2. URINE CULTURE MEDIA
1. Blood agar – indicator HB
2. MacConkey agar – indicator neutral red (crystal
violet + bile salts)
3. CLED agar – indicator is bromothymol blue
3. POSSIBLE MICRO-ORGANISMS IN URINE
1. E-coli – causes UTI
2. Klebsiella – causes UTI
3. Proteus species – causes UTI
4. Pseudomonas species – causes UTI
5. Salmonella typhi & Para typhi – causes typhoid
- Most common sites of UTI are urinary bladder (cystitis), ureters (uretitis),
and kidney (pyelonephritis)
- Gram positive may also be present: Staphylococcus saprophyticus,
Enterococcus faecalis, Streptococcus agalactiae.
4. SPECIMEN COLLECTION FOR URINE CULTURE
1. Clean catch for a normal individual / urine
containers
2. Suprapubic aspirations
3. Catheterization
4. Sterile urine bag
5. CULTURE AND INTERPRETATIONS.
The culture & interpretation procedure includes the following steps:
1. Examination of a Gram-stained smear.
2. A screening test for significant bacteriuria.
3. A definitive culture for urine specimens found to be positive in the
screening test, and for all specimens obtained by cystoscopy, suprapubic
bladder puncture (SBP), or catheterization.
4. Susceptibility tests on clinically significant bacterial isolates.
6. INTERPRETATION CONT.
-Count the approximate number of colonies. Estimate the number of
bacteria, i.e. colony-forming units (CFU) per ml of urine. Report the
bacterial count as:
● Less than 10 000 organisms/ml (104/ml), not significant.
● 10 000–100 000/ml (104–105/ml), doubtful significance (suggest
repeat specimen)
● More than 100 000/ml (105/ml), significant bacteriuria.
7. CULTURE PLATE READINGS
1. E-coli
-normal flora of GI tract but causes UTI in urinary systems
BLOOD AGAR: no hemolysis, Greyish colonies, small colonies
MCA: small, red/pinkish colonies, lactose fermentation
CLED: small, yellowish colonies, lactose fermentation
8. 2. Klebsiella oxytoca
- Causes UTI in urinary system
BLOOD AGAR: small, smooth, greyish colonies no hemolysis
MCA: large elevated, mucoid, pinkish colonies , lactose
fermentation
CLED AGAR: highly mucoid, large, yellowish colonies, lactose
fermentation
9. 3. Proteus species
-swarming on blood agar and urease activity and causes UTI
BLOOD AGAR: no hemolysis, concentric circles.
MCA: smooth colorless colonies, swarming, non lactose
CLED AGAR: smooth colorless colonies, no swarming, non lactose
10. 4. Pseudomonas aeruginosa.
-can cause UTI
BLOOD AGAR: Gray/whitish colonies with undulating membranes
MCA: colorless colonies, non lactose
CLED: colorless/green colonies with typica mattered surfaces and rough
periphery
11. BIOCHEMICAL TESTS.
1. SIM (SULPHUR INDOLE MOTILITY)
- To differentiate E-coli from klebsiella which are both lactose fermenters.
- determines the ability of an organism to produce indole from the degradation
of the amino acid tryptophan.
- NEG TEST: klebsiella
- POS TEST: E-coli
CONCLUSION: reddish/pinkish ring is
formed
12. 2. CITRATE TEST.
-the ability to utilize citrate as its carbon and energy source.
-color changes from green to blue
-The shift in pH turns the bromothymol blue indicator
POS TEST: Klebsiella
NEG TEST: E.coli & shigella
13. 3. UREASE TEST.
-indicator is phenol red, its color changes from green to pink
-ability of an organism to split urea, through the production of the
enzyme urease.
POS TEST: Klebsiella & proteus
NEG TEST: H. pylori etc.
14. 4. OXIDASE TEST
-To differentiate pseudomonas from E-coli and other Enterobacteriaceae.
-Oxidase reagent used is 1% tetra-methyl-phenylenediamine.
-Organisms which contain cytochrome c as part of their respiratory chain
are oxidase-positive and turn the reagent blue/purple.
POS TEST: pseudomonas (ox+)
NEG TEST: Enterobacteriaceae (ox-)
15. BASIC SETS OF DRUGS.
1. Sulfonamide
2. Clotrimazole
3. Ampicillin
4. Nitrofurantoin
5. Tetracycline
6. Gentamycin
7. amoxiclav
- After biochemical tests antimicrobial susceptibility testing
follows according to procedures.
