PROCESSING OF URINE

PURPOSE OF EXAMINATION

Diagnosis of urinary tract infection accomplished by semi-quantitative culture of urine and antimicrobial susceptibility testing of potential pathogens present in significant numbers

PRIMARY SAMPLE COLLECTION

ACCEPTABLE SPECIMENS

Clean catch MSU- Mid stream urine is used because the first few ml of urine passed will contain skin flora from the urethral orifice and will yield potentially misleading misleading results.

Foley’s catheter sample- it is reserved for hospitalized patients and

patients unable to void urine. For collection the catheter tubing should be clamped off above the port to allow collection of freshly voided urine. The catheter port or wall of the tubing should then be cleaned with 70% ethanol , and urine aspirated via needle and syringe and collect into a sterile container

SPECIMENS

Suprapubic aspirate- it is usually reserved for infants from whom it is difficult to obtain urine specimens. For this skin above the bladder is cleaned with disinfectant. Urine Is withdrawn directly into the syringe through percutaneously inserted needle thereby ensuring a contamination free specimen. The specimen is then collect into a sterile container

SPECIMENS

Cystoscopy specimen -collected from the bladder during cystoscopy to avoid urethral contamination

PEDIATRIC URINE CULTURES

COLLECTION OF SPECIMENS

Urine, which should be obtained before the initiation of antimicrobial therapy, can be collected by various method

1-clean catch midstream urine 2-urethral catheterization 3-suprapubic aspiration

REJECTION OF SPECIMEN, WHICH ARE UNSUITABLE FOR CULTURE

1) bedpan urine 2) specimen received in non sterile

container 3) bag urine { because organism can

multiply there , obscuring the true relative numbers.}

4) unlabelled and improper labeled specimens

5) specimen that have leaked out the container.

SPECIMEN TRANSPORTATION

Urine should reach lab immediately after collection and should be cultured within 2 hrs. if it is not possible it can be refrigerated at 4 degree c maximum for 18 hrs

MEDIA USED

Well dried sheep blood agar maCconkey agar brain heart infusion agar

SPECIMEN PROCESSING

SCREENING TEST

GRAM STAINING. The gram stain is the easiest, least expensive, and probably the most sensitive and reliable screening method for identifying urine specimens that contain greater than 10^5 CFU/ml.

A drop of well-mixed urine is allowed to air dry. The smear is stained and examined under oil

immersion. Presence of at least one organism per oil immersion

field.( examining 20 fields ) corelates with significant bacteriuria (>105 CFU/ml

PROCEDURAL STEPS;

Calibrated loop methoda. Gently mix the urine.b. Hold calibrated sterile loop vertically and

immerse the loop just below the surface of the urine and there by sucked up into loop. Do not put loop deep into the urine

c. Streak urine on blood agar and MacConkey agar without touching the edge of the plate.

d. After culturing place one drop full of urine for wet mount or gram staining on clean slide

e. Stab one loop full of urine on BHI plate with staphylococcus aureus lawn culture for urine antimicrobial activity.

f. Incubate the plates at 37oc for up to 48 hrs and check for the growth from 24 hr onwards

INTERPRETATION OF RESULT

Check the growth from 24 hr onwards and incubate the plates up to 48 hrs. interpretation of result is correlated with the wet mount and gram stain report. Identify the predominant bacteria/yeast colonies by morphology stained preparation and biochemical tests. Note antimicrobial test positive( clear zone on BHI plate) or as negative (no zone). Do sensitivity test of isolate by Kirby-Bauer method. Bacterial or yeast count per ml is calculated by multiplying number of colonies by 100.

Pus cells more than 10, it is suggestive of UTI

POTENTIAL PATHOGENS

Enterobacteriacea such as E.coli, proteus spp., klebsiella spp. Pseudomonas aeruginosa Staphylococcus aureus Staphylococcus saprophyticus Beta hemolytic streptococci Streptococcus pnuemoniae Enterococcus spp Yeast spp Acinetobacter spp

PARASITES

Schistosoma haematobium Trichomonas vaginalis

RESIDENT MICROFLORA OF THE URETHRA

Coagulase negative staphylococci (excluding staph. Saprophyticus) Viridian and non hemolytic streptococci Lactobacilli Diphtheriods

These organisms are normally considered contaminant, but may be significant upon repeat isolation

Any female with group B streptococci bacteriuria in any concentration during her pregnancy should receive intrapartum antibiotics

REPORTING THE RESULT

Report identified bacterial/yeast isolates with colony count and antibiotic sensitivity

THANKS