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Chapter 55
Sexually Transmitted
Infections
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STIs
• Sexually transmitted infections (STIs) encompass a
broad range of infectious diseases that are spread by
sexual contact.
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Agents of Transmission of Sexually
Transmitted Diseases
• Bacteria
• Chlamydiae
• Viruses
• Fungi
• Protozoa
• Parasites
• Unidentified microorganisms
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Portals of Entry for STDs
• Mouth
• Genitalia
• Urinary meatus
• Rectum
• Skin
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Organisms Caused by Some STDs
• Condylomata acuminata, or genital warts, are caused by the
human papillomavirus (HPV).
• Genital herpes is caused by nine types of herpesviruses,
belonging to three groups, which cause infections in
humans.
• Molluscum contagiosum is a common poxvirus.
• Chancroid is caused by the gram-negative bacterium
Haemophilus ducreyi.
• Granuloma inguinale (i.e., donovanosis, granuloma
venereum) is caused by a gram-negative bacillus, Klebsiella
granulomatis (previously known as Calymmatobacterium
[Donovania] granulomatis).
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Organisms Caused by Some STDs (cont.)
• Lymphogranuloma venereum (LGV) is an acute and
chronic venereal disease caused by Chlamydia
trachomatis types L1, L2, and L3.
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STDs Affecting the Mucocutaneous
Tissues of the External Genitalia
• Condylomata acuminata
• Human papillomavirus (HPV) infection
• Genital herpes
• Molluscum contagiosum
• Chancroid
• Granuloma inguinale
• Lymphogranuloma venereum (LGV)
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AMA Classification Genital Warts (HPV)
• Condylomata acuminata: cauliflower-shaped lesions
that tend to appear on moist skin surfaces (vaginal
introitus or anus)
• Keratotic warts: display a thick, horny layer; develop
on dry, fully keratinized skin (penis, scrotum, or labia
majora)
• Papular warts: smooth surface, typically develop on
fully keratinized skin
• Flat warts: macular, sometimes faintly raised, usually
invisible to the naked eye, occur on either fully or
partially keratinized skin
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Types of Herpesviruses
• Neurotropic α-group viruses
– Herpes simplex virus type 1
– Herpes simplex virus type 2
– Varicella-zoster virus
• Lymphotropic β-group viruses
– Cytomegalovirus
– Epstein-Barr virus
– Human herpesvirus type 8
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High-Risk Strains of HPV
• Infection with some HPV types results in genital warts,
cervical dysplasia and cervical cancer.
• Sexually transmitted infections can selectively infect the
mucocutaneous tissues of the external genitalia, cause
vaginitis in women, or produce both genitourinary and
systemic effects.
• Some STIs may be transmitted by an infected mother to
a fetus or newborn, causing congenital defects or death
of the child.
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Question
• Is the following statement True or False?
• HPV infections have been implicated in the development
of vaginal cancer.
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Answer
• False
• Rationale: HPV has been shown to be involved in cervical
cancer. Recently, a vaccine, the first cancer vaccine, has
been introduced to combat HPV infection.
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Pathogenesis of Genital Herpes Infections
• These viruses replicate in the skin and mucous
membranes at the site of infection (oropharynx or
genitalia).
• They grow in neurons and share the biologic property of
latency.
• In genital herpes, the virus ascends through the
peripheral nerves to the sacral dorsal root ganglia.
During the dormant or latent period, the virus replicates
in a different manner so that the immune system or
available treatments have no effect on it.
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Pathogenesis of Genital Herpes Infections
(cont.)
• Host responses to infection influence initial development
of the disease, severity of infection, development and
maintenance of latency, and frequency of HSV
recurrences.
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Diagnosis of Genital Herpes
• Based on the symptoms
• Based on appearance of the lesions
• Identification of the virus from cultures taken from the
lesions
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Sexually Transmitted Vaginal Infections
• Candidiasis
• Trichomoniasis
• Bacterial vaginosis
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Candidiasis
• Causative organism is Candida, yeast-like fungi
– Most commonly identified species is Candida
albicans.
– Candida glabrata and Candida tropicalis have caused
symptoms.
• Present in 20% to 55% of healthy women without
causing symptoms
– Alteration of the host vaginal environment usually is
necessary before the organism can cause pathologic
effects.
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Causes of Candidiasis
• Antibiotic therapy
– Suppresses the normal protective bacterial flora
• High hormone levels owing to pregnancy
• The use of oral contraceptives
– Cause an increase in vaginal glycogen stores
• Diabetes mellitus or HIV infection
– Compromise the immune system
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Trichomoniasis
• Definition
– An anaerobic protozoan that feeds on the vaginal mucosa
and ingests bacteria and leukocytes
• Symptoms
– Copious, frothy, malodorous, green or yellow discharge
– Erythema and edema of the affected mucosa
– Occasional itching and irritation
– Sometimes strawberry spots appear on the cervix.
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Diagnosis of Bacterial Vaginosis
• At least three of the following characteristics present:
– Homogeneous discharge
– Production of a fishy, amine odor when a 10%
potassium hydroxide solution is dropped onto the
secretions
– Vaginal pH above 4.5 (usually 5.0 to 6.0)
– Appearance of characteristic “clue cells” on wetmount microscopic studies
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STDs Infecting Male and Female Genital
and Extragenital Structures
• Chlamydial infections
• Gonorrhea
• Syphilis
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Gonorrhea
• Agent: a pyogenic, gram-negative diplococcus that
evokes inflammatory reactions characterized by purulent
exudates
• Host: Humans are the only natural host.
• Growth: warm, mucus-secreting epithelia
• Portal of entry: the genitourinary tract, eyes,
oropharynx, anorectum, or skin
• Transmission: heterosexual or homosexual intercourse
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Two Forms of Chlamydiae
• Elementary bodies
– The infectious particles capable of entering
uninfected cells
• Initiator or reticulate bodies
– Multiply by binary fission to produce the inclusions
identified in stained cells
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Complications from Chlamydia,
Gonorrheal, and Syphilis
• Gonorrheal and chlamydial infections can cause a wide
variety of genitourinary complications in men and women,
and both can cause ocular disease and blindness in
neonates born to infected mothers.
• Syphilis is caused by a spirochete, T. pallidum. It can
produce widespread systemic effects and is transferred to
the fetus of infected mothers through the placenta.
• When syphilis does progress to the symptomatic tertiary
stage, it commonly takes one of three forms: development
of localized destructive granuloma-like lesions called
gummas, development of cardiovascular lesions, or
development of central nervous system lesions.
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Syphilis
• Primary syphilis
– Appearance of a chancre at the site of exposure
• Secondary syphilis
– Lasts from 1 week to 6 months
– Symptoms of a rash fever, sore throat, stomatitis,
nausea, loss of appetite, and inflamed eyes
• Tertiary syphilis
– Delayed response of the untreated disease
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Complications from Chlamydia,
Gonorrheal, and Syphilis (cont.)
• When syphilis does progress to the symptomatic tertiary
stage, it commonly takes one of three forms:
development of localized destructive granuloma-like
lesions called gummas, development of cardiovascular
lesions, or development of central nervous system
lesions.
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Treatment Options
• Chlamydial infections
– Azithromycin, doxycycline, amoxicillin
• Gonorrhea
– Tetracycline, penicillin, ceftriaxone, cefixime,
ciprofloxacin, ofloxacin, levofloxacin, azithromycin
• Syphilis
– Penicillin
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Question
• Of the following conditions, which is known to have
neurological implications?
− A. Chlamydial infections
− B. Gonorrhea
− C. Candidiasis
− D. Trichomoniasis
− E. Syphilis
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Answer
• E. Syphilis
• Rationale: Syphilis will spread to the CNS and cause
significant neurological dysfunction.
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