Microbiology lab Urinary system

Urine culture steps 1.Collect the sample in sterile container: 1.Midstream catch. 2.Through a catheter. 3.Suprapubic aspiration. 2.Urine analysis: 1.Physical: urine color 2.Chemical: Glucose, protein, nitrite. 3.Microscopically: RBCs, WBCs, casts, Schistosoma hematobium ova. 3.Transfer 1 μl of urine to the culture media using a calibrated loop. – Enriched media: blood agar. – Differential/selective media: MacConkey agar or CLED.

4.Streak the agar in network streaking method. other inoculating methods: 4.Four quadrant streaking method: semi-quantitative method. 5.Plate spreading method: For antibiotic sensitivity test 6.Microbroth dilution method: therapeutic dose of antibiotic. 5.Incubate at 35 C for 24 hours. 6.Count the colonies to calculate the CFU/ml from the network streaked agar. – Significant bacteriuria: Dysuria + pyuria + cutoff value of CFU/ml For midstream catch urine = (5*10 4 ) CFU/ml For catheterized urine = 10 2 CFU/ml For suprapubic urine = any growth. In immunocompromised patients = any growth. – Asymptomatic bacteriuria: bacteria in the urine without dysuria and without pyuria; contamination or immunocompromised.

7.Identify the growing bacteria according to the gram stain morphology: – Gram negative bacilli. – Gram positive cocci.

Gram negative bacilli Oxidase negative: Enterobacteriaceae Lactose fermenter: IMViC test – E.coli: metallic green sheen on EMB agar, indole positive. – Klebsiella, Enterobacter, Citrobacter Non lactose fermenter: – Proteus merabilis: swarming on blood agar, H2S production, urease production. – Morganella morganii. Serratia marcescens: Red insoluble pigment at 25 C. Oxidase positive: Pseudomonas aeruginosa: green- yellow water soluble pigment.

Gram positive cocci Catalase positive Coagulase positive: Staphylococcus aureus. Coagulase negative: – Novobiocin sensitive: Staphylococcus epidermidis. – Novobiocin resistant, mannitol fermenter: Staphylococcus saprophyticus. Catalase negative Black colonies on Bile Salt Esculin Agar: Enterococcus faecalis.

Schistosoma adult (male + female) cercariae (infective stage)