A 78-year-old man is brought to the emergency department due to fever, cough, and shortness of breath. The patient recently moved into an assisted living facility after living with his family that owned several pets. He has a 40-pack-year smoking history. Temperature is 39.4 C (103 F), blood pressure is 106/62 mm Hg, pulse is 112/min, and respirations are 28/min. There is dullness to percussion and bronchial breath sounds over the left lung. Chest x-ray reveals a left lower lobe consolidation. Sputum microscopy shows gram-positive diplococci. Which of the following would have been most helpful in preventing this patient's lung infection?

Question

A 78-year-old man is brought to the emergency department due to fever, cough, and shortness of breath.  The patient recently moved into an assisted living facility after living with his family that owned several pets.  He has a 40-pack-year smoking history.  Temperature is 39.4 C (103 F), blood pressure is 106/62 mm Hg, pulse is 112/min, and respirations are 28/min.  There is dullness to percussion and bronchial breath sounds over the left lung.  Chest x-ray reveals a left lower lobe consolidation.  Sputum microscopy shows gram-positive diplococci.  Which of the following would have been most helpful in preventing this patient's lung infection?

Quizplus · Accepted Answer

11ec160b_3892_f921_9249_3fe89b31e327_MD0001_00 This patient with fever, pulmonary symptoms, and a lobar consolidation on chest x-ray has pneumonia. The presence of gram-positive diplococci in the sputum indicates the underlying pathogen is Streptococcus pneumoniae, the leading cause of community-acquired pneumonia. Over 90 strains of S pneumoniae have been identified; they are distinguished based on antigenic variations in the capsular polysaccharide, the major virulence factor of the bacteria. Antibodies against the polysaccharide capsule are generated during infection and provide long-lasting immunity against that strain. The pneumococcal vaccine contains polysaccharide antigens from the most common disease-causing serotypes leading to the generation of protective antibodies against these strains. In the United States, 2 types of pneumococcal vaccinations are available: Pneumococcal polysaccharide vaccine contains capsular material from 23 serotypes. Because polysaccharides cannot be displayed by the major histocompatibility complex of antigen-presenting cells (only peptides can), immunogenicity to this vaccine is T-cell independent and generates a mild antibody response with no memory cells. Although polysaccharide vaccines are fairly effective for most adult patients, they are not useful for infants (age <2). Pneumococcal conjugate vaccine consists of capsular polysaccharides from 13 serotypes that have been covalently attached to recombinant, inactivated diphtheria toxin. Protein conjugation allows the polysaccharide to be displayed by the major histocompatibility complex and induces a much stronger immunogenic response that involves T-cell-mediated B-lymphocyte activation. This generates high- affinity IgG antibodies and memory B-cells and also creates mucosal IgA antibodies, which reduce colonization rates. Pneumococcal vaccination significantly reduces the risk of invasive pneumococcal disease. Routine vaccination is recommended for all children as part of their childhood immunization series. Adults age >65 and those at high risk for invasive disease (eg, HIV, asplenia, other immunosuppressed states) should also be vaccinated. (Choice A) Histoplasma is a fungal infection that is primarily transmitted by inhalation of particles from soil contaminated with bird or bat droppings. Diagnosis is usually made by urine or serum antigen testing, but yeasts can sometimes be identified on histology/culture using specialized stains. (Choice B) Close contacts of patients who have pertussis should be given antibiotic chemoprophylaxis. Pertussis is a gram-negative encapsulated coccobacillus; infected adults usually develop a few weeks of malaise and rhinorrhea followed by several weeks of severe, paroxysmal cough. (Choice C) The influenza vaccine contains 3 or 4 strains of inactivated influenza virus. Influenza usually causes abrupt-onset fever, headache, myalgia, and malaise and would not appear on Gram stain. (Choice D) Legionella is a common cause of atypical pneumonia and is usually transmitted by contaminated water systems. However, Legionella is a gram-negative bacterium (not a gram-positive diplococcus) and is usually diagnosed with urine antigen testing. Educational objective: Streptococcus pneumoniae vaccination reduces the risk of invasive disease and is recommended for young patients and the elderly. The pneumococcal polysaccharide vaccine is an unconjugated vaccine that induces a T-cell-independent humoral immune response. In contrast, the pneumococcal conjugate vaccine contains polysaccharide material attached to a protein antigen, which creates a robust T-cell-mediated humoral immune response.

A 78-Year-Old Man Is Brought to the Emergency Department Due