STD's Flashcards
What is an STI?
More than 1 million sexually transmitted infections (STIs) are
acquired every day worldwide.
*
Each year, there are an estimated 357 million new infections with 1
of 4 STIs: chlamydia, gonorrhoea, syphilis and trichomoniasis.
*
The majority of STIs have no symptoms or only mild symptoms
that may not be recognised as an STI.
*
STIs such as HSV type 2 and syphilis can increase the risk of HIV
acquisition.
*
Over 900 000 pregnant women were infected with syphilis
resulting in approximately 350 000 adverse birth outcomes
including stillbirth in 2012.
*
In some cases, STIs can have serious reproductive health
consequences (e.g., infertility or mother to child transmission)
What is Syphilis?
Caused by the spirochete Treponema
pallidum
*
T. pallidum is a helically coiled microorganism
usually 6 15 μm long and 0.1 0.2 μm wide.
*
T. pallidum does not have a tricarboxylic acid
cycle or oxidative phosphorylation resulting in
low metabolic activity.
*
Often considered Gram but lacks LPS!
*
Extremely hard (almost impossible to culture)
due to long time culture requirements.
What are the characteristics of syphilis?
T. pallidum has a worldwide distribution, with
syphilis remaining a serious health problem.
*
Complex systemic illness.
*
Used to be known as “the great imposter”.
*
Transmitted by sexual contact.
*
Cannot be diagnosed by isolating causative
organism as T. pallidum does not normally
grow in in vitro cultures.
Pathogenesis of T. pallidum
Not all patients go through all three stages; a substantial proportion remains
permanently free of disease after suffering the primary or secondary stages of
infection.
*
Unlike most bacterial pathogens, T. pallidum can survive in the body for many
years despite a vigorous immune response.
*
The healthy treponeme evades recognition and elimination by the host by
maintaining a cell surface rich in lipid.
*
This layer is antigenically unreactive. T. pallidum membrane antigens are only
uncovered in dead and dying organisms when the host is then able to respond.
*
Tissue damage is mostly due to the host response.
Stages of disease
Initial contact
2-10 wks
primary syphilis
1-3 mnths
secondary syphilis
2-6 wks
latent syphilis
3-30yrs
tertiary syphilis
How does primary syphilis present?
Enlarged inguinal nodes
Spontaneous healing
How does secondary syphilis present?
Flu like illness
Myalgia
Fever
Headache
Mucocutaneous rash
Spontaneous resolution
Pathogenesis of initial contact of syphilis
Multiplication of treponema at site of infection.
Associate host response.
Pathogenesis of primary syphilis
Proliferation of treponema in regional lymph nodes
Pathogenesis of secondary syphilis
Multiplication and production of lesion in lymph nodes
liver
joints
skin
muscles
mucous membranes
Pathogenesis of latent syphilis
Treponemas dormant in liver or spleen
Pathogenesis of syphilis in 3-30yrs
Re-awakening and multiplication of treponema
Tertiary syphilis
Symptoms
Neurosyphilis
General paralysis of the insane
Tabes dorsalis
Cardiovascular syphilis
Aortic lesions
Heart Failure
Progressively destructive disease
Pathogenesis of tertiary syphilis
Further dissmination and invasion and host response
Cell-mediated hypersensitivity
Gummas in skin, bones, testis
What is congenital syphilis?
An infected woman can transmit T pallidum to
her baby in utero
*
Congenital syphilis is acquired after the first 3
months of pregnancy The disease may manifest as
Serious infection resulting in intrauterine death
Congenital abnormalities, which may be obvious at
birth
Silent infection, which may not be apparent until
about 2 years of age (facial and tooth deformities
“Hutchinson’s Teeth”)
How is syphilis diagnosed by lab>
T. pallidum partile agglutination assay
Rapid plasma reagin
As T. pallidum cannot be grown in vitro.
*
Exudate from the primary chancre used to be
examined by microscopy (silver stain on picture).
*
Antibody detection.
What is the treatment for syphilis?
Penicillin is the drug of choice for treating people with syphilis and
their contacts
*
Penicillin is very active against T. pallidum .
*
For patients who are allergic to penicillin, treatment with doxycycline
should be given.
*
Only penicillin therapy reliably treats the foetus when administered to a
pregnant mother.
*
Prevention of secondary and tertiary disease depends upon early
diagnosis and adequate treatment.
Contact tracing with screening and treatment is also important. Several
STIs may be present in one patient concurrently.
*
Patients with other STIs should be screened for syphilis.
*
Congenital syphilis is completely preventable if women are screened
serologically early in pregnancy (< 3 months) and those who are positive
are treated with penicillin.
What is Gonorrhoea?
Is caused by the Gram negative coccus
Neisseria gonorrhoeae (the gonococcus
*
This bacterium is a human pathogen that does
not cause natural infection in other animals
*
Therefore, its reservoir is human and
transmission is direct, usually through sexual
contact, from person to person
The organism is sensitive to drying and does not
survive well outside the human host, so intimate
contact is required for transmission.
*
Asymptomatically infected individuals form the
major reservoir of infection.
*
Infection may also be transmitted vertically from
an infected mother to her baby during childbirth
*
Infection in babies usually manifests as
ophthalmia neonatorum.
What is the clinical presentation of gonnorhea
Symptoms develop within 2 7 days of infection and are characterised:
*
In the male by urethral discharge and pain on passing urine (dysuria).
*
In the female by vaginal discharge.
*
At least 50% of all infected women have only mild symptoms or are completely
asymptomatic.
*
Women may not be alerted to their infection unless or until complications arise,
such as:
Pelvic inflammatory disease (PID)
Chronic pelvic pain
Infertility resulting from damage to the fallopian tubes.
How to diagnose gonorrhea
Microscopy and culture of appropriate
specimens
*
Urethral and vaginal discharges.
*
Purulent discharge is characteristic.
*
Culture is essential in the investigation of
antibiotic susceptibility.
*
Commercial nucleic acid based
approaches (PCR) are now routinely
used, providing reliable results.
Treatment of gonorrhoea
Antibiotics used to treat gonorrhoea are cefixime or ceftriaxone
*
Penicillinase producing N. gonorrhoeae were first observed in 1976 with
increasing resistance that has severely compromised the effective treatment of
gonorrhoea in many parts of the world.
*
Resistance to fluoroquinolones has also occurred.
*
Since patients with gonorrhoea may also be infected with chlamydia, treatment
regimens often include a combination of agents targeting both organisms (e.g.
ceftriaxone and doxycycline, respectively).
*
Infection can be prevented by the use of condoms.
*
Follow up of patients and contact tracing are vital to control the spread of
gonorrhoea.
What is Chllamydial infection?
Chlamydia trachomatis cause sexually
transmitted genital infections.
*
Chlamydiae are very small Gram bacteria.
*
Considered obligate intracellular parasites.
*
They have a more complicated life cycle than
free living bacteria because they can exist in
different forms:
The elementary body (EB).
The reticulate body (RB).
Asymptomatic infection is common,
especially in women.
What is the cycle of life for chlamydia>
- Attachment and entry of elementary body to target cell
- Formation of reticulate body
- binary fusion of reticulate bodies
- Reorganisation of reticulate bodies into elementary bodies
- Multiplication ceases
- Release of elementary bodies
What is the clinical manifestation of Chlamydia
Can be asymptomatic.
*
Common symptoms include unusual discharge from vagina or penis
and pain when peeing.
*
Most people with chlamydia do not notice any symptoms and do not
know they have it.
If symptoms are developed, patients may experience:
Pain when peeing
Unusual discharge from the vagina, penis or bottom
In women, pain in the tummy, bleeding after sex and bleeding between
periods
In men, pain and swelling in the testicles
