STI's

Chlamydia, Genital Herpes, HPV

STI vs STD

STI - infections that have not yet developed into diseases; transmitted during sexual activities or exchange of bodily fluids

STD - diseases that result from STI’s; all STD’s start as STI’s

Chlamydia 

• Causative agents; 

  • Chlamydia trachomatis

Lymphogranuloma Venereum (LGV)

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Chlamydia Trachomatis - Life Cycle

Chlamydia begins infection of a host when the metabolically inactive elementary bodies enter an epithelial cell.

• Once inside the host cell, the elementary bodies turn into active reticulate bodies.

• The reticulate bodies multiply and release more elementary bodies when the cell dies after the Chlamydia uses all of the host cell’s ATP.

Chlamydia Trachomatis - Pathogenesis

• Only infects human non-ciliated columnar epithelial cells (Except Biovar mouse)

• Stimulates the infiltration of polymorphonuclear cells and lymphocytes leading to lymphoid follicle formation and fibrotic changes,

• Cell wall prevents phagosome from fusing with lysosome in phagocytosis

• Cell destruction/host inflammatory response

• Does not stimulate long-lasting immunity

• Reinfection results in an inflammatory response and subsequent tissue damage

Chlamydia - Treatment & Prevention

• Azithromycin (!)

• Tetracycline

• Erythromycin (Macrolides)

• Vaccines are of little value and are not used.

• Condom use

• Treatment, coupled with improved sanitation to prevent reinfection, is the best way to control infection.

Chlamydia - Lab Diagnosis

1. Cytology

• Examination of stained cell scrapings for the presence of inclusion bodies 

2. Culture

• most specific method for diagnosis

• cultures of susceptible cells

• iodine-staining inclusion bodies

• The McCoy cell line originally derived from human synovial fluid in 1955, has been later found useful for cultivation of Chlamydia trachomatis

• HeLa

3. Serology

• Detection of high titer IgM antibodies is indicative of a recent infection

• Use IgG because of recurrence

Chlamydia - Clinical Features

• Male - Non-gonococcal urethritis (NGU - mimics gonorrhea, discharge, painful urination)

• Female - Urethritis, Cervicitis, Bartholinitis, Discharge

  • Nearly 75% infections are asymptomatic - puts women at risk for PID

• Neonates - Inclusion conjunctivitis 

• Infants - Infant Pneumonia

Herpes

• sexually transmitted disease

• virus infection - Herpes Simplex Virus (HSV-1 & HSV-2)

• spreads via sexual intercourse, kissing someone w/ Herpes, skin to skin contact

HSV Structure

• relatively large

• double stranded linear DNA encased in an icosahedral protein cage (capsid)

• capsid is wrapped in a lipid bilayer called the envelope which is joined to the capsid by a tegument

• the complete particle is a VIRION

HSV-1

• primarily oral to oral contact (kissing)

• typically causes cold sores (oral herpes)

• cold sores around/on mouth

• white, creamy colour - ooze clear liquid when popped

• controlled by creams

HSV-2

• sexually transmitted disease (sexual intercourse)

• causes genital herpes around the genitals in the form of warts

• very painful to urinate and have sexual intercourse

• antivirals - acyclovir, valcyclovir (Zovirax, Valtrex)

• condoms are protective

Herpes - Lab Diagnosis

• scrape of vesicle/genital vesicle fluid/ulcer swab

• Pap smear

• Culture: Primary cell cultures 

• Serology: CFT, TORCH

Herpes - Clinical Features & Complications

• single/multiple vesicles on genitalia, perineum, thigh, buttocks

• vesicles are small and filled with clear fluid

• painful to touch 

• accompanied by malaise, anorexia, fever, bilateral swelling, tenderness in groin

Complications

• Meningitis or encephalitis

Human Papillomavirus (HPV)

• group of 150 different kinds of viruses; some strains are high-risk and can lead to cancers, like cervical, vulvar and vaginal cancers

• sexually transmitted disease - vaginal/oral/anal sex or by skin-to-skin touching during sex

• virus infection - Human Papillomavirus

HPV Structure & Types

• non-enveloped virus - more virulent 

• high risk HPV types; HPV 16, 18, 31, 33, 35, 39, 45, 51, 56, 59, 66, 68

• HPV16 & HPV18 - responsible for most HPV-related cancers

• HPV6 & HPV1 - cause 90% of genital warts which barely develop into cancer

HPV - Molecular Detection

• gold standard for HPV detection - can identify women at risk or cervical cancer

• three categories of molecular assays for detection of HPV DNA:

  • Non-amplified hybridization assays

  • Signal amplified hybridization assays

  • Target amplification assays