STI III Flashcards
Syphilis epidemiology and transmission
Causative organism: Treponema pallidum subspecies pallidum (also written as Treponema pallidum subsp. pallidum):
- does not grow in cell-free cultures so have to do PCR
- often cultured in tissue culture using epithelial cells
- they lack to ability to synthesise growth factors
Syphilis transmission
- Sexually transmissible
- Bacteria enter the skin via abrasions and can invade mucous membranes
- Can also spread to the fetus (congenital syphilis) or by transfusion with contaminated blood*
- Does not appear to be spread via fomites (inanimate objects like towels, etc)
- Syphilis is characterised by three phases: *primary, secondary *and tertiary (late)
Primary syphilis
- Generally only one lesion (papule) develops (10-90 days) after initial infection*
- Lesion develops at the point of entry of bacteria
- Papule soon after erodes into a painless ulcer with raised borders
- If untreated, the ulcer generally heals spontaneously (2-8 weeks) but the disease is still progressive
- Note: the patient is infectious
Secondary syphilis
This is the disseminated stage of the the disease. Patients typically show intiial flu-like syndrome:
- Sore throat
- Headache
- Fever
- Myalgias (muscle pain)
- Anorexia (loss of apetite)
- Lymphadenopathy (enlarged lymph nodes)
- Mucocutaneous rash involving the entire body, including the palms and soles
If untreated at this stage, rash and symptoms generally resolve in a few weeks and patient tners the ‘clinically inactive/asymptomatic/latent’ stage of the disease
- Note: the patient is infectious in the second stage of the disease
Tertiary syphilis
‘Late’ syphilis
If disease is not treated earlier, a tertiary stage usually develops (after 5-30 years after initial infection) in about 30-40% of patients. In tertiary stage the disease symptoms and signs are grouped into:
- Neurosyphilis: seizures, changes in personality, slurring speech, pupillary disturbances (Argyll Robertson pupils)
- Cardiovascular syphilis: predilection for destruction of the ascending aorta
- Gummatous syphilis: lesions on skin, bones, mucous membranes
Congenital syphilis
Fetus infected during pregnancy leading to multi-orgam malformations, or death.
Infants who survive initial stage of disease often present with:
- Hutchinson’s teeth
- Saddle nose
- Sabre shins
- Intellectual disabilities
- Blindness
- Cardiovascular syphilis
Laboratory diagnosis syphilis
Syphilis cannot be cultivated in vitro.
- Dark-field microscopy of exudates from skin lesions - not really used in TAS.
- PCR: swab from base of the lesion
- Treponema-pallidum particle agglutination (TP-PA) test: gelatin particles containing *T. pallidum *antigens are mixed with patient serum; if antibodies are produced by patient, the particles agglutinate.
Bacterial vaginosis epidemiology
- A phenomenon initially observed in sexually active women
- Usually associated with new or multiple sex partners
- Most noted in women who have sex with women; individuals (source/partner) eventually share the same cohort of vaginal flora.
Bacterial vaginosis pathophysiology
- This is not well understood.
- Microscopic examination of vaginal discharge reveals a predominant flora of coccobacilli (gram negative rods)
Causative organisms for bacterial vaginosis
- Gardnerella vaginalis* (facultative G –ve anaerobe)
- Prevotella
- Megasphaera
- Coriobacterineae
- Lachnospira
- Sneathia
- Mycoplasma hominis*
- Ureaplasma urealyticum*
It is not just one bacteria - it is a whole cohort of gram negative organisms. When pH changes during sexual intercourse, Lactobacilli die, and their place is taken over by these organisms.
Bacterial vaginosis differential diagnosis
Women with bacterial vaginosis are at increased risk of infection by HSV-2, N. gonorrhoeae, and C. trachomatis
Bacterial vaginosis clinical manifestations
- Homogenous vaginal discharge
- ‘Fishy’ vaginal odor, most notably
- During menstruation
- After sexual intercourse
- Minimal itching or irritation
- Associated with an increased ris of:
- Salpangitis
- Post partum fever and post partum endometritis
- Premature labour and delivery
- Chorioamnionitis
- Increased risk fo UTI
- PID
Diagnosis for bacterial vaginosis
- Homogenous vaginal discharge
- Vaginal pH greater than 4.6 (normally 3.5-4.5)
- Positive ‘whiff’ test (amines are volatile at increased pH); in the lab, odour is detected by mixing vaginal discharge samples with 10% KOH
- Presence of ‘clue’ cells (epithelial cells coated with bacteria)
At least 3 of the 4 criteria must be met for the diagnosis.
Gram stain: should show reduced numbers of lactobacilli.
Trichomonas vaginalis epidemiology
T. vaginalis, a parasitic protozoan is a common cause of vaginitis in women of all ages. WHO estimates infection by T. vaginalis accounts for 50% of all curable infections worldwide.
Its presence is often also seen as a marker of risky sexual behaviour, and is commonly found with other STIs, like gonorrhoea.
In men, it may cause urethritis BUT it is more often asymptomatic*
Trichomonas vaginalis clinical manifestations in women
In women, the squamous epithelium of the vagina is infected, resulting in micro-ulceratiosn via direct contact with the organism.
The incubation period is 4-28 days before:
- ‘frothy’ vaginal discharge (50-75%)
- Pruritis (23-82%)
- Dysuria (30-50%)
- Lower abdominal discomfort (5-12%)
- Colpitis mascularis (strawberry cervix)
Possible complications: premature rupture of membranes; preterm delivery
trichomonas vaginalis clinical manifestations in men
This is becoming a recognised cause of NGU (non-gonococcal urethritis?).
Rarely causes:
- Epididymitis
- Prostatitis
- Penile ulceration
Trichomonas vaginalis laboratory diagnosis
- Microscopic examination of the vaginal fluid
- pH > 4.5
- Positive ‘whiff’ test
- PCR - useful to some degree but not necessary
Klebsiella granulomatis epidemiology
K. granulomatis is an encapsulated, pleomorphic, gram negative bacillus (can be found in the cytoplasm of mononuclear cells - WBCs).
Causes Donovanosis. This is a chronic, progressive ulcerative disease of the genital region.
Notably a cause of genital ulceration in:
- India
- Papua New Guinea
- Carribean
- South America
- Parts of Africa (Zambia, South Africa, Zimbabwe)
- South East Asia
- Amounst Aboriginal and Torres Strait Islander populations
Hence, it is important to take a travel history.
Donovanosis clinical manifestations
- Primary lesion is usually small, painless papule
- After an incubation period of 8-80 days, the lesion ulcerated producing a ‘beefy’ red ulcer with rolled edges that bleeds on contact.
- Disease then spreads subcutaneously resulting in tissue destruction*
In men, most common sites are:
- Prepuce
- Corona
- Penile shaft
In women:
- Labia
- Rarely, vaginal wall and cervix
- Oral lesions (?) - history of oral-genital contact
Diagnosis of Donovanosis
Diagnosis is usually made on clinical manifestations. Confirmation is proven by:
- Histological examination of biopsies/scrapings taken from the edge of the active lesion
- Demonstration of ‘donovan’ bodies is the gold reference standard
- Culture of K. granulomatis in monocytes and hep-2 cells
- PCR and DNA extracted from the biopsy material (i.e. specific for the *phoE *gene of the organism)
Candida albicans epidemiology and transmission
- This is part of the norma flora of women
- Is the cause of approximately 80-90% of vulvovaginal cadidiasis in patients
- Estimated that 75% of adult women will suffer at least one episode of vulvovainal candidiasis during their lifetime
- Carriage rates are higher in women using oral contraceptives
- Imuno-insufficiency also predisposes to overgrowth/infection
- Transmission is poorly understood. What we do know is that
- Colonisation increases with onset of sexual activity
- Having multiple partners does not appear to increase incidence of infection in women.
Clinical manifestations of vulvovaginal candiditis
- Perivaginal pruritis
- Vulvar irritation
- Dysuria
- Abnormal (candidal) discharge is usually thick and adherent (‘cottage cheese’)
Diagnosis of Candida albicans vulvovaginal cadidiasis
- Vaginal pH is usually nromal (pH 3.8-4.5)
- No odour on ‘whiff’ test
- Microscopic examination of vaginal material show yeast cell or hyphal forms
- Culture of vaginal material
Classification of vulvovaginal cadidiasis
Uncomplicated infection
- Sporadic or infrequent
- Mild to moderate severity
- Likely to be caused by Candida albicans
- Patient is not immunocompromised
Complicated infection
- Recurrent infection (4 or more episodes a year)
- Severe infection
- Caused by non-albicans species of Candida
- Uncontrolled diabetes, debilitation, immunosuppression, or pregnancy
