Urinary tract infections-Lab diagnosis

1. UTI-lab diagnosis MGMC&H,Jaipur 1

2. UTI-lab diagnosis MGMC&H,Jaipur 2
• It is defined as a disease caused
by microbial invasion of the
genitourinary tract that extends
from the renal cortex of the
kidney to the urethral meatus.
•Route of infection to reach the
urinary tract can be either-
Ascending route
Haematogenous route

3. UTI-lab diagnosis MGMC&H,Jaipur 3
• E.coli
• Klebsiella
• Pseudomonas
• Proteus
Gram –ve Bacilli
• Staphylococcus
• EnterococciGram +ve Bacilli
• M.tuberculosis
• Citrobacter
• Salmonella
Miscellaneous
• Candida albicans
Fungus
E.coli
c.albicans
Citrobacter
Staphylococcus

4. UTI-lab diagnosis MGMC&H,Jaipur 4
UTI causing organisms
E.coli (63%)
Klebssiella(15%)
Pseudomonas(5%)
Proteus(5%)
Other Gram -ve bacteria
Staphylococcus
Enterococcus

5. UTI-lab diagnosis MGMC&H,Jaipur 5
•Sterile pyuria is urine which contains white blood cells
while appearing sterile by standard culturing techniques.
• Sterile pyuria is listed as a side effect from some
medications such as paracetamol (acetaminophen).

6. UTI-lab diagnosis MGMC&H,Jaipur 6
•An infection contracted outside of a health care setting or
an infection present on admission.
•E.Coli is the most common cause followed by
stapylococcus saprophyticus
s.saprophyticus

7. UTI-lab diagnosis MGMC&H,Jaipur 7
•Acquired by a patient during a hospital visit.
•Most common organism causing it-
Klebsiella

8. UTI-lab diagnosis MGMC&H,Jaipur 8
Patients with urinary catheters have a
higher chance of getting UTI’s.This is
because germs can travel along the tubing
of the catheter and cause infection in the
urinary system.This is then referred to as a
“catheter associated” UTI.
Complications –
•Cystitis
• pyelonephritis
• bacteremia
• prostatitis
•Rarely, endocarditis, septic arthritis, and
meningitis

9. UTI-lab diagnosis MGMC&H,Jaipur 9
Poor aseptic insertion of catheter: periurethral flora inserted
into bladder.
Migration of bacteria along outer surface of catheter.
Open drainage.
Breaks in the closed drainage system.

10. UTI-lab diagnosis MGMC&H,Jaipur 10
1.
2.
3.

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•Collected PRIOR to antibiotics.
•WASH hands properly.
•Specimen is collected in a STERILE container
BEFORE ANTIBIOTICS
STERILE CONTAINER

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First morning specimen should be taken.
FEMALES- MALES-
Clean the area with soap and
water , hold the labia apart
and discard few ml of urine
and then collect the
midstream sample directly
into the sterile container.
Clean the glans with soap and
water, retract the foreskin,
discard few ml of urine and
the collect the mid stream
sample directly into the sterile
container .
•Discard the rest of the urine.
•The first portion of urine adequately flushes out the normal urethral flora.

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•Urine should be collected directly from the catheter and not from
the collection bag.
•The catheter should not touch the container.
•Catheterization to obtain urine is not done because of risk of
introducing infection though it yields excellent results.
A clean catch specimen after cleansing of genitalia.
OR
Supra pubic aspiration.

15. UTI-lab diagnosis MGMC&H,Jaipur 15

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THE SPECIMEN SHOULD BE
TRANSPORTED IMMEDIATELY.
•Urine is a good medium for the growth of
microorganisms, hence delay in processing
will hamper the results.
•If delay is unavoidable, the specimen can
be refrigerated for up to four hours at 4˚c.

17. UTI-lab diagnosis MGMC&H,Jaipur 17
Urine transport tubes have shown to
preserve bacteria without refrigeration.
It consistes of-
-Boric acid
-Glycerol
-Sodium formate

18. UTI-lab diagnosis MGMC&H,Jaipur 18
MICROSCOPY
CULTURE
IDENTIFICATION
OTHER METHODS
ANTIBIOTIC SENSTIVITYTEST

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Urine is centrifuged and
deposit is examined
under the microscope.
Following can be seen-
•Pus cell( 0-5/hpf is the normal
value for pus cells in the human body).
•RBC
•Epithelial cells
•Bacteria
Bacteria
Pus cell

20. UTI-lab diagnosis MGMC&H,Jaipur 20
Most lab use a semi quantitative method (STANDARD LOOPTECHNIQUE) for
culture.
This technique involves a standard calibrated loop which transfers a fixed and
small volume of urine.
STANDARDCALIBRATED LOOP

21. UTI-lab diagnosis MGMC&H,Jaipur 21
Fixed and small amount of uncentrifuged urine is
transferred to BLOOD and MacCONKEY’S AGAR.
Incubate at 37˚c for 24 hours
Next day, the number of colonies grown is
counted and total count per ml is calculated.
•BLOOD AGAR- gives a quantitative measurement of bacteriuria.
•Mac CONKEY’SAGAR- gives presumptive diagnosis of the bacteria.

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INTERPRETATION OF RESULTS
•Bacteriological diagnosis of UTI is carried out by ‘SIGNIFICANT
BACTERIURIA’ using quantitative cultures developed by KASS(1956).
•This is based on the fact that normal urine is sterile but during voiding
may become contaminated with genital commensals.
SIGNIFICANT
BACTERIURIA
DOUBTFUL
SIGNIFICANCE
NO SIGNIFICANT
GROWTH
•When bacterial count is
more than 105/ml of a
single species.
•It indicates ACTIVE UTI.
•Between 104 to 105
bacteria per ml.
•Specimen should be
repeated for culture.
• <103 bacteria per ml are
regarded as contaminated.
• Contamination is also
considered when 3 or more
bacteria are isolated.

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The organisms are
identified by-
 colony characters
 gram staining
 motility
 biochemical test
 slide agglutination test
 serological test

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SIZE 1-2 mm
COLONY CHARACTER
Blood agar
Mac Conkey agar
Grey-white, moist, smooth, opaque, non
mucoid
Pink colony( due to lactose fermentation)
GRAM STAINING Gram –ve bacteria
BIOCHEMICALTEST
Indole
Methyl red
Voges-Proskauer(VP)
Citrate
+
+
-
-
MOTILITY Motile

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BLOOD AGAR MacCONKEY’S AGAR
GRAM STAINING

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SIZE 2-4 mm
COLONY CHARACTER
Blood agar
Mac Conkey agar
Grey-white, moist, smooth, opaque,
mucoid
Pink colony( due to lactose fermentation)
GRAM STAINING Gram –ve bacteria
BIOCHEMICALTEST
Indole
Methyl red
Voges-Proskauer(VP)
Citrate
-
-
+
+
MOTILITY Non-Motile

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BLOOD AGAR
GRAM STAINING
MacCONKEY’S AGAR

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COLONY CHARACTER
Blood agar
Nutrient agar
Mac Conkey agar
Exhibits SWARMING(fishy odour)
Exhibits SWARMING
Smooth pale colonies
GRAM STAINING Gram –ve bacteria
BIOCHEMICALTEST
Indole
TSI
PPA
Urease
Oxidase
-(P.mirabilis)
+(P.vulgaris)
H2S production
+
+
-
MOTILITY Motile

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BLOOD AGAR
GRAM STAINING
NUTRIENT AGAR

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SIZE 2-4mm
COLONY CHARACTER
Blood agar
Nutrient agar
Mac Conkey agar
Smooth, large, convex,
translucent(sweetish aromatic odour)
Same as on blood agar
Smooth pale colonies
GRAM STAINING Gram –ve bacteria
BIOCHEMICALTEST
Indole
TSI
PPA
Urease
Oxidase
Citrate
-
K/ no change (without H2S production)
-
+/-
+
-
MOTILITY Motile

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BLOOD AGAR
GRAM STAINING
NUTRIENT AGAR

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Dip slides Pour plate method
Triphenyltetrazolium
chloride (TTC) test
Griess nitrite test Glucose test paper
Polymorphonuclear
neutrophils (PMNs)
Catalase test Leucocyte esterase
Detection of
lipopolysaccharide
(endotoxin)

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In this test commercially available plastic slides coated
with CLED agar (cysteine lactose electrolyte deficient)
on one side and MacConkey’s agar on the other is
dipped in urine then placed in a sterile container is
incubated at 37˚c.

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•It is a quantitative method
•But, is cumbersome for routine diagnostic work

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•It is based on nitrate reducing enzymes produced by
bacteria present in urine.
•Gram -ve bacteria-
NITRATES NITRITES
•The presence of nitrite detected by the test indicates
UTI.
•Normal urine does not contain nitrite.

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(TTC TEST)
TTC is reduced by
several frequently
encountered
urinary tract
pathogens and
produce a pink
red precipitate.

37. UTI-lab diagnosis MGMC&H,Jaipur 37
•Certain bacteria have an enzyme catalase which acts on hydrogen peroxide to
release oxygen.
H2O2 H2O + O
[Nascent
oxygen]
•The presence of catalase is evident by formation of bubbles.
•It indicates bacteriuria.
(test present only in catalase +ve organisms.)
catalase

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It is based on utilisation of
the minute amount of
glucose present in normal
urine, by bacteria causing
the infection.
Hence, it indicates
bacteriuria.

39. UTI-lab diagnosis MGMC&H,Jaipur 39
(PMNs)
•PMNs are counted
in uncentrifuged
urine specimen with
the help of
haemocytometer.
8 PMN/mm3 is
indicative of
infection.

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Presence of the enzyme in urine indicates infection.
This test helps in the detection of gram –ve
bacteria in urine.

41. UTI-lab diagnosis MGMC&H,Jaipur 41
•Esch. coli and other
common urinary pathogens
develop multiple drug
resistance and of the
transferable variety.
•Antibiotic sensitivity is
necessary to administer
proper antibiotic.
•Done by STOKES DISC
DIFFUSION method.

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