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Pneumonia%20-%20community-acquired Signs and Symptoms
Introduction
- Acute infection of the pulmonary parenchyma accompanied by symptoms of acute illness and abnormal chest findings
- Occurs at highest rates in the very young and the very old
- Potentially life-threatening especially in older adults and those with comorbid disease
- Still the leading cause of death from an infectious disease in adults and in children <5 years old
- 6th major cause of morbidity and mortality
- Rate higher in children <5 years old and in adults >60 years of age
- More common in men than in women
- In the Asia-Pacific region, mortality is estimated at 1.1-30%, with Japan, India, Philippines, Pakistan, Malaysia and Cambodia having the highest mortality rates
- Mortality is higher in patients who are hospitalized, with comorbidities, those belonging to low-income countries, in nursing homes or with advanced age
Definition
- Lower respiratory tract (LRT) infection acquired in the community within 24 hours to <2 weeks or occurring ≤48 hours of hospital admission in patients who do not meet the criteria for healthcare-associated pneumonia (HCAP)
Etiology
- In most patients with community-acquired pneumonia (CAP), the causative organism is not known
- Success rate in determining the etiologic agent is usually about 50%
- Streptococcus pneumoniae is the most frequently isolated organism
- Drug-resistant S pneumoniae (DRSP) may be found in patients with antibiotic use within the past 3 months, alcoholism, >65 years old, immunosuppression or resident of nursing home
- Haemophilus influenzae, atypical pathogens (eg Mycoplasma pneumoniae, Chlamydophila pneumoniae, Legionella pneumophila, Chlamydophila psittaci) and viruses are the other commonly identified pathogens of CAP
- Viruses may account for 10-20% of cases
- Klebsiella pneumoniae and Burkholderia pseudomallei are present in Southeast Asia
- K pneumoniae is mostly seen in Taiwan, Thailand, India, the Philippines and Malaysia; infrequently found in Europe and America
- Melioidosis caused by B pseudomallei has been reported in Southeast Asia (ie Malaysia, Thailand, Singapore, Cambodia, Hong Kong), Northern Australia, Taiwan, Southern China, and India
- Gram-negative bacilli (Enterobacteriaceae and Pseudomonas aeruginosa) are frequent causative agents in patients who have had previous antimicrobial treatment or who have pulmonary comorbidities (eg bronchiectasis or chronic obstructive pulmonary disease [COPD])
- Anaerobes are usually associated with aspiration pneumonia
- The development of CAP may be due to microaspiration, presence of defect in the host defenses, possible exposure to a virulent microorganism, or due to presence of an overwhelming inoculum
- Microaspiration is a mechanism by which the constituents of both the microbiota and pathogens reaches the lungs
- Hematogenous spread, contiguous spread and macroaspiration are the other mechanisms that a pathogen may gain access to the lungs
- Virulence factors:
- Chlamydia pneumoniae - possesses ciliostatic factor
- Mycoplasma pneumoniae - shears off the cilia
- Influenza virus - causes marked reduction on the tracheal mucus velocity for up to 12 weeks postinfection
- S pneumoniae and Neisseria meningitides - produces proteases and splits secretory IgA
- Other virulence factors: Inhibition of phagocytosis, pneumolysin, thiol-activated cytolysin
- Mycobacterium spp, Nocardia spp, and Legionella spp - resistant to microbicidal activity (phagocytes)
Signs and Symptoms
- It commonly presents with any of the typical signs and symptoms listed below with at least 1 abnormal chest finding of diminished breath sounds, rhonchi, crackles or wheeze and X-ray may show lobar consolidation, bilateral infiltrates or cavitation
- Respiratory:
- Acute cough (nonproductive or productive of purulent or rust-colored sputum)
- At least 1 abnormal chest finding (eg diminished breath sounds, rhonchi, crackles or wheeze)
- Systemic:
- Pleuritic chest pain
- Chills or rigors
- Confusion
- Abnormal vital signs:
- Respiratory rate (RR) >20 breaths/minute
- Heart rate (HR) >100 beats/minute
- Fever >37.8oC
- Respiratory:
Risk Factors
- Alterations in the level of consciousness that predisposes to both macroaspiration of stomach contents and microaspiration of upper airway secretions during sleep
- Administration of immunosuppressive agents (eg recipients of solid organ or stem cell transplant or those receiving chemotherapy, long-term steroids)
- Comorbid conditions:
-
- Chronic respiratory disease (eg bronchial asthma, chronic bronchitis, cystic fibrosis, bronchiectasis, COPD, pulmonary edema)
- Genetic disorder (eg Kartagener's syndrome)
- Influenza
- Chronic renal disorders
- Hepatic conditions
- Diabetes mellitus
- Malignancy (eg myeloma, lung cancer)
- Immunocompromised states: Human immunodeficiency virus (HIV) infection, hypogammaglobulinemia (IgG2 immunodeficiency), hyperimmunoglobulin E (Job) syndrome, surgical asplenia or sickle cell disease
- Continual contact with children (eg young children attending childcare, preschool teachers)
- Cigarette smoking, alcoholism
- Elderly (age >65 years old)
- Immunosuppression, malnutrition
- Medications (eg inhaled corticosteroids, proton pump inhibitors and H2 blockers, antipsychotic drugs, and sedatives)
- Oxygen and inhalation therapy (particularly containing steroids or using plastic spacers)
- Other risk factors for young adults: Military trainees and presence of low cholesterol or albumin levels
- People who are homeless and overcrowding inside jails and human shelters
