A 56-year-old immigrant from Haiti comes to the hospital with a three week history of cough and fever. He has a history of hypertension, hyperlipidemia, and has a 30 pack year smoking history. On physical exam, the upper right lung field is dull to percussion. There are no other significant exam findings. Her temperature is 98.7 °F (37 °C), blood pressure is 142/85 mmHg, pulse is 87/min, respirations are 18/min. Sputum cultures grown on a selective medium demonstrate mycobacteria that appear as parallel chains (serpentine cords) under microscopy. This observed growth pattern in culture medium most strongly correlates with which of the following?

Question

A 56-year-old immigrant from Haiti comes to the hospital with a three week history of cough and fever. He has a history of hypertension, hyperlipidemia, and has a 30 pack year smoking history. On physical exam, the upper right lung field is dull to percussion. There are no other significant exam findings. Her temperature is 98.7 °F (37 °C), blood pressure is 142/85 mmHg, pulse is 87/min, respirations are 18/min. Sputum cultures grown on a selective medium demonstrate mycobacteria that appear as parallel chains (serpentine cords) under microscopy.  This observed growth pattern in culture medium most strongly correlates with which of the following?

Quizplus · Accepted Answer

Eductional Objective: Mycobacterium tuberculosis grows in long, serpentine cords due to the presence of cord factor, a surface glycolipid, on the cell wall.  Cord factor is a primary virulence factor of M tuberculosis; it prevents macrophages from being bactericidal due to the inhibition of phagolysosome acidification and also leads to the formation of caseating granulomas.

A 56-Year-Old Immigrant from Haiti Comes to the Hospital with a Three