A while ago, I came across a joint fluid result whilst I was reviewing results to be released to the ward doctors. The
patient was in her mid 80s, and her joint fluid contained a small Gram-negative bacillus. The organism was identified as a Pasteurella multocida however, the unusual piece of the story was that this fluid was from her wrist, a very
uncommon place to get a septic arthritis.
I explained to her that her painful and swollen wrist was infected with bacteria which are part of a cat’s normal mouth flora and that that was how I knew she had a cat. The bacteria could only have got into her wrist by being introduced directly from a cat’s bite. She said I couldn’t blame Tigger, as it was her fault for picking him up when he didn’t want to come in, as a cat lover too, I agreed.
She was treated initially with IV Co-amoxiclav, which was then converted to PO Co-amoxiclav for a further 4 weeks, she made an excellent recovery. As far as I know Tigger is doing fine as well…
Bites can be troublesome clinical problems because the severity of the infection is related to the normal mouth flora of the individual doing the biting (human or animal), the type of wound it causes (puncture or laceration) and whether a foreign body is present (i.e. a broken bit of tooth). Most of the oral flora of humans and animals are anaerobic, but there are some aerobes or facultative
anaerobes in their as well (see below for definitions). Most of these are sensitive to either penicillins or tetracyclines (if the patient is allergic to penicillin) but some of the anaerobes can be resistant, so Clavulanic acid is often added to the Amoxicillin in the form of Co-amoxiclav. Metronidazole is given with Doxycycline as an equally good alternative to Co-amoxiclav. Trying to remember a list of which anaerobes are resistant is not possible as resistance is unpredictable, bacteria in same species can be sensitive or resistant.
Grows in the presence of oxygen
Grows in the absence of oxygen
Able to grow in the presence or absence of oxygen
Grows in the presence of oxygen at lower concentrations than in
Thorough cleaning of the wound is essential and it should usually be left open, to allow air in to try and kill off the anaerobes which will have been introduced. The normal practice is to either allow it to heal by secondary intention (i.e. heal on its own) or to carry out delayed surgical closure after 48 hours. Most patients make a good recovery and fortunately severe infections, tissue necrosis, abscess formation and septicaemia, are rare but these need
aggressive antibiotics and surgical debridement. Complications to bites include sepsis, osteomyelitis and septic arthritis and tend to occur if either there is inadequate or delayed initial management or extensive tissue damage in the original injury.
So how is my cat? Just in case you were wondering. A quick visit to the vets, a thorough cleaning of the remains of the abscess, left open so it can drain and an injection of co-amoxiclav (so she doesn’t bite us giving her tablets!) and
she is starting to feel much better, although she’s a little put out that they had to remove some of her whiskers :-”