Yes, that is the basic methodology behind urine cultures. However, with
specialized patients, i.e. urology or kidney patients with longstanding infections
and/or treatments, the docs sometimes treat with counts of <10,000/ml.
If the gentlemen is getting into a situation where he might have a chronic
prostatitis, low numbers could be significant, depending on the opinion of the
urologist. I have personally seen orders from urologists that say "work up all
organisms regardless of count."
Also, about ten years ago, I attended a workshop on urinary tract infections -
guidelines for reporting, given by the Cleveland Clinic. At that time (I don't know
whether this is still done at this institution), they plated most urines with a .001
microliter loop (each colony equalling 1,000 organisms/ml). However, with women of
childbearing age (15-45 years) they also plated with a .01 microliter loop (each
colony equalling 100 organisms/ml), as these women were at risk for UTI's with low
counts. My laboratory plates catheterized urines with a .01 and clean catch urines
with .001.
This is why I think it important that the original poster check with a urologist and
talk to him about low numbers in a urine culture if he has a relapse. Urologists
should know what guidelines their lab uses for urine culture reporting.
Judy Dilworth, M.T. (ASCP)
Microbiology
pmonk at attglobal.net wrote:
> Urine is considered a sterile fluid. 0.01ml of urine is plated onto a BAP or MAC
> agar plate. Take the number of colonies that grow and multiply by 100. Some
> labs use complex protocols for working up urine cultures. A good guide line is
> one organism that is greater then 100000, work it up. If a urine has more then
> one organisim with each colony or 100000 then do not report and ask for a new
> specimen. If less then 10000 then it is probable contamination from when it was
> collected and will not be worked up.
