Chapter 24
Sexually Transmitted Infections
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Sexually Transmitted Infections
(STI)
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STI: general term for any disease that can be
spread by intimate and/or sexual contact

Includes systemic diseases like hepatitis and
tuberculosis
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Sexually Transmitted Infections
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Bacterial
Viral
Protozoal
Parasitic
Fungal
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Sexually Transmitted
Urogenital Infections
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Bacterial infections
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Gonorrhea
• Caused by Neisseria gonorrhoeae

Aerobic, non–spore-forming, gram-negative diplococcus
• Transmission generally requires contact of epithelial
surfaces
• Gonorrhea also crosses amniotic membranes
• Humans are the only natural hosts
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Sexually Transmitted
Urogenital Infections
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Gonorrhea
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Presence of pili helps microorganisms attach to
the epithelial cells of mucous membranes
Infections can result in:
• Disseminated gonococcal infection (DGI)
• Perihepatitis
• Ophthalmia neonatorum
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Sexually Transmitted
Urogenital Infections
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Gonorrhea common sites
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Endocervical canal (inner portion of the cervix)
Urethra
Skene and/or Bartholin glands
Oral (pharynx)
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Sexually Transmitted
Urogenital Infections
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Gonorrhea clinical manifestations
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Symptoms of uncomplicated gonorrhea in women
may be absent (50% of women have
asymptomatic infection) or severe
Includes dysuria, increased vaginal discharge,
abnormal menses (increased flow or
dysmenorrhea), or dyspareunia
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Sexually Transmitted
Urogenital Infections

Syphilis
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Treponema pallidum
• Corkscrew-shaped, anaerobic bacterium that cannot be
cultured in vitro
• Infects any body tissue
• Syphilis becomes a systemic disease shortly after
infection

Maternal-fetal transmission can occur as early as 9 weeks’
gestation
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Syphilis
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Stages
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Primary syphilis
• Local manifestations
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
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Granulomatous tissue reaction—hard chancre
Microorganisms drain with the lymphatic fluid
Secondary syphilis
• Systemic manifestations

Fever, malaise, sore throat, hoarseness, anorexia, joint
pain, skin rash, and lesions (condylomata lata)
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Syphilis
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Stages
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Latent syphilis
• Medical evidence of the infection, but patient is
asymptomatic
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Tertiary syphilis
• Most severe stage
• Formation of gummas

Destructive skin, bone, and soft tissue lesions
• Destructive systemic manifestations
• Neurosyphilis
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Syphilis
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Congenital syphilis
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Vasculitis, necrosis, fibrosis, and generalized
tissue destruction
Manifest in the first 2 years of life
Late-stage manifestations occur near puberty
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Sexually Transmitted
Urogenital Infections
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Chancroid
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Typical in underdeveloped or developed tropical
climates
Painful, tender, soft chancre
Acute infectious disease caused by Haemophilus
ducreyi (gram-negative bacillus)
Inguinal buboes
Women often asymptomatic but can have dysuria,
dyspareunia, vaginal discharge, pain on defecation, or
rectal bleeding
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Sexually Transmitted
Urogenital Infections
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Granuloma inguinale
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Chronic, progressive, destructive bacterial
infection
• Cause: Klebsiella granulomatis; gram-negative, non–
•
•
•
•
spore-forming, encapsulated bacillus
Mildly contagious; repeated exposure is required
Concurrent infection with syphilis is common
Does not occur in the United States
Donovan bodies

Bacteria-filled vacuoles within white cells
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Sexually Transmitted
Urogenital Infections
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Bacterial vaginosis
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Sexually associated condition, but not always an STI
Cause: Gardnerella vaginalis and other anaerobes
Manifestations
• Gray vaginal discharge, pH >4.5, odor, presence of “clue” cells
on wet mount
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

Bacterial catalytic enzymes degrade proteins and elevate the
vaginal pH to produce a fishy odor
Clue cells are vaginal epithelial cells covered with bacteria
50% asymptomatic
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Chlamydial Infections
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Chlamydia
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Infections caused by Chlamydia trachomatis
Most common STI in the United States
Obligate, gram-negative, intracellular bacterium
Growth cycle (two parts)
• Elementary body

Small, resilient, metabolically inert, able to survive extracellularly
• Metabolically active parasite
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Chlamydial Infections
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Lymphogranuloma venereum
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Caused by C. trachomatis (invasive serovars of strains
L1, L2, and L3)
Chronic STI
Begins as a skin lesion and spreads to genital and
rectal lymphatic tissue
• Inflammation, necrosis, buboes, abscesses, and infections
• Can spread to the CNS
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Chlamydial Infections
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Nongonococcal or nonspecific urethritis
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Nonreportable STI
Syndrome caused by a variety of microbes
• Most common is C. trachomatis
• Trichomonas vaginalis, herpes simplex virus, Ureaplasma
urealyticum, and Mycoplasma
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Sexually Transmitted
Viral Infections
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Genital herpes
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Two serotypes
• Herpes simplex virus type 1
• Herpes simplex virus type 2
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80% of initial and 98% of recurrent infections are type 2
Not a reportable disease
Transmitted through contact with a person who is
shedding the virus in a secretion or from a peripheral
lesion or mucosal surface
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Sexually Transmitted
Viral Infections
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Genital herpes
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Initial virus replication occurs locally
Virus spreads to contiguous cells and into sensory
nerves
Virus is transported intra-axonally to the dorsal root
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Sexually Transmitted
Viral Infections
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Genital herpes
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Virus remains latent until reactivated
• Oral infection

Virus resides in the trigeminal ganglion
• Genital infection

Virus resides in the dorsal sacral nerve roots
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Sexually Transmitted
Viral Infections
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Human papillomavirus (HPV)
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120 different types of HPV
• 30 serotypes are unique to stratified squamous epithelium
• Divided into high-risk and low-risk serotypes for cervical
cancer
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HPV is a nonenveloped, circular double-stranded DNA
virus
Belongs to the Papovaviridae family
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Sexually Transmitted
Viral Infections
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Human papillomavirus (HPV)
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Condylomata acuminata (genital warts)
• Soft, skin-colored, whitish pink to reddish brown benign
growths caused by HPV
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Treatment is considered cosmetic, not curative
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Sexually Transmitted
Viral Infections
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Molluscum contagiosum
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Benign viral infection of the skin
Primarily infects the face, hands, lower abdomen, and
genitalia
Taken into epithelial cells by phagocytosis
• Replicates to produce molluscous bodies
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Sexually Transmitted
Parasitic Infections
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Trichomoniasis
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Caused by T. vaginalis
• Anaerobic, unicellular, flagellated, parasitic protozoan
Adheres to and damages squamous epithelial cells
• Urethra, vagina, and Skene and Bartholin glands
Accounts for 25% of infectious vaginitis cases
Often coexists with gonorrhea
Presence confirmed by microscopic examination of
vaginal secretions or urine
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Sexually Transmitted
Parasitic Infections
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Scabies
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Caused by the adult female itch mite, Sarcoptes
scabiei
Transmission of scabies requires prolonged close
skin-to-skin contact
• Typically occurs between family members or sexual partners
Burrows through the horny layer of the stratum and
begins laying 2-3 large eggs per day
• New larval forms appear in about 10 days
Classic symptom is intense pruritus
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Scabies
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Sexually Transmitted
Parasitic Infections
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Pediculosis pubis
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Caused by the crab louse Phthirus pubis
 Transmitted by intimate sexual contact or contact with
infected bed linens or clothing
 Crab louse has a 25- to 30-day life cycle
• Stages: egg or nit, three nymphal stages, and an adult stage
 Symptoms
• Mild to severe itching, allergic sensitization, and secondary
infections from scratching
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Pediculosis Pubis
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Sexually Transmitted
Gastrointestinal Infections
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Shigellosis and Campylobacter enteritis
Giardiasis and amebiasis
Hepatitis B
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Sexually Transmitted
Systemic Diseases
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Epstein-Barr virus
Acquired immunodeficiency syndrome
Cytomegalovirus
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