Snapshot An 88-year-old man presents to the emergency department from home after developing increasing shortness of breath, fatigue, poor appetite, and malaise. His symptoms began approximately 4 days ago, when he noticed he had a productive cough with green-yellow sputum. His temperature is 101°F (38.3°C), blood pressure is 136/93 mmHg, pulse is 101/min, and respirations are 22/min. Physical exam is notable for crackles in the right lower lobe and dullness to percussion. Chest radiography demonstrates a lobar consolidation. Introduction Definition pulmonary parenchymal infection of the lower respiratory tract acquired outside the healthcare setting Epidemiology Incidence a leading cause of morbidity and mortality worldwide Risk factors chronic lung disease (e.g., chronic obstructive pulmonary disease [COPD]) diabetes mellitus proton pump inhibitors smoking high alcohol consumption aspiration Etiology Bacterial Streptococcus pneumoniae (most common) Staphylococcus aureus (seen postinfluenza) Mycoplasma pneumoniae (in young patients) Chlamydophila pneumoniae (in young patients) Legionella species(in elderly patients, immunocomprosed, and smokers) Hemophilus influenzae (in COPD) Moraxella catarrhalis (in COPD) Mixed flora, especially anaerobes like Klebsiella pneumoniae (in alcohol use disorder and aspiration) Viral influenza respiratory syncytial virus rhinovirus parainfluenza virus coronavirus Fungal pneumocystis jiroveci (in patients with HIV) Presentation Symptoms productive or non-productive cough dyspnea pleuritic chest pain fatigue and malaise Physical exam fever tachypnea increased work of breathing pulmonary auscultation rales/crackles rhonchi tactile fremitus egophony dullness to percussion Imaging Radiography of the chest findings lobar consolidation pleural effusion cavitary lesions Studies Sputum Gram stain and culture Blood cultures acquire before administering antibiotics Other studies depend on clinical suspicion, such as urine legionella antigen testing induced sputum acid-fast bacillus stain and myocbacterial culture for tuberculosis direct fluorescent-antibody or PCR testing of a nasopharyngeal swab or sputum for viral causes procalcitonin elevated in bacterial pneumonia useful in differentiating bacterial vs. viral pneumonia Bronchoscopy is considered in critically ill patients patients who fail to respond to therapy chronic pneumonia immunosuppressed Differential COPD exacerbation differentiating factor patient has a history of COPD Treatment Prevention PPSV23 in > 65 years of age 19-64 with chronic medical conditions such as asplenia immunocompromised smokers PCV13 in all children and young patients yearly influenza vaccination incentive spirometry proper oral hygiene tooth brushing, denture care, and fixing dental caries oral flora contains gram-positive, gram-negative, and anaerobic bacteria reducing number of medications that decrease salivation since this has a protective effect on oral bacteria proper positioning upright sitting during eating or at least have bed be set at > 30°of incline especially during comatose states Medical empiric antibiotics in the outpatient setting medications amoxicillin clavulinic acid can add one of the following azythromycin doxycycline empiric antibiotics in the inpatient setting medications levofloxacin or moxifloxacin ceftriaxone and azithromycin if aspiration cover for anaerobes clindamycin or ampicillin-sulbactam Complications Respiratory failure Sepsis Septic shock Empyema requires both drainage and antibiotics for successful treatment Prognosis Improved mortality with administration of antibiotics