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Rubor, Dolor, Calor, Tumor

When is a knee infection like a lemon?

Mark Crislip, MD, Infectious Diseases, 11:07PM Apr 19, 2011

The patient has had an artificial knee for about a year and it has worked flawlessly. Until the day of admission when it developed rubor, dolor, calor, and tumor.

Infected prosthetic knee.  Not an unusual cause of consultation.  Usually a staphylococcus or a streptococcus.  This time? Gram negative rod.  Hmm.  Then it is identified as a Citrobacter koseri. Double Hmm. There are virtually no joint infectious with this organism, prosthetic or otherwise.

Citrobacters are a minor constituent of the bowel and a rare cause of human disease, usually UTI's. The patient has a long history of diverticulosis and -itis, so I am presuming for the time being it came from a leaky tic, although abdominal exam is normal.

But what to do? The literature is surprisingly optimistic on gram negative prosthetic joint infections.

"The 2-year survival rate free of treatment failure was 94% (95% CI, 63-99%). Prosthesis retention with surgical debridement, in combination with antibiotic regimens including ciprofloxacin, was effective and should be considered for patients with early Gram-negative prosthetic joint infection."

Although this is not an early infection. It is an acute infection, which is probably a good prognostic sign

"Treating GN PJI with debridement was associated with a lower 2-year cumulative probability of success than treating GP PJI with debridement (27% vs. 47% of episodes were successfully treated; P=.002); no difference was found when a PJI was treated with 2-stage exchange or resection arthroplasty. A longer duration of symptoms before treatment with debridement was associated with treatment failure for GN PJI, compared with for GP PJI (median duration of symptoms, 11 vs. 5 days; P=.02)."

I am surprised they cured 1 in three. Taking a knee out in the elderly is not without significant morbidity, and with no co-morbidities I may have a reasonable shot at salvaging the knee.  

The good news?  Citrobacters complexes uranium.

"A Citrobacter sp. accumulates heavy deposits of metal phosphate, derived from an enzymically liberated phosphate ligand. The cells are not subject to saturation constraints and can accumulate several times their own weight of precipitated metal. This high capacity is attributable to biomineralization; uranyl phosphate accumulates as polycrystalline HUO2PO4 at the cell surface."

Accumulate several times their own weight. I can do that with ice cream.  Being just across the Pacific from a leaky nuclear reactor this may come in handy.

BTW: the name evidently has nothing to do with lemons.  Citro intended to mean a citrate-utilizing rod. 


Clin Microbiol Infect. 2010 Sep 3.  Gram-negative prosthetic joint infection treated with debridement, prosthesis retention and antibiotic regimens including a fluoroquinolone.

Clin Infect Dis. 2009 Oct 1;49(7):1036-43. Gram-negative prosthetic joint infections: risk factors and outcome of treatment.

Uranium bioaccumulation by a Citrobacter sp. as a result of enzymically mediated growth of polycrystalline HUO2PO4 . Science 257 (5071): 782–784.

About This Blog

For the Benefit of Mr Kite, there will be ID tonight. Infectious Diseases! Antibiotics! Viruses and Bacteria and Fungi! Oh my! Exclamation marks!!!!!! No trampolines, nor will any band be playing at 10 to 6. And Henry the Horse died of the Strangles. Sorry. That's the problem with infections.

The endless excitement that is the daily practice of Infectious Diseases in a Portland teaching hospital! The need for meta data!

Every day I make infectious disease rounds in the hospital and see at least one cool case or learn something new. 25 years and I still do not know everything. Why be selfish and keep all of that wonder and knowledge to myself? This blog will be a mostly qod account of days events, a cool ID case, a referenced pearl, and a minimum of 1 horrible, yet ultimately feeble, attempt at humor. I write these at night or in spare moments. There is always someone who will quibble about spelling, punctuation or grammer. My response is live with it. It's a blog, not Mandel.

Read and listen to more of me at my multimedia empire linked below.
Because The World Needs More Mark Crislip (tm).

Disclosure: Mark A. Crislip, MD, has disclosed the following relevant financial relationships:
Received income in an amount equal to or greater than $250 from: Pusware LLC
Have a 5% or greater equity interest in: Pusware LLC (owner)

  • Mark Crislip

    Mark Crislip, MD, has been practicing in infectious diseases in Portland, Oregon, since 1990. He is nobody from nowhere, but he has an enormous ego that leads him to think someone might care about what he has to say about infectious diseases. And so he blogs and podcasts and writes on the most endlessly fascinating specialty in all of medicine.

    Mark A. Crislip, MD, has disclosed the following relevant financial relationships: Owner, Pusware LLC. He as not talked to a drug rep in over 25 years and does not even eat the pizza provided at conferences. But he is for sale for the right price. Please. Someone. Buy me.

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