COMMUNITY ACQUIRED PNEUMONIA 

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

History COMMUNITY ACQUIRED PNEUMONIA

• 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.

Physical Exam COMMUNITY ACQUIRED PNEUMONIA

• 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

Physical signs COMMUNITY ACQUIRED PNEUMONIA

• 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

Initial Lab Tests COMMUNITY ACQUIRED PNEUMONIA

• 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.

Serology:

• 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.

Treatment for COMMUNITY ACQUIRED PNEUMONIA

• 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