Genital and Serology

What are the most common normal flora in the female genital tract?

"Lactobacilli, Staphylococcus epidermidis, streptococci, E. coli, anaerobes (Peptococci, Bacteroides), Ureaplasma urealyticum, Mycoplasma hominis."

Why are diagnostic tests recommended for genital infections?

"Symptoms overlap; testing allows targeted therapy, reduces transmission, improves compliance, and avoids unnecessary antibiotics."

What organism causes syphilis?

"Treponema pallidum subsp. pallidum, a spirochete."

Primary syphilis presentation?

Painless chancre (indurated ulcer) appearing ~10-70 days after infection.

Secondary syphilis presentation?

"Generalized rash including palms/soles, lymphadenopathy, fever, systemic symptoms."

Key feature of latent syphilis?

Asymptomatic period that may last years.

Major manifestations of tertiary syphilis?

"Gummas, cardiovascular disease, neurosyphilis, tabes dorsalis."

Congenital syphilis findings?

"Snuffles, rash, fever, hepatosplenomegaly, hydrops, thrombocytopenia."

What test is RPR?

A nontreponemal test detecting antibodies to cellular damage caused by syphilis.

Difference between treponemal and nontreponemal antibodies?

Treponemal antibodies are organism-specific and persist for life; nontreponemal antibodies decline over time.

Most common cause of abnormal vaginal discharge in women of childbearing age?

Bacterial vaginosis (BV).

What microbiologic change occurs in BV?

"Loss of Lactobacillus and overgrowth of anaerobes such as Gardnerella, Mobiluncus, and Prevotella."

Classic BV symptom?

Fishy odor with vaginal discharge.

Nugent score interpretation?

"0-3 normal, 4-6 intermediate, 7-10 bacterial vaginosis."

Amsel criteria for BV?

"3 of 4: pH >4.5, clue cells, positive whiff test, homogeneous discharge."

Most common cause of vulvovaginal candidiasis?

Candida albicans.

Typical VVC symptoms?

"Pruritus, soreness, dysuria, dyspareunia, thick curdy discharge."

Microscopic finding in VVC?

"Budding yeast, hyphae, or pseudohyphae."

Treatment examples for VVC?

Nystatin or miconazole.

What organism causes trichomoniasis?

Trichomonas vaginalis.

Classic trichomoniasis findings in women?

Yellow-green frothy discharge and strawberry cervix.

Diagnostic wet mount finding for trichomoniasis?

Motile trichomonads with jerky/spinning motion.

Best diagnostic test for Trichomonas?

NAAT (very high sensitivity and specificity).

Morphology of Neisseria gonorrhoeae?

Gram-negative diplococcus.

Typical gonorrhea symptoms?

Dysuria and purulent discharge; many infections are asymptomatic.

Current recommended treatment for gonorrhea?

Ceftriaxone; add doxycycline if chlamydia has not been excluded.

Most sensitive test for gonorrhea and chlamydia?

NAAT.

Major complications of Chlamydia trachomatis infection in women?

"PID, ectopic pregnancy, infertility."

Recommended specimens for chlamydia testing?

Vaginal/cervical swab or first-void urine.

Why is Mycoplasma genitalium not visible on Gram stain?

It lacks a cell wall.

Best test for Mycoplasma genitalium?

NAAT/PCR.

When are pregnant patients screened for Group B Streptococcus?

36-37 weeks gestation.

Why is enrichment broth used for GBS testing?

Improves recovery of GBS before culture/NAAT testing.

What is serology?

Detection of antibodies (and sometimes antigens) in serum or other body fluids.

When do antibodies typically first appear after primary exposure?

About 10-14 days after antigen exposure.

Which antibody appears first in a primary immune response?

IgM.

Which antibody predominates in a secondary immune response?

IgG.

Difference between active and passive immunization?

Active = host produces antibodies; passive = antibodies transferred from another source.

Which immunoglobulin crosses the placenta?

IgG.

What does IgM in a newborn suggest?

Possible in utero infection because IgM does not cross the placenta.

Advantages of serology?

"Useful for unculturable, hazardous, or difficult-to-culture organisms and may distinguish recent vs past infection."

Major disadvantage of serology early in infection?

False negatives before antibodies develop.

Common causes of false-positive serology?

"Cross-reactivity, rheumatoid factor, autoantibodies, anti-reagent antibodies."

What is a convalescent serum sample?

"A specimen collected after recovery, usually >2 weeks after the acute sample."

What rise in antibody titer is typically diagnostic of recent infection?

Four-fold increase between acute and convalescent samples.

What does ELISA detect?

Antigens or antibodies using an enzyme-generated signal.

Most sensitive ELISA format?

Sandwich ELISA.

What is a multiplex serologic assay?

A test that measures antibodies to multiple pathogens simultaneously from one sample.

What is a titer?

Highest dilution of serum that still yields a detectable antibody response.

Why are Western blots often used?

As confirmatory tests due to higher specificity.

CDC Lyme disease testing algorithm?

Initial ELISA/EIA followed by a confirmatory immunoblot or second-tier assay.

Why is Coccidioides often diagnosed by serology?

"Culture is slow, hazardous, and obtaining direct specimens can be difficult."