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Urine Examination
Dr. Shler Ghafour RaheemBSc., MSc., PhD Medical Microbiology
Lab. No. 10, 11
Objectives
1. What Normal and abnormal appearance of urine.
2. Examination of urine only required in which condition?
3. Appropriate procedures for collection of specimen including suitable (time, site and container).
4. Appropriate transportation and preservation of specimen.
5. General urine examination.
6. Urine culture.
7. Interpretation of culture Plates
8. Common pathogen related to diseases.
Examination of urine
• Is the physical, chemical, and microscopic examination of urine. It involves a number of tests to detect and measure various compounds that pass through the urine.
Normal and abnormal appearance of the urine :
Urine amount:
• Normal:
Urinary out put is about 1200 – 1500 ml
• Abnormal:
Urinary out put under 1200ml or
Over 1500 ml as in
-Diabetes
Urine color
• Normal:
Yellow, amber, or transparent
• Abnormal:
Pink or red urine: due to presence of blood in urine due to specific disease
Orange urine: some drugs like pyridium
Cloudy or murky urine: due to urinary tract infection or kidney stones
Dark yellow to brown: mainly it occur by decrease of fluid intake
Urine consistency
• Normal:
clear liquid
• Abnormal:
mucous plugs, viscid, thick
It could be occur due to infection process
Urine odor• Normal:
Faint aromatic odor due to the presence of some volatile acids
• Abnormal:
In some pathological conditions such in
- fruity odor is due to acetone such in diabetic patient
- offensive odor due to bacterial action of pus
Urine PH
• normal PH for urine ranges from 4.5 – 6.0
• A PH <7 indicates acid urine and a PH > 7 alkaline urine.
• Some foods (such citrus & dairy products) and medications (such as antacids) can affect urine PH
• In a diet high in protein the urine is more acidic, while a diet high in vegetable material yields a urine that’s more alkaline.
Urine glucose
• Normal:
not present
• Abnormal: present
Diabetes mellitus
Urine blood
• Normal :
Not present
• Abnormal: occult
- kidney disease
Or bright red
- hemorrhage
Examination of urine required in:
• As part of a routine medical exam to screen for early signs of disease.
• If the patient have signs of diabetes or kidney disease.
• To check for blood in the urine.
•To diagnose a urinary tract infection.
Appropriate time for collection
• Urine for a urinalysis can be collected at any time.
•The first morning sample is considered the most valuable because it is more concentrated and more likely to yield abnormalities if present.
Appropriate site for collection
• Should avoid contamination by bacteria.
• Women should spread the labia of the vagina and clean from front to back.
• Men should wipe the tip of the penis.
•Midstream collection
Midstream collection:
General urine examination
• Urinalysis can reveal diseases that have goneunnoticed because they do not produce signs orsymptoms. Examples include diabetes mellitus,various forms of glomerulonephritis, and chronicurinary tract infections.
General urine examination cont.
It involves :
•Macroscopic analysis .
•Chemical analysis .
•Microscopic analysis .
General urine examination cont.Macroscopic analysis : is direct visual observation of
color , clarity
General urine examination cont.
Chemical analysis : The most frequently performed chemical tests are:
Specific gravity
pH
Protein
Glucose
Ketones
Chemical Tests for Significant Bacteriuria
1- Nitrite test:
Nitrites are not present in normal urine.
Ingested nitrites are converted to nitrate and excreted in urine.
If gram-negative bacteria (e.g. E.coli,Salmonella, Proteus, Klebsiella, etc.) are present in
urine. Nitrites are then detected in urine by reagent strip tests.
2- Leucocyte esterase test:
It detects esterase enzyme released in urine from granules of leucocytes.
Thus the test is positive in pyuria. If this test is positive, urine culture should be done.
General urine examination cont.
• Microscopic analysis : a sample of urine is
centrifuged until a cohesive substance is
produced at the bottom of the tube the fluid at
the top is discarded and the remaining fluid is
examined under microscope to identify crystals ,
bacteria , RBC , WBC …
Urine culture
• The urine culture is used to diagnose urinarytract infection and to identify the bacteria oryeast causing the infection.
• It may be done in conjunction withsusceptibility testing to determine whichantibiotics will inhibit the growth of the microbecausing the infection.
Culturing Procedure
Culture for Causative Agents of Urinary Tract Infections
• Generally, routine urine cultureshould include plating onto oneselective medium (e.g., MacConkeyagar) and one nonselectivemedium Blood agar (BA).
• CLED agar can be used as a solemedium, reducing the cost withoutcompromising the quality.
CLED (cysteine-, lactose-, and electrolyte-deficient) agar
• is a differential culture medium for use in isolating and enumerating bacteria in urine from the suspected cases of Urinary Tract Infection.
• Supports the growth of all potential urinary pathogens
• CLED agar can be used as a sole medium
• It’s economy and convenience
.wp.com/microbeonline.com/wp-content/uploads/2015/03/Lactose_non_lactose_fermenters_on_CLED_agar.jpg
Benefits and Disadvantages of Using CLED Agar for UrineCulture
• Good discrimination of gram-negative bacteria on the basis of
lactose fermentation and colony appearance;
• Inhibits swarming of Proteus spp
• Relatively low cost.
Disadvantages: poor growth of some gram-positive bacteria.
• After inoculation the cultureplates are incubated at 370cextending to > 18 hours are read
• Uropathogenic Escherichia coli (UPEC)is the predominant etiological agent ofuncomplicated urinary tract infection.
Significance of Colony Counts:
• In women, vaginal flora may contaminatethe urine; many of the organisms thatcolonize the vagina are also implicated inUTIs. Therefore, it could be difficult to knowwhether growth in urine cultures was indicative ofinfection or contamination.
• In general > 100,000 bacteria/ml = infection
•Single organism
Reading the culture plates
• A true infection in the absence of prior antibiotic therapy thenumber of bacteria is likely to be at least 105 or more.
• Contaminated specimens present with colony counts <104
• Several studies prove counts >104 to be considered aspresence of Urinary tract infection with the supporting clinicalhistory.
• On some occasions, more than one pathogen is isolated ( E.coli
along with Streptococcus fecalis).
• On few occasions even counts 103 are proved significant
Interpretation of culture Plates
• A true infection in the absence of prior antibiotic therapy the number of bacteria is likely to be at least 105 CFU or more with patients symptomatic for urinary tract infection, 95% probability of true bacteriuria
Interpretation of culture Plates
• Several studies prove counts>104 to be considered aspresence of Urinary tractinfection with the supportingclinical history
• Ignore mixed urethral flora at<104
Reporting of negative urine cultures
• Negative culture resultsshowing no bacterialgrowth are available after24 hours.
Common uropathogens
• Escherichia coli
• Other enterobacteriaceae (Klebsiella, Enterobacter, Proteus)
• Pseudomonas aeruginosa
• Enterococcus
• Staphylococcus aureus
• Staphylococcus saprophyticus
• Candida
Antibiotic sensitivity test
Antibiotic sensitivity test by Kirby-Bauer's method on Muller-Hinton agar
Antibiotic sensitivity testing or antibioticsusceptibility testing is the measurementof the susceptibility of bacteriato antibiotics. It is used because bacteriamay have resistance to some antibiotics.
References
Luis M. de la Maza, Marie T. Pezzlo, Cassiana E. Bittencourt,Ellena M. Peterson. 2020. Color Atlas of MedicalBacteriology. (2020, Wiley) - libgen.lc.
Konemman’s color atlas and textbook of DiagnosticMicrobiology, 6th edition
Robert W. Bauman, Todd P. Primm. 2018. Microbiology withDiseases by Body System. Fifth edition, Pearson.