Microbiology of the Vagina and Penis - Skildum Flashcards
What does the normal microbial communities of the vagina consist of?
In ~80% of healthy women, lactobacilli are the dominant microorganisms.
Lactobacilli are gram positive rods/bacilli, facultative anaerobes
*Lactobacilli iners, *L. gasseri, L. cripsatus and L. jensenii are the most common.
What are the three products of Lactobacilli that help maintain the microbiota of the vagina?
- Lactic acid: through anaerobic fermentation, decreases pH (lactic acid makes environment more hostile to other pathogens, lactate is substrate for immune system)
- Hydrogen peroxide; hydroxyl radicals (makes hostile environment)
- Bacteriocins proteins that depolarize pathogenic bacteria => kill bacteria
What does the vaginal microbial community depend on for maintaining healthy colonies of Lactobacilli?
Estrogen!
Estrogen causes vaginal epithelial expansion => vaginal epithelial glycogen production => epithelial cell sloughing => extracellular glycogen converted to glucose => Glucose taken up by lactobacilli
Why do pre-pubertal and post-menopausal women have different microbial communities with less robust pathogen defense activity?
decreased estrogen production
less glucose for lactobacilli to utilize
What are the two ways (enzymes) Lactobacilli can utilize to make hydrogen peroxide?
- From pyruvate via Pyruvate oxidase (requires oxygen)
2. From glucose via Glucose oxidase
Hydrogen peroxide does not inhibit the growth of what common vaginal pathogen?
Gardnerella vaginosis
What are Bacteriocins? Primary fxn?
proteins produced by bacteria that are lethal to other bacteria
***Bacteriocins form a pore in the target cell’s membrane, resulting in depolarization and outflow of cytoplasmic contents.
Which molecule has an inhibitory effect on other pro-inflammatory cytokines?
IL-10
What receptors recognize common molecular patterns in pathogens and mediate inate immune response such as cytokine and chemokine production?
A. Major Histocompatibility Complex I (MHC I)
B. Major Histocompatibility Complex II (MHC II)
C. T Cell receptors
D. Toll Like Receptors (TLR)
D. Toll Like Receptors (TLR)
Which pathogen is least likely to be sensitive to ceftriaxone?
A. Escherischia coli B. Mycoplasma genitalium C. Neisseria gonorrheae D. Staphylococcus aureus E. Streptococcus pyogenes
B. Mycoplasma genitalium => has no cell wall
Ceftriaxone = cell wall inhibitor
After a bacteria is phagocytosed and digested by a macrophage, how are its antigens presented to cells of the immune system?
A. Between Va and Vb domains of the T cell receptor B. On the B cell receptor (IgM) C. On MHC I D. On MHC II E. On CD4
D. On MHC II
Bacteria are more harmful if they carry genomic pathogenicity islands, which often encode toxins. Transfer of the Staphylococcus aureus SAPI1 pathogenicity island depends on _______________.
A. Conjugation
B. Mutation
C. Transduction
D. Transformation
C. Transduction
What is different about the non-dominant lactobacilli microbiotos of healthy females?
pH slightly higher more basic (5.3 – 5.5)
What causes bacterial vaginosis?
Not caused by a single pathogen!!!!
***It is a DISRUPTION of the normal vaginal microflora!
What type of bacteria is typically most abundant in BV patients?
Gardnerella vaginalis
BV is associated with increasing concentrations of what bacteria?
Anaerobic:
***Gardnerella vaginalis (gram variable, facultative anaerobic bacilli)
Mycoplasma hominis (tiny, lack a cell wall, require cholesterol in growth media) Mobiluncus sp. (gram negative, anaerobic, motile curved rod) Atopobium vaginae (gram positive, anaerobic, elliptical cocci or rod shaped)
How does Metronidazole treat bacterial vaginosis?
Metronidazole can only be reduced to its active form in anaerobic organisms.
Once active it:
1) Interferes with bacteria’s fuel metabolism
2) Generates reactive nitrogen, damaging nucleic acids
What damage does PID cause in the upper reproductive tract?
selective loss of ciliated epithelial cells in the fallopian tube
can result in infertility or ectopic pregnancy
What does the microscopic examination of vaginal samples show in PID?
Clue cells
What pathogens cause PID?
Most common: Neisseria gonorrhoeae
(gram negative diplococci, non-motile, not acid fast, oxidase positive)
Most common: Chlamydia trachomatis
(gram negative, obligate intracellular parasite)
Haemophilus influenza - often accompany Neisseria and Chlamydia
(gram negative coccobacilli)
Streptococcus pyogenes - often accompany Neisseria and Chlamydia
(gram positive chained cocci, facultative anaerobic)
Rare causes: Streptococcus pneumonia, Escherischia coli, Klebsiella sp., Proteus mirabilis
Emerging cause: Mycoplasma genitalium
(tiny, lack a cell wall, require cholesterol in growth media)
What is the treatment for PID?
Ceftriaxone (or Cefoxitin): Cephalosporin derivatives that binds penicillin binding proteins and inhibits bacterial cell wall synthesis, resulting in osmotic imbalance and death of dividing cells. It is effective against bacteria that produce b-lactamase.
Doxycycline: Binds to bacteria’s 30S ribosome and prevents tRNA binding, preventing protein synthesis.
+/- Metronidazole: Action require a redox reaction only possible in anaerobes.
What signs/symptoms characterize Toxic shock syndrome (TSS)?
fever
diffuse rash
hypotension
organ dysfunction: renal, hepatic, muscle, etc.
90% of TSS cases are associated with what pathogen?
Staphyloccus aureus
Strep pyogenes accounts for the rest
What is the pathogenesis of TSS?
Superantigens produced by bacteria bind both TCR and MHC II, creating an immunological synapse without any specific antigen.
This causes systemic activation of T cells regardless of the specificity of their TCR.
Th1 response: IL-2 and IFNg + Macrophage response: IL-1 and TNF
