Microbiology of the Vagina and Penis - Skildum Flashcards Preview

Hormonal & Reproductive Week 6 - WLB > Microbiology of the Vagina and Penis - Skildum > Flashcards

Flashcards in Microbiology of the Vagina and Penis - Skildum Deck (33)
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1
Q

What does the normal microbial communities of the vagina consist of?

A

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.

2
Q

What are the three products of Lactobacilli that help maintain the microbiota of the vagina?

A
  1. Lactic acid: through anaerobic fermentation, decreases pH (lactic acid makes environment more hostile to other pathogens, lactate is substrate for immune system)
  2. Hydrogen peroxide; hydroxyl radicals (makes hostile environment)
  3. Bacteriocins proteins that depolarize pathogenic bacteria => kill bacteria
3
Q

What does the vaginal microbial community depend on for maintaining healthy colonies of Lactobacilli?

A

Estrogen!

Estrogen causes vaginal epithelial expansion => vaginal epithelial glycogen production => epithelial cell sloughing => extracellular glycogen converted to glucose => Glucose taken up by lactobacilli

4
Q

Why do pre-pubertal and post-menopausal women have different microbial communities with less robust pathogen defense activity?

A

decreased estrogen production

less glucose for lactobacilli to utilize

5
Q

What are the two ways (enzymes) Lactobacilli can utilize to make hydrogen peroxide?

A
  1. From pyruvate via Pyruvate oxidase (requires oxygen)

2. From glucose via Glucose oxidase

6
Q

Hydrogen peroxide does not inhibit the growth of what common vaginal pathogen?

A

Gardnerella vaginosis

7
Q

What are Bacteriocins? Primary fxn?

A

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.

8
Q

Which molecule has an inhibitory effect on other pro-inflammatory cytokines?

A

IL-10

9
Q

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)

A

D. Toll Like Receptors (TLR)

10
Q

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
A

B. Mycoplasma genitalium => has no cell wall

Ceftriaxone = cell wall inhibitor

11
Q

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
A

D. On MHC II

12
Q

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

A

C. Transduction

13
Q

What is different about the non-dominant lactobacilli microbiotos of healthy females?

A

pH slightly higher more basic (5.3 – 5.5)

14
Q

What causes bacterial vaginosis?

A

Not caused by a single pathogen!!!!

***It is a DISRUPTION of the normal vaginal microflora!

15
Q

What type of bacteria is typically most abundant in BV patients?

A

Gardnerella vaginalis

16
Q

BV is associated with increasing concentrations of what bacteria?

A

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)
17
Q

How does Metronidazole treat bacterial vaginosis?

A

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

18
Q

What damage does PID cause in the upper reproductive tract?

A

selective loss of ciliated epithelial cells in the fallopian tube

can result in infertility or ectopic pregnancy

19
Q

What does the microscopic examination of vaginal samples show in PID?

A

Clue cells

20
Q

What pathogens cause PID?

A

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)

21
Q

What is the treatment for PID?

A

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.

22
Q

What signs/symptoms characterize Toxic shock syndrome (TSS)?

A

fever
diffuse rash
hypotension
organ dysfunction: renal, hepatic, muscle, etc.

23
Q

90% of TSS cases are associated with what pathogen?

A

Staphyloccus aureus

Strep pyogenes accounts for the rest

24
Q

What is the pathogenesis of TSS?

A

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

25
Q

How does Staph aureus produce the Superantigen in TSS?

A

TSST-1 is encoded on the SaPI1 pathogenicity island spread by phage transduction.

Thus a community of S. aureus that is in benign equilibrium with the vaginal microbiome can become pathologic quickly if SaPI1 spreads through the community.

26
Q

Do patients with Toxic Shock Syndrome have positive S. aureus blood cultures?

A

Rarely

27
Q

Do patients with S. aureus sepsis (bacteria present in blood) get Toxic Shock Syndrome?

A

Rarely

28
Q

What does the normal microbiome of the penis consist of?

A

The penis microbiome in healthy males is similar to the vaginal microbiome in healthy reproductive age women: dominated by lactobacillus.

29
Q

What may be a consequence of having reduced Lactobacillus in the penis microbiome?

A

Infection

Infection with an STI is associated with a depletion of lactobacillus.

30
Q

What effect does circumcision have on HIV-1 transmission?

A

Decreased potential for HIV-1 transmission

Circumcission => alters microbiome/macrophages further from surface => less chance of HIV

31
Q

How does circumcision shifting the normal microbial community towards aerobic bacteria help prevent infection?

A

reduces inflammation and reduces the number of CD4+/CCR5+ macrophages in the urethra

32
Q

What are the common causes of Epididymitis in Prepubertal boys, men 35?

A

Prepubertal boys: Escherichia coli

Men younger than 35 years: Chlamydia trachomatis, Neisseria gonorrheae

Men 35 years and older: E coli, Pseudomonas species

33
Q

What does the normal microbiome of the prostate consist of?

A

Trick question!

It is not known whether there is a ‘prostate microbiome’ or ‘normal prostate microflora’.