community-acquired pneumonia: Pneumonia occurring in outpatients, often caused by infection with streptococcus, Haemophilus influenzae, Staphylococcus aureus, and atypical organisms. Mortality is approximately 15% but depends on many host and pathogen features


  • Cough, fever, dyspnea, chills
  • Chest pain (pleuritic or nonpleuritic)
  • Thick, yellow-green, bloody or rusty sputum
  • Mental status changes: Anxiety, confusion, restlessness, obtundation, coma
  • Abdominal pain, anorexia, diarrhea
  • Atypical:
  • Insidious onset of dry cough
  • Extrapulmonary symptoms: Diarrhea, headache, myalgias, sore throat
  • Alcoholics
  • Asthma patients
  • Immunosuppressed patients
  • Age more than 70 years
  • Dementia
  •   Seizures
  • Congestive heart failure
  • Cerebrovascular disease
  • Tobacco smoking
  • COPD
  • Male patients
  • Black race
  • HIV infected patients
  • Malignancy
  • Diabetes
  • End stage renal disease Leukopenia.


Etiology of Community Acquired Pneumonia (CAP)

  • The organism causing pneumonia may be isolated from:
  • Blood culture  Sputum
  • Pleural fluid
  • Pulmonary tissue Bronchial secretion
  • Pleural fluid
  • Nasopharyngeal swab.
  • Community acquired pneumonia or CAP may be caused by bacteria, fungi, viruses and parasites.
  • The infecting agent is usually
  • Streptococcus neumoniae Hemo hilus influenzae Staphylococcus aureus B’ycoplasma pneumon@e C. pneumoniae
  • Moraxella catarrhalis k-egionel@
  • Aerobic gram negative bacteria Influenza virus
  • Adenovirus
  • respiratory syncytial virus.
  • Out of all these S. pneumoniae is the commonest.

Clinical manifestations of CAP

  • Onset may be sudden, or slow / insidious.

Typical symptoms:

  •  Fever
  •   Pleuritic chest pain
  • Chills and rigors
  • . Shortness of breath

Other Additional symptoms:

  • Headache
  • Nausea, vomiting, diarrhoea Myalgia, arthralgia
  • Fatigue, weakness Confusion
  • Cough, with no sputum or rust-coloured or pu­rulent sputum.


  • Pulse oximetry to evaluate oxygenation
  • Tachypnea, tachy/bradycardia, cyanosis
  • Decreased breath sounds, rales, friction rub
  • Consolidation: Egophony, increased fremitus, pectoriloquy, dullness to percussion
  • Abdominal tenderness or pain
  • VAP is suspected when a patient receiving mechanical ventilation develops a new or progressive infiltrate with fever, leukocytosis, or purulent tracheobronchial secretions; increased respiratory rate, increased minute ventilation, decreased tidal volume, decreased oxygenation, or a need for more ventilator support or inspired oxygen


  • Tachynea – Respiratory rate more than 25/ min.
  • Iness on percussion of lungs
  • Increased vocal fremitus
  • Aegophony
  • Whispering pectoriloquy Crackles
  • Pleural friction rub.
Pneumonia is considered severe and has a bad prognosis if :
  • Patient has confusion Blood urea is increased
  • Respiratory rate is more than 30/min
  • Systolic blood pressure is less than 90 mmHg Patient needs ventilator
  • Patient requir~s vasopressors
  • There is multi lobar involvement
  • Mortality rate is high with infection with Pseudomonas aeruginosa, Klebsiell, E. coli, Staph aureus, Acinetobacter
  • In healthy patients it takes 5 – 14 days to re­cover from community acquired pneumonia.
Fatal complications are:
  • Respiratory failure Congestive heart failure Shock
  • Atrial arrhythmias Myocardial infarction GI bleeding
  • Renal failure.

Community acquired pneumonia in immuno­compromised persons

  • Pneumonia is common in HIV patients, transplant recipients, patients of malignancy.

Investigations  and Chest x-ray




  • Routine diagnostic tests to identify an etiologic diagnosis are optional for outpatients with CAP.
  • Complete blood count (CBC) with differential (leukocytosis with left shift), Chem 7
  • If age >60 years or with coexisting illness, arterial blood gases (ABGs) for low PO2or for suspected acidosis
  • Sputum Gram stain and culture: Good sample >25 polymorphonuclear neutrophils (PMNs) and <10 epithelial cells/low-power field (LPF)
  • Blood culture before antibiotics: 5–14% positive

CT scan:

  • These show conasolidation, pulmonary opacities, cavity, lung abscess, air-fluid levels, cres­cent or meniscus sign in aspergillosis, miliary shad­ows, pleural effusion.

Blood culture:

  • Should be taken if patient has temperature more than 38.50C i.e. hyperthermia,
  • tem­perature <36°C i.e. hypothermia, patient is alcoholic, and hospitalized patients.
  • Two blood cultures should be sent.
  • Most commonly S. pneumoniae, S. aureus and E. coli
  • are isolated

Sputum slide and culture:

  • Gram’s stain of sputum should be done to see Gram positive diplococi,
  • M. tuberculosis,
  • Hemophilus,
  • Legionella.
  • AFB stainin for tuberculosis.
  • Monoclonal antibody staining for pneumocystis pneumonia.
  • Special stain for fungi.

Detection of Antigens in urine:

  • Legionnaires dis­ease can be diagnosed by antigen in urine of patients by ELISA (enzyme linked immunosorbent assay).
  • S. pneumoniae can also be diagnosed by ELISA for urinary antigen.


  • IgM antibody. levels for specific patho­gens are increased in
  • M. pneumoniae,
  • C. pneumoniae,
  • Chlamydia,
  • Legionella,
  • C. burnettii,
  • adenovirus,·
  • parainfluenza,
  • influenza.
  • Other tests are complement fixation, ELISA, IgG an­tibodies.

Polymerase chain reaction (PCR) :

  • A multiplex PCR detects DNA of the pathogen.


  • Outpatient treatment and no risk factors for drug-resistant S. pneumoniae(DRSP) infection:
  • Macrolide e.g., azithromycin, clarithromycin, or erythromycin, doxycycline
  • Doxycycline is alternative in face of comorbidities or other risk for DRSP infection: Chronic heart failure; lung, liver, or renal disease; diabetes mellitus; alcoholism; malignancies; asplenia; immunosuppressing conditions or use of immunosuppressive drugs; use of antimicrobials within the previous 3 months (in which case an alternative from a different class should be selected)
  • Respiratory fluoroquinolone (e.g., moxifloxacin, gemifloxacin, or levofloxacin 750 mg) Lactam plus a macrolide High-dose amoxicillin (1 g t.i.d.) or amoxicillin-clavulanate (2 g b.i.d.); alternatives include ceftriaxone, cefpodoxime, and cefuroxime (500 mg b.i.d.) and doxycycline


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