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Clinical presentations and microbiology |
Clinically, animal bites can result in:
- pain
- disfigurement and loss of function
- Only a small percentage of bites actually result in permanent
disability.
- INFECTION
- local cellulitis/abscessation
- osteomyelitis
- This is particularly a problem with bites to the hands or
feet because of the proximity of the underlying bones to the
skin surface.
- bacteremia with subsequent infection of internal organs (CNS,
heart, kidneys, lungs)
- disseminated intravascular coagulation (DIC), endotoxic shock
>>> death
- exsanguination >>> death (Exsanguination is especially
a concern with dog bites to the face or neck of children.)
The microbiology of animal bites - organisms of greatest
concern:
- PASTEURELLA MULTOCIDA and other Pasteurella
spp.
- Pasteurella bacteria are implicated as a major pathogen
in 20-50% of dog bites and an even higher % of cat bites.
- There are also reports of human infant infections due to
non-traumatic contact (i.e., licking) with animal saliva.
- Pasteurella spp. are a common member of the oral
flora in dogs and cats (50-66% of dogs; 70-90% of cats).
- These infections tend to lead rapidly to cellulitis, with
subsequent abscessation, osteomyelitis, septic arthritis and
potentially systemic dissemination.
- There is also evidence for human infections (not necessarily
via bites) with P. multocida strains from pigs.
- "CDC alphanumerics"
- CDC DF2 ("dysgonic fermenter-2") = Capnocytophaga
canimorsus
- slender, Gram (-) rods
- a particular concern for splenectomized or otherwise immunosuppressed
patients, with a 30+% fatality rate in cases of C. canimorsus
septicemia
- These organisms may often be missed because of their fastidious
growth requirement.
- Recently, Capnocytophaga was implicated as the cause
of chronic sinusitis and rhinitis in a cat. Previously, the
potential for this bacterium to cause disease in the animals
themselves has not been appreciated, perhaps because of fastidious
growth in vitro.
- CDC NO-1 ("non-oxidizer"; similar in characteristics
to Acinetobacter)
- another recently described alphanumeric organism associated
with dog bites (77% of isolates) and, to a lesser degree (18%
of isolates), cat bites
- wound infections and capable of producing septicemia
- 58% of 22 victims in one study required hospitalization
- Staphylococcus intermedius and Streptococcus spp.
- There is also a limited amount of evidence for reverse zoonotic
infections of dogs (as well as cats and horses) with human Staphylococcus
aureus, including dangerous methicillin-resistant (MRSA)
strains.
- Proteus, Klebsiella, Enterobacter spp.
- Bacteroides, Clostridium spp.
- anaerobes
- You must specifically request anaerobic culture conditions
for these organisms.
- Erysipelas rhusiopathiae (usually associated with
pigs) has been isolated from cat bites.
Dog and cat bite wounds are often colonized by a mixed flora
of both aerobes and anaerobes!
Bites from other animals:
- Serratia marcescens infection has been associated
with an iguana bite.
- Bites from rats can lead to "rat bite fever," a
syndrome of fever, lymphadenitis, and rash that occur following
infection with Streptobacillus moniliformis (U.S.) and
Spirillium minus (Asia). Disease typically develops in
people days to weeks (even months) after the initial bite has
already healed. Additionally, S. moniliformis can also
be acquired by ingestion as a foodborne disease, leading to the
"Haverhill fever" form of infection, accompanied by
muscle and joint pain.
- Halomonas vensuta (a halophilic, Gram [-] rod) infection
has been associated with a salt water fish bite.
- Aeromonas hydrophila-induced cellulitis, septicemia,
and diarrhea have been associated with water environments.
- MRSA infections have also been associated with ocean water.
In addition to being concerned with infections related to the
bite wound, it is important to realize that biting may also be
a mode of transmission of specific zoonotic pathogens:
