Microbiology of UTI Flashcards
What increases the probability of HIV acquisition?
Genital ulcers
What STIs cause urethritis?
Gonorrhea and chlamydia
Describe the normal vaginal flora
Lactobacillus predominate and are protective
Why is the normal pH of the vagina acidic?
Lactobacillis produce lactic acid +/- hydrogen peroxide
What organisms aside from lactobacillus species are normal vaginal flora?
Group B beta-haemolytic streptococcus
Candida spp.
Strep viridans group
What would be seen on a gram film of Candida albicans?
Budding yeasts and hypae
Candida infection; ___% of females are asymptomatically ________ with small numbers of mostly candida _______
Candida infection; 30% of females are asymptomatically colonised with small numbers of mostly candida albicans
What are the predisposing factors for candida?
- Recent antibiotic therapy
- High oestrogen levels (pregnancy, certain types of contraceptive)
- Poorly controlled diabetes
- Immunocompromised patients
What is this infection?
Candida albicans
What is the presentation of a candida infection?
Intensely itchy white vaginal discharge
How is candida diagnosaed?
High vaginal swab for culture- the majority of cases are caused by candida albicans
What are the treatments for candida infections?
- Topical clotrimazole pessary or cream
- Oral fluconazole
When might candida infections be resistant to azole treatment?
Non-albicans candida species responsible
What is this infection?
How is it acquired
Candida balanitis
Not sexually transmitted
What is this infection?
Gonorrhoea
Describe the pathogenesis of gonorrhoea?
Attaches to host epithelial cells and is endocytosed into the cell to replicate within the host cell and are released into the subepithelial space
How does the inflammation occur in typical urethral gonococcal infections?
Release of toxic lipo-oligosaccharide and peptidoglycan fragments as well as the release of chemotactic factors that attract neutrophilic leukocytes
Why are some gonococcal infections asymptomatic?
Related to differences in the organisms ability to bind complement-regulatory proteins that downregulate the productin of chemotactic peptides
What parts of the body does neisseria gonorrhoea infect?
Urethra, rectum, throat & eyes, endocervix
Describe the appearance of neisseria gonorrhoea
Looks like 2 kidney beans facing each other
Easily phagocytosed by polymorphs, so often appear intracellularly
Neisseria gonorrhoea is a _________ organism, it _______ survive outside the body
Neisseria gonorrhoea is a fastidious organism, it doesn’t survive outside the body
How is N. gonorrhoea tested for?
- microscopy of urethral/endocervical swabs (90+% specificity in males)
- culture on selective agar plates
Culture on selective agar plates for n. gonorrhoea is done on what samples?
Endocervical, rectal and throat swabs NOT vaginal swabs
What does selective agar do?
Suppresses growth of normal flora
When can non selective media be used in culture
When no competing flora are expected (synovium)
Where are cultures on selective agar plates taken?
Only done in SRH clinic- die in transit
What are NAATs
Nucleic Acid Amplification Tests
When are NAATs used?
To diagnose gonorrhoea and chlamydia
What is the treatment for gonorrhoea?
What is the commonest bacterial STI in the UK?
Chlamydia trachomatis
Where does chlamydia infect?
Infects the urethra, rectum, throat and eyes, and endocervix
Describe the nature of chlamydia trachomatis
Obligate intracellular bacteria with biphasic life cycle- does NOT reproduce outside host cell
Which STI does not stain with gram stain
Chlamydia trachomatis
What are the three serological groupings of chlamydia trachomatis?
- serovars A-C = trachoma (eye infection) not STI
- serovars D-K= genital infection
- serovars L1-L3= lymphogranuloma venereum
Describe the chlamydia infectious cycle
- attachment and entry
- migration to perinuclear area and EB -> RB transition
- inclusion biogenesis and bacterial replication
- RB -> EB transition and cell lysis (48h)
Descirbe the diagnosis of chlamydia and gonorrhoea
Combined NAATs or polymerase chain reaction for both organisms in one test
Done on;
- male patients- first pass uring sample
- female patients- HVS or vulvovaginal swab (can be self-taken by patient or clinician-taken endocervical swab if bhaving speculum examination)
- Rectal and throat swabs
- Eye swabs (babies and adults)
