Sexually Transmitted
Infections
Chapter 24
1
Sexually Transmitted Urogenital
Infections

Bacterial infections

Gonorrhea

Caused by microorganisms of the species 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
2
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Sexually Transmitted Urogenital
Infections

Gonorrhea


Presence of pili helps the microorganisms attach
themselves to the epithelial cells of mucous
membranes
Infections can result in:



Disseminated gonococcal infection (CGI)
Perihepatitis
Ophthalmia neonatorum
3
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Sexually Transmitted Urogenital
Infections

Syphilis

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
4
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Syphilis

Stages

Primary syphilis

Local manifestations



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)
5
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Syphilis

Stages

Latent syphilis


Medical evidence of the infection, but patient is
asymptomatic
Tertiary syphilis


Most severe stage
Formation of gummas


Destructive skin, bone, and soft tissue lesions
Destructive systemic manifestations
6
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Syphilis

Congenital syphilis



Vasculitis, necrosis, fibrosis, and generalized
tissue destruction
Manifest in the first 2 years of life
Late stage manifestations occur near puberty
7
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Sexually Transmitted Urogenital
Infections

Chancroid



Typical in underdeveloped or developed tropical
climates
Painful, tender, soft chancre
Acute infectious disease caused by Haemophilus
ducreyi


Gram-negative bacillus
Inguinal buboes
8
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Chancroid
9
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Sexually Transmitted Urogenital
Infections

Granuloma inguinale

Chronic, progressive, destructive bacterial
infection





Caused by 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
10
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Sexually Transmitted Urogenital
Infections

Bacterial vaginosis



Sexually associated condition, but not always an STI
Caused by Gardnerella vaginalis and various other
anaerobes
Manifestations

Gray vaginal discharge, pH > 4.5, odor, presence of “clue” cells on
wet mount

Bacterial catalytic enzymes degrade proteins and elevate the
vaginal pH to produce a fishy odor

Clue cells are vaginal epithelial cells covered with bacteria
11
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Chlamydial Infections

Chlamydia




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
12
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Chlamydial Infections

Lymphogranuloma venereum



Caused by Chlamydia 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
13
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Chlamydial Infections

Nongonococcal or nonspecific urethritis


Nonreportable STI
Syndrome caused by a variety of microbes


Most common is C. trachomatis
Trichomonas vaginalis, herpes simplex virus,
Ureaplasma urealyticum, and Mycoplasma
14
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Sexually Transmitted Viral
Infections

Genital herpes

Two serotypes


Herpes simplex virus type 1
Herpes simplex virus type 2



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
15
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Sexually Transmitted Viral
Infections

Genital herpes



Initial virus replication occurs locally
Virus spreads to contiguous cells and into sensory
nerves
Virus is transported intraaxonally to the dorsal
root
16
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Sexually Transmitted Viral
Infections

Genital herpes

Virus remains latent until reactivated

Oral infection


Virus resides in the trigeminal ganglion
Genital infection

Virus resides in the dorsal sacral nerve roots
17
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Sexually Transmitted Viral
Infections

Human papillomavirus (HPV)

120 different types of HPV




30 serotypes are unique to stratified squamous
epithelium
Divided into high-risk and low-risk serotypes
HPV is a nonenveloped, circular double-stranded
DNA virus
Belongs to the Papovaviridae family
18
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Sexually Transmitted Viral
Infections

Human papillomavirus (HPV)

Condylomata acuminata (genital warts)


Soft, skin-colored, whitish pink to reddish brown
benign growths caused by HPV
Treatment is considered cosmetic, not curative
19
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Sexually Transmitted Viral
Infections

Molluscum contagiosum



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
20
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Sexually Transmitted Parasitic
Infections

Trichomoniasis

Caused by Trichomonas vaginalis


Adheres to and damages squamous epithelial cells




Anaerobic, unicellular, flagellated, parasitic protozoan
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
21
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Sexually Transmitted Parasitic
Infections

Scabies
 Caused by the adult female itch mite, Sarcoptes
scabiei
 Transmission of scabies requires prolonged close
skin-to-skin contact


Burrows though the horny layer of the stratum per
day


Typically occurs between family members or sexual
partners
New larval forms appear in about 10 days
Classic symptom is intense pruritus
22
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Scabies
23
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Sexually Transmitted Parasitic
Infections

Pediculosis pubis



Caused by the crab louse Phthirus pubis
Transmitted primarily by intimate sexual contact
or contact with infected bed linens or clothing
A 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
24
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Pediculosis Pubis
25
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Sexually Transmitted
Gastrointestinal Infections



Shigellosis and Campylobacter enteritis
Giardiasis and amebiasis
Hepatitis B
26
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Sexually Transmitted Systemic
Diseases



Epstein-Barr virus
Acquired immunodeficiency syndrome
Cytomegalovirus
27
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