WBR0381: Difference between revisions

Jump to navigation Jump to search
No edit summary
No edit summary
Line 23: Line 23:
|Prompt=A 45-year-old woman presents to the emergency department with complaints of fever and flank pain for the past day. Upon further questioning, the patient admits to recent-onset dysuria and urinary frequency, for which she did not seek medical care. In the ED, her temperature is 38.9 °C (102 °F), her heart rate is 96/min, and blood pressure is 116/88 mmHg. Physical examination is remarkable for a positive Murphy’s punch sign (costovertebral angle tenderness). The patient is diagnosed with acute pyelonephritis. Urine sample are sent for culture and antibiotic therapy is initiated. The next day, eosin methylene blue (EMB) agar demonstrates the growth of a specific bacterial strain as displayed in the image below.  Which of the following virulence factors is implicated in this patient’s condition?
|Prompt=A 45-year-old woman presents to the emergency department with complaints of fever and flank pain for the past day. Upon further questioning, the patient admits to recent-onset dysuria and urinary frequency, for which she did not seek medical care. In the ED, her temperature is 38.9 °C (102 °F), her heart rate is 96/min, and blood pressure is 116/88 mmHg. Physical examination is remarkable for a positive Murphy’s punch sign (costovertebral angle tenderness). The patient is diagnosed with acute pyelonephritis. Urine sample are sent for culture and antibiotic therapy is initiated. The next day, eosin methylene blue (EMB) agar demonstrates the growth of a specific bacterial strain as displayed in the image below.  Which of the following virulence factors is implicated in this patient’s condition?


[[Image:Metallic sheen Ecoli.png|300px]]
[[Image:Metallic sheen Ecoli.png|500px]]
|Explanation=''Escherichia coli'' ''(E. coli)'' that express P fimbriae are the most common causative agent of acute pyelonephritis and cystitis. ''E. coli'' is a lactose-fermenting gram-negative, catalase-positive rod that grows on selective EMB agar. As depicted in the image above, metallic green sheen is characteristic of ''E. coli'' strains grown on EMB. ''E. coli'' contains several virulence factors, such as P fimbriae, which are proteinaceous appendages on bacterial surfaces that mediate the adhesion of ''E. coli'' to the apical surface of the uroepithelium (bind to Gal-alpha[1 to 4] Gal disaccaride). The presence of P fimbriae is crucial for ''E. coli'' ascending along the urogenital tract.  
|Explanation=''Escherichia coli'' ''(E. coli)'' that express P fimbriae are the most common causative agent of acute pyelonephritis and cystitis. ''E. coli'' is a lactose-fermenting gram-negative, catalase-positive rod that grows on selective EMB agar. As depicted in the image above, metallic green sheen is characteristic of ''E. coli'' strains grown on EMB. ''E. coli'' contains several virulence factors, such as P fimbriae, which are proteinaceous appendages on bacterial surfaces that mediate the adhesion of ''E. coli'' to the apical surface of the uroepithelium (bind to Gal-alpha[1 to 4] Gal disaccaride). The presence of P fimbriae is crucial for ''E. coli'' ascending along the urogenital tract.
|AnswerA=Capsule
|AnswerA=Capsule
|AnswerAExp=The capsule is a virulence factor of ''E. coli'' that is implicated in pneumonia and neonatal meningitis.  It has no significant role in acute pyelonephritis.
|AnswerAExp=The capsule is a virulence factor of ''E. coli'' that is implicated in pneumonia and neonatal meningitis.  It has no significant role in acute pyelonephritis.
|AnswerB=P fimbriae
|AnswerB=P fimbriae
|AnswerBExp=''E. coli'' is a a lactose-fermenting gram-negative, catalase-positive rod, which grows on EMB agar and appears as green metallic sheen. Expression of the virulence factor P fimbriae is important in the pathogenesis of acute pyelonephritis and cystitis.  
|AnswerBExp=''E. coli'' is a a lactose-fermenting gram-negative, catalase-positive rod, which grows on EMB agar and appears as green metallic sheen. Expression of the virulence factor P fimbriae is important in the pathogenesis of acute pyelonephritis and cystitis.
|AnswerC=Lipopolysaccaride (LPS) endotoxin
|AnswerC=Lipopolysaccaride (LPS) endotoxin
|AnswerCExp=The LPS endotoxin is a virulence factor of ''E. coli'' that is implicated in septic shock.
|AnswerCExp=The LPS endotoxin is a virulence factor of ''E. coli'' that is implicated in septic shock.
Line 38: Line 38:
|References=Stapleton A. Novel mechanism of P-fimbriated Escherichia coli virulence in pyelonephritis. J Am Soc Nephrol. 2005;16(12):3458-60.<br>
|References=Stapleton A. Novel mechanism of P-fimbriated Escherichia coli virulence in pyelonephritis. J Am Soc Nephrol. 2005;16(12):3458-60.<br>
Rice JC, Peng T, Spence JS, et al. Pyelonephritic ''Escherichia coli'' expressing P fimbriae decrease immune response of the mouse kidney. J Am Soc Nephrol. 2005;16:3583-91.<br>
Rice JC, Peng T, Spence JS, et al. Pyelonephritic ''Escherichia coli'' expressing P fimbriae decrease immune response of the mouse kidney. J Am Soc Nephrol. 2005;16:3583-91.<br>
Image Attribution: "E. coli on EMB agar" (Coli levine.JPG) from Wikipedia.org. User:Witmadrid licensed under public domain. Retrieved Feb 16 2015.
First Aid 2014 page 139
First Aid 2014 page 139
|RightAnswer=B
|RightAnswer=B

Revision as of 19:07, 16 February 2015

 
Author [[PageAuthor::Yazan Daaboul, M.D. (Reviewed by Yazan Daaboul, M.D. and Alison Leibowitz [1])]]
Exam Type ExamType::USMLE Step 1
Main Category MainCategory::Microbiology
Sub Category SubCategory::Genitourinary
Prompt [[Prompt::A 45-year-old woman presents to the emergency department with complaints of fever and flank pain for the past day. Upon further questioning, the patient admits to recent-onset dysuria and urinary frequency, for which she did not seek medical care. In the ED, her temperature is 38.9 °C (102 °F), her heart rate is 96/min, and blood pressure is 116/88 mmHg. Physical examination is remarkable for a positive Murphy’s punch sign (costovertebral angle tenderness). The patient is diagnosed with acute pyelonephritis. Urine sample are sent for culture and antibiotic therapy is initiated. The next day, eosin methylene blue (EMB) agar demonstrates the growth of a specific bacterial strain as displayed in the image below. Which of the following virulence factors is implicated in this patient’s condition?

]]

Answer A AnswerA::Capsule
Answer A Explanation AnswerAExp::The capsule is a virulence factor of ''E. coli'' that is implicated in pneumonia and neonatal meningitis. It has no significant role in acute pyelonephritis.
Answer B AnswerB::P fimbriae
Answer B Explanation [[AnswerBExp::E. coli is a a lactose-fermenting gram-negative, catalase-positive rod, which grows on EMB agar and appears as green metallic sheen. Expression of the virulence factor P fimbriae is important in the pathogenesis of acute pyelonephritis and cystitis.]]
Answer C AnswerC::Lipopolysaccaride (LPS) endotoxin
Answer C Explanation AnswerCExp::The LPS endotoxin is a virulence factor of ''E. coli'' that is implicated in septic shock.
Answer D AnswerD::Streptolysin O
Answer D Explanation AnswerDExp::Streptolysin O is a hemolytic toxin of group A streptococci; it is not usually found in ''E. coli''.
Answer E AnswerE::Erythrogenic toxin
Answer E Explanation [[AnswerEExp::Erythrogenic toxin is produced by Streptococcus pyogenes and is implicated in scarlet fever. The toxin itself is encoded in a lysogenic phage by specialized transduction.]]
Right Answer RightAnswer::B
Explanation [[Explanation::Escherichia coli (E. coli) that express P fimbriae are the most common causative agent of acute pyelonephritis and cystitis. E. coli is a lactose-fermenting gram-negative, catalase-positive rod that grows on selective EMB agar. As depicted in the image above, metallic green sheen is characteristic of E. coli strains grown on EMB. E. coli contains several virulence factors, such as P fimbriae, which are proteinaceous appendages on bacterial surfaces that mediate the adhesion of E. coli to the apical surface of the uroepithelium (bind to Gal-alpha[1 to 4] Gal disaccaride). The presence of P fimbriae is crucial for E. coli ascending along the urogenital tract.

Educational Objective: E. coli is a lactose-fermenting gram-negative, catalase-positive rod, which grows on EMB agar and appears as green metallic sheen. The virulence factor responsible for pyelonephritis in E. coli is P fimbriae.
References: Stapleton A. Novel mechanism of P-fimbriated Escherichia coli virulence in pyelonephritis. J Am Soc Nephrol. 2005;16(12):3458-60.
Rice JC, Peng T, Spence JS, et al. Pyelonephritic Escherichia coli expressing P fimbriae decrease immune response of the mouse kidney. J Am Soc Nephrol. 2005;16:3583-91.
Image Attribution: "E. coli on EMB agar" (Coli levine.JPG) from Wikipedia.org. User:Witmadrid licensed under public domain. Retrieved Feb 16 2015. First Aid 2014 page 139]]

Approved Approved::Yes
Keyword WBRKeyword::Fimbriae, WBRKeyword::P fimbriae, WBRKeyword::E. coli, WBRKeyword::Escherichia coli, WBRKeyword::Acute pyelonephritis, WBRKeyword::Pyelonephritis, WBRKeyword::Cystitis, WBRKeyword::Dysuria, WBRKeyword::Urinary frequency, WBRKeyword::Pathogenesis, WBRKeyword::Pathophysiology, WBRKeyword::Mechanism of action
Linked Question Linked::
Order in Linked Questions LinkedOrder::