WBR281
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| Author | PageAuthor::Gerald Chi (Reviewed by Serge Korjian) |
|---|---|
| Exam Type | ExamType::USMLE Step 1 |
| Main Category | MainCategory::Microbiology, MainCategory::Pharmacology |
| Sub Category | SubCategory::Infectious Disease |
| Prompt | [[Prompt::A 55-year-old man presents to the emergency department after being bitten by his brother during a domestic dispute. On physical examination, the physician notices a 3 by 3 inch wound on his arm lined by human teeth marks. What is the most appropriate agent to prevent infection of the wound in this case?]] |
| Answer A | AnswerA::Cefazolin |
| Answer A Explanation | [[AnswerAExp::Agents that lack anaerobic coverage as well as coverage against Eikenella corrodens, Haemophilus species, and Staphylococcus aureus are not appropriate for prophylaxis. Cefazolin does not cover anaerobic organisms or Eikenella species.]] |
| Answer B | AnswerB::Dicloxacillin |
| Answer B Explanation | AnswerBExp::Agents that lack anaerobic coverage as well as coverage against ''Eikenella corrodens'', ''Haemophilus'' species, and ''Staphylococcus aureus'' are not appropriate for prophylaxis. Dicloxacillin lacks ''Eikenella'' coverage. |
| Answer C | AnswerC::Erythromycin |
| Answer C Explanation | AnswerCExp::Agents that lack anaerobic coverage as well as coverage against ''Eikenella corrodens'', ''Haemophilus'' species, and ''Staphylococcus aureus'' are not appropriate for prophylaxis. Erythromycin lacks coverage for all three. |
| Answer D | AnswerD::Clindamycin |
| Answer D Explanation | [[AnswerDExp::Agents that lack anaerobic coverage as well as coverage against Eikenella corrodens, Haemophilus species, and Staphylococcus aureus are not appropriate for prophylaxis. Although clindamycin has anerobic and staphylococcal coverage, it does not cover Eikenella.]] |
| Answer E | AnswerE::Amoxicillin-Clavulanate |
| Answer E Explanation | AnswerEExp::Amoxicillin-Clavulanate may be used for post-exposure prophylaxis in cases of human bite wounds. It has adequate coverage for ''Eikenella corrodens'', ''Staphylococcus aureus'' (MSSA), and anaerobic organisms. |
| Right Answer | RightAnswer::E |
| Explanation | [[Explanation::Human bite wounds can be divided into 2 different types: occlusive injuries, defined as a wound from a direct bite, or clenched-fist injuries, defined as a wound from a fist striking teeth. Bacteria associated with human bite injuries are usually part of the oral flora and include viridans Streptococci, Staphylococci, anaerobic organisms (Fusobacterium nucleatum, Prevotella, Peptostreptococci), and Eikenella corrodens. E. corrodens is a facultatively anaerobic, pleomorphic bacillus that requires ample carbon dioxide concentrations to thrive. E. corrodens is part of the normal flora of the oral cavity and the upper respiratory tract. E. corrodens infections are common in untreated human bite wounds, especially clenched fist injuries. E. corrodens infections typically progress slowly and can manifest clinically one to two weeks after inoculation. Complications include osteomyelitis, loss of joint function, and bacteremia with endocarditis. General treatment of human bite wounds includes irrigation and topical wound cleansing, however, unlike animal bites, prophylactic antimicrobials should be administered to all patients regardless of the wound appearance. Antibiotic regimens should cover: E. corrodens, S. aureus, Haemophilus species, and anaerobes. Notably, E. corrodens is resistant to first-generation cephalosporins, macrolides, clindamycin, and aminoglycosides. Adequate agents include amoxicillin-clavulanate, ampicillin-sulbactam, carbapenems, and doxycyline. Intravenous antibiotics are preferred in clenched-fist injuries. Educational Objective: Prophylactic antimicrobials should be administered to all patients with human bite injuries. Antibiotic regimens should cover: E. corrodens, S. aureus, Haemophilus species, and anaerobes. Adequate agents include amoxicillin-clavulanate, ampicillin-sulbactam, carbapenems, and doxycyline. |
| Approved | Approved::Yes |
| Keyword | WBRKeyword::Eikenella corrodens, WBRKeyword::Human bite injuries, WBRKeyword::Bite injuries, WBRKeyword::Clenched fist injuries, WBRKeyword::Antibiotics, WBRKeyword::Prophylaxis, WBRKeyword::Emergency |
| Linked Question | Linked:: |
| Order in Linked Questions | LinkedOrder:: |