Describe the main sexually transmitted pathogens from a microbiology point of view (pathogen classification, virulence, transmission mechanisms and diagnosis method) Flashcards
What is this?
The treponemal antibody absorption test for syphilis
What are obligate intracellular bacterium?
microparasites that are capable of growing and reproducing inside the cells of a host
How is virulence defined in HIV?
as the rate of progression to AIDS in untreated infections
How is Neisseria gonnorrhoeae sexually transmitted?
the pathogen induces a discharge that allows spread through close sexual contact
Which virulence factor assists the binding of Neisseria gonnorrhoeae to epithelial cells?
Opa proteins
How do LOS (lipooligosaccharide) contribute to the virulence of Neisseria gonnorrhoeae?
endotoxin activity
How does T. pallidum spread vertically?
via transplacental infection of the fetus
What is the virulence of chlamydia trachimatis
the fact that it is an obligate intracellular bacterium
How do pilus contribute to the ability of Neisseria gonnorrhoeae to cause an STD?
they contain constant and hypervariable regions that contribute to antigenic diversity in gonocci
What are 4 features of non-specific syphilis tests?
- they show up as positive within 4-6 weeks of infection
- they decline in positivity in 3º syphilis or after effective antibiotic treatment of 1º/2º syphilis
- they are useful for screening
- they may give biological false positives
What do ELISA tests for syphilis detect?
IgM and IgG
What pathogen causes gonorrhoea?
Neisseria gonnorrhoeae
Which pathogen causes chlamydia?
chlamydia trachimatis
How is HIV classified?
the human immunodeficiency virus is a retrovirus
How does T. Pallidum enter the body?
Through minute abrasions on the skin or mucous membranes
What do laboratory tests for HIV infection involve?
- serological analysis
- molecular analysis
What pathogen causes syphilis?
Treponema pallium
What are the 3 most common mucosal surfaces that provide a transmission route for HIV?
- cervicovaginal
- penile
- rectal
Which sexually transmitted disease is linked with cervical cancer?
the human papillomavirus
How does IgA protease contribute to the virulence of Neisseria gonnorrhoeae?
core contains an enzyme that is released by the cell to destroy IgA1
Which virulence factor aids attachment of Neisseria gonnorrhoeae to human mucosal epithelium?
Pilus
Which virulence factor allows Neisseria gonnorrhoeae to resist phagocytosis?
capsule
What are the symptoms of chlamydia?
- pain when peeing
- bleeding after sex and bleeding between periods
- pain and swelling in the testicles
True or false?
Neisseria gonnorrhoeae is stable on drying
false - it is unstable
How do we diagnose chlamydia?
with a variety of nucleic-acid based tests that are commercially available
Which 3 methods are used to diagnose gonorrhoea?
- microscopy
- culture of appropriate specimens
- molecular tests
What infection does Gardnerella vaginalis cause?
bacterial vaginosis
Which chlamydia trachimatis serotypes cause sexually transitted genital infections?
serotypes D-K
What STD is caused by Treponema pallium?
Syphilis
What STD is caused by Haemophilus ducreyi?
Chancroid
What type of pathogen is Treponema pallidum?
Spirochetes
True or false?
Herpes simplex virus (HSV)-1 is the most common cause of genital herpes
false. (HSV)-2 is the most common cause of genital herpes
Which sexually transmitted disease is spread by Neisseria gonnorrhoeae?
Gonnorrhoea
How does T. pallidum spread horizontally?
Through sexual contact
How does the fluorescent treponemal antibody absorption (FTA-ABS) test work?
The patient’s serum is absorbed with non-pathogenic treponemes to remove cross-reacting antibodies before reaction with T. pallidum antibodies
What are the symptoms of HIV?
- Fever
- Night sweats
- Muscle aches
What is the definition of antigenic?
A substance that causes the body to make an immune response against the substance
What 3 pathogens could cause a genital tract infection?
- Mycoplasma hominis
- M. genitalium
- Ureaplasma urealyticum
True or false? the T. pallidum genome sequence does not reveal any classical virulence factors that could account for syphilis symptoms
True
What are spirochetes?
gram-negative, motile, spiral bacteria
What are 2 examples of opportunist STIs?
- salmonellae
- hepatitis A
What 3 transmission routes can HIV take?
- involving mucosal surfaces (>80% of adults)
- intravenous routes
- percutaneous routes
What are the symptoms of gonorrhoea?
- a thick green/yellow discharge from the vagina or penis
- pain when peeing
- itching and soreness
Which 3 specific tests are available to diagnose syphilis?
- the enzyme-linked immunosorbent assay (ELISA)
- the fluorescent treponemal antibody absorption (FTA-ABS) test
- the microhaemagglutination assay for T.pallidum
How does chlamydia trachimatis infect human cells?
- they bind to specific receptors on the host cells and enter the cells by ‘parasite-induced’ endocytosis
- once inside the cell, fusion of the chlamydia-containing vesicle with lysosomes is inhibited and the EB begins its developmental cycle
What is a retrovirus?
a virus that uses RNA as its genetic material
What are the symptoms of syphilis?
- small sores around the genitals or bottom
- a rash, usually on the hands and feet
- white patches in the mouth
What infection does Trichomonas vaginalis cause?
vaginitis (with copious discharge)
How is chlamydia trachimatis classified?
it is a gram-negative bacteria that are obligate intracellular parasites
What do por proteins do and how do they contribute to the virulence of Neisseria gonnorrhoeae?
- form pores through outer membrane
- antigenic
When is congenital syphilis acquired?
after the first 3 months of pregnancy
How does chlamydia trachimatis enter the body?
through minute abrasions in the mucosal surface
How is Neisseria gonnorrhoeae classified?
It is a gram-negative coccus
Which 2 non-specific/non-treponemal tests
- the venereal disease laboratory (VDRL) test
- the rapid plasma reagin (RPR) test
What type of cell does HIV initially target? What are 3 examples of these cells?
CD4 receptor-bearing cells
- T-helper cells
- monocytes
- macrophages
What is horizontal spread?
transmission of organisms between humans that are not parent + child
What is the window period for detecting HIV?
7-21 days
What pathogen causes HIV?
Human immunodeficiency virus