Essential criteria in diagnosis of urinary tract infections
ESSENTIAL CRITERIA IN DIAGNOSIS OF URINARY TRACT INFECTIONS
With many years of experience in reporting the Urinary tract infections with culturing, I still feel we
have not perfected in many matters, and getting optimal conclusions are difficult and opinions vary
in the individuals when reporting. The reasons being not inadequacies in Laboratory testing as we
find three or more species of bacteria in a urine specimen, it usually indicates contamination at the
time of collection and interpretation are fraught with error. Well said and not done cleaning of the
Genital area carries a real priority because urine is so easily contaminated with commensal flora,
specimens for culture of bacterial urinary tract pathogens should be collected with attention to
minimizing contamination from the perineal and superficial mucosal microbiota. Although some
literature suggests that traditional skin cleansing in preparation for the collection of midstream or
“clean catch” specimens is not of benefit, many laboratories find that such specimens obtained
without skin cleansing routinely contain mixed flora and if not stored properly and transported
within one hour to the laboratory, yield high numbers of one or more potential pathogens on
culture. Interpretation of such cultures is difficult, so skin cleansing is still recommended. We have
to educate the concerned physicians, not ask the laboratory to report “everything that grows”
without first consulting with the laboratory and providing documentation for interpretive criteria for
culture that is not in the laboratory procedure manual. This is the grave error of many private
laboratories without a qualified supervision report many commensals and contaminates as potential
pathogens and testing with Antibiotic sensitivity pattern. The differentiation of cystitis and
pyelonephritis requires clinical information and physical findings as well as laboratory information,
and from the laboratory perspective the spectrum of pathogens is similar for the two syndromes.
Culturing only urines that have tested positive for pyuria, either with a dipstick test for leukocyte
esterase or other indicators of PMNs may increase the likelihood of a positive culture, but
occasionally samples yielding positive screening tests yield negative culture results and vice versa,
and undue dependency by physicians on Dip stick method should be understood. The Gram stain is
not the appropriate method to detect PMNs in urine but it can be ordered as an option for detection
of high numbers of gram-negative rods when a patient is suspected of suffering from urosepsis. The
use of urine transport media in vacuum-fill tubes or refrigeration immediately after collection may
decrease the proliferation of small numbers of contaminating organisms and increase the numbers
of interpretable results. Straight or “in-and-out” catheterization of a properly prepared patient
usually provides a less contaminated specimen Specimens from urinary catheters in place for more
than a few hours frequently contain colonizing flora due to rapid biofilm formation on the catheter
surface, which may not represent infection. Culture from indwelling catheters is therefore strongly
discouraged, but if required, the specimen should be taken from the sampling port of a newly
inserted device. We should insist that the Clinicians should indicate whether they are sending a
catheterised specimen Cultures of Foley catheter tips are of no clinical value and will be rejected.
Even we find resistance when we reject these specimens from even the senior practitioners
Collection of specimens from urinary diversions such as ileal loops is also discouraged because of the
propensity of these locations to be chronically colonized Laboratories routinely provide antimicrobial
susceptibility tests on potential pathogens in significant numbers .Specimens obtained by more
invasive means, such as cystoscopy or suprapubic aspirations should be clearly indicated, to the
laboratory, Identification of a single potential pathogen in numbers as low as 200 cfu/mL may be
significant, such as in acute urethral syndrome, but requests for culture results reports of <10 000
cfu/mL should be coordinated with the laboratory so that an appropriate volume of urine can
reprocessed. Recovery of yeast, usually Candida spp, even in high cfu/mL is not infrequent from
patients who do not actually have yeast UTI, thus interpretation of cultures yielding yeast is not as
standardized as that for bacterial pathogens. Yeast in urine may rarely indicate systemic infection,
for which additional tests must be conducted for confirmation.
Changing Trends on Detection of AFB from urine – The current peer reviewed information indicates
Recovery of Mycobacterium tuberculosis is best accomplished with first-voided morning specimens
of >20 mL, and requires a specific request to the laboratory so that appropriate processing and
media are employed. The collection of 24 hours urine is totally abandoned in future testing for AFB
detection. Never forget that genital cleaning with disinfect is essential to reduce the contamination
with the Saprophytic Acid Fast bacilli as M.smegmatis.
How to collect a urine from a young child or infant a question has few best solutions however the
method described below has scientific success
A recent paper from Madrid proposes a method to produce a flow of urine on demand in infants.
And I can report that our own unit has found it to be quite effective for both neonates, infants and
some older babies.
It takes a minimum of two people to perform this procedure. However, it is better with three, one
dedicated to making the catch.
Encourage oral fluid intake.
25 minutes following this feed, the baby/infants genitals are cleaned thoroughly with warm soapy
water and dried with sterile gauze.
Sterile container is prepared to collect specimen.
Baby is held under the armpits (just above the bed) with legs dangling (the parents can easily assist
The nurse then starts bladder stimulation which consists of gentle tapping in the suprapubic area
at a rate of 100 taps per minute for 30 seconds.
Next, the lumbar paravertebral zone (think the small of the lower back) is massaged in a light
circular motion for 30 seconds.
Step 5 and six are repeated until urine is released.
Stand clear & catch the mid-stream.
Ref and Abstracts from A Guide to Utilization of the Microbiology Laboratory for Diagnosis of
Infectious Diseases:2013 Recommendations by the Infectious Diseases Society of America (IDSA) and
the American Society for Microbiology (ASM)Ellen Jo Baron,et al
Dr.T.V.Rao MD Professor of Microbiology. Freelance writer