The presence of bacteria in a urine specimen may indicate a urinary tract infection, but it may also be contamination if the specimen has been held at room temperature for a prolonged period of time and/or if the specimen was not collected using a clean-catch protocol. It is essential to perform a urinalysis on a freshly collected mid-stream specimen to determine the significance of the bacteria that may be seen.
The presence of increased numbers of WBCs is also an indication of urinary tract infection. Bacteria are indicated by the arrows in the image on the right. Several WBCs are also present in this field. In this case, the presence of bacteria most likely indicates urinary tract infection.