What is the common causative agent of hand infection resulting from a human bite, with options including Staphylococcus aureus, Clostridium difficile, Herpes simplex, Eikenella corrodens, and Candida species?

From the Guidelines

The correct answer is (d) Eikenella corrodens, as it is a characteristic organism found in hand infections caused by human bites, according to the practice guidelines for the diagnosis and management of skin and soft-tissue infections 1.

Key Points

• Hand infections caused by human bites are typically polymicrobial, but Eikenella corrodens is a prominent aerobic pathogen, along with streptococci, staphylococci, and Haemophilus species 1.
• Eikenella corrodens is part of the normal oral flora in humans and is particularly associated with "fight bite" injuries, where a person's knuckle strikes another person's teeth.
• These infections can be severe due to the deep inoculation of oral bacteria into the closed spaces of the hand.
• Treatment typically involves surgical debridement of the wound and antibiotic therapy with agents that cover both aerobic and anaerobic organisms, including amoxicillin-clavulanate or a combination of fluoroquinolone and metronidazole.

Rationale

While Staphylococcus aureus can be present in human bite infections, it is not the characteristic organism, as the bacteriologic characteristics of these wounds reflect the normal oral flora of the biter, with a variety of pathogens, including Eikenella corrodens 1. Clostridium difficile is associated with antibiotic-associated colitis, Herpes simplex causes viral infections, and Candida species are fungi that typically cause opportunistic infections, making them less relevant to the typical bacterial causes of hand infections from human bites.

From the FDA Drug Label

Amoxicillin/clavulanic acid has been shown to be active against most isolates of the following bacteria, both in vitro and in clinical infections... Gram-negative bacteria... Eikenella corrodens

The correct answer is (d) Eikenella corrodens, as it is mentioned in the drug label as one of the bacteria against which amoxicillin/clavulanic acid is active. 2

From the Research

Hand Infection Causes

• The most likely cause of hand infection due to a human bite is Eikenella corrodens 3, 4, 5, 6
• Other possible causes of hand infections include:
  • Staphylococcus aureus 4, 6
  • Streptococcus species 4, 6
  • Anaerobic bacterial species 4, 6
• The following options are less likely to be the primary cause of hand infection due to a human bite:
  • Clostridium difficile
  • Herpes simplex
  • Candida species

Key Findings

• Eikenella corrodens is a common cause of hand infections due to human bites 3, 4, 5, 6
• Human bites can lead to polymicrobial bacterial infections with a mixture of aerobic and anaerobic organisms 4, 6
• Delayed medical consultation, lack of medical care, and inadequate wound care can increase the rate of complications 7