WBR279

Author	PageAuthor::Gerald Chi (Reviewed by Serge Korjian)
Exam Type	ExamType::USMLE Step 1
Main Category	MainCategory::Microbiology, MainCategory::Pharmacology
Sub Category	SubCategory::Dermatology
Prompt	[[Prompt::A 15-year-old girl presents to the emergency department after being bitten by a stray dog in her neighborhood. On physical examination, she has a 5 by 3 inch wound on her calf with evidence of deep punctures. The wound is cleaned and sutured and the patient is sent home. The next day, she returns to the emergency department with fever and a swollen and erythematous wound. Which of the following antimicrobial agents is most likely indicated in this case?]]
Answer A	AnswerA::Amoxicillin-Clavulanate
Answer A Explanation	AnswerAExp::Pasteurella multocida is sensitive to amoxicillin-clavulanate, which can be used in the prophylaxis and treatment of pasteurellosis. The disease may also be treated with fluoroquinolones or tetracyclines.
Answer B	AnswerB::Cephalexin
Answer B Explanation	AnswerBExp::P. multocida is reported to be resistant to dicloxacillin, cephalexin, and clindamycin; many strains are resistant to erythromycin.
Answer C	AnswerC::Clindamycin
Answer C Explanation	AnswerCExp::P. multocida is reported to be resistant to dicloxacillin, cephalexin, and clindamycin; many strains are resistant to erythromycin.
Answer D	AnswerD::Dicloxacillin
Answer D Explanation	AnswerDExp::P. multocida is reported to be resistant to dicloxacillin, cephalexin, and clindamycin; many strains are resistant to erythromycin.
Answer E	AnswerE::Erythromycin
Answer E Explanation	AnswerEExp::P. multocida is reported to be resistant to dicloxacillin, cephalexin, and clindamycin; many strains are resistant to erythromycin.
Right Answer	RightAnswer::A
Explanation	[[Explanation::Pasteurella multocida is a non-motile, penicillin-sensitive, Gram-negative coccobacillus that causes zoonotic infections in humans following bites or scratches from pets (such as cats and dogs). Many mammals and fowl harbor it as part of their normal respiratory flora. Inflammatory signs of pasteurellosis are very rapid to develop. Classical presenting signs include severe pain, fever, swelling and exudation hours to a few days following a cat or a dog bite. Patients with more severe disease and bacteremia can present with vomiting, headache and diarrhea. Lymphangitis is common among infected patients. Untreated, the disease could lead to septic shock, septic arthritis, meningitis, endocarditis, or osteomyelitis. Depending on the stage of the infection, diagnosis is made by tissue or blood culture. Most cases of pasteurellosis can be prevented with a short-course of oral antibiotics following a cat or dog bite. Severe or progressing infections may require IV antibiotics, or surgical intervention. Pasteurella is generally susceptible to oral amoxicillin, amoxicillin/clavulanate, fluoroquinolones, trimethoprim-sulfamethoxazole, and tetracyclines. Most isolates are resistant to second generation cephalosporins, dicloxacillin, macrolides and clindamycin. Educational Objective: Pasteurella multocida is sensitive to amoxicillin, amoxicillin-clavulanate, fluoroquinolones, and tetracycline. Most strains are resistant to second generation cephalosporins, dicloxacillin, macrolides and clindamycin. References: Oehler RL, Velez AP, Mizrachi M, Lamarche J, Gompf S. Bite-related and septic syndromes caused by cats and dogs. Lancet Infect Dis. 2009;9(7):439-47. Weber DJ, Wolfson JS, Swartz MN, Hooper DC. Pasteurella multocida infections. Report of 34 cases and review of the literature. Medicine (Baltimore). 1984;63(3):133-54.]]
Approved	Approved::Yes
Keyword	WBRKeyword::Pasteurella multocida, WBRKeyword::Parteurellosis, WBRKeyword::Dog bite, WBRKeyword::Cat bite, WBRKeyword::Zoonotic infections, WBRKeyword::Antibiotics
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