Sexually transmitted infections

Question 1

what is the predominant colonising species of the vaginal microbiome

Answer 1

Lactobacillus

Question 2

how does lactobacillus inhibit growth of pathogenic species in the vagina

Answer 2

• Produce lactic acid – helps maintain low pH. (prevents growth of many invading species)
• Adhere to vaginal epithelial cells (create biofilm) and prevent long-term colonisation by other species.
• Produce hydrogen peroxide (antimicrobial compound)– inhibits growth of other microorganisms directly or via human myeloperoxidase
• produce antimicrobial peptides - bacteriocins

Question 3

what pathogens can be inactivated by lactobacillus in the vaginal microbiome

Answer 3

HIV-1, herpes simplex virus type 2, Trichomonas vaginalis, Gardnerella vaginalis, Peptostreptococcus bivia and E. coli.!!!

Question 4

what antimicrobial components of semen

Answer 4

antibacterial peptides including: 
–	Lysozyme
–	Lactoferrin
–	Phospholipase A2
–	Secretory leukocyte protease inhibitor
–	Semenogelin 1-derived peptides

Question 5

give some features of gonorrhoea

Answer 5

caused by Neisseria gonorrhoeae. different manifestations, characterised by symptoms and disease profile. can be uncomplicated or disseminated.

Question 6

how is gonorrhoea transmitted

Answer 6

almost always transmitted sexually in adults:
– genital – genital; genital – anorectal; orogenital; oro – anal
– autoinoculation of the eye

Question 7

where is the uncomplicated gonorrhoeal infection found

Answer 7

localised, affecting the mucous membranes of urethra, endocervix, rectum, pharynx and conjunctiva.

Question 8

whats the difference between uncomplicated and disseminated gonorrhoea

Answer 8

Uncomplicated infection is localised, usually affecting the mucous membranes of urethra, endocervix, rectum, pharynx and conjunctiva.
Less common (< 1% people) is disseminated gonorrhoea – (spreads to other areas of the body) can present as septic arthritis or dermatitis

Question 9

what are the complications of gonorrhoea for men

Answer 9

epididymitis, penile lymphangitis, per-urethral abscess, acute prostatitis, seminal vesiculitis.

Question 10

what are the complications of gonorrhoea for women

Answer 10

• Bartholin’s abscess
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

Question 11

give 5 features of Neisseria gonorrhoeae

Answer 11

Fastidious, Gram negative diplococci.

Facultatively intracellular

Question 12

what are the virulence factors of Neisseria gonorrhoeae

Answer 12

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 bacteriacidal action of semen.
IgA protease – destroys IgA1.
Capsule - can resist phagocytosis.

Question 13

what is used for the initial diagnosis of gonorrhoea

Answer 13

Nucleic acid amplification tests (NAATs) (gonorrhoea is hard to grow this is better than culture methods)

Question 14

what is the current treatment for gonorrhoea

Answer 14

a single dose of 500 mg of intramuscular ceftriaxone.

Question 15

what is the most common curable STI in the UK

Answer 15

Chlamydia

Question 16

what is chlamydia caused by

Answer 16

obligate intracellular bacterium, Chlamydia trachomatis

Question 17

where does Chlamydia trachomatis infect in men

Answer 17

the urethra

Question 18

where does Chlamydia trachomatis infect in women

Answer 18

endocervix or urethra or both.

Question 19

what percentage of chlamydia infections are asymptomatic

Answer 19

At least 70% women/50% men

Question 20

what are the two types of chlamydia infection, how do they differ

Answer 20

• Uncomplicated – if not ascended into upper genital tract.

* Complicated – if in upper genital tract, causing pelvic inflammatory disease (PID) (women), epididymo-orchitis (men).

Question 21

what complications can chlamydia cause

Answer 21

• 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.

Question 22

how is chlamydia diagnosed

Answer 22

Nucleic acid amplification tests (NAATs)

Question 23

what are the virulence factors of Chlamydia trachomatis

Answer 23

• 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. – harder to target
• Needle-like projection type III secretion apparatus – injects bacterial proteins into cell cytoplasm, avoids lysosomes. – so it isn’t registered as foreign as quickly
• Infested vacuole can divert lipids to itself rather than another part of the host cell.

Question 24

describe the unique lifecycle of Chlamydia trachomatis

Answer 24

metabolically inert, spore-like elementary bodies (EBs) infect host cells and develop into metabolically active, replicative reticulate bodies (RBs) within a membrane-bound inclusion. RBs redifferentiate into EBs 24–48 hours after infection (once they reach a certain number) and the EBs are eventually released by lysis of the host cell and go on to infect other host cells

Question 25

how is syphilis transmitted

Answer 25

Person to person transmission via direct contact with infectious lesions

Question 26

what causes syphilis

Answer 26

Spirochete bacterium, Treponema palladium.

Question 27

what are the symptoms of primary syphilis

Answer 27

painless ulcer (chancre), commonly affecting genitals, and localised lymphadenopathy

Question 28

what are the symptoms of secondary syphilis

Answer 28

severe multisystem
–	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.

Question 29

what are the stages of syphilis infection

Answer 29

• Primary - easily treated and cured with medication
• Secondary - symptoms will go away, even if you don’t get treated. But if you’re not treated, your infection will get worse
• 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. (bale to confirm infection)
Tertiary – rare due to widespread antibiotic use. Divided into neurosyphilis, cardiovascular and gummatous syphilis. can cause death

Question 30

give some features of treponema palladium

Answer 30

• Obligate, intracellular parasite.
• Fastidious, Gram negative.
• Helically coiled, corkscrew shaped.
• 6 –10 μm long and 0. 15 μm – 0.2 μm wide.
• Relies on host cells for nutrients, making it hard to culture in lab

Question 31

what is the structure of Treponema palladium

Answer 31

Outer sheath composed of glycosaminoglycan.
Outer membrane contains peptidoglycan and maintains structure.
Axial filament (endoflagella) – inside the inner membrane which provides osmotic stability and covers the protoplasmic cylinder and structure

Question 32

how do Treponema palladium replicate

Answer 32

transverse fission (binary fission along the transverse axis)

Question 33

what are the virulence factors of Treponema palladium

Answer 33

• Outer membrane proteins associated with adherence.
• Can produce hyaluronidase, may allow perivascular infiltration.
• Coated with host cell produced fibronectin – protects against phagocytosis. -disguise

Question 34

what serological tests can be used to diagnose syphilis

Answer 34

• 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).

Question 35

how is syphilis diagnosed

Answer 35

Microscopy:
•	Dark field illumination.
•	Direct immunofluorescence antibody staining.
Culture:
•	Generally unsuccessful.
Serology

Question 36

when were the first written records of syphilis

Answer 36

• 1st written records of a European outbreak come from 1494/5.

Question 37

when was treponema palladium first identified

Answer 37

1905

Question 38

what were the Tuskegee & Guatemala studies

Answer 38

uninformed human subjects infected with syphilis
• Study by US Public Health Service, started in 1932.
• Widespread problem and no effective, safe treatment.
• Measure progression of untreated disease.
• By 1947, penicillin was being used but it wasn’t until 1960’s that it was found that many participants had not been given this.
• Predominantly black male participants and not until 1972 that study was stopped.