(NU11) Effect of Iodinated Non-ionic Contrast on Cultures of Canine Urine Inoculated with E. coli.

Background: The effect of iodinated contrast media on bacterial growth has been investigated in human medicine, however, results from scientific studies are conflicting and evidence in veterinary medicine is lacking.

 
Objective: To investigate the effect of iohexol on standardized quantitative urine culture results in dogs. The authors hypothesized that presence of iohexol in inoculated urine samples would result in lower bacterial concentrations (CFU/ml), and therefore decrease culture sensitivity.
 
Samples: Urine sample aseptically collected during cystoscopy from a single client-owned dog untreated with antibiotics.
 
Procedures: Experimental controlled study. The urine sample was divided into 38 aliquots (0.5 ml each) which were used as negative controls or inoculated with an equal amount of E. coli (10⁵ CFU/ml). Different volumes (0.1 and 0.5 ml) of contrast or saline were added to the aliquots and quantitative culture results were compared. Two different incubation times between preparation of aliquots and culture were evaluated (15 minutes and 24 hours).
 

Results: All aliquots from samples inoculated with E. coli (positive controls and iohexol-group) had the same reported quantitative result (10⁴ CFU/ml). No growth was reported for the negative controls. Iohexol did not show any anti E. coli properties in canine urine cultures for dilutions up to 1:2 contrast:urine and concentrations up to 120 mgI/ml. No difference was reported when iohexol was incubated with inoculated urine for 15 minutes or 24 hours.
 
Clinical relevance: Based on the experimental in vitro conditions described, administration of iohexol prior to collection of urine during urologic procedures does not negatively impact the isolation and growth of E. coli.