
      • Vancomycin 15 mg/kg q12h
      • Linezolid 600 mg q12h
      • Telavancin is an antibiotic which covers MRSA infection, and it was approved by FDA in 2013. Telavancin is approved for the treatment of HAP and VAP caused by S. aureus. This medication is indicated only when alternative agents cannot be used (3).
  • Pediatric, outpatient (≥3 months)
    • Antibiotic treatment in preschool-aged children is not routinely required because viral pathogens are more common (9)[A].
    • Oral antibiotics are as efficacious as IV in CAP (length of stay and oxygen requirement were reduced in those given oral antibiotics).
    • Typical bacterial pneumonia
      • Amoxicillin 90 mg/kg/day PO BID (max 4 g/day) (9)[A]
      • Amoxicillin-clavulanate 90 mg/kg/day PO BID (max 4 g/day) (9)[A]
      • Alternative: levofloxacin 16 to 20 mg/kg/day PO BID for children 6 months to 5 years, 10 mg/kg/day daily for children ≥5 years (max 750 mg/day) (9)[C]
    • Atypical bacterial pneumonia
      • Azithromycin 10 mg/kg PO on day 1 (max 500 mg), then 5 mg/kg/day (max 250 mg) on days 2 to 5 (8)[C]
      • Clarithromycin 15 mg/kg/day PO BID (max 1 g/day) (8)[C]
      • Erythromycin 40 mg/kg/day PO daily (8)[C]
Admission Criteria/Initial Stabilization
  • Clinical judgment and use of a validated severity of illness score are recommended to determine if inpatient management is indicated.
  • The Pneumonia Severity Index (PSI) is a clinical prediction rule used to calculate the probability of morbidity and mortality among patients with CAP. PSI is risk stratified from I to V. PSI risk class from I to III can be treated as outpatients and IV to V should be hospitalized. PSI can be calculated at http://pda.ahrq.gov/clinic/psi/psicalc.asp
  • The CURB-65 or CRB 65 (confusion, urea nitrogen-respiratory rate, blood pressure, age >65 years) (http://www.mdcalc.com/curb-65-severity-score-community-acquired-pneumonia/) is a severity of illness score for stratifying adults with CAP into different management groups (7).
  • The SMART-COP (systolic BP, multilobar chest radiography, albumin, respiratory rate, tachycardia, confusion, oxygen level, and arterial pH) is a new method to predict which patients will require intensive respiratory/vasopressor support. A score of ≥3 has sensitivity of 92% to identify those patients who will receive intensive treatment (7).
  • Patients with COPD or CHF are more likely to require ICU admission when suffering from CAP.
  • Clinical prediction tools do not replace a physician's clinical judgment.
Pediatric Considerations
Inpatient treatment of children is recommended in the following settings: infants ≤3 to 6 months; presence of respiratory distress (tachypnea, dyspnea, retractions, grunting, nasal flaring, apnea, altered mental status, O2 sat <90%); or if known to have CAP as result of a virulent pathogen such as community-associated MRSA should be hospitalized (10).
Discharge Criteria
Clinical stability: temperature ≤100°F (37.8°C); HR ≤100 beats/min; RR ≤24 beats/min; systolic BP ≤90 mm Hg; O2 sat ≥90% or PaO2 ≥60 mm Hg on room air; ability to maintain oral intake; normal mental status
Patient Monitoring
Consider chest CT if patient is failing to improve on current management.
Smoking cessation, vaccinations
1. Marrie TJ, Huang JQ. Epidemiology of community-acquired pneumonia in Edmonton, Alberta: an emergency department-based study. Can Respir J. 2005;12(3):139-142.
2. Davidson M, Parkinson AJ, Bulkow LR, et al. The epidemiology of invasive pneumococcal disease in Alaska, 1986-1990—ethnic differences and opportunities for prevention. J Infect Dis. 1994;170(2):368-376.
3. FDA news release. FDA approves Vibativ for hospitalized patients with bacterial pneumonia. http://www.fda.gov/newsevents/newsroom/pressannouncements/ucm358209.htm. Accessed 2013.
4. Black RE, Cousens S, Johnson HL, et al. Global, regional, and national causes of child mortality in 2008: a systematic analysis. Lancet. 2 010;375(9730):1969-1987.
5. Jain S, Williams DJ, Arnold SR, et al. Community-acquired pneumonia requiring hospitalization among U.S. children. N Engl J Med. 2015;372(9):835-845.
6. File TM Jr. Recommendations for treatment of hospital-acquired and ventilator-associated pneumonia: review of recent international guidelines. Clin Infect Dis. 2010;51(Suppl 1):S42-S47.
7. Watkins RR, Lemonovich TL. Diagnosis and management of community-acquired pneumonia in adults. Am Fam Physician. 2011;83(11): 1299-1306.
8. Pugh R, Grant C, Cooke RP, et al. Short-course versus prolonged-course antibiotic therapy for hospital-acquired pneumonia in critically ill adults. Cochrane Database Syst Rev. 2011;(10): CD007577.
9. Bradley JS, Byington CL, Shah SS, et al. The management of community-acquired pneumonia in infants and children older than 3 months of age: clinical practice guidelines by the Pediatric Infectious Diseases Society and the Infectious Diseases Society of America. Clin Infect Dis. 2011;53(7):e25-e76.
10. Devitt M. PIDS and IDSA issue management guidelines for community-acquired pneumonia in infants and young children. Am Fam Physician. 2012;86(2):196-202.
  • J15.9 Unspecified bacterial pneumonia
  • J15.4 Pneumonia due to other streptococci
  • J14 Pneumonia due to Hemophilus influenzae
Clinical Pearls
  • Bacterial pneumonia can usually be treated empirically based on its classification as CAP or HCAP/HAP/VAP.
  • A severity of illness score is helpful in determining the need for hospitalization of adult patients but does not replace a physician's clinical judgment.