Urine Examination

Dr. Shler Ghafour RaheemBSc., MSc., PhD Medical Microbiology

shler.ghafour@tiu.edu.iq

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.