tommyk
05-16-2006, 07:37 PM
Hy 2219 Respiratory Physiology and Bacteriology, Classic Step 1
You next see a 70-year-old woman who presents to her physician because of 50 hours of persistent fevers, shaking chills, and a productive cough. She is a former smoker who quit 20 years ago who smoked 3 packs a day. (She owned a ton of Philip Morris, now Altria stock). She is in otherwise good health and a multimillionaire in stock, except for a history of a transient ischemic attack 2 yeas ago. On physical examination, there are coarse rhonchi at the left posterior lung base with increased fremitus and hyperresonance to percussion. A chest x-ray film reveals a lobar consolidation in the left lower posterior lung segment. Which of the following would be most likely to appear on a sputum Gram's stain? (What is the bug?)
1-Gram positive cocci in clusters
2-Gram positive cocci in chains
3-Gram positive rods in clusters
4-Gram positive rods
5-Gram neg rods
a) Most common is…well, most common. Ans is … #2! The most likely organism in an otherwise healthy patient residing at home ("community-acquired pneumonia") is Streptococcus pneumoniae, otherwise known as the "pneumococcus." This organism appears as a gram-positive, lancet-shaped diploccus in short chains on a Gram's stain of sputum. It is usually present in very large numbers in clinical cases of pneumococcal pneumonia. S. pneumoniae accounts for about two thirds of community acquired pneumonias and occurs most frequently in the very young and the elderly. More than 80 distinct serotypes exist, which is why the pneumococcal vaccine (directed against 23 different polysaccharide antigens), although very useful, does not protect perfectly against pneumonia caused by S. pneumoniae. Gram-negative cocci in chains is consistent with gonococcus, which rarely causes a bacterial pneumonia—and almost always in people who have gonorrhea of the genital organ systems. The patient has no underlying diseases to suggest that there might be a predisposition to a gram-negative pneumonia, such as due to Pseudomonas or Escherichia coli. E. coli pneumonia is seen in patients with underlying E. coli infection elsewhere, notably in the urinary tract. Pseudomonas pneumonia is common in patients with underlying cystic fibrosis, neutropenia, AIDS, bronchiectasis, or other organ system disease serious enough to require therapy in an intensive care unit. Gram-positive cocci in clusters suggest Staphylococcus aureus. Although S. aureus can occur (2% of the time) in community-acquired pneumonias and may affect the elderly, it is more commonly seen as a nosocomial infection, particularly in patients who have tracheostomy, endotracheal intubation, immunosuppression, or recent surgery. Other particularly vulnerable patients include those with underlying cystic fibrosis, granulomatous lung disease, IV drug abuse with staphylococcal endocarditis, or bacterial superinfection following viral pneumonia.
You next see a 70-year-old woman who presents to her physician because of 50 hours of persistent fevers, shaking chills, and a productive cough. She is a former smoker who quit 20 years ago who smoked 3 packs a day. (She owned a ton of Philip Morris, now Altria stock). She is in otherwise good health and a multimillionaire in stock, except for a history of a transient ischemic attack 2 yeas ago. On physical examination, there are coarse rhonchi at the left posterior lung base with increased fremitus and hyperresonance to percussion. A chest x-ray film reveals a lobar consolidation in the left lower posterior lung segment. Which of the following would be most likely to appear on a sputum Gram's stain? (What is the bug?)
1-Gram positive cocci in clusters
2-Gram positive cocci in chains
3-Gram positive rods in clusters
4-Gram positive rods
5-Gram neg rods
a) Most common is…well, most common. Ans is … #2! The most likely organism in an otherwise healthy patient residing at home ("community-acquired pneumonia") is Streptococcus pneumoniae, otherwise known as the "pneumococcus." This organism appears as a gram-positive, lancet-shaped diploccus in short chains on a Gram's stain of sputum. It is usually present in very large numbers in clinical cases of pneumococcal pneumonia. S. pneumoniae accounts for about two thirds of community acquired pneumonias and occurs most frequently in the very young and the elderly. More than 80 distinct serotypes exist, which is why the pneumococcal vaccine (directed against 23 different polysaccharide antigens), although very useful, does not protect perfectly against pneumonia caused by S. pneumoniae. Gram-negative cocci in chains is consistent with gonococcus, which rarely causes a bacterial pneumonia—and almost always in people who have gonorrhea of the genital organ systems. The patient has no underlying diseases to suggest that there might be a predisposition to a gram-negative pneumonia, such as due to Pseudomonas or Escherichia coli. E. coli pneumonia is seen in patients with underlying E. coli infection elsewhere, notably in the urinary tract. Pseudomonas pneumonia is common in patients with underlying cystic fibrosis, neutropenia, AIDS, bronchiectasis, or other organ system disease serious enough to require therapy in an intensive care unit. Gram-positive cocci in clusters suggest Staphylococcus aureus. Although S. aureus can occur (2% of the time) in community-acquired pneumonias and may affect the elderly, it is more commonly seen as a nosocomial infection, particularly in patients who have tracheostomy, endotracheal intubation, immunosuppression, or recent surgery. Other particularly vulnerable patients include those with underlying cystic fibrosis, granulomatous lung disease, IV drug abuse with staphylococcal endocarditis, or bacterial superinfection following viral pneumonia.