Gram – Joint Fluid: 1-5/oif (2+) neutrophils, 2-10/oif  (2+) gram negative diplococci and gram positive bacilli (Moraxella catarrhalis and Bacillus circulans). – Shipped August 10, 2020


A simulated joint fluid sample from a 55 year old male, with prosthetic knee collected from the OR was sent to category A and C1 laboratories for Gram staining.


  1. The presence of more than one species and of the morphotypes observed is more suggestive of contamination during the surgical procedure rather than true infection in this clinical setting
  2. The observation of a probable Bacillus species and gram negative diplococci in this clinical operating room situation generally points to contamination. However, in a prosthetic joint which may be destroyed by infection, it is important to report the microorganisms observed, so that the clinician can make a judgement based on the pathophysiology of the joint they are operating on.


Full critique (PDF)

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