SW - STIs Flashcards
What bacterium is predominant in the vaginal microbiome?
Lactobacilli
What are some features of Lactobacilli? (3)
- Lactobacilli pre-dominant colonisers.
- Inhibit growth of pathogenic organisms.
- Adhere to vaginal cells and prevent long-term colonisation by other species.
What 3 things do Lactobacilli produce?
1) Produce lactic acid – helps maintain low pH
2) Produce hydrogen peroxide – inhibits growth of other microorganisms directly or via human myeloperoxidase
3) Produce antimicrobial peptides – bacteriocins
What organisms do lactobacilli inactivate? (6)
Can inactivate
- HIV-1
- herpes simplex virus type 2
- Trichomonas vaginalis
- Gardnerella vaginalis
- Peptostreptococcus bivia
- E. coli
Describe the antimicrobial activity of semen (3)
1) Contains a number of antibacterial peptides.
2) Protection of spermatazoa.
3) Includes:
- Lysozyme
- Lactoferrin
- Phospholipase A2
- Secretory leukocyte protease inhibitor
- Semenogelin 1-derived peptides
What are some features of Gonorrhoea? (2)
- Infection caused by the bacterium, Neisseria gonorrhoeae.
- Uncomplicated infection is localised, usually affecting the mucous membranes of urethra, endocervix, rectum, pharynx and conjunctiva
What are some complications of gonorrhoea in men vs women
Men
- Acute – epididymitis, penile lymphangitis, per-urethral abscess, acute prostatitis, seminal vesiculitis.
Women
- 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.
What is Neisseria gonorrhoeae? (5)
- 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.
What are the virulence factors of gonorrhoeae? (7)
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.
What are some features of Chlamydia and how it infects men vs women?
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.
- Uncomplicated – if not ascended into upper genital tract.
- Complicated – if in upper genital tract, causing pelvic inflammatory disease (PID) (women), epididymo-orchitis (men).
What technique can be used to confirm diagnosis of Chlamydia?
NAATs
What are the virulence factors of Chlamydia? (5)
- 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.
How does chalmydia replicate?
Can only replicate inside eukaryotic host cells
- Metabollically inert spore-like elementary bodies (EBs) infect host cells and develop into metabollically active, replicative reticulate bodies (RBs) within a membrane-bound inclusion
- RBs redifferentiate into EBs 24–48 hours after infection and the EBs are eventually released by lysis of the host cell.
Describe some features of Syphilis? (3)
- 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
What are the primary and secondary features of Syphilis?
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.
What are the 2 stages late syphilis can progress through?
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
What are some features of Treponema palladium bacterium? (5)
- Obligate, intracellular parasite.
- Fastidious, Gram negative.
- Helically coiled, corkscrew shaped.
- 6 –10 μm long and 0. 15 μm 1 – 0.2 μm wide.
- Relies on host cells for nutrients, making it hard to culture in lab.
Describe the structure of Treponema palladium (4)
- 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.
What are the virulence factors of Treponema palladium? (3)
- Outer membrane proteins associated with adherence
- Can produce hyaluronidase, may allow perivascular infiltration
- Coated with host cell fibronectin – protects against phagocytosis
What are the main diagnostic techniques of Treponema palladium? (3)
1) Microscopy:
- Dark field illumination.
- Direct immunofluorescence antibody staining.
2) Culture:
- Generally unsuccessful
3) Serology:
- Non-treponemal – detect IgG and IgM antibodies in early stages of disease.
- Treponemal – specific antibody tests.
- Fluorescent Treponemal Antibody Absorption (FTA-ABS) test.
- Trepanomal Palladium Haemagglutinin test (TPPA, TPHA).
