Pasteurella, a bacteria.
Pasteurella are short, encapsulated, gram-negative rods
such as you see on the gram-stain on the slide.
They have bipolar staining meaning that their staining is
the ends of the organism.
Making them look almost like a barbell or a dumb bell.
The pasteurella are normal flora of domestic cats and dogs
so even if those animals don't travel outside their flat,
they will still most likely be colonized with the organism.
Therefore when those animals with their normal flora bite on
ingesting them or doing whatever to show their affection,
then they can transmit that normal flora into, and past
that skin barrier which is our best defense causing
When human infection occurs it is most often caused by
Here we see an active transmission of pasteurella multocida
into the finger of a helpless victim in the upper image.
Yes, that is a normally pleasant cat that is transmitting
after having it's ears groped, fondled or rubbed.
I'm not quite sure what, in any event that is where the
actual transmission occurs.
Importantly, the transmission is penetrating the organism
deep into the soft tissue
of that victims finger because the sharp fangs of the cat
are much longer
than they are seen in dogs or other chewing type animals.
When infection develops it is preceded by swelling, followed
by redness or cellulitis
and then a bloody or purulent discharge coming out to the
site of the inoculum of the wound.
If the infection is unrecognized and untreated,
it has great potential to spread to nearby joints, infecting
cartilage and bone
and therefore causing infectious arthritis and also
Cat bites especially because they are so deep and so
difficult to treat effectively
have great potential to keep on going because bone
infections known as osteomyelitis.
Dog bites account for 90% of animal bites
but cat bites
of the more commonly infected. Because cat
teeth deliver deep puncture wounds.
50% of bites from a cat become infected
versus just 7% for dogs.
In assessing the patient
the first step is to perform
a good physical exam,
starting with a good global picture.
You then assess the patient's
overall hemodynamic status.
Next, take special care
to assess the structures near the wound,
especially in cases with deep wounds
on the head, neck, trunk or joints.
Fractures and ligament injuries
are very common in severe dog bites.
Finally, you must always assess the
neurovascular status distal to the wound
and treating the wound.
the first step is to achieve hemostasis,
typically by applying direct pressure.
Next, a thorough irrigation of the wound
should be performed using local anesthetic
If an infection is suspected,
obtain cultures prior to initiating
antibiotics finally apply an appropriate
dressing to the wound.
Keeping in mind that the vast majority
of bite wounds should not be sutured,
especially those deep
penetrating cat bite wounds.
Occasionally, however, facial bites
or other sensitive areas
may need to be sutured to prevent scarring
and to protect cosmetic outcome.
There are multiple considerations
that impact our treatment choice.
Bite wound infections typically are
polymicrobial, with an average number
of cultured organisms
actually being five or more.
Pasteurella is found in 75% of
cat bites and 50% of dog bites.
to consider are capnocytophage
which can cause a fatal sepsis
in asplenic patients.
transmitted by cat scratches or fleas,
such anaerobic bacteria
as Bacteroides and fuser bacteria,
and of course normal flora and human skin
such as staph or strep,
which has been inoculated into the wound.
The empiric treatment of choice
is amoxicillin-clavulanate orally,
but intravenous antibiotics can also
be considered for more severe infections,
especially those with rapidly progressive
erythema, delayed wound
healing or bite
that is near an indwelling device.
Treatment and can be guided
by results of cultures as needed.
The next thing to consider is a patient's
immunization status for tetanus
and to provide updated prophylaxis
Finally, one was always assess
the patient's risk of rabies.
If the animal is wild or feral
and or cannot be caught for testing.
Rabies prophylaxis should be given
consisting of both rabies immunoglobulin
and rabies vaccine.
So, pasteurella multocida coming from our animal friends in
the home situation
most often when they bite, the key to respond to such a bite
is to wash out effectively.
Don't suture it.
Consider the use of ampicillin which should be quite
But most importantly, be nice to our animal friends
so they don't bite us in the first place.