PRACTICAL
URINE CULTURE
Assist Prof
Dr. Syed Yousaf Kazmi
LEARNING OBJECTIVES
1. Discuss the process of urine culture
2. Compare the different methods
employed to obtain urine specimens
suitable for microbiologic analysis
3. Identify the organisms causing Urinary
tract infections and List organisms that
are often urine contaminants
4. Compare urine screening methods
available
URINE CULTURE
 Urine cultures performed
for diagnosing urinary
tract infections
 Most frequently requested
sample
 Most incorrectly
performed test
 Erroneous & misleading
results
 Affects treatment
 Should not be used for
diagnosing gonococcal
urethritis/ typhoid fever,
bacterial vaginosis etc.
URINE CULTURE
NORMAL FLORA OF
URETHRA
 Diphtheroids
 Alpha-streptococci
 Lactobacilli
 Coagulase-negative
staphylococci
 E. coli and other
Enterobacteriaceae
 Enterococcus species
URINE SAMPLES
1. MID STREAM CLEAN CATCH URINE SPECIMEN
 Mid stream-i.e. discard first part of stream
 First part of stream contains urethral flora/ skin
flora organisms
 Hold the urine
 Place the container in the direction of stream
 Restart micturition reflex
 Collect the middle part of stream
 Discard last part of stream
 Avoid urine stream to touch outside of
container/ other objects
URINE SAMPLES
2. INDWELLING CATHETER
SPECIMEN
 Foley catheterized patientrisk of UTI
 Never take sample from
collecting bag
 From tubing of catheter
 Clean tube with antiseptics
 Clamp the tube
 Allow urine to collect
 Needle in direction of urine
flow
URINE SAMPLES
3. SUPRAPUBIC
SPECIMEN
 In infants/ urinary
obstruction
 Usually in full bladder
 Ultrasound guided
 Suprapubic area
disinfected–antisepsis
 Through syringe collect
urine sample
URINE SAMPLES
4. CYSTOSCOPY
SPECIMEN
 During cystoscopy
 Significant bacteriuria 102
CFU/ml
 Even take sample from
ureters
 Not routinely performed
URINE CULTURE &
SENSITIVITY TESTING
SPECIMENS TRANSPORT
Must be inoculated on
urine culture plate
within 30 min
If delay inevitable-can
refrigerate or put boric
acid solution
Do not keep in open at
room temp
URINE CULTURE TECHNIQUES
SEMI-QUANTITATIVE METHOD
Wire loop that can hold 0.001 ml urine
Inoculated on CLED agar plate
Incubated at 35oC overnight
Count colonies
e.g. if we observe 10 colonies then
Colony count is= colony count (10)× urine
dilution factor (1000) which equals
10000= 104 CFU/ml
QUESTION
1. A wire loop that can hold urine 0.01
ml urine, gives colony count of 20
next day. Is it significant bacteriuria?
2. A wire loop that can hold urine 0.001
ml gives colony count of 100 bacteria
on CLED plate. Is it significant
bacteriuria or not?
ORGANISMS CAUSING UTIs
Community acquired:
 E coli (75%), Klebsiella, Proteus, Staph saphrophyticus, other
Enterobacteriaceae
 Usually drug sensitive organisms
Hospital acquired:
 Enterococcus, Pseudomonas aeruginosa., E coli, Staphylococcus
sp., Candida spp
 Mostly multidrug resistant, catheter related
URINARY CONTAMINANTS
Lactobacillus spp. alpha-haemolytic Streptococci
Most Gram positive rods such as Diphtheroids
URINE SCREENING METHODS
1. GRAM STAIN OF UN-CENTRIFUGED
URINE




One drop of un-centrifuged urine on slide
Allowed to dry
Gram stain
Presence of one or> bacteria per oil
immersion- count greater than 105/ ml
 Presence of one or > PMNs per oil
immersion field indicates pyuria
 Sensitive method
URINE SCREENING METHODS
DIPSTICK LEUKOCYTE ESTERASE
Identifies the enzyme leukocyte esterase in
leukocytes
Presence correlates with pyuria
Mostly seen in UTIs
Alone performed-sensitivity is low
Can be combined with Nitrate reduction test
URINE SCREENING METHODS
DIPSTICK NITRATE TEST
Enterobacteriaceae reduce nitrate to
nitrite
This test detects nitrite in urine
Positive test means presence of
Enterobacteriaceae in significant
amount