Urine: To Culture, Or Not To Culture

To culture urine, or not to culture, that is the question for today.

Usually the first laboratory confirmation that a pet has a urinary tract infection (UTI) is the microscopic finding of bacteria during a urinalysis.

Bacteria come in two common shapes: round and rod-shaped. The round ones are properly termed cocci, the rod-shaped ones bacilli.

Broadly speaking, we worry more when we see bacilli on a urinalysis because they have a greater likelihood of causing a bad infection, are more likely to be resistant to a lot of antibiotics and have a greater tendency to recur after treatment is finished.

That is not to say we don’t worry when cocci are visible on the microscope. Bad round bacteria such as MRSA (methicillin-resistant-Staphylococcus aureus) can be a tremendous challenge to cure.

Previous number of UTIs is a big factor that your pet’s doctor evaluates. A patient whose urinary tract becomes infected over and over usually has an underlying problem that predisposed him to the recurrences. If that problem is one or more species of resistant bacteria, the sensitivity portion of the urine culture and sensitivity will reveal the problem, as well as the proper treatment.

Degree of illness is an important determiner. If there is no blood in the urine, no straining to urinate, an absence of frequent urination and accidents and the patient is eating, drinking and acting normally, his case will be approached differently from a pet who displays abnormalities in one or more of those areas.

Age is also a consideration. No, not age of the doctor, but age of the patient. A young pet with a first-time UTI who is also not ill will be more likely to receive treatment without culturing the urine.

In summary, the factors that make veterinarians more likely to want to culture a sample of infected urine include:

  • rod-shaped bacteria on the microscopic portion of the urinalysis
  • recurrent infection
  • a patient who is clinically ill
  • an older patient.

See you tomorrow, Dr. Randolph.

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