STI Flashcards
lactobilli
Lactobacilli pre-dominant colonisers.
Inhibit growth of pathogenic organisms.
Produce lactic acid – helps maintain low pH.
Adhere to vaginal cells and prevent long-term colonisation by other species.
Produce hydrogen peroxide – inhibits growth of other microorganisms directly or via human myeloperoxidase.
Can inactivate HIV-1, herpes simplex virus type 2, Trichomonas vaginalis, Gardnerella vaginalis, Peptostreptococcus bivia and E. coli.
Produce antimicrobial peptides – bacteriocins.
antimicrobial activity of semen
Contains a number of antibacterial peptides.
Protection of spermatazoa.
Includes:
Lysozyme
Lactoferrin
Phospholipase A2
Secretory leukocyte protease inhibitor
Semenogelin 1-derived peptides
gonorrhoea
Infection caused by the bacterium, Neisseria gonorrhoeae.
Uncomplicated infection is localised, usually affecting the mucous membranes of urethra, endocervix, rectum, pharynx and conjunctiva.
Less common (< 1% people) is disseminated gonorrhoea – can present as septic arthritis or dermatitis.
Almost always transmitted sexually in adults:
genital – genital; genital – anorectal; orogenital; oro – anal
autoinoculation of the eye
prevelance- gonorrhoea
Most common in young adults (15 – 25 yrs).
2010 Gonoccocal Resistance to Antimicrobial Surveillance Programme indicated:
the majority of gonococci (83%) were collected from men. The age range of the patients was less than one year to 76 years, with a median of 29 years; 34% of patients were younger than 25 years.
co-infection with chlamydia found in 38% heterosexual men and 40% of women.
Gonococcal antimicrobial susceptibility surveillance in Europe
men- gonorrhoea
Acute – epididymitis, penile lymphangitis, per-urethral abscess, acute prostatitis, seminal vesiculitis.
women- gonorrhoea
Less understood. Often asymptomatic and can remain undiagnosed.
Bartholin’s abscess can be complication, often polymicrobial infection.
10 – 20% pelvic inflammatory disease.
During pregnancy, can cause spontaneous abortion, premature labour, early rupture of fetal membranes, etc.
disseminated gonorrhoea
Rare but serious – lead to arthritis-dermatitis syndrome, gonococcal bacteremia and gonococcal endocarditis.
neisseria gonorrhoeae
Fastidious, Gram negative diplococci.
Facultatively intracellular.
In most cases, commercially available nucleic acid amplification tests (NAATs) are used for initial diagnosis.
NAATs also detect chlamydia.
Have increased sensitivity over culture methods but culture is still used to track development of antimicrobial resistance.
virulence factors- neisseria gonorrhoeae
Pilus – attach to epithelium. Contain constant & hypervariable regions, contribute to antigenic diversity.
Por proteins – form pores in membrane. Antigenic properties.
Opa proteins – aid in attachment.
LOS – contains lipopolysaccharide, has endotoxin activity.
Rmp proteins – inhibit ‘cidal’ action of semen.
IgA protease – destroys IgA1.
Capsule - can resist phagocytosis.
chlamydia
Most common curable bacterial STI in UK.
Caused by the obligate intracellular bacterium, Chlamydia trachomatis.
Men – infects urethra.
Women – infects endocervix or urethra or both.
At least 70% women/50% men with infections are asymptomatic.
Uncomplicated – if not ascended into upper genital tract.
Complicated – if in upper genital tract, causing pelvic inflammatory disease (PID) (women), epididymo-orchitis (men).
complications and prognosis- chlamydia
Untreated infections can persist or resolve.
PID – in up to 16% untreated women.
Epididymo-orchitis – pain, swelling or inflammation of the epididymous and/or testicles.
Adult conjunctivitis – mainly caused by autoinoculation.
Lymphogranuloma venereum (LGV) – infection of lymphatic system.
Sexually acquired reactive arthritis (SARA) – polyarthritis of weight-bearing joints.
Anxiety and distress.
In pregnancy, can result in increased risk of membrane rupture, pre-term delivery, low birth weight, etc.
virulence factors- chlamydia
Outer LPS cell membrane contains cysteine-rich proteins, inhibit phagosome fusion.
Adhesion to sialic acid receptors on mucous membranes, presence at sites inaccessible to phagocytes, T cells and B cells.
Antigenic variation so many serotypes.
Needle-like projection type III secretion apparatus – injects bacterial proteins into cell cytoplasm, avoids lysosomes.
Infested vacuole can divert lipids to itself rather than another part of the host cell.
syphilis
Spirochete bacterium, Treponema palladium.
Person to person transmission via direct contact with infectious lesions.
Untreated syphilis can go from early syphilis (1st 2 yrs following infection) to late syphilis through various stages:
Primary – painless ulcer (chancre), commonly affecting genitals, localised lymphadenopathy.
Secondary – multisystem, can affect one or more of:
- Rash, commonly on palms or soles.
- Moist, wart-like lesions, commonly in perianal and vulval regions, under breasts, axillae.
- Patchy lesions on oral mucosa.
- Generalised lymphadenopathy.
- Low grade fever, headaches.
syphilis stages
- Early latent – within 1st 2 yrs of infection but no clinical features.
- Late syphilis can progress through two stages:
- Late latent stage – serological confirmation, 2 yrs after infection, no clinical features.
- Tertiary – rare due to widespread antibiotic use. Divided into neurosyphilis, cardiovascular and gummatous syphilis.
- Primary & secondary are most infectious stages.
Prevalence – in the UK, increasing with more cases in men than women.
stucture of syphilis- Treponema palladium
Outer sheath composed of glycosaminoglycan.
Outer membrane contains peptidoglycan and maintains structure.
Axial filament (endoflagella) – inside is the inner membrane which provides osmotic stability and covers the protoplasmic cylinder.
Reproduces by transverse fission.
