URINE SAMPLES AND MOLECULAR TESTING Flashcards
Random samples
may be collected at any time, with no additional preparation or cleansing
random urine samples are used for
urine chemistry testing (creatinine, total protein,
electrolytes, microalbumin), but they are to be avoided for routine urinalysis or culture testing due
to the possibility of erroneous results and an increased chance of contamination
Midstream clean catch collection
comprises cleansing the skin near and around the urethra
Midstream clean catch is ideal for
urinalysis, bacterial culture,
and sensitivity testing
Catheterized specimens
collected by passing a hollow tube, or catheter, through the urethra
and into the bladder.
what are catheterized specimens useful for
bacterial culture testing, but it may
be used for other routine tests as well.
Suprapubic collection
a sterile environment when a needle is placed through the
abdomen and into the bladder.
Aspirated urine provides
a sterile sample that is free of outside
contamination and is ideal for bacterial cultures and cytologic examination
Nephrostomy tubes
catheters placed through the skin and directly into the kidney
What are nephrostomy catheters used for?
to drain or collect urine when output through the ureters in not possible. Samples may be
used for routine urinalysis testing or bacterial culture
The colony count is in colony forming units per mL
(number of colonies) × 100
No growth observed on media after 48 hours of incubation is
expected in normal clean-catch,
catheterized, suprapubic aspirate and in surgically obtained urine samples
Fewer than 10
colonies observed is
not considered a significant finding in clean-catch or catheterized specimens,
and no further workup is needed
**any bacterial growth of urine collected from sterile
sources is significant and requires further investigation
colony counts between 10
and 100 may be tested further if
a patient is having symptoms indicative of a urinary tract infection
(UTI)
> 100 colonies of mixed organisms exhibiting one
predominant organism is
a significant finding, and the predominant bacteria will be tested further
> 100 of a pure, single organism is
indicative of a UTI, and further workup is required to properly
identify the organism and perform antibiotic sensitivity testing for guide treatment options
Microscopic and macroscopic urinalysis findings are evaluated and correlated with
urine culture
findings in the determination of UTIs
which chemical reactions on a
urine dipstick indicate the presence or absence of bacteria in a sample?
Nitrite, pH, and leukocyte esterase
positive nitrite dipstick result indicates
infection is from common UTI-causing
bacteria, including E. coli, Klebsiella, Proteus, Pseudomonas, and Enterobacter species, as they will reduce
nitrate to nitrite
positive leukocyte esterase result indicates
UTI because WBCs are
commonly found in areas of infection
alkaline pH may indicate
the presence of infection-
causing bacteria in urine because some bacteria hydrolyze urea into the alkaline substance
ammonia
Macroscopic observations of WBCs and bacteria in urine sediment are
correlated
with urine culture results in the determination of a UTI
Colony morphology is evaluated by the following characteristics in urine cultures
- Colony size
- Form and margins
- Elevation
- Surface features, texture, and consistency
- Color, transparency, and iridescence
Colony morphology is categorized by
size, form, margins, and elevation characteristics
Colony size is categorized by diameter
o Pinpoint or punctiform < 1 mm
o Small 1–2 mm
o Medium 3–4 mm
o Large > 5 mm
Morphological Forms are categorized as
o Circular, symmetrical circle
o Irregular, lacking symmetry
o Filamentous, exhibiting threadlike branching
o Rhizoid, exhibiting a branching, rootlike shape
The margins, or edges, of a colony are most commonly evaluated as
o Entire, meaning smooth
o Undulate, meaning wavy
o Lobular, fingerlike growth spreading outward
o Scalloped, rounded projections resembling a scallop shell
o Filiform, thin and wavy layers spreading outward
Colony elevations are
categorized by the following shapes:
o Flat
o Raised
o Convex, curved or rounded upward
o Crateriform, sunken in the middle
o Umbonate, with the middle protruding upward
Textures are described with the following terms:
o Smooth,
o Wrinkled, shriveled
o Rough, granular
o Dull, no shine
o Glistening, shining
The consistency of colonies is described as the following:
o Moist
o Dry
o Viscid, thick and sticky
o Mucoid, moist and sticky
o Butyrous, butter-like
Colony transparency is categorized as
o Transparent, clear, see-through
o Translucent, semiclear, frosted-glass appearance
o Opaque, unable to see through
o Iridescent, color changing in reflective light
Sheep blood and chocolate agars often yield the following colony colors
o White
o Cream
o Yellow
Differential and selective medias can produce many colors based on the organism’s
biochemical properties such as:
o Pink
o Green
o Blue
o Black
Catalase positive
bubbling produced
catalase negative
no bubbling produced
coagulase positive
visible clumping
coagulase negative
no visible clumping or agglutination
oxidase test
is used for a presumptive identification of Neisseria species and P.
aeruginosa
oxidase positive
development of a dark-purple color within 10 seconds
oxidase negative
colorless, or remains the original color of the colony
