SW - STIs Flashcards

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1
Q

What bacterium is predominant in the vaginal microbiome?

A

Lactobacilli

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2
Q

What are some features of Lactobacilli? (3)

A
  • Lactobacilli pre-dominant colonisers.
  • Inhibit growth of pathogenic organisms.
  • Adhere to vaginal cells and prevent long-term colonisation by other species.
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3
Q

What 3 things do Lactobacilli produce?

A

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

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4
Q

What organisms do lactobacilli inactivate? (6)

A

Can inactivate

  • HIV-1
  • herpes simplex virus type 2
  • Trichomonas vaginalis
  • Gardnerella vaginalis
  • Peptostreptococcus bivia
  • E. coli
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5
Q

Describe the antimicrobial activity of semen (3)

A

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
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6
Q

What are some features of Gonorrhoea? (2)

A
  • Infection caused by the bacterium, Neisseria gonorrhoeae.
  • Uncomplicated infection is localised, usually affecting the mucous membranes of urethra, endocervix, rectum, pharynx and conjunctiva
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7
Q

What are some complications of gonorrhoea in men vs women

A

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.
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8
Q

What is Neisseria gonorrhoeae? (5)

A
  • 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.
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9
Q

What are the virulence factors of gonorrhoeae? (7)

A

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.

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10
Q

What are some features of Chlamydia and how it infects men vs women?

A

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).
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11
Q

What technique can be used to confirm diagnosis of Chlamydia?

A

NAATs

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12
Q

What are the virulence factors of Chlamydia? (5)

A
  • 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.
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13
Q

How does chalmydia replicate?

A

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.
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14
Q

Describe some features of Syphilis? (3)

A
  • 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
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15
Q

What are the primary and secondary features of Syphilis?

A

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.
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16
Q

What are the 2 stages late syphilis can progress through?

A

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

17
Q

What are some features of Treponema palladium bacterium? (5)

A
  • 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.
18
Q

Describe the structure of Treponema palladium (4)

A
  • 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.
19
Q

What are the virulence factors of Treponema palladium? (3)

A
  • Outer membrane proteins associated with adherence
  • Can produce hyaluronidase, may allow perivascular infiltration
  • Coated with host cell fibronectin – protects against phagocytosis
20
Q

What are the main diagnostic techniques of Treponema palladium? (3)

A

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).