UTI's Part 2: UTI vs Positive Urine Cultures

Not all positive urine cultures indicate that the patient has a UTI. Positive urine cultures can result from improper, non-aseptic collection technique, improper specimen handling, or the presence of an indwelling urinary catheter, in addition to an actual infection.

Signs that the positive urine culture is actually a false positive one include:

• multiple positive cultures, each one with a different bacterial species
  
• cultures with multiple organisms
• positive cultures in the face of a normal UA
• positive cultures in the absence of symptoms
• urine cultures that grow atypical organisms
• positive cultures in patients with chronic indwelling catheters and no symptoms
• cultures with low levels of bacterial growth
  

Any of the above should alert the physician to the fact that the culture may not be accurate. Use of antibiotics in these cases may not be indicated and can actually promote subsequent bacterial resistance.

Thanks for listening.

Dr S.

Diagnosing UTI's: Part 1

Correctly diagnosing urinary tract infections--or UTIs--can be among the most challenging of all diagnoses. I believe this is because of misconceptions by providers and patients alike about what constitutes a UTI.

Meeting the criteria for the presence of a UTI requires that the following features be present:

1. Bacteria that grow on a urine culture plate plus,
2. symptoms from the patient that are caused by the presence of the bacteria with,
3. the confirmation of proper specimen collection technique and,
4. the absence of other conditions that can cause the symptoms if proper collection technique cannot be verified.

If I can verify the above 4 items, I can say with little doubt that you have a UTI. Otherwise, I question the diagnosis.

The problem in clinical medicine is that seldom do all four criteria coexist. For this reason, and for other practical reasons, doctors often treat patients empirically--based on a hunch--for UTI's. If the patient gets better immediately, then the doctor was correct and nothing more needs to be done. If the patient does not get better, or if the symptoms keep on coming back, then additional testing is indicated.

And that will be the stuff of futures posts on this topic.

Thanks

Dr S