Sexually Transmitted Infections Flashcards
Names of three important bacterial causes of STIs
Chlamydia trachomatis
Neisseria gonorrhoeae
Treponema pallidum
Main cause of damage in chlamydia, gonorrhoea and syphilis
Immune response
Serovars
Serotypes
Serovars of Chlamydia trachomatis that cause trachoma
A, B, C
Serovars of Chlamydia trachomatis that cause conjunctivitis, uro-genital tract infections, reactive arthritis, pneumonitis
D - K
Serovars of Chlamydia trachomatis that cause lymphogranuloma venereum
L1, L2, L3
Disease caused by Chlamydophila pneumoniae
Atypical pneumonia
Disease caused by Chlamydophila psittaci
Acute respiratory disease in humans
Most common STI in developed countries
Chlamydia trachomatis serovars D-K
Common sites of Chlamydia trachomatis infections (D-K)
Cervix, urethra, pharynx, rectum, conjunctiva
Chlamydial infection that results in penile and vaginal discharge
Urethritis, cervicitis
Can Chlamydia trachomatis cause pelvic inflammatory disease?
Yes
Diseases that newborns can develop from contact with maternal Chlamydia trachomatis
Conjunctivitis, pneumonia
Features of Chlamydiae
Gram negative
Small (0.25-0.8micrometers)
Peptidoglycan not detected in cell wall (not detected by Gram stain)
Weakly endotoxic, truncated LPS
An energy parasite (obligate intracellular, uses host mitochondria)
Slow replication (2-3 days)
Damage mostly caused by host immune response
Elementary body of Chlamydia trachomatis
Infectious, extracellular particle
Reticulate body of Chlamydia trachomatis
Replicative, intracellular particle
Chlamydia trachomatis infection 1) 2) 3) 4) 5) 6) 7)
1) EB binds columnar epithelial cells with adhesins
2) Enters cell via cell-mediated endocytosis
3) Prevents endosome fusion with lysosome.
4) Endosomes clump together to form an ‘inclusion’
5) EB transforms into RB in inclusion
6) RB replicate in inclusion (200-1000RBs), feed with ‘drinking straws’ inserted into cytoplasm
7) RB converted to EB, released from cell
Target of antimicrobials directed against Chlamydia trachomatis
Reticulate bodies
Therefore antimicrobial has to be able to penetrate tissues and cells
Effect of interferon gamma on Chlamydia
RB phase is prolonged
Leads to low-level chronic inflammation
Cells that release interferon gamma
Activated CD4, CD8, macrophages
Damage caused by the immune response to a Chlamydial infection
1)
2)
3)
4)
1) Infected epithelial cells release chemokines, leading to an influx of neutophils, monocytes, DCs, NKs
2) T and B cells activated, T cells lead to a persistence of RB stage (IFN gamma). These cells and macrophages form follicles
3) Chlamydial heat shock protein 60 (hsp60) also contributes to chronic inflammation
4) Inflammation leads to scarring
Preferred method of testing for Chlamydia
PCR of samples (discharge, first-pass urine)
Treatment of Chlamydia
Tetracycline or macrolide antibiotics, given over a long period (good tissue penetration)
Single, long-acting dose of azithromycin
Neisseria gonorrhoeae features
Gram negative Diplococcus Often intracellular Extremely fastidious, doesn't survive drying, disinfectants Grows best in high-CO2 environment
