Cough Case 4

A 72-year-old woman presents to the emergency department with cough, fever, and shortness of breath. The woman lives alone at home, but spends part of each day shopping and riding public buses. Approximately 4 days previously she had developed an upper respiratory infection.
Approximately 2 days ago, she abruptly became much more ilI, and her symptoms started worsening, beginning with a single, Iong, shaking chill. Since that time, she has had fever, pain with breathing, cough, and dyspnea. She decided to come to the emergency department when
her temperature at home was 103.4 F. In the emergency department, her temperature is 39.9 C (103.8 F), blood pressure is 90/50 mm Hg, pulse is 120/min, and respirations are 30/min. No breath sounds are heard over her lower left lung field, but they can be heard at other sites.

Q 1

A chest x-ray film would be most likely to demonstrate which of the following:
/ A. A single roughly ovoid white area
/ B. Complete whitening over one lobe of her lungs
/ C. Marked dilation and elongation of bronchial spaces
/ D. Multiple small spotty areas of white found primarily near the bronchi
/ E. No obvious radiologic changes

Q 2
Gram's stain of a smear from a sputum sample demonstrates gram-positive lancet-shaped diplococci in short chains. Which of the following
would most likely be identified after culturing?

/ A. Chlamydia pneumoniae
/ B. Haemophilus influenzae
/ C. Legeonella pneumophila
/ D. Staphylococcus aureus
/ E. Streptococcus pneumoniae

Q 3
Which of the following is thought to contribute to the ability of gram-positive organisms to retain the Gram's stain during the decolorization
process?
/ A. Large periplasmic space
/ B. Presence of capsule
/ C. Presence of outer membrane
/ D. Presence of pili
/ E. Thick peptidoglycan layer

Q 4
Which of the following is a characteristic feature on culture of this patient's organism?
/ A. AIpha-hemolytic colonies inhibited by optochin on blood agar and lysed by bile
/ B. Beta-hemolytic colonies that are bacitracin-resistant on blood agar
/ C. Beta-hemolytic colonies that are inhibited by bacitracin on blood agar
/ D. Catalase-negative organisms that hydrolyze esculin in 40% bile and 6.5% NaCI
/ E. Catalase-positive, coagulase-positive organisms that cause beta-hemolytic, yellow colonies on blood agar

Q 5
At this stage of the disease (two days following onset of first symptoms), and before treatment is started, what are the expected histopathologic findings in the affected lung parenchyma?
/ A. Advanced organization with macrophages and fibroblasts
/ B. Interstitial lymphomonocytic inflammatory infiltration
/ C. Intra-alveolar purulent exudate admixed with erythrocytes
/ D. Resolution of inflammatory exudate with semifluid debris
/ E. Vascular congestion without intra-alveolar exudation

Q 6
The patient's infection is treated with parenteral penicillin, to which she promptly responds. This drug acts by which of the following mechanisms?
/ A. Inhibits bacterial protein synthesis
/ B. Inhibits growth of cell walls
/ C. Interferes with bacteriaI DNA synthesis
/ D. Interferes with folate metabolism
/ E. Punches holes in cell membranes

Q 7
A few minutes after the patient receives the antibiotic therapy, she develops an adverse reaction characterized by an itchy skin eruption and
acute respiratory distress. This reaction is most likely attributable to which of the following mechanisms?
/ A. Antibody-mediated cellular dysfunction
/ B. Complement-dependent reaction
/ C. Delayed-type hypersensitivity
/ D. IgE-mediated mast cell degranulation
/ E. Immune-complex deposition

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Cough Case 4 Answers
A1
The correct answer is B. This patient has lobar pneumonia, which is seen radiologically as a complete whitening of one or more lobes of the lungs.
Choice A describes the appearance of a mass lesion of the lung, such as tumor or tuberculosis
Choice C describes the radiologic changes accompanying bronchiectasis.
Choice D describes the radiologic appearance of bronchopneumonia, rather than lobar pneumonia.
While very early in lobar pneumonia, no obvious radiologic changes may be seen (choice E), this patient's lack of breath sounds over the lower left lung field indicates that her pneumonia is past this very early stage.

A2
The correct answer is E. Streptococcus pneumoniae is the most commonly identified causative organism for bacterial pneumonia. Up to two-thirds of bacteremic community-acquired pneumonias are due to this organism. 5-25% of healthy individuals carry S. pneumoniae in their pharynx. The classic description of S. pneumoniae on Gram's stain is that given in the question stem. S. pneumoniae can be verified by the Quellung reaction, or counterimmunoelectrophoresis to determine serotypes of isolated strains or for case detection using sputum specimens (there are more than 80 distinct serotypes based on studies of capsular antigens).
Chlamydia pneumoniae(choice A) is not identified on the basis of Gram's stain, but rather, can be seen with Giemsa or immunofluorescence.
Haemophilus influenzae(choice B) and Legionella pneumophila(choice C) are gram-negative rods.
Staphylococcus aureus(choice D) is also a gram-positive coccus, but the classic description of this organism typically includes a reference to "grape-like clusters."

A3
The correct answer is E. The peptidoglycan layer in the cell wall of gram-positive organisms is much thicker than that in gram-negative organisms, and is thought to contribute to the gram-positive staining reaction.
A large periplasmic space (choice A) and an outer membrane (choice C) are characteristics of gram-negative cell walls.
Capsules (choice B) can be seen in both gram-positive and gram-negative species.
Pili (choice D) are small hair-like structures that are most often seen in gram-negative organisms.

A4
The correct answer is A. These findings are used to identify Streptococcus pneumoniae. Optochin sensitivity is used to differentiate the viridans streptococci (resistant) from S. pneumoniae (sensitive). Another test used to identify S. pneumoniae is the Quellung reaction. The only medically important optochin-sensitive organism that gives a positive Quellung reaction is S. pneumoniae.
Choice B is seen with Streptococcus agalactiae.
Choice C is seen with Streptococcus pyogenes.
Choice D is seen with Enterococcus faecalis.
Choice E is seen with Staphylococcus aureus.

A5
The correct answer is C. Acute lobar pneumonia has classically been subdivided into four pathologic stages. The initial stage of congestion(choice E) lasts less than 24 hours and is characterized by engorgement of vessels, with intra-alveolar fluid containing few cells, but often, numerous bacteria. Over the following few days, an exuberant intra-alveolar exudate of red cells, neutrophils, and fibrin develops, heralding the stage of red hepatization (choice C; so-called because the lung resembles liver at this stage). During the last half of the first week of illness, the red cells begin to break down, but a fibrinous exudate remains in the alveoli; this is the stage of gray hepatization. If death does not supervene, resolution (choice D) occurs in the second week in untreated cases, with digestion of the exudate to leave semifluid debris that are phagocytized, or coughed up. In some cases, the exudate, rather than resolving in this manner, undergoes further organization (choice A).
An interstitial lymphomonocytic infiltrate (choice B) is characteristic of primary atypical pneumonia, caused by Mycoplasma or viruses.

A6
The correct answer is B. The penicillins and cephalosporins both inhibit cell wall synthesis. Penicillin G is the preferred antibiotic for sensitive strains; 25% of strains are resistant and can be treated with cephalosporins, erythromycin, and clindamycin. Pneumococcal pneumonia can be prevented in a number of cases; the pneumococcal vaccine contains 23 specific polysaccharide antigens found in 85-90% of the serious pneumococcal infections.
Inhibitors of bacterial protein synthesis (choice A) include aminoglycosides, chloramphenicol, macrolides, and tetracycline.
Inhibitors of nucleic acid synthesis (choice C) include fluoroquinolones and rifampin.
Inhibitors of folic acid synthesis (choice D) include sulfonamides, trimethoprim, and pyrimethamine.
Agents that disrupt cell membranes (choice E) include azole and polyene antifungal agents.

A7
The correct answer is D. This patient has had an acute allergic reaction to the antibiotic, which can be further classified as an immediate hypersensitivity reaction. These reactions are mediated in a way similar to hay fever, with preformed IgE binding to the antibiotic antigen, and then the antigen-antibody complex triggering degranulation of mast cells with release of histamine and other active substances. These substances then cause both the itchiness of the skin and the bronchospasm that caused the respiratory distress.
An example of a disease caused by antibody-mediated cellular dysfunction (choice A) is Graves disease, in which antibodies to the TSH receptor cause a non-physiologic chronic stimulation of thyroid epithelial cells.
An example of a complement-dependent reaction (choice B) is hemolytic disease of the newborn.
An example of delayed-type hypersensitivity (choice C) is the tuberculin reaction.
An example of an immune complex deposition disease (choice E) is the vasculitis seen in systemic lupus erythematosus.