Micro - STDs & Syphilis Flashcards by Kevin Tran

Reproductive tract infections can be transmitted in 3 different ways…

Endogenous infections - overgrowth of normally present organisms (ie bacterial vaginosis)

Iatrogenic infections - introduced by medical procedures

STDs - during sexual intercourse

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Are most bacterial STDs curable or incurable? Are most viral STDs curable or incurable?

Curable - syphilis, chancroid, gonorrhea, chlamydial infection, trichomoniasis (parasite)

Incurable - HIV/AIDS, HPV, Hepatitis B, genital herpes

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Curable STDs that are ulcerative (2)

Syphilis

Chancroid

-genital sores, ulcers

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Chancroids are caused by this bacteria…

Haemophilus ducreyi

gram negative small rods
looks like train tracks or school of fish

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Haemophilus ducreyi requires which factor(s)?

X and V

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Curable STDs that are non-ulcerative (3)

Gonorrhea

Chlamydia

Trichomoniasis (parasite)

-usually discharge or asymptomatic

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In women, untreated STDs can migrate upwards, causing this condition…

PID - pelvic inflammatory disease

-including endometritis

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In the US, the most common STD is… What is the organism that causes the disease?

Chlamydia
-alongside gonorrhea

Chlamydia trachomatis

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Chlamydia trachomatis is an obligate ___

Intracellular bacteria

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Can Chlamydia trachomatis be gram stained? Why or why not?

No peptidoglycan

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Chlamydia trachomatis causes infection to these organs (2)

Genitals

Eyes

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What are the 2 forms of Chlamydia trachomatis? Which form is bigger?

EB = elementary body
RB = reticulate body

RB is bigger

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Which form of Chlamydia trachomatis is infectious?

-binds to host cell receptor and endocytosed

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Which form of Chlamydia trachomatis is metabolically active and which is inactive?

EB = inactive

RB = active

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Two types of specimens sent to the lab for chlamydia are…

Swab from urethral/vaginal discharge

Urine
-for newer amplification tests (PCR)

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Chlamydia cultures are usually only done under these circumstances…

As confirmation the positive test
-backup for the faster tests

When substances in sample interfere with amplification tests

When medico-legal issues are involved
-child abuse

What type of cell line is used when culturing Chlamydia trachomatis?

McCoy cell line

mouse fibroblast cells
culture on coverslip in nutrient medium, add sample and centrifuge
coverslip can be stained after incubation

What are the 3 types of stains used to detect Chlamydia trachomatis after culturing the specimen sample with McCoy cells?

Iodine - inclusion bodies look dark brown
-use positive/negative controls

Giemsa - look for EB/RB inclusion bodies

DFA - infected cells fluoresce green
-very accurate and sensitive

When gonorrhea specimens are collected, one of these two transport media should be used…

Stuart’s charcoal medium

Amie’s charcoal medium

What is the confirmatory test to detect a gonorrhea infection for males? For females?

Males = gram stain showing intracellular diplococci
-no culture needed

Females = selective media since gram stain is NOT diagnostic
-diplococci confused with anaerobes or short gram negative rods in genital tract

What are the two important selective media for gonorrhea?

Modified Thayer-Martin (MTM)
-modified chocolate agar

NYC medium
-clear medium

-incubation system = JEMBEC plates

Why is MTM the preferred medium to isolate gonorrhea?

Contains vitamins and antibiotics to suppress normal flora

What is the purpose of culturing gonorrhea on a biplate containing both MTM and chocolate agar?

Some gonorrhea strains won’t grow on MTM and will grow on chocolate
-streak on both to avoid delays

Neisseria gonorrhoeae (and meningitidis) are catalase ___ and oxidase ___. Differentiation of Neisseria spp is based upon…

Positive

Sugar profile (ie CarboFerm)

Should we perform an AST on Neisseria spp?

Yes | -highly antimicrobial resistant now

Trichomoniasis is caused by this organism...

Trichomonas vaginalis

What specimen sample should we collect for Trichomoniasis?

Urine | -used to be swab sample or discharge

What are two ways that Trichomoniasis can be detected...

Wet mount of urine sample - sensitive organism - can round up, looking like a WBC Dipstick rapid test (OSOM Trichomonas Rapid Test)

Bacterial vaginosis is best diagnosed by...

Gram stain of vaginal discharge and look for clue cells - BV is not exclusively an STD - also use these criteria: fishy odor (whiff test), pH >4.5, lack of Lactobacilli

What agent causes syphilis?

Treponema pallidum

Can Treponema pallidum be gram stained? Why or why not?

No Spirochete

Is Treponema pallidum motile? Can it be cultured in vitro?

Yes No -can grow on armadillo's feet

What are the stages of a syphilis infection?

Primary Secondary Latent Tertiary - survives inside phagocytes - spread throughout any organ in the body

What kind of microscope should we use to see Treponema pallidum?

Darkfield microscopy

What methods are used to diagnose primary syphilis? Secondary? Latent? Tertiary?

Primary = darkfield microscopy, DFA, serology Secondary, latent, tertiary = serology only -darkfield microscopy and direct fluorescent antibody staining only possible during primary infection

What are the 2 categories of serological testing done for syphilis? Which one do we start with first?

Non-treponemal test = start with this first. Screening test -easy, inexpensive Treponemal test

Non-treponemal tests include (2)... What do the tests detect?

VDRL RPR non-specific antibodies that react to cardiolipin -false positives occur = old age, TB, Chagas', leprosy, autoimmune

Once a patient is positive for a non-treponemal test, what do we do next? Once a patient is CONFIRMED to have syphilis, what test is used to monitor their condition?

Treponemal test = confirmatory test Non-treponemal test - VDRL or RPR. Do one or the other, do not switch - titer falls with successful treatment - antibodies there for life at detectable levels

What are two commonly used treponemal tests?

FTA-ABS (fluorescent treponemal antibody absorption) MHA-TP (microhemagglutination test for T. pallidum) - test results remain positive - tests cannot be used to assess treatment response or reinfection; use non-treponemal test instead