block 6- sexually transmitted diseases Flashcards
(36 cards)
problems with sti’s
- Pregnancy complications
- Infertility
- Impact on health
challenges in reducing sti’s
-asymptomatic transmission= people have it but don’t know as they have no symptoms and so pass it on
-stigma= people don’t want to talk about and so don’t get checked
-antimicrobial resistance
spirochaetes
- group of bacteria with a unique spiral shape that helps them move in a corkscrew motion. They are long, thin, and have flexible bodies, which allow them to twist and spin through different environments, such as mucus or tissue.
treponema pallidum
- a type of spirochaetes
-important for global health
-obligate pathogen that can never be cultured in the lab as it only lives in humans
-small genome=limited metabolic capability
syphilis
-Transmission may be sexual or
congenital
- Congenital syphilis is
systemic and serious= bacteria in the baby via the mother. serious because babies have weak immune system
- STI has three stages of disease
with different symptoms:
-primary disease=
-secondary syphilis
-latent syphilis which can develop into tertiary syphilis
- Slow disease with latent periods
symptoms of primary syphilis
- trponema pallidium multiples at the site of infection
- 3 weeks incubation so usually don’t see the affects at first. painless. chacre (like a sore) appears and last for 2-6 weeks
symptoms of secondary syphilis
-After 2-24 weeks without
symptoms, there is bacteraemia
- Fever, headache, lesions, body rashes too
tertiary syphilis symptoms
-localised
symptoms after 3-30 years
-If syphilis remains untreated, it can eventually damage organs, including the heart, brain, nerves, eyes, and bones. This can lead to serious health issues like heart disease, mental health problems, blindness, or even death.
virulence/immune evasion in a chronic infection
- Untreated Treponema pallidum infection lasts for years
- No LPS and few outer membrane proteins – less stimulatory to the immune system - “stealth”
- Some T. pallidum antigens may modulate the immune response (influence T cell differentiation)
- Antigenic variation in outer membrane proteins= the pathogen can change its surface proteins (outer membrane proteins) to look different to the immune system. This helps it evade detection by the immune system because ach time it changes, the immune system has to start over in recognizing and fighting it.
- Invades central nervous system (less immune surveillance)
- Adhesion to extra cellular matrix proteins makes it easier to spread to tissues
diagnosis, treatment and prevention of syphilis
-Blood tests for antibodies
- Screening of all pregnant women
- Penicillin cures infection and prevents transmission
william Hinton test
-using bacterial
antigen to detect antibody) for rapid diagnostics with fewer false
positives
Jane Hinton(daughter of william)
-developed selective medium (agar) for isolation of Neisseria that is still used in diagnostics and antimicrobial susceptibility testing
-agar is supplemented with blood
(chocolate agar – brown colour) and antimicrobials:
- Nystatin (anti-fungal); vancomycin (anti-Gram-positives);
colistin (anti-Gram-negatives), trimethoprim and
sulfamethoxazole
Neisseria gonorrhoeae
-gram-negative beta proteobacteria
-oval(coffee bean) shaped diplococcus
-can be cultured in the lab
-micoscropy can be used to see the puss too
-only transmitted by intimate contact as it can only survive in humans
-obligate pathogen ,small genome
what happens when a person is infected with N.gonorrhoeae
-N. gonorrhoeae colonies the mucosa
- Adhesion to the surface
- Competition with microbiome
- Invasion of epithelial cells
- Release of virulence factors
- N. gonorrhoeae stimulates the innate immune system
- Influx of neutrophils that phagocytose bacteria
- Symptoms: pain and discharge (80% of female patients
have no symptoms), infertility, miscarriage
virulence factors of N.gonorrhoeae
-Adhesion: Opa protein and pili
- Release of peptidoglycan, lipooligosaccharides and outer membrane
vesicles, which stimulate the innate immune system
- Lipooligosaccharide (LOS) is like LPS but missing the O antigen
- Looks more like human glycosylation patterns – molecular mimicry for immune evasion
- Glycosylation on the surface helps adhesion, serum resistance, survival inside human cells
peptidoglycan-derived cytotoxin
-Peptidoglycan fragments released by N. gonorrhoeae damage epithelium of
Fallopian tubes, which may affect
fertility
diagnostic and prevention of gnoherria
– Nucleic acid amplification tests
- Microscopy
- Culture, oxidase test, catalase test
- Prevent in new-borns by screening and treating pregnant women
- Prevent in communities by protected sexual intercourse and screening
programmes to identify asymptomatic carriers
treatment and antimicrobal resistance of gnorroheria
- intravenous penicillin
- Azithromycin and a cephalosporin
- A cephalosporin and a fluoroquinolone
- Increasing cases of antimicrobial resistance (requiring second line
treatments, drug combinations, antimicrobial susceptibility testing) - GP/pharmacy awareness
“Super-gonorrhoea” &
Clinical trials of new drug
latent stages symptoms
-There are no noticeable symptoms during this stage, but the bacteria are still in the body. Some people may stay in this stage for years.
-Timing: This stage can last for years, and some people may never have symptoms again.
outer membrane proteins in N.menigitidus
- In N. meningitidis five classes of OMPs depending on molecular weight
- PorA and PorB are porins; anti-PorA antibodies
are bactericidal for N.meningitidis; PorB affects maturation of phagosome - Opa proteins are important for adherence and rearrangement of cytoskeleton
- Factor H-binding protein (fHBP) is critical forsurvival in the human
hos
two partner secretion systems
-gram neg proteins have two membranes and so need a special secretion system
-composed of TpsA and TpsB.
-TpsA= secreted through the I inner membrane via the SecA system.
-TpsB= outer membrane protein interacts with TpsA
-and aids its transport through the outer membrane
-Up to 5 Tps in N. meningitidis
* These systems are involved in adhesion and biofilm production
N.meninitidis infection and diseases
-* Septicaemia
* Meningitis (mainly affects babies, young children,
young adults)
* Pneumonia (elderly patients)
* Urogenital infections
N.meningitidis septicaemia
-Meningococcemia is an acute
and potentially life-threatening
infection of the bloodstream
leading inflammation of the
blood vessels (vasculitis). It
has a high mortality rate.
Symptoms:
high fever
characteristic rash
headache
neck stiffness
coma
meningitis
-N.meningitidis septicaemia can lead to this
-It is Inflammation of the meninges, the
protective membranes of the brain and spinal cord.
Symptoms:
* Headache
* High fever
* Neck stiffness
* Intolerance of light
* Characteristic rash
