Describe the main sexually transmitted pathogens from a microbiology point of view (pathogen classification, virulence, transmission mechanisms and diagnosis method)

Question 1

What is this?

Answer 1

The treponemal antibody absorption test for syphilis

Question 2

What are obligate intracellular bacterium?

Answer 2

microparasites that are capable of growing and reproducing inside the cells of a host

Question 3

How is virulence defined in HIV?

Answer 3

as the rate of progression to AIDS in untreated infections

Question 4

How is Neisseria gonnorrhoeae sexually transmitted?

Answer 4

the pathogen induces a discharge that allows spread through close sexual contact

Question 5

Which virulence factor assists the binding of Neisseria gonnorrhoeae to epithelial cells?

Answer 5

Opa proteins

Question 6

How do LOS (lipooligosaccharide) contribute to the virulence of Neisseria gonnorrhoeae?

Answer 6

endotoxin activity

Question 7

How does T. pallidum spread vertically?

Answer 7

via transplacental infection of the fetus

Question 8

What is the virulence of chlamydia trachimatis

Answer 8

the fact that it is an obligate intracellular bacterium

Question 9

How do pilus contribute to the ability of Neisseria gonnorrhoeae to cause an STD?

Answer 9

they contain constant and hypervariable regions that contribute to antigenic diversity in gonocci

Question 10

What are 4 features of non-specific syphilis tests?

Answer 10

1. they show up as positive within 4-6 weeks of infection
2. they decline in positivity in 3º syphilis or after effective antibiotic treatment of 1º/2º syphilis
3. they are useful for screening
4. they may give biological false positives

Question 11

What do ELISA tests for syphilis detect?

Answer 11

IgM and IgG

Question 12

What pathogen causes gonorrhoea?

Answer 12

Neisseria gonnorrhoeae

Question 13

Which pathogen causes chlamydia?

Answer 13

chlamydia trachimatis

Question 14

How is HIV classified?

Answer 14

the human immunodeficiency virus is a retrovirus

Question 15

How does T. Pallidum enter the body?

Answer 15

Through minute abrasions on the skin or mucous membranes

Question 16

What do laboratory tests for HIV infection involve?

Answer 16

1. serological analysis
2. molecular analysis

Question 17

What pathogen causes syphilis?

Answer 17

Treponema pallium

Question 18

What are the 3 most common mucosal surfaces that provide a transmission route for HIV?

Answer 18

1. cervicovaginal
2. penile
3. rectal

Question 19

Which sexually transmitted disease is linked with cervical cancer?

Answer 19

the human papillomavirus

Question 20

How does IgA protease contribute to the virulence of Neisseria gonnorrhoeae?

Answer 20

core contains an enzyme that is released by the cell to destroy IgA1

Question 21

Which virulence factor aids attachment of Neisseria gonnorrhoeae to human mucosal epithelium?

Answer 21

Pilus

Question 22

Which virulence factor allows Neisseria gonnorrhoeae to resist phagocytosis?

Answer 22

capsule

Question 23

What are the symptoms of chlamydia?

Answer 23

• pain when peeing
• bleeding after sex and bleeding between periods
• pain and swelling in the testicles

Question 24

True or false?

Neisseria gonnorrhoeae is stable on drying

Answer 24

false - it is unstable

Question 25

How do we diagnose chlamydia?

Answer 25

with a variety of nucleic-acid based tests that are commercially available

Question 26

Which 3 methods are used to diagnose gonorrhoea?

Answer 26

1. microscopy 2. culture of appropriate specimens 3. molecular tests

Question 27

What infection does *Gardnerella vaginalis* cause?

Answer 27

bacterial vaginosis

Question 28

Which *chlamydia trachimatis* serotypes cause sexually transitted genital infections?

Answer 28

serotypes D-K

Question 29

What STD is caused by *Treponema pallium*?

Answer 29

Syphilis

Question 30

What STD is caused by *Haemophilus ducreyi*?

Answer 30

Chancroid

Question 31

What type of pathogen is *Treponema pallidum*?

Answer 31

Spirochetes

Question 32

True or false? Herpes simplex virus (HSV)-1 is the most common cause of genital herpes

Answer 32

false. (HSV)-2 is the most common cause of genital herpes

Question 33

Which sexually transmitted disease is spread by *Neisseria gonnorrhoeae?*

Answer 33

Gonnorrhoea

Question 34

How does *T. pallidum* spread horizontally?

Answer 34

Through sexual contact

Question 35

How does the fluorescent treponemal antibody absorption (FTA-ABS) test work?

Answer 35

The patient's serum is absorbed with non-pathogenic treponemes to remove cross-reacting antibodies before reaction with *T. pallidum* antibodies

Question 36

What are the symptoms of HIV?

Answer 36

* Fever * Night sweats * Muscle aches

Question 37

What is the definition of antigenic?

Answer 37

A substance that causes the body to make an immune response against the substance

Question 38

What 3 pathogens could cause a genital tract infection?

Answer 38

1. *Mycoplasma hominis* 2. *M. genitalium* 3. *Ureaplasma urealyticum*

Question 39

True or false? the *T. pallidum* genome sequence does not reveal any classical virulence factors that could account for syphilis symptoms

Answer 39

True

Question 40

What are spirochetes?

Answer 40

gram-negative, motile, spiral bacteria

Question 41

What are 2 examples of opportunist STIs?

Answer 41

1. salmonellae 2. hepatitis A

Question 42

What 3 transmission routes can HIV take?

Answer 42

1. involving mucosal surfaces (\>80% of adults) 2. intravenous routes 3. percutaneous routes

Question 43

What are the symptoms of gonorrhoea?

Answer 43

* a thick green/yellow discharge from the vagina or penis * pain when peeing * itching and soreness

Question 44

Which 3 specific tests are available to diagnose syphilis?

Answer 44

1. the enzyme-linked immunosorbent assay (ELISA) 2. the fluorescent treponemal antibody absorption (FTA-ABS) test 3. the microhaemagglutination assay for *T.pallidum*

Question 45

How does *chlamydia trachimatis* infect human cells?

Answer 45

1. they bind to specific receptors on the host cells and enter the cells by ‘parasite-induced’ endocytosis 2. once inside the cell, fusion of the chlamydia-containing vesicle with lysosomes is inhibited and the EB begins its developmental cycle

Question 46

What is a retrovirus?

Answer 46

a virus that uses RNA as its genetic material

Question 47

What are the symptoms of syphilis?

Answer 47

* small sores around the genitals or bottom * a rash, usually on the hands and feet * white patches in the mouth

Question 48

What infection does *Trichomonas vaginalis* cause?

Answer 48

**vaginitis** (with copious discharge)

Question 49

How is *chlamydia trachimatis* classified?

Answer 49

it is a gram-negative bacteria that are obligate intracellular parasites

Question 50

What do por proteins do and how do they contribute to the virulence of *Neisseria gonnorrhoeae?*

Answer 50

1. form pores through outer membrane 2. antigenic

Question 51

When is congenital syphilis acquired?

Answer 51

after the first 3 months of pregnancy

Question 52

How does *chlamydia trachimatis* enter the body?

Answer 52

through minute abrasions in the mucosal surface

Question 53

How is *Neisseria gonnorrhoeae* classified?

Answer 53

It is a gram-negative coccus

Question 54

Which 2 non-specific/non-treponemal tests

Answer 54

1. the venereal disease laboratory (VDRL) test 2. the rapid plasma reagin (RPR) test

Question 55

What type of cell does HIV initially target? What are 3 examples of these cells?

Answer 55

CD4 receptor-bearing cells 1. T-helper cells 2. monocytes 3. macrophages

Question 56

What is horizontal spread?

Answer 56

transmission of organisms between humans that are not parent + child

Question 57

What is the window period for detecting HIV?

Answer 57

7-21 days

Question 58

What pathogen causes HIV?

Answer 58

Human immunodeficiency virus