Pneumonia, Bacterial

Naureen Rafiq, MD and Khalid Bashir, MD Reviewed 06/2018

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Subject: Pneumonia, Bacterial

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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 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; hemodialysis clinic within the past 30 days


  • Influenza and pneumonia are the eight leading cause of death in the United States with about 53,282 deaths in 2013.

  • HAP is the leading cause of death among nosocomial infections and is one of the leading causes of death in the ICU.

  • Rates of infection are 3 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.

  • Mortality rate in children is approximately 1.6 million a year. 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 (1).


  • 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 (2)[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) (3)


  • 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 4th dose at 12 to 15 months of age

  • Adults ≥65 years who have not received vaccine naïve, ACIP currently recommends PCV13 followed by pneumococcal polysaccharide (PPSV23) ≥1 year interval. If they received PPSV23 vaccine before age 65 years, they should receive a dose of PCV13 followed by a subsequent PPSV23 ≥1 year after PCV13 and at least 5 years have passed since their previous PPSV23 dose.

  • For adults ≥65 years old who have already received PPSV23, a dose of PCV13 is indicated after ≥1 year.

  • Adults 19 to 64 years who have chronic diseases, including alcoholism and tobacco use, should receive PPSV23.

  • Adults ≥19 years old with immunocompromising conditions, asplenia, CSF leaks, cochlear implants who have not received PPSV23 or PCV13 should receive one dose of PCV13 followed by PPSV23 after ≥8 weeks. If a second dose of PPSV23 is recommended, it should be given 5 years after 1st dose. Adults >19 years, previously given PPSV23 should receive a PPCV13 dose ≥1 year after last PPSV23. If additional PPSV23 is required, it should be given ≥8 weeks after PCV13 and 5 years after most recent dose of PPSV23.

  • Annual influenza vaccine



  • Fever, chills, rigors, malaise, fatigue

  • Dyspnea

  • Cough, with/without sputum

  • Pleuritic chest pain

  • Myalgias

  • GI symptoms


High fever (>104°F [40°C]), male sex, multilobar involvement, and GI and neurologic abnormalities have been associated with CAP caused by Legionella.

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, procalcitonin, 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 (2)[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

      • Previously healthy, no antibiotics in past 3 months

      • Comorbid conditions, immunosuppressed, antibiotic use in past 3 months

        • Levofloxacin 750 mg PO daily for 5 days; moxifloxacin 400 mg PO daily for 5 days; or

        • Amoxicillin 1 g PO TID; amoxicillin-clavulanate 2 g PO BID + macrolide/doxycycline for 5 days

        • Treatment may be stopped if

          • Afebrile for >48 hours

          • Supplemental oxygen no longer needed

          • No more than one of the following:

            • HR >100 beats/min

            • RR >24 breaths/min

            • Systolic blood pressure (BP) ≤90 mm Hg

    • CAP, inpatient (non-ICU)

    • Add vancomycin or linezolid HCAP/HAP/VAP.

      • Use IV antibiotics.

      • Early onset (<5 days) and no risk factors for multidrug-resistant pathogens

      • 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)

    • Adult IV antibiotic doses

  • Pediatric, outpatient (≥3 months)

    • Antibiotic treatment in preschool-aged children is not routinely required because viral pathogens are more common (5)[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) (5)[A]

      • Amoxicillin-clavulanate 90 mg/kg/day PO BID (max 4 g/day) (5)[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) (5)[C]

    • Atypical bacterial pneumonia


  • 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

  • The CURB-65 or CRB 65 (confusion, urea nitrogen RR, BP, age >65 years) ( is a severity of illness score for stratifying adults with CAP into different management groups.

  • The SMART-COP (systolic BP, multilobar chest radiography, albumin, RR, 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.

  • 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 (6).

  • 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 


Necrotizing pneumonia, respiratory failure, empyema, abscesses, cavitation, bronchopleural fistula, sepsis 


1 Jain S, Williams DJ, Arnold SR, et al; and CDC EPIC Study Team. Community-acquired pneumonia requiring hospitalization among U.S. children. N Engl J Med.  2015;372(9):835–845.  [View Abstract]
2 File TMJr. Recommendations for treatment of hospital-acquired and ventilator-associated pneumonia: review of recent international guidelines. Clin Infect Dis.  2010;51(Suppl 1):S42–S47.  [View Abstract]
3 Shindo Y, Ito R, Kobayashi D, et al. Risk factors for drug-resistant pathogens in community-acquired and healthcare-associated pneumonia. Am J Respir Crit Care Med.  2013;188(8):985–995.  [View Abstract]
4 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.  2015;(8):CD007577.  [View Abstract]
5 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.  [View Abstract]
6 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.  [View Abstract]



  • J15.9 Unspecified bacterial pneumonia

  • J15.4 Pneumonia due to other streptococci

  • J14 Pneumonia due to Hemophilus influenzae

  • J15.20 Pneumonia due to staphylococcus, unspecified

  • J15.3 Pneumonia due to streptococcus, group B

  • J15.5 Pneumonia due to Escherichia coli

  • J15.8 Pneumonia due to other specified bacteria

  • J15.0 Pneumonia due to Klebsiella pneumoniae

  • J13 Pneumonia due to Streptococcus pneumoniae

  • J15.29 Pneumonia due to other staphylococcus

  • J15.1 Pneumonia due to Pseudomonas

  • J15.6 Pneumonia due to other aerobic Gram-negative bacteria

  • J15.211 Pneumonia due to methicillin suscep staph

  • J15.7 Pneumonia due to Mycoplasma pneumoniae

  • J15.212 Pneumonia due to Methicillin resistant Staphylococcus aureus


  • 482.9 Bacterial pneumonia, unspecified

  • 482.30 Pneumonia due to Streptococcus, unspecified

  • 482.2 Pneumonia due to Hemophilus influenzae [H. influenzae]

  • 482.40 Pneumonia due to Staphylococcus, unspecified

  • 482.32 Pneumonia due to Streptococcus, group B

  • 482.1 Pneumonia due to Pseudomonas

  • 482.84 Pneumonia due to Legionnaires’ disease

  • 482.0 Pneumonia due to Klebsiella pneumoniae

  • 482.41 Methicillin susceptible pneumonia due to Staphylococcus aureus

  • 482.31 Pneumonia due to Streptococcus, group A

  • 482.42 Methicillin resistant pneumonia due to Staphylococcus aureus

  • 482.82 Pneumonia due to escherichia coli [E. coli]

  • 482.81 Pneumonia due to anaerobes

  • 482.89 Pneumonia due to other specified bacteria

  • 482.39 Pneumonia due to other Streptococcus

  • 482.83 Pneumonia due to other gram-negative bacteria

  • 482.49 Other Staphylococcus pneumonia


  • 53084003 Bacterial pneumonia (disorder)

  • 34020007 pneumonia due to Streptococcus (disorder)

  • 70036007 Haemophilus influenzae pneumonia

  • 22754005 Staphylococcal pneumonia (disorder)

  • 429271009 ventilator-acquired pneumonia (disorder)

  • 51530003 Pneumonia due to Escherichia coli

  • 425464007 Nosocomial pneumonia (disorder)

  • 409664000 Pneumonia due to anaerobic bacteria (disorder)

  • 64479007 Pneumonia due to Klebsiella pneumoniae


  • 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.