GENITAL TRACT Flashcards
Stuart media and Amies charcoal media
are often used for the preservation of
organisms detected in genital tract samples.
Genital tract
specimens are collected with the following methods:
urethral
vaginal
cervical
endocervical
Urethral collection is
best when preformed more than 1 hour after urination. After
discharge is removed from the opening of the urethra, a sterile swab is inserted 2–4 cm into
the urethra, rotated for 2–3 seconds to ensure adequate sampling, and then the swab is
removed
Vaginal collection requires
excess discharge to be wiped from the opening of the vaginal
canal before a swab is inserted. Once inserted into the vaginal canal, the swab is rotated to
collect secretions from the mucosal membranes
Cervical and endocervical collection uses a
speculum to view the cervical canal; however,
lubrication cannot be used when inserting the device because it can be harmful to
organisms for culture
Mucus and vaginal material are
removed with a swab that is then
discarded. A second sterile swab is inserted into the cervix, and the canal is swabbed in a
firm but gentle manner.
Endocervical samples for
chlamydia require more vigorous
swabbing to collect epithelial cells
INDIGENOUS ORGANISMS OF MALE & FEMALE URETHRA
o Gram-positive cocci
❖ S. epidermidis: opaque, gray, smooth, raised, nonhemolytic
❖ Enterococcus faecalis: small, smooth, gray nonhemolytic
o Gram-positive bacilli
❖ Corynebacterium species: small to medium, gray, white, or yellow, nonhemolytic
o Gram-negative diplococci
❖ Neisseria species: small, white to gray-brown, smooth, butter-like, translucent with a
green hue on agar underneath
INDIGENOUS ORGANISMS OF VAGINA
o Gram-positive cocci
❖ Staphylococcus species: opaque, white to yellow, smooth, circular
❖ Micrococcus species: opaque, white to bright yellow, smooth, raised
❖ Viridans streptococci: gray, translucent, umbonate center, alpha-hemolytic
❖ Enterococcus species: small, gray, circular
o Gram-positive bacilli
❖ Lactobacillus species: small to medium, gray, alpha-hemolytic
❖ Corynebacterium species: see description above
o Gram-negative bacilli
❖ Escherichia coli: circular, dull gray, smooth, convex.
METHODS FOR DETECTION OF PATHOGENS ASSOCIATED WITH VAGINITIS
wet mount
Immunochromatographic dipsticks
KOH
Calcofluor-white
clue cells
Trichomonas vaginalis can be detected in
fresh-void urine from males and females, prostatic
secretions, and the vaginal canal
The most common detection of Trichomonas is
through direct
observation on a wet mount or in urine sediment.
Microscopic detection of
Trichomonas reveals
a pear-shaped trophozoite similar in size to a neutrophil, moving by its flagella
in jerky, undulating movements
If microscopic analysis cannot immediately be observed
Trichomonas is still detectable, but it may not be motile and will take on a more spherical shape
making it more difficult to differentiate from a WBC
Immunochromatographic dipsticks that
detect
T. vaginalis antigens are available, and they eliminate the need for live organisms and
immediate testing
Candida species can be detected
under microscopic examination using a variety of methods and
stains
Yeast can be observed directly with
a light microscope in wet mount or urine sediment
samples.
The use of KOH reagent will
lyse cells and clear excess debris from samples, aiding in the
visualization of yeast and fungal elements
Calcofluor-white stain is used to detect
yeast species
under a UV microscope by fluorescing fungal elements as a bright-white color that is easily
visualized
Candida presents on a Gram stain as
Gram-positive
buds, pseudohyphae, or true hyphae.
A culture and biochemical testing of urine and vaginal
samples containing Candida organisms can be
used to determine the specific species of yeast
responsible for the infection
Bacterial vaginosis (BV) is most commonly associated with
an overgrowth of Gardnerella
vaginalis, but it can be caused by up to 35 unique species of aerobic and anaerobic bacteria
The presence of clue cells in urine sediment or on a wet mount are indicative of
A BV infection
Clue cells are
vaginal squamous epithelial cells that are covered in bacteria, giving the cytoplasm a lacy
appearance
Wet-prep samples will exhibit
clusters of sloughed-off clue cells covered in Gram-
variable bacilli and coccobacilli
A Gram stain of a vaginal swab positive for BV will show
mixed flora with a decrease in the normal vaginal flora, Lactobacillus species.
Although more advanced
methods are available, the mix of flora shown on a Gram stain can be
enumerated and a diagnosis of
BV may be made
Molecular PCR methods are also available for
detecting species of bacteria known
to cause BV.
N. gonorrhoeae is a
fastidious organism with specific storage and growth requirements for culture.
Specimens collected for N. gonorrhoeae culture should be
set up as soon as possible for the best
viability of the organism
If inoculating the medium is delayed
samples suspected for a gonorrheal
infection must stay at room temperature because refrigeration destroys viable organism
C. trachomatis is an
incredibly fastidious organism that requires complex and extensive nutrients
for cultivation and growth.
Due to its intracellular obligations, C. trachomatis requires a
host cell,
such as McCoy cells, to properly grow in a culture setting
Cells are inoculated with
sample,
incubated in 5–10% CO2 for 48–72 hours, and observed for brown intracellular growth.
Samples
suspected of chlamydial infections should be
submitted to the lab immediately or frozen at –70 °C
for organisms to remain viable
Women in the third trimester of pregnancy are screened for
Streptococcus agalactiae, or group B
strep, colonization in their vaginal canal and rectum
Infants are able to contract a
group B strep
infection during delivery that can cause sepsis if not treated promptly and properly
Samples for
culture of group B strep are
inoculated onto sheep blood agar with vertical stabs made in the agar
to promote hemolysis, and they are incubated overnight in 5–10% CO2.
S. agalactiae is indicated by
colony growth with a
narrow zone of beta-hemolysis underneath each colony.
CAMP test can be
performed on
sheep blood agar to distinguish group B strep from other beta-hemolytic
streptococcus species.
Diffusible extracellular CAMP proteins produced by
S. agalactiae react with
beta-lysin produced by S. aureus to create an arrowhead-shaped zone of hemolysis at the
intersection of an S. agalactiae streak made perpendicular to a streak of S. aureus.
Molecular methods for the detection of N. gonorrhoeae, C. trachomatis, and S. agalactiae are
advantageous because they do not rely on organisms’ viability and are more specific and time
efficient than culture methods
Probe technologies use
hybridization and amplification of the
bacterial genetic material to detect its presence in samples
Hybridization detects
bacterial
ribosomal RNA with the use of chemiluminescent DNA probes or an RNA/DNA hybrid using
antibody-mediated recognition
Some hybridization techniques allow for
the detection of N.
gonorrhoeae and C. trachomatis to be determined from a single sample
Amplification methods are
more
sensitive by employing the detection and amplification of nucleic acids in organism-specific genes
PCR methods are able to detect
small amounts of DNA or RNA in a sample and replicate, or
amplify, a target nucleic acid sequence for the detection of specific organisms
COMMON GENITOURINARY TRACT PATHOGENS
Trichomonas vaginalis
Candida albicans
N. gonorrhoeae
C. trachomatis
Treponema pallidum
Infections of the genitourinary tract are commonly caused by
opportunistic pathogens and manifest
into urethritis, vaginitis, and cervicitis.
Bacterial vaginitis is a
polymicrobial infection that occurs
when the balance of normal vaginal flora is disrupted
Vaginitis can also develop from
the sexual
transmission of the parasite Trichomonas vaginalis
Opportunistic fungal infections caused by
Candida albicans arise when normal flora are inhibited by the use of antibiotics, and these
infections often lead to itching, irritation, thick discharge, and burning while urinating.
Sexual
transmission of N. gonorrhoeae and C. trachomatis will also lead to
genitourinary tract infections
and are causative agents in pelvic inflammatory disease that may induce infertility in women
Other
common symptoms of gonorrheal and chlamydial infections include
lower abdominal pain,
discharge from the penis in males, vaginal discharge in females, and painful urination
Herpes
simplex virus type 1 (HSV-1) and herpes simplex virus type 2 (HSV-2) are spread by
sexual contact
causing itching, bumps, rashes, or sores near the genitals, as well as painful urination.
Syphilis
infections caused by
sexual transmission of Treponema pallidum begin with enlarged lymph
nodes near the groin and painless sores on the body and genitals.
If not treated, syphilis infections
can progress into
its secondary, latent, and tertiary stages that lead to irreversible systemic
damage
CULTURE AND MOLECULAR DETECTION OF MYCOPLASMA SPECIES
Urine, urethral, vaginal, and endocervical swabs are appropriate samples for detecting Mycoplasma
species that are responsible for infections of the genital tract
Culture of Mycoplasma organisms requires
sterol-enriched media containing cholesterol and fatty acids from human or horse serum and incubation
at 35–37 °C in a 95% nitrogen and 5% carbon dioxide environment.
Mycoplasma is a slow-growing organism and
may take up to
four weeks after culture setup to grow small colonies with an inverted, “fried egg”
appearance
Molecular detection of Mycoplasma has become
the method of choice for testing due to its high
sensitivity and increased time efficiency
Real-time PCR and nucleic acid amplification methods
have been
established for the rapid diagnosis of Mycoplasma infections in the genital tract
Mycoplasma genitalium
common cause of genital tract infections,
is detected molecularly via the tuf gene
How does Chlamydia trachomatis function?
functions in two forms: an infectious, extracellular elementary body and a
noninfectious, intracellular reticulate body.
what is responsible for adhering to and
entering host cells in Chlamydia trachomatis?
elementary body
What in Chlamydia trachomatis is the metabolically active form responsible for the
intracellular reproduction of bacteria?
reticulate body
Gardnerella vaginalis adheres to
host epithelial cells and becomes cytotoxic to these cells with
vaginolysin
What is critical for survival of Gardnerella vaginalis?
Sialidase; because it aids in colonization and the
formation of a bacterial biofilm within a host
Neisseria gonorrhoeae possesses
pili
What does pili aid in?
organism adherence to host mucosal cells and
express antiphagocytic properties.
Host IgA antibodies normally block
bacterial adhesion
IgA protease enzymes in the bacteria hydrolyze IgA, allows
adhesion of host cells to occur and an
infection to establish
Treponema pallidum’s adherence to host cells is promoted by
outer membrane proteins and
infiltration into host cells is facilitated by hyaluronidase
Fibronectin prevents
the organism from
phagocytosis by macrophages
