STIS Flashcards
What are the different types of microorganisms?
- viruses
- protozoa
- bacteria
- algae
- fungi
What are the most common STIs in the UK?
- Chlamydia
- Gonorrhoea
- Trichomoniasis
- Genital warts
- Genital herpes
- Pubic lice
- Scabies
- Syphilis
- Human papillomavirus (HPV)
What are the most common bacterial STIs?
- Gonorrhoea
- Chlamydia
- Syphilis
- Chancroid
What is gonorrhea?
- Caused by Neisseria gonorrhoeae (gram neg)
- Gram neg cocci (diplococci)
Virulent factors : - pilus for cell attachment
- LPS endotoxin
- Capsule rendering phagocytosis resistant
- IgA protease destroy IgA1 (mucosal immunity)
What is the clinical presentation of Gonorrhoea and diagnosis:?
- Symptoms develop 2-7 days after infection
- Around 50% female asymptomatoc
- Purulent urethral / vaginal discharge
- Dysuria
- Rectal/ oral infection
- Neonatal gonococcal eye infection
- Pelvic inflammatory disease
- Untreated may result in infertility
DIAGNOSIS
- MC+s
- Microscopy on discharge reveals intracellular ( phagoctyosed) and extracellular Gram neg diplococci.
- Culture swabs from infected area or discharge ( kept warm in charcoal-enriched transport medium and sent to lab without delay) and urine. Chocolate agar-
- Nucleic Acid amplification test (NAAT)
- Culture still vital - need antibiotics sensitivity for treatment due to multi-resistant strains
What is chlamydia?
- Caused by chalmydia trachomatis serotypes D to K
- Very small obligate intracellular bacteria
- Gram neg if stained ( normally very weak)
What is the clinical presentation and diagnosis of chlamydia?
- Clinical presentation
- Approx male 50%, female 70% asymptomatic
- If sympotomatic :
- Female :
- vaginal discharge , intermenstrual bleeding, deep dyspareunia, lower abdominal pain or discomfort
- Male : Urethral discharfe, dysuria
- Occular infections in neonates infected during birth may cause blindness. Infected neonates also prone to C trachomatis pneumonia
DIAGNOSIS:
- MC+ S not suitable
- Microscopy unreliable
- Requires specialised techniques (cell culture usinf McCoy cell lines)
- Nucleic Acid Amplification test (NAAT)
- Enzyme linked immunosorbent Assay (ELISA)
- off the shelf test kits available
What is syphilis?
- Caused by treponema pallidum (spirochete)
- Gram neg
- Motile corkscrew pattern
- Sensitive to heat, drying (50-60 degrees)
- Cannot be cultured in vitro
What are the four stages of clinical presentation of syphilis?
- Primary : onset = 20-90 days post infection. Presentation : small , red oral lesions on genitalm chancre (painless lesions)
- Secondary lesions - 2-10 weeks after primary stage . Presentation = Brown rash on palms and soles, fever, lymphadenopathy, muscle and joint pain, hair loss in patchy pattern, rash on mucosa (mouth, throat and cervix)
- Latent - after secondary stage. Asymptomatic
- Tertiary - can manifest many years after latency. Disfiguration, neuropathy, CVS abnormality, gumma (rubbery after latency)
What is the diagnosis of syphilis?
- MC + S not suitable
- Microscopy - dark grounf or immunofluorescent
- Cannot be cultures
- Most commonly used serological tests :
- RPR (rapid plasma reagin)
- VDRL ( Venereal Disease Reference Laboratory)
- TPHA (Treponema Pallidum HaemAgglutination)
What is chancroid?
- caused by haemophilius ducreyi
- Gram neg cococbacilli
- Primarily in Africa and Asia but also becoming a sexual health issue in UK
What is the clinical presentation and diagnosis of Chancroid?
- Painful non-indurated genital ulcers
- Ulcers may look like herpes
- Lymmohadenopathy
- Diagnosis:
- MC + S
- Gram stain on aspirate from ulcer
- Culture may take 2-9 days
What are the most common viral STIs?
- Herpes
- Genital wart
- HIV
- Hepatitis
What is herpes?
- Caused by herpes simplex virus
- Conventionally type I oral and Type II genital. More recently mixed patterns
What is the herpes virus family?
- Herpesviridae
- Different viral pathogens expressed in different diseases e.g.:
- chickenpoc, shingles
- cold sore
- genital herpes
- ## Cytomegalic inclusion disease
What is hepres latency?
Incominf HSV-1 virion
a.) Establishment : retrogade transport of incominf capsids denuded of tegument proteins. Diffusion barrier. Cell body compartment.
b.) Nuclear accumulation of VP16 & HCF-1 supporting IE gene expression leading to productive reactivation
- Shedding of new HSV-1 virions
What is genital wart?
- Caused by HPV
- HPV over 120 typesm with less than 50% homology in genome
- HPV 6 and 11 cause 90% genital warts
- HPV 16 AND 18- high risk types causing 70% cervical cancer
- NHS vaccines available for 12- 18 yr old females
- Clinical presentation:
- itchy or burning sensation developing into raised lu,ps with characteristic cauliflower appearance
- Treatment: surgical or liquid nitrogen removal, topical applications such as richloroacteic acid, imiquimod, cinecatechins
- HPV transformation of cervical epithelial cells results in pre-cancerous squamous intra-epithelial lesions - neoplasia grading 1-3 according to severity
- Progression of cancer formation genetic and cellular changes results in invasive cancer masses
What are the mechanisms of HPV-induced carcinogenesis?
- HPV induces inflammatory responses
- Inflammatory immune cells release reactive oxygen and nitric species (ROS/RNS)
- ROS and RNS induces DNA strand breaks, allows integration of viral genome into infected host cell genome
- HPV genome contains tumour promoting sequences
- Prolonged inflammation - risk for cancer development
- Host cell exposed to infflammatory signals which undergo cellular changes pre-disposing to cancer development
What is HIV?
- Double-stranded RNA
- Enveloped
- Attachment molecules (Receptors)
- HIV pathogenesis:
- HIV attachment molecule gp120 (gp = glycoproteinm 120 MW)
- GP120 binds to helper lymphocyte CD4 cell surface molevule
- Viral envelope fuses with host cell membrane
- Viral particle internalised by host cells
What is Kaposi sarcoma (AIDS)?
- Caused by Herpesvirus family member
- Human herpes virus 8
- Opportunistic infection (only when host immunity collapses)
What are hepatitis infections?
- Primarily Hep B as STI
- Hep B infection route - body fluid and maternal transfer
- Hep C co-infection with HIV also been reported
- Hep C infection route - blood
- Transmitted during sex due to presence of bleeding lesions
- Other factors involved for Hep B and C infection as STI- drug use
What are the most common protozoan STIs?
- Trichomoniasis- caused by trichomonas vaginalis
- Both male and fenale approx 50% asymptomatoc
Common symptom - vaginal or urethral discharge, dysuria, vaginitis
Diagnosis:
Microscopy and culture both successful
NAAT
What is pubic lice?
- Caused by the crab louse Phthirus pubis
- Clinical presentation:
- Incubation between 5 days to weeks
- Itch caused by hypersenitivuty reaction. Bites may become visible
- Eggs on hair may be visible
Diagnosis :
- Microscopy reveals adult lice and eggs
-Treatment
- Malathion applied to dry hair and wash out permethrin cream (same as head lice)
What is scabies?
- Caused by sarcoptes scabiei
- Can survive for up to 7 days
- Symptoms may begin 3-6 weeks , nocturnal pruritus, Microscopy, NAAT or antibody assays
- Treatment as per head lice
- Peremethrin or malathion cream
What is candidiasis?
- Thrush
- 80-90% caused by Candida albicans, Other candida species also involved
- Vaginal discharge being main clinical presentation
- Microscopy reveal yeast particles sometimes with hyphae
- Vaginal swab culture also reveal fungal growth (pure or heavy growth. If scanty or light growth, non-significant)
- Although candidasis can be transmitted sexually, most cases of candidiasis are general health issues rather than STIs
