Definition
“UTI is defined as a disease caused by microbial
invasion of the genito urinary tract that
extends from the renal cortex of the kidney to
the urethral meatus.”
Causative Agents
Gram negative bacilli:
• E.coli
• Klebsiella sp.
• Proteus sp.
• Pseudomonas sp.
Gram positive cocci:
• Enterococci
• Staphylococcus aureus
• Staphylococcus epidermidis
• Staphylococcus saprophyticus
Miscellaneous :
• M.tuberculosis
• Citrobacter
Fungus:
Candida albicans
Laboratory Diagnosis
• Collection of specimen
• Transport of specimen
Laboratory methods
• Microscopy
• Culture
• Identification
• Antibiotic sensitivity testing
Specimen : Urine
• Midstream urine
• Suprapubic aspiration
• Catheter specimen
Tuberculosis
• Early morning specimen (3 consecutive days)
Transport of specimen
• Process immediately
• If delay, refrigerate at 4oC
Laboratory methods
Microscopy
• Centrifuge – small portion
• Examine deposit
• Look for pus cells, epithelial cells, RBCs,
bacteria
• Pus cells + bacteria : Active UTI
• Bacteria only : contamination
Culture
Standard loop technique
• Principle: Standard calibrated loop is used to
culture fixed volume of urine.
• Loop delivering 0.05ml
• 1ml = 200 loopful
• Media : Blood agar, Mac Conkey agar
• Incubate at 37oC; 24 hours
• Count bacterial colonies
• Multiply by 200
Interpretation of results
Significant bacteruria : > 105 bacteria/ml
Doubtful significance : 104 – 105 bacteria /ml
No significant growth : < 103 bacteria / ml
Identification:
• Colony characters
• Gram’s staining
• Motility
• Biochemical reactions
Slide agglutination test
Antibiotic sensitivity test:
• To administer proper antibiotics