Human Bites

Wounds caused from human bites, striking the teeth of another person, or resulting from objects that have been in a person's mouth are common and can result in very serious infections. Rarely, diseases such as syphilis, tuberculosis, and hepatitis B are transmitted this way. Much more commonly, it is the normal mouth flora that cause trouble.


The wound may appear insignificant at first but then becomes painful and swells massively. Discharged pus often has a foul smell. Most of the wounds are on the extensor surface on the hand, and here the swelling may soon involve the palm also, and movement of some or all of the fingers becomes difficult or impossible.

Causative Agents

Stains and cultures usually show members of the normal mouth flora, including anaerobic streptococci, fusiforms, spirochetes, and Bacteroides sp., often in association with Staphylococcus aureus.

Table 27.9 Streptobacillary Rat Bite Fever


Chills, fever, muscle aches, headache, and vomiting; later, rash and pain in one or more of the large joints

Incubation period

Usually 2 to 10 days (range, 1 to 22) after a rat bite

Causative agent

Streptobacillus moniliformis, a highly pleomorphic Gramnegative bacterium that spontaneously produces L-forms


Bite wound heals without treatment; S. moniliformis quickly invades bloodstream. Fevers come and go irregularly. Most victims recover without treatment; in others, infection established in various body organs, results in death if treatment is not given


Wild and laboratory rats can carry S. moniliformis. Bites of other rodents and animals that prey on them can transmit the disease to humans. Food or drink contaminated with rodent excreta can also transmit the infection; foodborne disease is called Haverhill fever

Prevention and treatment

Control wild rats and mice, care in handling laboratory animals. Effectively treated with penicillin, other antibacterial medications


The crushing nature of bite wounds provides suitable conditions for anaerobic bacteria to establish infection. Although most members of the mouth flora are harmless alone, together they produce an impressive number of toxins and destructive enzymes. These include leukocidin, collagenase, hyaluronidase, ribonuclease, various proteinases, neuraminidase, and enzymes that destroy complement and antibody. Capsules of some species inhibit phagocytosis. Facultatively anaerobic organisms reduce available oxygen and thus encourage the growth of anaerobes. The result of all these factors is a synergistic infection, meaning that the sum effect of all the organisms acting together is greater than the sum of their individual effects. Irreversible destruction of tissues such as tendons and permanent loss of function can be the result. ■ facultative anaerobes, p. 89


Most of the serious human bite infections occur in association with violent confrontations related to alcohol ingestion, or during forcible restraint, as in law enforcement and in mental institutions. The risk is greatly increased when the biting individual has poor mouth care and extensive dental disease. Bites by little children are usually inconsequential.

Prevention and Treatment

Prevention involves avoiding situations that lead to uncivilized behavior such as biting and hitting. Prompt cleansing of wounds followed by application of an antiseptic are advised, and most important is immediate medical attention if there is any suspicion of developing infection. Treatment of infected wounds consists of opening the infected area widely with a scalpel, washing the

27.5 Fungal Wound Infections

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  • emppu lehtinen
    What is the causative agent of human bite?
    5 years ago

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