WBR279
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| Author | Gerald Chi (Reviewed by Serge Korjian) |
|---|---|
| Exam Type | USMLE Step 1 |
| Main Category | Microbiology, Pharmacology |
| Sub Category | Dermatology |
| 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 | Amoxicillin-Clavulanate |
| Answer A Explanation | 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 | Cephalexin |
| Answer B Explanation | P. multocida is reported to be resistant to dicloxacillin, cephalexin, and clindamycin; many strains are resistant to erythromycin. |
| Answer C | Clindamycin |
| Answer C Explanation | P. multocida is reported to be resistant to dicloxacillin, cephalexin, and clindamycin; many strains are resistant to erythromycin. |
| Answer D | Dicloxacillin |
| Answer D Explanation | P. multocida is reported to be resistant to dicloxacillin, cephalexin, and clindamycin; many strains are resistant to erythromycin. |
| Answer E | Erythromycin |
| Answer E Explanation | P. multocida is reported to be resistant to dicloxacillin, cephalexin, and clindamycin; many strains are resistant to erythromycin. |
| Right Answer | A |
| 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. |
| Approved | Yes |
| Keyword | Pasteurella multocida, Parteurellosis, Dog bite, Cat bite, Zoonotic infections, Antibiotics |
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