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Essentials of Diagnosis
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Cat and human bites are more likely to become infected than dog bites
Bites to the hand are of special concern because of the possibility of closed-space infection
Antibiotic prophylaxis indicated for noninfected bites of the hand; hospitalization required for infected hand bites
All infected wounds need to be cultured to direct therapy
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General Considerations
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Biting animals are usually known by their victims, and most biting incidents are provoked (ie, bites occur while playing with the animal or waking it abruptly from sleep)
Important determinants of whether bites become infected
Bites on the extremities are more likely to become infected than bites on the head, face, and neck
Failure to elicit a history of provocation is important, because an unprovoked attack raises the possibility of rabies
Human bites
Usually inflicted by children while playing or fighting
In adults, bites are associated with alcohol use and closed-fist injuries that occur during fights
Infections following human bites are variable
Because bites inflicted by children are superficial, they rarely become infected
Bites by adults become infected in 15–30% of cases, with a particularly high rate of infection in closed-fist injuries
"Through and through" bites (eg, involving the mucosa and skin) have an infection rate similar to closed-fist injuries
Cat bites
Dog bites, for unclear reasons, become infected only 5% of the time
Puncture wounds become infected more frequently than lacerations, probably because the latter are easier to irrigate and debride
The bacteriology of dog and cat bites is polymicrobial
Over 50% of infections are caused by aerobes and anaerobes
36% are caused by aerobes alone
Pure anaerobic infections are rare
Pasteurella species are the single most common pathogen—75% of cat bites and 50% of dog bites
Other common aerobes include
Streptococci
Staphylococci
Moraxella
Neisseria
Common anaerobes include
Fusobacterium
Bacteroides
Porphyromonas
Prevotella
Human bites are a mixture of aerobes and anaerobes in 54% and aerobes alone in 44%
Staphylococci and streptococci are the most common aerobes
Eikenella corrodens (isolated in 30% of infections), Prevotella, and Fusobacterium are the most common anaerobes
Although the above-named organisms are the most common, numerous others have been isolated such as Capnocytophaga (dogs and cats), Pseudomonas, and Haemophilus, emphasizing the need to culture all infected wounds to define microbiology
HIV transmission following a bite has been rarely reported; saliva not contaminated with blood is very low risk
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About 1000 dog bite injuries require emergency department attention each day in the United States, most often in urban areas
Dog bites occur most commonly in the summer months