Lecture 26 - Sexually Transmissable Infections 1 Flashcards
Which general organisms can cause STIs?
- Bacteria
- Viruses
- Protozoans
- Fungi
- Arthropods (lice)
Which bacteria cause STIs?
- Chlamydia trachomatis
- Neisseria gonorrhoeae
- Treponema pallidum
Where do STIs cause infection?
Female: all areas of genital tract • vaginitis • cervicitis • endometritis • salpingitis • urethritis
Male: • urethritis • epididymitis • proctisis • prostatitis
What is the name for inflammation of the Fallopian tubes?
Salpingitis
Why is dealing with STIs difficult?
- Stigma
- Embarrassment
- Morals
- Tendency to ignore the infection
→ even though we have good treatment and prevention, we can’t eradicate them
What can salpingitis lead to?
Infertility
What are the common features of STIs?
- Shared mode of transmission
- Shared mode of prevention
• All may be asymptomatic
How is HIV transmitted
• Sexual route
Also, other routes:
• needles
• congenital
What does ‘STIs hunt in packs’ mean?
More than one infectious rate present at once
One infection facilitates the uptake of other agents as well
Under what conditions is HIV transmission rate increased?
Underlying STI → altered barriers
Can an infection be transmitted from asymptomatic individuals?
Yes
What is the main cause of damage in STIs?
Immune response
What are the animal reservoirs of the bacteria causing STIs?
No animal reservoir
Human pathogens only
In general, how are STIs treated?
Antibiotics
In general, how are STIs prevented?
Condoms
Which is one of the most common STI in young people in Australia?
Chlamydia
What infections do Chlamidia trachomatis serovars A,B and C cause?
Trachoma
What is trachoma?
How is it caused?
Ocular infection, scarring of eye and eyelids
Repeated infection with Chlamydia
Especially seen in Aboriginal populations in Australia
How can trachoma transmission be stemmed?
Eye washing
Because flies move the eye secretions between individuals
What do serovars D-K cause?
- Conjunctivitis
- Urogenital tract infections
- Reactive arthritis
- Pneumonitis
What do serovars L1-L3 cause?
Where are these infections commonly seen?
• Lymphogranuloma venereum
- Invades lymph nodes of genital tract
- Abscesses form
- Africa, India, South America
What does Chlamydophila pneumoniae cause?
Atypical pneumonia
What does Chlamydophila psittaci cause?
What is this infection associated with?
Acute respiratory disease
Associated with birds
How many cases per year of C. trachomatis in Victoria?
Why so many?
10,000
People don’t know they have it
Which sites are commonly infected with serovars D-K?
Cervix Urethra Pharynx Rectum (Conjunctivitis)
May also be:
- endometritis
- salpingitis
- epididymitis
- proctitis
What does serovar D-K infection present as?
Discharge in males and females
Watery (non-puralent)
Can chlamydia be spread congenitally?
Yes, during vaginal delivery, bacteria may get into eye or be inhaled
Conjunctivitis
Pneumonia
Describe the morphology of Chlamydiae spp.
Gram negative
V. small
No peptidoglycan
Why can Chlamydiae spp. be gram stained?
No peptidoglycan → can’t be gram stained
Describe the LPS in Chlamidae spp.
Truncated
Not very endotoxic
Describe the replication of Chlamydia spp.
Obligate intracellular replication
because it is an energy parasite (required ATP)
2 stages:
• Elementary body (EB)
• Reticulate body (RB)
How do we culture Chlamydia?
Must be cultured in cells
Because it is an energy parasite
What are the EB and RB ?
EB: non-replicating
• infectious
• extracellular
RB: actively replicating
• intracellular
• non-infectious
Which cells does Chlamidae spp. infect?
Columnar epithelial cells
Describe Chlamydia entry into cells
- EB bind with adhesins
- Receptor mediated endocytosis
- Lysosome doesn’t fuse
- Inclusion forms
- EB → RB
- RBs replicate inside inclusions
- RB → EB
- EB released in secretions
- Spread to other people
What is an inclusion?
Fusion of endosomes containing chlamydia bacteria
Contain 200-1000 bacteria
How do bacteria in an inclusion get nutrients?
‘Drinking straws’ inserted into host cytoplasm
Which form of chlamydia is susceptible to anti-microbial agents?
Reticulate bodies only
What is the effect of IFN-gamma on chlamydia?
Where is this coming from?
- Prolonged RB phase
- Persistance
- Low grade chronic inflammation
IFN-gamma is coming from activated T cells
Describe the immune response to chlamydia
- Infected epithelial cells produce chemokines and other inflammatory mediators
- Influx of neutrophils, monocytes, DC, NK
- T and B cell activation
- Lymphocytes and macrophages form follicles
- Chronic inflammation
- Scar tissue formation
What toxin that chlamydia produces can cause damage?
hsp60
Heat shock protein
Persistent inflammation
How do we diagnose chlamydia infection?
- Collect sample
2a. PCR
2b. EIA, immunofluorescence
What samples are collected for diagnosing chlamydia?
Cervical and urethral swabs
First pass urine
How is chlamydia infection treated?
Why these ones?
Tetracycline
Macrolide antibiotics
Azithromycin
They are good at penetrating into the cells
Describe the morphology of Neisseria gonorrhoeae
Gram negative
Diplococcus
Is Neisseria gonorrgoeaea hardy?
Not at all
Susceptible to drying
Susceptible to disinfectants
Extremely fastidious
In what conditions do N. gonorrhoeae grow best?
CO2 enriched
What are the clinical presentations of gonorrhoea?
Similar to chlamydia
Are symptoms always seen in gonorrhoea?
Females: Asymptomatic infection is common
Males: less so
To where does N. gonorrhoea somtimes spread in females?
Ascending genital tract:
Pelvic inflammatory disease
Disseminate throughout the body
Under what circumstances will babies get gonorrhoea?
Describe the infection in babies
Congenital transmission from their mothers
Extremely purulent conjunctivitis
Which groups are most commonly infected with gonorrhoea in Australia?
Men who have sex with men
Infection from overseas
- SE Asia sex tour
Aboriginal communities
What is important about gonorrhoea infections from overseas?
More profound antibiotic resistance
Which cells are infected by N. gonorrhoeae?
Columnar epithelial cells
Describe the gonorrhoea pathogenesis
- Adhesins binds
- Replicate on cell surface
- Spread in mucosal secretions
(May occasionally infect cells and disseminate)
What are the gonorrhoeal adhesins?
Pili
Outer membrane proteins
Lipo-oligosaccharide
Describe dissemination of gonorrhoea
Strain specific
ie not all strains will do this normally
Dissemination occurs when there is poor complement and neutrophil activation (to keep it at the site)
How does gonorrhoea cause damage?
Inflammatory response
No exotoxins
Outline the inflammatory response to gonorrhoea
- LPS and peptidoglycan interat w/ PRR
- Pus, pain
- TNF production → loss of ciliated epithelial cells
- Avoidance of C’ cascade and neutrophils
Which damage is more severe, that of chlamydia or gonorrhoea?
Gonorrhoea
What does TNF production during gonorrhoea infection bring about?
Loss of ciliated epithelia
Why is there poor complement and neutrophil activation in gonorrhoea infection?
Because the altered LPS doesn’t stimulate this as well
How does gonorrhoea avoid antibody responses?
Antigenic variation
of the pili and surface proteins at high frequency
Escape the antibody response
Describe horizontal transmission of genetic material in gonorrhoea bacteria
Readily take up DNA from other sources
- plasmids
- transposons
Implications:
- rapid antibiotic resistance
How do we diagose gonorrhoeal infection?
- Swab collection, discharge collection
- Gram stain + microscopy
Males: presence of diplococci (intracellular and extra. is diagnostic
PCR
Which samples must be collected in order to perform PCR?
Urine
Vaginal swab
How do we culture N. Gonorrhoeae?
GC: gonoccocus medium
or Chocolate agar
Fastidious
Need to select out normal flora in sample
Won’t grow on HBA
Describe the bi-plate
Both sides: lysed HBA (GC)
One side: antibiotic
- only gonococci will gorw
Other side: no antibiotics
This allows us to find the gonococci amongst the normal flora
Describe treatment of gonorrhoea
Check guidelines for ‘Empiral’ treatment
Beta-lactamase resistance cephalosporin
- Ceftriaxone
Azithromycin
What does Treponema pallidum cause?
Syphilus
Describe morphology and staining of T. pallidum
Spirochete: spiral rod
Can’t be Gram stained
- need special Dark-ground microscopy
Describe the motility of T. pallidum
Corkscrew like movement
Periplasmic contractile flagella
Is T. pallidum hardy?
Not at all
Very labile
How do we culture T. pallidum?
non-culturable
Is syphilis common in Australia?
Rates dropped amongst homosexuals
Epidemics in heterosexuals recently
- fly-in fly-out mining communities
Can babies get syphilis?
Bacteria cross the placenta in utero
Are there always symptoms with syphilis?
Not always
Asymptomatic as well as symptomatic
In general, describe the stages of syphilis
- Infection
- Primary syphilis
- Secondary syphilis
- Tertiary syphilis
What is primary syphilis?
How long does it last?
• Local ulcer
• Chancre
(on penis)
Can be asymptomatic
• 2-6 weeks
What is secondary syphilis?
When does it occur?
How long does it last?
- Rash
- Warty genital lesions
- Lymphadenopathy
Occurs if the 1° infection isn’t treated, or if asymptomatic
• Lasts up to 6 months
How long the asymptomatic period between 2° and 3° syphilis last?
3-30 years
When will syphilis infection be transmitted from person to person?
- Local ulcer
* Disseminated bacteria
What is tertiary syphilis?
- Gummas
- Eyes
- Ears
- Heart
- Brain
How is syphilis diagnosed?
- Droplet from lesion
- Dark-ground microscopy
- PCR
- Serology
What does serology tell us about T. pallidum?
Detection of antibodies to treponemal antigens
Cross reactive antibodies
Describe the features of the Rapid plasma reagin test
Measures antibodies made against cariolipin
Highly sensitive (few false negatives) Not very specific (some false-positives) Cheap
How is syphilis treated?
Penicillin
When are gummas seen?
What are they?
Tertiary Syphilis
They are a type of granuloma
What is controlling syphilis in the asymptomatic period?
- Macrophages
- Th cells
- B cells
