Bacterial Pneumonia Clinical Presentation

Updated: Sep 30, 2020
  • Author: Justina Gamache, MD; Chief Editor: Guy W Soo Hoo, MD, MPH  more...
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During the intake history, the patient’s potential exposures, aspiration risks, host factors, and symptoms should be reviewed.

Potential exposures

A history of various exposures, such as travel, animal, occupational, and environmental exposures, can be helpful in determining possible etiologies and the likelihood of bacterial pneumonia, as follows:

  • Exposure to contaminated air-conditioning or water systems – Legionella species

  • Exposure to overcrowded institutions (eg, jails, homeless shelters) -S pneumoniae, Mycobacteria, Mycoplasma, Chlamydophila

  • Exposure to various types of animals - Cats, cattle, sheep, goats (C burnetii, B anthracis [cattle hide]; turkeys, chickens, ducks, or other birds (C psittaci); rabbits, rodents (F tularensis, Y pestis)

Aspiration risks

As previously discussed, patients at increased risk of aspiration are also at increased risk of developing pneumonia secondarily. Associated factors are as follows:

  • Alcoholism

  • Altered mental status

  • Anatomic abnormalities, congenital or acquired

  • Drug use

  • Dysphagia

  • Gastroesophageal reflux disease (GERD)

  • Seizure disorder

Additional host factors

As always, a thorough interview and determination of past medical history is of utmost utility. Inquire about the following:

  • Comorbid conditions (eg, asthma, COPD, smoking, and a compromised immune system are risk factors for H influenzae infection.)

  • Previous surgeries

  • Possibility of immunosuppression

  • Social and sexual history

  • Family history

  • Medication history

  • Allergy history


The clinical presentation of bacterial pneumonia varies. Sudden onset of symptoms and rapid illness progression are associated with bacterial pneumonias. Chest pain, dyspnea, hemoptysis (when clearly delineated from hematemesis), decreased exercise tolerance, and abdominal pain from pleuritis are also highly indicative of a pulmonary process.

The presence of cough, particularly cough productive of sputum, is the most consistent presenting symptom. Although not diagnostic of a particular causative agent, the character of the sputum may suggest a particular pathogen, as follows:

  • S pneumoniae is classically associated with a cough productive of rust-colored sputum.

  • Pseudomonas, Haemophilus, and pneumococcal species may produce green sputum.

  • Klebsiella species pneumonia is classically associated with a cough productive of red currant-jelly sputum.

  • Anaerobic infections often produce foul-smelling or bad-tasting sputum.

Nonspecific symptoms such as fever, rigors or shaking chills, and malaise are common. For unclear reasons, the presence of rigors may suggest pneumococcal pneumonia more often than pneumonia caused by other bacterial pathogens. [34] Other nonspecific symptoms that may be seen with pneumonia include myalgias, headache, abdominal pain, nausea, vomiting, diarrhea, anorexia and weight loss, and altered sensorium. [24]

Pertussis is often characterized by its long course of symptomatic cough in adults and by the presence of a whooping sound and/or posttussive vomiting in children.

Pneumonia from H influenzae most commonly arises in the winter and early spring. This pneumonia is more often associated with hosts who are debilitated.

Patients with Legionella pneumonia often present with mental status changes or diarrhea. Patients may develop hemoptysis or pulmonary cavitations. In addition, unlike other pneumonias, more than 50% of the time Legionella pneumonia has gastrointestinal (GI) symptoms associated with it, such as anorexia, nausea, vomiting, and diarrhea. Hyponatremia is often noted.

L pneumophila seems to have 2 forms: Pontiac fever and frank Legionella pneumonia. Pontiac fever has a viruslike presentation, with malaise, fever and/or chills, myalgias, and headache. This form of Legionella pneumonia usually subsides without sequelae. However, frank Legionella pneumonia is very aggressive, with a mortality rate as high as 75% unless treatment begins rapidly. This form typically occurs in individuals who are elderly and debilitated, as well as in smokers and those with COPD, alcoholism, immunocompromise, or have experienced trauma.


Physical Examination

Physical examination findings may vary, depending on the type of organism, severity of infection, coexisting host factors, and the presence of complications. [24, 35]

Signs of bacterial pneumonia may include the following:

  • Hyperthermia (fever, typically >38°C) [1] or hypothermia (< 35°C)

  • Tachypnea (>18 respirations/min)

  • Use of accessory respiratory muscles

  • Tachycardia (>100 bpm) or bradycardia (< 60 bpm)

  • Central cyanosis

  • Altered mental status

Physical findings may include the following:

  • Adventitious breath sounds, such as rales/crackles, rhonchi, or wheezes

  • Decreased intensity of breath sounds

  • Egophony

  • Whispering pectoriloquy

  • Dullness to percussion

  • Tracheal deviation

  • Lymphadenopathy

  • Pleural friction rub

Examination findings that may indicate a specific etiology for consideration are as follows:

  • Bradycardia may indicate a Legionella etiology.

  • Periodontal disease may suggest an anaerobic and/or polymicrobial infection.

  • Bullous myringitis may very rarely indicate Mycoplasma pneumoniae infection (largely disproven).

  • Physical evidence of risk for aspiration may include a decreased gag reflex.

  • Cutaneous nodules, especially in the setting of central nervous system (CNS) findings may suggestion Nocardia infection.


Risk Stratification

Severity-of-illness scores or prognostic models, such as the CURB-65 criteria or the Pneumonia Severity Index (PSI) can be used to help identify patients that may be candidates for outpatient treatment and those that may require admission (see below). The Infectious Disease Society of America (IDSA) and American Thoracic Society (ATS) proposed guidelines and criteria to determine the severity of community-acquired pneumonia (CAP), which would affect whether inpatient treatment would occur on the ward or require ICU care. [36] Although many of these predictive models were originally designed for assessment of CAP, a retrospective cohort study determined that they may also be applicable to HCAP. [37]


CURB-65 is a scoring system developed from a multivariate analysis of 1068 patients that identified various factors that appeared to play a role in patient mortality. [38] One point is given for the presence of each of the following:

  • C onfusion – Altered mental status

  • U remia – Blood urea nitrogen (BUN) level greater than 20 mg/dL

  • R espiratory rate –30 breaths or more per minute

  • B lood pressure – Systolic pressure less than 90 mm Hg or diastolic pressure less than 60 mm Hg

  • Age older than 65 years

Current guidelines suggest that patients may be treated in an outpatient setting or may require hospitalization according to their CURB-65 score, as follows:

  • Score of 0-1 – Outpatient treatment

  • Score of 2 – Admission to medical ward

  • Score of 3 or higher – Admission to intensive care unit (ICU)

The percentage of mortality at 30 days associated with the various CURB-65 scores increases with higher scores. The drastic increase in mortality between scores of 2 and 3 highlights the likely requirement for ICU admission in patients with a score of 3 or higher, as shown below:

  • Score of 0 – 0.7% mortality

  • Score of 1 – 2.1% mortality

  • Score of 2 – 9.2% mortality

  • Score of 3 – 14.5% mortality

  • Score of 4 – 40% mortality

  • Score of 5 – 57% mortality

Pneumonia severity index

The PSI, also known as the PORT score (for the study by which it was validated), is a prediction rule for mortality based on characteristics derived from cohorts of patients hospitalized with pneumonia. [39] For each of the various characteristics, a predetermined value of points is assigned. In a retrospective cohort comparison of different predictive models applied to HCAP, the PSI had the highest sensitivity in predicting mortality. However, alternative tools, including the IDSA/ATS, SCAP, and SMART-COP (mentioned below), are considered easier to calculate. [37]

Demographic factors are scored as follows:

  • Age, men – Starting point value is age in years

  • Age, women – Starting point value is age in years minus 10 points

  • Nursing home resident – Add 10 points

Coexisting illnesses are scored as follows:

  • Neoplasia – Add 30 points

  • Liver disease – Add 20 points

  • Congestive heart failure, cerebrovascular disease, renal disease – Add 10 points for each

Physical examination findings are scored as follows:

  • Altered mental status – Add 20 points

  • Respiratory rate of 30 breaths or more per minute – Add 20 points

  • Systolic blood pressure less than 90 mmHg – Add 20 points

  • Temperature less than 35°C or that is 40°C or higher – Add 15 points

  • Pulse greater than 125 bpm – Add 10 points

Laboratory and radiographic findings are scored as follows:

  • Arterial pH less than 7.35 – Add 30 points

  • BUN value of 30 mg/dL or greater – Add 20 points

  • Sodium level less than 130 mmol/L – Add 20 points

  • Glucose level of 250 mg/dL or greater – Add 10 points

  • Hematocrit value less than 30% – Add 10 points

  • Partial arterial pressure (PaO2) less than 60 mm Hg or peripheral oxygen saturation (SpO2) less than 90% while breathing room air – Add 10 points

  • Pleural effusion – Add 10 points

The combined total points make up the risk score, which stratifies patients into 5 PSI mortality risk classes, as follows:

  • 0-50 points = Class I (0.1% mortality)

  • 51-70 points = Class II (0.6% mortality)

  • 71-90 points = Class III (0.9% mortality)

  • 91-130 points = Class IV (9.3% mortality)

  • More than 130 points = Class V (27% mortality)

Current guidelines suggest that patients may be treated in an outpatient setting or may require hospitalization depending on their PSI risk class, as follows:

  • Classes I and II – Outpatient management

  • Class III – Admission to an observation unit or for short hospital stay

  • Classes IV and V – Treatment in inpatient setting

The Agency for Healthcare Research and Quality (AHRQ) has provided a PSI calculator. [40]

It is important to remember that objective criteria and scores should be used as guides only and should always be supplemented with physician determination of the patient's therapeutic needs. The risks and benefits of hospitalization should be weighed carefully, because hospitalization can put patients at additional risk (eg, thromboembolic events, nosocomial superinfection). When a pneumonia is due to mixed etiologies, it is often underestimated by severity scores. [33]

IDSA/ATS CAP criteria

Prediction rules like the CURB-65 and PSI have proven useful for standardizing clinical assessments and identifying low-risk patients who may be appropriate candidates for outpatient therapy, but they have been less useful for discriminating between moderate (ward-appropriate) and high-risk (ICU-appropriate) patients. [41]

The IDSA/ATS criteria for severe community-acquired pneumonia (CAP) are composed of both major and minor criteria. Although the major criteria indicate clear need for ICU-level care, the minor criteria for defining severe CAP have been validated for the use of differentiating between patients requiring ward-level versus ICU-level care. [41, 36, 42]

These criteria are particularly helpful in identifying those patients who are appropriate for admission to the ICU but who do not meet the major criteria of requiring mechanical ventilation or vasopressor support.

The presence of three of the following minor criteria indicates severe CAP and suggests the likely need for ICU-level care:

  • Respiratory rate of 30 breaths or more per minute

  • Ratio of PaO2 to fraction of inspired oxygen (ie, PaO2/FiO2) of 250 or less

  • Need for noninvasive ventilation (bilevel positive airway pressure [BiPAP] or continuous positive airway pressure [CPAP])

  • Multilobar infiltrates

  • Confusion/disorientation

  • Uremia (BUN 20 mg/dL or greater)

  • Leukopenia (white blood cell [WBC] count less than 4000 cells/µL)

  • Thrombocytopenia (platelet count less than 100,000/µL)

  • Hypothermia (core temperature less than 36°C)

  • Hypotension requiring aggressive fluid resuscitation

The major criteria are as follows:

  • Invasive mechanical ventilation

  • Septic shock requiring vasopressor support

Direct admission to an ICU is mandated for any patient with septic shock and a requirement for intravenous vasopressors support or with acute respiratory failure requiring intubation and mechanical ventilation.

Biological markers

Over the past 10 years, great enthusiasm has been noted regarding the potential of biological markers, such as C-reactive protein (CRP) and procalcitonin (PCT), for the diagnosis and prognostication of pneumonia. PCT appears to be promising, especially as a prognosticator. [43]

Other scoring models

Multiple other scoring models exist that can be used to aid in the prediction of mortality in severe illness (namely in the ICU setting), including the acute physiology and chronic health evaluation (APACHE II) score, [44] simplified acute physiology score (SAPS II), [45] and sepsis-related organ failure assessment (SOFA) score. [46]

Whereas most scoring models have been used for predicting outcomes in patients carrying a diagnosis of CAP, the systolic blood pressure, oxygenation, age, respiratory rate (SOAR) model has been validated for predicting 30-day mortality in patients hospitalized with nursing home-acquired pneumonia (NHAP). [47]

Still other prediction models regarding pneumonia severity and outcomes are currently being explored and developed, such as the Spanish CURXO-80 tool [48] ; predisposition, insult, response, and organ dysfunction (PIRO) tool [49] ; and systolic blood pressure, multilobar involvement, albumin level, respiratory rate, tachycardia, confusion, oxygenation and arterial pH (SMART-COP) tool. [50]



Potential complications of bacterial pneumonia include the following:

  • Destruction and fibrosis/organization of lung parenchyma with scarring

  • Bronchiectasis

  • Necrotizing pneumonia

  • Frank cavitation

  • Empyema

  • Pulmonary abscess

  • Respiratory failure

  • Acute respiratory distress syndrome

  • Ventilator dependence

  • Superinfection

  • Meningitis

  • Death

Parapneumonic pleural effusions and empyema

Parapneumonic effusions are common complications of bacterial pneumonia. These pleural effusions occur adjacent to a bacterial pneumonia, resulting from migration of excess interstitial lung fluid across the visceral pleura. Small-volume parapneumonic effusions typically resolve with treatment of the bacterial pneumonia and thus do not require drainage. However, pleural effusions greater than 10mm on lateral decubitus radiographic view should undergo thoracentesis and pleural fluid analysis, Gram stain, and culture to further guide antibiotic selection. Parapneumonic effusions with radiographic evidence of loculated or thickened pleura suggestive of empyema, or pleural fluid pH less than 7.2 or a glucose value less than 60, typically require thoracostomy tube drainage and possible thorascopic debridement via thoracic surgery. Empiric antibiotics for bacterial pneumonias complicated by empyema should include anaerobic coverage, as anaerobic bacteria are often cultured from empyemas. [51]

Go to Parapneumonic Pleural Effusions and Empyema Thoracis  for complete information on this topic.