A 10-year-old girl is brought to the emergency department for evaluation of a bite wound. Last night, the girl had a fight with her 12-year-old stepbrother, who bit her on the forearm. This morning, the girl's arm "looks worse." The stepbrother is HIV-positive and acquired it from his mother at birth. He takes antiretroviral therapy; his most recent CD4 count was 1100 cells/µL, and his HIV viral load was undetectable. The patient has no known medical problems, and takes no medications. Her vital signs are normal. Examination shows 2 deep puncture wounds on the left forearm. There is warmth, erythema, and swelling around the bite marks. The skin is mildly tender to palpation. No fluctuance is palpated.
The patient is at greatest risk for developing an infection from which of the following organisms?

Question

A 10-year-old girl is brought to the emergency department for evaluation of a bite wound.  Last night, the girl had a fight with her 12-year-old stepbrother, who bit her on the forearm.  This morning, the girl's arm "looks worse."  The stepbrother is HIV-positive and acquired it from his mother at birth.  He takes antiretroviral therapy; his most recent CD4 count was 1100 cells/µL, and his HIV viral load was undetectable.  The patient has no known medical problems, and takes no medications.  Her vital signs are normal.  Examination shows 2 deep puncture wounds on the left forearm.  There is warmth, erythema, and swelling around the bite marks.  The skin is mildly tender to palpation.  No fluctuance is palpated. 
The patient is at greatest risk for developing an infection from which of the following organisms?

Quizplus · Accepted Answer

Explanation: 11ec2b69_bfa3_4023_8f63_6deb6c9e4ef4_MD0005_00 This patient has warmth, swelling, and tenderness around a human bite site that are concerning for cellulitis. All human and animal bites carry a high rate of polymicrobial infection. Infections with human bites are associated with aerobic (α-hemolytic streptococci, Staphylococcus aureus) and anaerobic bacteria. Eikenella corrodens is a gram-negative anaerobe found commonly in infections due to human bites. Depending on the depth and severity of the bite, the infection can involve soft tissue, bone, and joints. Initial evaluation includes a thorough skin and musculoskeletal examination; imaging may be needed if deep infection is suspected. The wound should be debrided and irrigated. With the exception of facial injuries (where cosmetic outcome is important and infection risk is relatively low), primary closure should be avoided. Most wounds are left open to heal by secondary intention. Antibiotics are indicated, and tetanus prophylaxis should be considered depending on the patient's vaccination status and the severity of the bite. (Choice A) Clostridium perfringens causes gas gangrene or myonecrosis after deep, penetrating injuries or wounds, especially when there is a disruption in the blood supply to the traumatized tissue. However, this organism is not found in human oral flora. (Choice C) HIV is present in minimal quantities in the saliva of HIV-positive patients, and there are case reports of HIV transmission from bites. However, a minor bite wound from a patient with no detectable viral load is considered a low-risk exposure. (Choice D) Pasteurella multocida wound infections and osteomyelitis are seen after bite injuries from cats and dogs. Due to their sharp, pointed teeth, cats are especially capable of implanting the bacteria under the periosteum, causing osteomyelitis. P multocida is rarely found in human oral flora. (Choice E) Unlike α-hemolytic streptococci (viridans group streptococci), which are a significant component of human oral flora, Streptococcus pyogenes is uncommon after a human bite. Educational objective: Human bites can be complicated by a polymicrobial soft-tissue infection. Eikenella corrodens, a gram-negative anaerobe, is a common finding in infections from human bites. As in animal bites, management of human bites includes local wound care, antibiotics, and consideration of tetanus prophylaxis. References: Management of human and animal bite wounds: an overview. (http://www.ncbi.nlm.nih.gov/pubmed/15920371)

A 10-Year-Old Girl Is Brought to the Emergency Department for Evaluation