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Reproductive > 7. Microbiology of the Genital and Urinary Tract > Flashcards

7. Microbiology of the Genital and Urinary Tract Flashcards

1
Q

What constitutes normal vaginal flora? Properties?

A

Lactobacilli normally dominate the vaginal flora, comprising >95% of the bacteria

Many other microorganisms are isolated from healthy women

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2
Q

What is the contribution of lactobacilli to vaginal environment?

A

Lactobacilli metabolise glucose to lactic acid, resulting in a normal vaginal pH of 3.5 to 4.6

Lactobacilli may also produce hydrogen peroxide, which is bactericidal. = Crucial role in homeostasis.

  • Maintains normal vaginal ecosystem
  • Low pH protects against exogenous organisms
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3
Q

What constitute normal vaginal secretions?

A

Normal secretions are a heterogenous suspension of epithelial cells and Lactobacilli in fluid that emanates from the cervix and vaginal walls

pH 3.5 to 4.6, no odour, no itching or irritation, off-white and heterogenous.

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4
Q

Describe the relationship between normal vaginal secretions and lactobacilli?

A

Vaginal epithelial cells contain glycogen and are continually shed into the vaginal lumen

The cells autolyse and glycogen depolymerises to glucose, which serves as an energy source for Lactobacilli bacteria.

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5
Q

Describe the ecosystem of the Female Lower Genital Tract?

A

10^9 bacterial c.f.u.’s per gram of secretions.

Variety of aerobic and anaerobic bacteria and also yeasts, viruses and parasites.

Vaginal flora will vary depending on influences of age, sexual activity, contraceptive use, pregnancy, childbirth, surgery and antimicrobial therapy

Varies from woman to woman and time to time

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6
Q

What greatly increases the risk of genital tract infection?

A

Loss of the normal Lactobacillus-dominated flora increases the likelihood of exogenous infections

e.g. exposure to STD’s and endogenous infection after childbirth and surgery

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7
Q

What are the main influences of Vaginal Flora?

A
  1. Age
  2. Sexual Activity
  3. Contraception
  4. Pregnancy and Childbirth
  5. Surgery
  6. Antibiotics
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8
Q

How does age influence vaginal flora?

A

Birth: sterile

Maternal oestrogen (few weeks): lactobacilli for a short time

Puberty: endogenous oestrogen and the vaginal flora becomes dominated by lactobacilli (commensals)

Post-menopausal: decrease in lactobacilli

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9
Q

How does sexual activity influence vaginal flora?

A

Increases in genital mycoplasma’s (low virulent pathogens)

Sexually transmitted diseases (pathogens)

  • Neisseria gonorrhoeae
  • Chlamydia trachomatis
  • Trichomonas vaginalis
  • HIV
  • Human papilloma virus
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10
Q

How does contraception influence vaginal flora?

A

Oral contraceptives:
- minimal effect on vaginal flora

Intrauterine contraceptive devices (coils):

  • Increases anaerobic bacteria in cervix, including actinomycosis.
  • Increases risk for bacterial vaginosis.
  • Increase in anaerobic bacteria (inc Actinomyces) since biofilm formed on what is essentially a foreign bodies. (risk ?after had for>7 years, change regularly)
  • Increases risk for pelvic inflammatory disease.
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11
Q

How does pregnancy and birth influence vaginal flora?

A

Progressive increase in colonisation by Lactobacilli during pregnancy

Delivery:

  • Marked increases in anaerobes by Day 3
  • Pre-disposing factors include trauma, presence of lochia, suture material, multiple vaginal examination during labour, changes in hormonal levels
  • Return to normal flora at 6 weeks postpartum

(• Increase in lactobacilli during preg
• Vaginal tears, multiple examinations during
• Labour can introduce infection
• Usually return to normal 6 weeks post partum
• In the 1st 2 weeks following childhood at risk of infection like endometritis)

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12
Q

How does surgery influence vaginal flora?

A

Major gynae procedures:

  • Decrease in lactobacilli
  • Increase in aerobic and anaerobic gram negative bacilli/rods e.g. E. coli, Bacteroides
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13
Q

How do antibiotics influence vaginal flora?

A

Decrease in ‘susceptible’ flora

Increase in ‘resistant’ flora with…

  • Inherent resistance e.g. yeasts
  • Acquired resistance
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14
Q

Describe the ecosystem of the Female Upper Genital Tract?

A

Normally sterile.

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15
Q

What causes the UGT to loose its sterility? Risk factors for this?

A

Bacteria may ascend into the uterine cavity, fallopian tubes or pelvic peritoneum.

Predisposing factors include

  • Instrumentation
  • Foreign body
  • Surgery
  • Menstruation
  • Certain infections (Chlamydia trachomatis, Neisseria gonorrhoeae)
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16
Q

What is the difficulty in isolating the cause pathogenic organisms in the female genital tract?

A

Many pathogens isolated from the genital tract do not cause disease

How to decide whether a genital tract organism requires antimicrobial therapy?

Why? Because complex interplay between

  • potentially pathogenic organism (virulence)
  • host
  • predisposing factors
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17
Q

What are considered common ‘occasional’ pathogens and also commensals? W

A

Candida species
Gardnerella vaginalis
Group B Streptococcus (Generally a perinatal pathogen only, i.e. can cause problems at birth and post partum)
Staph aureus
Bacteroides (anaerobe)
E. Coli (can be normal but can cause problems around birth )

Ureaplasma urealyticum
Mycoplasma hominis

(HVS: ALL EASILY CULTURED EXCEPT UREAPLASMA AND MYCOPLASMA = Specific media only on request).

18
Q

What are considered genital tract pathogens?

A 
Group A Streptococcus
Neisseria gonorrhoeae (NeissG+chlamydia not detected on HVS. Either lab (difficult, time factor) instead PCR is the more effective)
Chlamydia trachomatis
Trichomonas vaginalis
Herpes simplex virus
Treponema pallidum
Human papilloma virus
19
Q

What are the challenges in lab detection of gential tract pathogens? How are they overcome?

A

Challenging
Need to know specifically what you are looking for (STD’s)

Need to take appropriate specimens
Rapid transport to lab required for certain organisms

20
Q

What should be analysed on the high vaginal swab?

A

Epithelial cells Y/N (not clinically important except if none present, question whether swab was performed)

White cells
• Normal 10 >30/HPF
• Usually not raised in vaginosis

Red Cells (not particularly significant)

Clue Cells (if seen = bacterial vaginosis = not req for bv to be there)

Yeast Cells (if seen, the its probably symptomatic, only treat if symptomatic)

o Trichomonas
o Gram Stain

21
Q

Group A strep detection?

A

Easily Cultured

22
Q

Trichomonas Vaginalis

A

Microscopy or culture

23
Q

Neisseria gonorrhoeae

A

Endocervical or urethral: culture on NYC agar immediately. Also PCR.

24
Q

Chlamydia trachomatis

A

Endocervical or urethral PCR swab or first stream urine (since epithelial cells required)

25
Q

Herpes simplex virus

A

HSV: viral swab or slide

26
Q

Treponema pallidum

A

Syphilis: serum or slide of exudate for dark ground microscopy

27
Q

Human papilloma virus

A

HPV: usually clinical diagnosis

28
Q

Describe the urinary tract environment?

A

Bladder urine is normally sterile

The vaginal introitus and peri-urethral areas are colonised with various organisms

29
Q

How does urinary tract infection develop?

A

Urinary tract infection (UTI) develops from ascending infection

  • Cystitis
  • Pyelonephritis
30
Q

From where do the causative organisms of UTI’s usually originate? Why?

A

GIT

Since only aerobic and facultative species can infect the urinary tract

31
Q

What are the normal defense mechanisms of the urinary tract?

A

Males: longer urethra

Hydrodynamic factors (flushing)

Phagocytosis by polymorphs

Humoral activity (IgA)

Non-specific antibacterial substances in urethral, bladder (and prostatic) mucosa secretions

pH and chemical content

Absence of residual urine after micturition

32
Q

What are the predisposing factors for UTI?

A

Female:

  • Short urethra
  • Coitus facilitates movement of organisms up the urethra
  • Pregnancy (Ureteral compression+Progesterone effect- smooth muscle relaxation and decrease ureteral peristalsis)
  • Periurethral colonisation (personal hygiene)

Increasing age

Instrumentation

Structural abnormalities

Neurological abnormalities
- incomplete emptying, loss of sphincter control

Immunosuppression

(Prostatic hypertrophy)

33
Q

What are the common pathogens which cause UTI’s?

A
  1. E. coli
    - Some strains adhere easily to the uroepithelium and these strains are more likely to cause UTI’s than other strains
    - Most common: causes 50-75% UTI’s
  2. Proteus species (associated with urinary calculi)
  3. Klebsiella species
  4. Enterococci
  5. Staphylococcus saprophyticus (sexually active females usually)
  6. Group B Streptococci (women)
34
Q

Where UTI pathogens initially colonise?

A

Colonise the vaginal introitus/periurethral area.

35
Q

What is the relationship between Candida and UTI?

A

Candida is an uncommon cause of UTI, but a common cause of contamination (especially in women). More likely in:

  • Diabetes
  • ICU patient
  • Immunosuppressed
36
Q

What are the physiological properties of urine?

A

Bladder urine is normally sterile urine specimen passes through the urethra

Contamination is common when obtaining urine specimen (Urethral, vaginal, perineal flora).

UTI is invariably caused by a single organism (Genuine mixed infections are rare)

Mixed organisms usually indicates contamination of specimen.

37
Q

How do you enhance the quality of specimen collection?

A

Educate patient regarding appropriate specimen

Mid stream urine (MSU) = specimen of choice

If recurrent contamination, may cleanse the genitalia before collection

38
Q

What alternative methods for urine specimen collection exists?

A
  1. Bag urine (infants)
    - Contamination common
    - Cleanse skin
    - Remove promptly once urine collected
    - Often contaminated
  2. Suprapubic specimen
    - Should be sterile
    - Can be used if difficulty obtaining a MSU or clean catch specimen (e.g. infants)
  3. Catheterised specimen of urine
    - Organisms will ascend the urinary tract along the catheter or may be introduced at time of catheterisation.
39
Q

How is UTI diagnosed?

A

M.S.U.

  • No epithelial cells (urethral)
  • Raised urinary white cell count (>10 but usually 10^5 bacteria per ml (can be as few as 104 per ml)
  • Single organism

Signs of Contamination

  • Many epithelial cells
  • WCC <10^4 bacteria per ml
  • Mixed growth
40
Q

What is Sterile Pyuria?

A

Sterile pyuria is the presence of elevated numbers of white cells (>10 white cells/mm3) in urine which appears sterile using standard culture techniques.

CAUSES
Antibiotic Therapy? 
Orgs not routinely cultured? 
- Chlamydia trachomatis
- Neisseria gonorrhoeae
- Mycobacterium tuberculosis
- Mycoplasma
- Ureaplasma
- Schistosoma haematobium
41
Q

Take Home

A

Genital tract flora

  • Vary from woman to woman and time to time
  • Interpret culture results with patient symptoms and signs

Most ‘potential’ pathogens are also commensal flora

Danger in treating all ‘potential’ pathogens

  • Misinterpret the real cause of patients symptoms
  • Antibiotic resistance
  • Side effects e.g. thrush

Know your genuine pathogens

  • Group A Streptococcus
  • STD’s
42
Q

UTI – Principles

A

Quality of specimen very important

  • Should have NO epithelial cells
  • White cell count >10 or higher
  • Pure growth

Reproductive (6 decks)

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