Microbiology Flashcards
What bacterial species predominates in healthy vaginal flora?
Lactobacillus spp.
What does Lactobacillus spp. produce and what is the effect of these products?
Lactic acid +/- hydrogen peroxide
Suppresses growth of other bacteria creating INNATE IMMUNITY
List some bacteria other than Lactobacillus spp. that can be part of the normal vaginal flora
Strep viridans
Group B Strep
Candida spp. (small numbers)
What are the 3 main non-sexually-transmitted genital tract infections?
Vaginal thrush
Bacterial vaginosis
Prostatitis
Which bacteria causes vaginal thrush?
Candida (usually albicans)
The presence of Candida on vaginal swab indicates vaginal thrush. True/False?
False
30% of females are colonised by small numbers of Candida as part of normal flora
List some predisposing factors to developing Candida infection
Recent antibiotic therapy
High oestrogen levels (pregnant, contraceptives)
Poorly controlled diabetes
Severely immunocompromised
Describe clinical presentation of vaginal thrush
Intensely itchy
White vaginal discharge “like cottage cheese”
How is the diagnosis of vaginal thrush made?
Clinical diagnosis/appearance
High vaginal swab to culture for C. albicans
How is vaginal thrush treated?
Topical clotrimazole
Oral fluconazole if no response
What is characteristic of Candida albicans on gram film?
Appearance of budding
Who typically gets other forms of Candida infection (other than albicans)? How does this present?
Poorly controlled diabetics
Immunosuppressed
C. balanitis: ‘spotty rash’ in males
Which organisms are the main causes of bacterial vaginosis?
Gardnerella vaginalis
Mobiluncus sp.
Other anaerobes
Describe clinical presentation of bacterial vaginosis
Thin, watery, bubbly, fish-smelling discharge that reeeeaally stinks (positive whiff test)
How is a diagnosis of bacterial vaginosis made?
Clinical diagnosis/examination
Raised vaginal pH greater than 4.5
The presence of what cells on microscopy suggest bacterial vaginosis?
Clue cells - vaginal epithelial cells coated with coccobacilli
How is bacterial vaginosis treated?
Oral metronidazole for 7 days
Describe the clinical presentation of acute bacterial prostatitis
UTI-like
Abdominal/back/perineal/penile pain
Tender prostate
A mid-stream sample of urine is required to test for urethral infection in acute bacterial prostatitis. True/False?
False
Mid-stream for upper UTI, first-pass for lower UTI
How is acute bacterial prostatitis treated?
Ciprofloxacin for 28 days
Trimethoprim if high C. diff risk
List the 3 main sexually-transmitted bacterial infections
Chlamydia
Gonorrhoea
Syphilis
What is the commonest bacterial STI in the UK? What organism causes it?
Chlamydia, caused by Chlamydia trachomatis
What areas of the body can chlamydia infect?
Eyes Throat Rectum Urethra Cervix
Chlamydia reproduces both in and out -side the host cell. True/False?
False
Obligate bacteria that only reproduces inside the host
Does chlamydia stain with Gram stain?
No because no peptidoglycan in cell wall
What are the 3 serological groupings of chlamydia and their respective infections?
Serovars A-C = trachoma/eye infection
Serovars D-K = genital infection
Serovars L1-L3 = lymphogranuloma venereum
What condition does lymphogranuloma venereum mimic on presentation?
Inflammatory bowel disease - features of proptosis, PR bleed, irritation, fullness
How is chlamydia infection treated?
Doxycycline for 7 days
3 weeks if LGV
Which bacteria causes gonorrhoea?
Neisseria gonorrhoeae
Gonorrhoea is more common than chlamydia. True/False?
False
Describe the appearance of Neisseria gonorrhoeae on gram stain
Gram -ve
Diplococcus
(2 kidney beans facing each other)
Neisseria gonorrhoea is a fastidious organism. What does this mean?
Doesn’t grow well in less than ideal conditions i.e. outside the body
What is the typical clinical appearance of gonorrhoea?
Purulent discharge
Pus cells under microscope
How are both chlamyida and gonorrhoea diagnosed?
Nucleic acid amplification test
PCR
Microscopy of swabs
Specific agar culture (gonorrhoea only)
What are the advantages of NAAT/PCR over culture?
Quick
Less invasive
More sensitive
What are the disadvantages of NAAT/PCR over culture?
Will detect dead organisms so have to wait 5 weeks before retest
Cannot detect antibiotic sensitivity
Many strains of gonorrhoea are now antibiotic resistant. True/False?
True
What is the recommended treatment for gonorrhoea?
IM ceftriaxone (+azithromycin orally)
Which bacteria causes syphilis?
Treponema pallidum, spirochaete organism
Treponema pallidum does not stain with gram stain. True/False?
True
Treponema pallidum cannot be grown in culture. True/False?
True
How does stage 1 syphilis present?
Chancre (painless ulcer)
How does stage 2 syphilis present?
Flu-like symptoms
Ulcers
Generalised rash, palms and soles affected
How does latent stage (stage 3) syphilis present?
No symptoms
How does late-stage (stage 4) syphilis present?
Cardiovascular (aortic aneurysm)
Neurovascular (high-stump gait)
Syphilis is not infectious in the latent period. True/False?
True
What method is used to diagnose syphilis, and chancre?
PCR
How is serology testing for syphilis done?
Test for non-specific and specific antibodies to T. pallidum in blood for developed disease
What is the main non-serological test done for syphilis? When is it useful?
Rapid plasma regain
Useful for monitoring response to therapy
List the main specific serological tests done for syphilis
TPPA
TPHA
IgM + IgG ELISA (screening test)
What is the gold-standard treatment for syphilis?
Penicillin injection
What are the 3 main sexually-transmitted viral infections?
Genital warts
Genital herpes
Hepatitis and HIV
What is the commonest viral STI and its cause?
Genital warts, caused by human papilloma virus
What subtypes of HPV are the most common causes of genital warts?
6 + 11
What subtypes of HPV are associated with increased risk of cervical cancer?
16 + 18
How is genital warts diagnosed?
Clinical diagnosis as no lab test
How are genital warts treated?
DESTRUCTION via
cryotherapy/toxic cream (topical podophylin)
Vaccination given to 11-13 year old girls
What virus causes genital herpes?
Herpes simplex virus types 1 &2
Type 1 also cold sores
How is genital herpes diagnosed?
Swab for PCR
No good test between recurrent episodes
How is genital herpes treated?
Aciclovir
Pain relief
Counselling
What is the most common sexually-transmitted parasitic disease?
Trichomonas vaginalis (single cell protozoal parasite)
How is Trichomonas vaginalis diagnosed?
High vaginal swab for microscopy
How is Trichomonas vaginalis treated?
Oral metronidazole
Which parasite causes pubic lice? How is it spread?
Phthirus pubis
Close genital skin contact
How are pubic lice treated?
Malathion lotion
What are the clinical consequences of bacterial vaginosis infection?
Increased risk of upper UTI
Premature rupture of membranes and preterm delivery
Increased risk of acquiring HIV
Sole extragenital gonorrhea infection is most common in which group of people?
MSM - rectal gonorrhea as a single site of infection (50%) and is routinely screened for
How is genital herpes spread?
Genital-genital contact
Oropharyngeal-genital contact
Describe the pathogenesis of genital herpes
Virus replicates in dermis and epidermis spreading to nerves and causing painful inflammation
Virus hides from the immune system in sacral roots
Virus can reactivate and cause recurrent attacks
What are the clinical signs of Trichomonas vaginalis?
Vaginal discharge and irritation in females
What are the clinical signs of Phthirus pubis?
Itching in pubic areas
