I am sure everyone has been
eagerly awaiting the answer to last week’s post. First I am going to explain
the organisms NOT responsible.
Staphyloccocus aureus – Gram positive cocci in clusters
S. aureus
is infamous for its ability to infect skin and soft tissue. The infection would
resemble the same characteristics except timing. S. aureus would typically take more time to develop this infection,
close to 3 to 5 days after the incident instead of overnight.
Eikenella corrodens – Fastidious gram negative rods
E. corrodens is an organism frequently involved with human bite infections, and at
times present in dog or cat bite infections. These animal bite infections are
often on the head and neck area, which would match the profile of our patient. Again,
this organism would require a longer incubation time (days to weeks) to develop
the severe state of this infection.
Pasteurella multocida – Gram negative coccobacilli
To be honest, I immediately
guessed this organism before finishing the article. It is often involved with
infected cat bites, as well as some dog bites. The features of a P. multocida infection would show similar
results to this infection with the rapid onset and progression, but it did not
grow in the culture of this infection.
Our culprit is Streptococcus pyogenes (Group A
Streptococcus), a Gram positive cocci in chains.
The speed of this infection
well represents the rapid progression of S.
pyogenes infections. Lab results, though not listed in the article, would
show a beta hemolysis, positive PYR, and susceptible Bacitracin test. The
patient’s clinicians changed his treatment ultimately to 80mg/kg/day of
amoxicillin, and the patient thankfully recovered.
My first guess for the bacteria would also have been Pasteurella multocida. I remember from Micro last semester that if there was an animal bite, one of the first things to think of would be Pasteurella multocida. And then my second guess would have been Staphylococcus aureus, just from the child having an infection from the wound. But I would definitely not have suspected Group A strep. That is definitely an interesting article, because strep is not one of the bacteria’s that I would expect to show up from a bite wound.
ReplyDeleteI agree, based on my knowledge from Microbiology, that Pasteurella multicoda would be the first organism I would suspect to be the cause of the bite wound infection. S. aureus did cross my mind but like you said, the infection occurred rather quickly. I would have been sure that P. multicoda caused the infection, but it very surprising to find that S. pyogenes is the source. Usually Group A strep is not associated with bite wound infections since we primarily associate them with more throat/respiratory infections. I think it's very cool to see Group A strep away from it's typical source of infection.
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