Pathogenesis of HIV and major STIs Flashcards
What is the difference between STI and STD?
Both transmitted through sexual contact
Disease = evidence of disease symptoms (infection could be asymptomatic!)
What are genital infectious disease?
Disease not necessarily acquired by sexual contact but act can precipitate it
Examples inc commensal vaginal flora/GI flora
What are the main bacteria associated with STIs?
N gonorrhoea
Chlamydia trachomatis
Ureaplasma
Mycoplasma
T pallidum - syphillis
What does phthirus pubis cause?
Crabs
What does sarcoptes scabiei cause?
Scabies
What are the predominant sites of infection/disease?
Local e.g. T vaginalis, C trochomatis, HSV, HPV, N gonorrhoeae
Mixed - syphillis
Other sites - HIV, Hep B
Other than sexual contact i.e. M-F, oral, M-M, F-F; how else can STIs be spread?
Vertical transmission - mother to baby
e.g. conjunctivitis/keratinits
What is the risk of infection/acquisition mainly related to?
Number of sexual partners (without barriers/contraception)
What type of bacteria is Neisseria gonorrhoea?
-Gram negative, -Diplococcus (looks like a pair of hairy balls) “clap”
What are the characteristics of N gonorrhoeae?
- Intracellular pathogen - pathocytosed and multiplies intracellularly
- Pili on surface - attaches to surface mucosal membranes (mainly cuboidal/columnar epithelium)
- Cell envelope
Where can gonorrhoea infect/effect?
Genital urethral tract
Rectum
Pharynx
How does gonorrhoea present?
Majority of women = asymptomatic
Urethral discharge
Dysuria
What are the complications of gonorrhoea (local and distant)?
- Epididymitis
- Prostatitis
- Pelvic inflammatory disease
- Fitz-Hugh curtis syndrome (perihepititis)
-Disseminated gonococcal infection - causes arthritis, meningitis
What can N gonorrhoea cause in pregnancy?
- Spontaneous abortion,
- premature labour,
- conjunctivitis (ophthalmia neonatorum - blindness if not treated!!)
How is gonorrhoea diagnosed?
- Urethral swab
- Culture
- Nucleic acid amplification test e.g. PCR
What is the treatment for gonorrhoea?
Cephlasporins eg. cefixime (oral), ceftriaxone (IV)
Azithromycin
What is the cause for non-gonococcal urethritis? (NGU)
Chlamydia
Ureaplasma urealyticum
What type of bacterium is chlamydia trachomatis? In what two forms does it exist?
Obligate intracellular pathogen
Extracellular infective - elementary body
Intracellular replicative - reticular body
What cells does chlamydia trachomatis target?
Squamocolumnar epithelium
Females - cervix, upper genital tract
Males/females - urethra, rectum, conjunctiva
How does chlaymdia infection present?
Osten asymptomatic (females more)
Urethritis
Cervicitis - strawberry cervix
Dysuria/frequency (painful, burning pee!)
What are the complications of chlamydia?
- Pelvic inflammatory disease - cause of infertility
- Conjunctivitis
- Epididymitis
- Tubal infertility
- Infant pneumonia
How is chlamydia diagnosed?
NAAT (i.e. PCR)
What is the treatment for chlamydia?
Azithromycin
Doxycycline
What is the main cause of genital warts?
HPV 6 and 11
HP 16 and 18 = cervical cancer
What is the treatment for genital warts?
Cervarix (16, 18)
Gardasil (HPV 6, 11, 16, 18)
- burn/freeze/cut
What type of virus is the herpes simplex virus> Which one (type 1 or 2) causes genital herpes>
Double stranded DNA
Type 2 - genital hypes
What are the classical symptoms of genital herpes?
Pain Itching Dysuria Vaginal/urethral discharge Vesicles/ulcers - shedding (Spread)
CAN REACTIVATE
What is the treatment for genital herpes?
Acyclovir
What is the complications of Herpes?
Meningitis
Encephalitis
How is genital herpes diagnosed?
Clinical, PCR (HSV 1 or 2), histology
What bacteria caused syphilis? What type of bacteria is it?
treponema pallidum
Spiralchaete (looks like a SPIRAL)
Cannot be grown/cultured in lab
How does it cause its symptoms and signs?
Penetrate intact mucosal membranes or abraded skin
Disseminates through lymph and blood quickly
Thereafter, causes symptoms and signs
What does the primary stage of syphillis consist of?
Time
Pathology
Symptoms
Incubation
3-90 days
First chancre - site of inoculation, heals spontaneously within 3-6 weeks
Asymptomatic
What does the secondary stage of syphillis consist of?
Time
Pathology
Symptoms
VERY INFECTIOUS
-6-8 weeks after primary
infection
-Rash - trunk, limb, soles, palms
-Condylomata lata - papules under armpits/genital regions
- Malaise, fever, weight loss
- CNS involvement - headache, meningism (rare)
What does the latent/teriary stage of syphillis consist of?
Time
Pathology
Symptoms
Spontaneous resolution after 3-12 weeks (latent = no clinical manifestation)
Tertiary - >2yrs
Gummas - non-specific granulomas (organs) - chronic inflammation
Cardiovascular - aortic regurg/aneurysms
Neuro - seizures, hemiplegia, mania/pyschoses/personality change, ataxic wide based gait
Argyll Robertson pupils - constrict to accommodation but not light
Can Syphillis cross the placenta and cause infection?
Yes - presents with snuffles/hepatosplenomegaly initially then saddle nose, frontal bosses, dental abnormalities later
What is the treatment for syphillis?
penecillin
What causes trichomoniasis? What is its characteristics?
Trichomoniasis vaginalis
Protozoan, lacks mitochondria
Humans only host
What are the clinical characteristics of trichomoniasis? How is it diagnosed?
FROTHY GREEN VAGINAL DISCHARGE (mmmm…)
Microscopy/culture
How is trichomoniasis treated?
Metronidazole
What is bacterial (anaerobic) vaginosis caused by?
Reduced vaginal lactobacilli
Increased gardnerella vaginalis and anaerobes
What is the characteristics of bacterial (anaerobic) vaginosis?
Watery discharge
Fishy odour
pH >4.5
What are the treatment for bacterial vaginosis?
Metronidazole
What is the cause for thrush? How is it transmitted?
Candida (usually albicans)
Sex, broad spectrum antibiotics, diabetes (poorly controlled, oral contraceptives)
What is thrush characterised by
Vaginal, vulval and penile erythema (redness)
Itchiness
Thick discharge
How is thrush diagnosed and treated?
Clinical diagnosis/culture
Treated with clotrimazole/fluconazole
What is HIV marked by?
Loss of CD4 lymphocytes
What are the characteristics of HIV?
Retrovirus - possesses reverse transcriptase
RNA dependent DNA polymerase
What HIV glycoprotein interacts with cell CD4 receptor and CCR5?
p120
