PANCE Blueprint Pulmonary (9%)

Streptococcus pneumoniae (pneumococcus) is the most common bacterial cause of community-acquired pneumonia (CAP) at every age after the newborn period. The classic picture is abrupt fever with a single shaking chill, pleuritic chest pain, rust-colored sputum and lobar consolidation. Gram stain shows gram-positive diplococci (lancet-shaped). Respiratory viruses are found about as often as pneumococcus when molecular testing is done, but pneumococcus remains the leading bacterial cause and the board answer for typical lobar pneumonia.

Pneumonia is suspected clinically (fever, cough, sputum, pleuritic pain, crackles, egophony, dullness) but is confirmed by a new infiltrate on chest radiograph. A chest radiograph is required to diagnose community-acquired pneumonia and to look for complications such as a parapneumonic effusion, cavitation or multilobar disease. Outpatients with mild disease usually need no sputum culture, blood cultures or urinary antigens; those tests are added for patients who are hospitalized with severe disease or who have risk factors for MRSA or Pseudomonas.

This healthy adult has community-acquired pneumonia with a CURB-65 score of 0, so he is treated as an outpatient. For outpatients with no comorbidities and no risk factors for resistant organisms, first-line therapy is high-dose amoxicillin. Doxycycline is an alternative, and a macrolide (azithromycin or clarithromycin) is used only where pneumococcal macrolide resistance is below 25%. Outpatients with comorbidities (chronic heart, lung, liver or kidney disease, diabetes, alcohol use disorder, cancer, asplenia) receive amoxicillin-clavulanate or a cephalosporin plus a macrolide or doxycycline, or a respiratory fluoroquinolone alone. Most outpatients are treated for 5 days.

Gradual onset over a week or more in a teen or young adult, sore throat, headache and a dry, persistent cough with patchy interstitial infiltrates that look worse than the patient ("walking pneumonia") and a normal white count point to Mycoplasma pneumoniae, the most common atypical cause of pneumonia. Extrapulmonary clues include bullous myringitis, erythema multiforme and hemolytic anemia. Cold agglutinins are nonspecific and are no longer used for diagnosis; when testing is needed, nucleic acid amplification (PCR) of a respiratory specimen is preferred. Treatment is a macrolide (azithromycin) or doxycycline, since Mycoplasma lacks a cell wall and is not killed by beta-lactams.

Community-acquired pneumonia is one of the leading infectious causes of death in the U.S. Important risk factors for increased morbidity and mortality include advanced age, alcoholism, comorbid medical conditions, altered mental status, respiratory rate ≥30 breaths/min, hypotension, and an elevated BUN. Note that the BUN cutoff depends on the score: CURB-65 counts a BUN >19 mg/dL (urea >7 mmol/L), while the Pneumonia Severity Index assigns points for a BUN ≥30 mg/dL.

Patients hospitalized on a general ward with non-severe community-acquired pneumonia are treated with a beta-lactam (ceftriaxone, cefotaxime or ampicillin-sulbactam) plus a macrolide (azithromycin), or with a respiratory fluoroquinolone (levofloxacin or moxifloxacin) alone. The macrolide is added to cover atypical organisms (Legionella, Mycoplasma, Chlamydophila); the beta-lactam covers pneumococcus and H. influenzae. Vancomycin or linezolid (MRSA) and antipseudomonal agents are added only for severe disease or specific risk factors.

The 23-valent polysaccharide vaccine (PPSV23) is not part of routine childhood immunization; it is used only in children 2 years and older with conditions that raise the risk of invasive pneumococcal disease. Those conditions include chronic heart, lung (not asthma alone), liver, or kidney disease, diabetes, cerebrospinal fluid leak, cochlear implant, sickle cell disease or asplenia, HIV, and other immunocompromising conditions. PPSV23 is not immunogenic in children younger than 2 years.

A high-risk child who completed the conjugate series with PCV13 or PCV15 receives PPSV23 at least 8 weeks later; a child who receives PCV20 needs no PPSV23 at all, and PCV20 is now the preferred approach. All infants receive a conjugate vaccine (PCV15 or PCV20) at 2, 4, 6, and 12 to 15 months.

Chlamydia trachomatis pneumonia of infancy (afebrile "staccato" cough at 1 to 3 months of age, often with conjunctivitis and eosinophilia, acquired during vaginal delivery) is treated with a macrolide. Oral azithromycin for 3 days is preferred; erythromycin for 14 days is the alternative but carries a higher risk of infantile hypertrophic pyloric stenosis, so infants given either drug are watched for vomiting. Doxycycline is avoided in young children and fluoroquinolones are not used, and ceftriaxone does not treat Chlamydia. The mother and her partner(s) also need testing and treatment.

Late inspiratory crackles are a physical examination finding that is consistent with lobar pneumonia.

Empiric or directed therapy for MRSA pneumonia is intravenous vancomycin or linezolid. Nafcillin and other antistaphylococcal penicillins do not cover methicillin-resistant strains, doxycycline is not adequate for serious MRSA pneumonia, and clindamycin is used only for susceptible isolates and is not a first-line choice for severe disease. Risk factors for MRSA include prior MRSA colonization or infection, recent hospitalization with IV antibiotics, post-influenza necrotizing pneumonia and injection drug use.

The presence of increased polymorphonuclear leukocytes and the absence of squamous epithelial cells are the criteria utilized to evaluate the adequacy of a sputum sample.

This patient has pneumonia caused by Staphylococcus aureus which is commonly associated with a history of intravenous drug use, influenza epidemics and the hospital setting.

The indolent course suggests an atypical pneumonia and Mycoplasma is the most common atypical agent.

Klebsiella pneumoniae classically affects people with alcohol use disorder, diabetes or aspiration risk. Clues are thick "currant jelly" sputum, upper lobe consolidation with a bulging fissure, gram-negative rods on Gram stain and a tendency to necrosis, abscess and cavitation. Empiric therapy follows the community-acquired pneumonia regimens (for example ceftriaxone plus azithromycin) and is narrowed by culture results; extended-spectrum beta-lactamase producers require a carbapenem.

Transmission of vocal sounds through consolidation leads to the changes heard with egophony.

Legionella is a water-borne pathogen that can cause diarrhea as a complication of its infection.

Increased tactile fremitus occurs in the presence of fluid or a lung consolidation such as lobar pneumonia.