The utility of Amies charcoal bacteriology swabs for storage of canine urine prior to culture

OBJECTIVE

To determine the usefulness of bacteriology swabs as a storage method of canine urine samples and the effect on quantitative bacterial culture.

MATERIALS AND METHODS

Two hundred fourteen canine urine samples were collected by cystocentesis. The reference aliquot was placed in a sterile tube and processed for quantitative bacterial culture within 6 hours. A bacteriology swab was then immersed in the urine for 5 seconds and returned to the charcoal Amies media container. The urine samples in the sterile tube and bacteriology swab were stored at room temperature for 48 hours and processed for quantitative bacterial culture.

RESULTS

Thirty-seven of the samples were positive on reference culture with a total of 42 bacterial isolates. Samples stored in sterile tube and bacteriology swab had identical sensitivity and specificity for detection of bacteriuria (94.7% and 100%, respectively) with very good agreement (κ = 0.92; 95% CI 0.81 to 1.00). Agreement between the bacterial species of the reference sample and the bacteriology swab was higher (κ = 0.85; 95% CI 0.71 to 0.99) than compared to the sterile tube (κ = 0.78; 95% CI 0.62 to 0.94), but the overlapping confidence intervals mean improved agreement cannot be inferred.

CLINICAL SIGNIFICANCE

Bacteriology swabs stored in Amies charcoal transport media should be considered an alternative method to preserve canine urine sample when immediate processing for quantitative bacterial culture is not possible. The sensitivity of culturing plain urine, stored for 48 hours in a sterile tube, for detection of bacteriuria, was higher than previously reported.