WBR281

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. References: Stevens DL, Bisno AL, Chambers HF, et al. Practice guidelines for the diagnosis and management of skin and soft-tissue infections. Clin Infect Dis. 2005;41(10):1373-406. Decker MD. Eikenella corrodens. Infect Control. 1986;7(1):36-41.]]
Approved	Approved::Yes
Keyword	WBRKeyword::Eikenella corrodens, WBRKeyword::Human bite injuries, WBRKeyword::Bite injuries, WBRKeyword::Clenched fist injuries, WBRKeyword::Antibiotics, WBRKeyword::Prophylaxis, WBRKeyword::Emergency
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