November 12 is recognized as “World Pneumonia Day” around the globe. Pneumonia is a significant cause of morbidity and mortality among both adult and pediatric populations.  According to the World Health Organization (WHO), pneumonia is the leading cause of death among children worldwide, accounting for 15% of deaths in children under the age of 5 in 2017. Elderly individuals, those that are immunocompromised, and those with underlying structural lung disease are also at higher risk for mortality from pneumonia.  

Pneumonia is caused from bacteria, viral, or fungal infection of the lungs. The organism then proliferates in the parenchyma of the lung tissue.  This typically leads to edema and production of an exudate within the alveoli, leading to the characteristic infiltrative pattern seen on chest imaging.  Streptococcus pneumoniae is the most common cause of community acquired pneumonia (CAP).  Patients with CAP may present with pneumonia caused by viruses or atypical organisms.  Some communities are also at risk for community acquired MRSA (CA-MRSA) infection leading to pneumonia. These cases are often associated with hemoptysis, but the absence of hemoptysis does not exclude the diagnosis. Patients that are hospitalized, have been hospitalized frequently, are immunocompromised, or have underlying structural lung disease may be at risk for more invasive organisms.  Recommendations on overall treatment and antibiotic choice are outside of the scope of this post.  However, it is noteworthy to mention that patients who fall within one of these categories should be evaluated on a case-by-case basis for the likelihood of needing antibiotic coverage for Pseudomonas aeruginosa and/or an extended-spectrum producing beta-lactamase organism.

Patients with pneumonia are typically febrile, exhibit a cough, tachypnea, dyspnea, chills and malaise.  It is imperative to ask if the patient has been taking an antipyretic, which may mask a fever.  Auscultation often reveals crackles over the area of consolidation.  Chest x-ray is diagnostic, revealing a focal area of infiltration.  The utility of blood and sputum cultures in patients who are not critically ill has been debated as no evidence has been able to prove outcomes have been impacted by directing therapy according to culture results. Less than 15% of blood cultures from patients with CAP are positive and less than 50% of sputum cultures are positive.  In the critically ill patient population, cultures should always be obtained in an effort to guide therapy.

As previously noted, treatment is outside the scope of this post.  However, without culture results, or in the absence of positive cultures, an educational empiric antimicrobial therapy guide for CAP can be found here.  

The pneumococcal polysaccharide vaccine (PPSV23) and a protein conjugate pneumococcal vaccine (PCV13) are available for prevention of pneumonia caused by pneumococcal infections. The CDC guidelines for pneumonia vaccination can be found here.  In efforts to prevent against infleunzae-related pneumonia, it is recommended that all patients receive their annual flu vaccinations according to the CDC recommendations.

Harrison's Principles of Internal Medicine, 20e: Pneumonia

Centers for Disease Control and Prevention

World Health Organization: Pneumonia

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