Bacterial STDs Flashcards
1
Q
Bacteriological features of Neisseria (morphology, growth characteristics)
A
Morphology
- Gram-negative diplococcus
- Individual cocci are kidney-shaped, together look like a donut
Growth characteristics
- Grow only on rich media in presence of 5% CO2
- Sensitive to fatty acids and salts in growth medium
- Chocolate agar
- Thayer-Martin (VPN = Vanco, Polymyxin, Nystatin)
- Transgrow bottle used in doc offices rurally –> provies CO2 in a bottle to send off to lab
- Undergo rapid autolysis at 25C and at alkaline pH
- Gonorrhoeae ferments only glucose, oxidase (+)
- Meningitidis ferments both glucose and maltose
2
Q
Diagnosis of gonorrhea
A
- Gram-stained smears: urethral, endocervical, or conjunctival exudates
- May be diplococci within PMNs
- Cuture: on enriched selective medium at 37C in 5% CO2 atmosphere for 48 hours
- Thayer Martin
- Chocolate agar
- Nucleic acid amplification tests (NAATS)
- Preferred testing method to distinguish N. gonorrhoeae and C. trachomatis infection
- Closest test to > 90% sensitivity and 99% specificity
- Oxidase production and oxidative utilization of carbohydrates used for identification and differentiation between Neisseria spp.
- Also between Neisseria and Moraxella
3
Q
Most effective diagnostic procedures for Neisseria/Moraxella
A
- Gram stained smears
- Sensitivity: 90% for men, 50% for women
- Specificity: 99% for men, 90% for women
- True ONLY of urogenital infection with N. gonorrhoeae
- Lower for women because they are more likely to be infected with other organisms (e.g. Moraxella) that would make diagnosis less clear (both are gram (-) diplococci)
4
Q
Asymptomatic carriers of N. gonorrhoeae: men or women?
A
- Both men and women can be asymptomatic carriers
- Prevalence is higher among women
5
Q
Epidemiological significance of asymptomatic carriers of gonorrhea
A
- Major problem in control of gonorrhea
- Asymptomatic infection can lead to more serious infections like PID, especially in women
- “Toilet seat” theory unlikely as it doesn’t survive well
6
Q
Clinical manifestations of gonorrhea
A
- Range from asymptomatic to disseminated infection
- Depend on site and type of infection
- Lower tract infection:
- Cervicitis
- Abscess formation in glands adjacent to vagina
- Urethritis
- Upper tract infection
- Endometritis
- PID
- Epididymitis
- Other sites:
- Proctitis: homosexual men
- Pharyngitis
- Ophthalmia neonatorum - bilateral conjunctivitis in infants born to infected mothers
- Peritonitis
- Perihepatitis
7
Q
Disseminated gonococcal infection (DGI)
A
- Dermatitis-arthritis-tenosynovitis syndrome
- Reiter’s syndrome/reactive arthritis
- “can’t see, can’t pee, can’t climb a tree”
- also found post-chlamydial infection
- Monoarticular septic arthritis
- Endocarditis (rare)
- Meningitis (rare)
8
Q
Importance of antigenic heterogeneity in pathogenesis of gonorrhea
A
- Means that N. gonorrhoeae is antigenically very heterogeneous
- Capable of changing surface structures to avoid host defenses
- So much antigenic variation –> single person can be infected with N. gonorrhoeae many times in the lifetime
- Several types of pili: cause inability of vaccinations to gonorrhea
- One person can be infected, treated, then reinfected due to Ab specificity to one single pili
- Bug can synthesize a new and different type of pili for survival advantage
- Bug can also turn pili on and off for attachment and detachment from host (phase variation)
9
Q
Bacterial structures undergoing antigenic variation/phase variation in gonorrhea
A
- Pili
- Important for attachment to mucosal epithelium
- Phase variation –> bacteria capable of switching on/off the expression of pili
- Hundreds of antigenic types of pili
- Important for attachment to mucosal epithelium
- Opa proteins
- Outer membrane proteins
- N. gonorrhoeae either transparent, opaque, or mixed depending on presence of Opa proteins at bacterial surface
- Important for attachment and may influence site and type of infection
- Hundreds of antigenic types of Opa proteins
- LOS
- Equivalent of LPS of gram-negative bacteria, but without long O-side chains
- 8+ types of LOS
- Toxic for ciliated cells in tissue culture
- Responsible for many of inflammatory processes during infection
- IgA protease
- Cleaves Fc portion of IgA –> prevents opsonized bacteria from being phagocytosed
- 2 types
10
Q
Guidelines for treatment of gonorrhea
A
- No quinolones in US because of widespread resistance
- Treatment of choice:
- Third-generation cephalosporins: cefixime (oral, single dose); ceftriaxone (IM, single dose)
- Also treat concurrently for Chlamydia (travel together)
- Ophthalmia neonatorum - preventable by administration of drops/ointment into eyes at birth
- Silver nitrate (2%) or
- Antibiotics - erythromycin or tetracyline ointment
11
Q
Relationship of gonorrhea treatment to other STD treatment
A
- Dual therapy recommended for chlamydial and gonococcal urogenital infections because:
- Patients infected with one are often infected with the other
- Cost of treating for both is less than cost of testing
- Therapy for N. gonorrhoeae
- Third generation cephalosporin - cefixime, ceftriaxone
- do NOT use quinolones - too much resistance in US
- Therapy for C. trachomatis
- Macrolides (azithromycin - oral, single dose) OR
- Tetracycline (doxycycline - oral, 7 days)
- Ocular infection with N. gonorrhoeae
- Ceftriaxone (IV or IM, single dose)
- Topical abx alone are inadequate
- Ocular infection with C. trachomatis
- Erythromycin (oral, 10-14 days)
- Topical abx alone are inadequate
- Treatment of infected pregnant women
- N. gonorrhoeae - 3rd generation cephalosporin or spectinomycin
- C. trachomatis - erythromycin (oral, 7 days) or amoxicillin (oral, 7 days)
12
Q
Major characteristics of spirochetes & differences from other bacteria
A
- Large, heterogeneous group of spiral, motile bacteria
- Gram negative
- LPS not exposed due to outer phospholipid rich membrane with few exposed proteins
- Endoflagella between cell wall and outer membrane
- Reproduce by transverse fission
- Grown only in broth with 1-4% O2 at 25C
- Other bacteria have variety of other shapes, metabolism, growing conditions, reproduction, motility, other characteristics
13
Q
Primary syphilis: pathogenesis, manifestations, diagnostic tests, infectiousness
A
- Pathogenesis:
- Enter body through mucous membranes, epithelial abrasions, or skin contact with ulcer
- Manifestations:
- One or more painless chancres
- Regional nontender lymph node enlargement
- Diagnosis:
- Specimens in darkfield microscopy or direct fluorescence Ab (DFA-TP)
- Infectiousness:
- Very! Wear gloves to touch a chancre.
- Blood transmissible
14
Q
Secondary syphilis: pathogenesis, manifestations, diagnostic tests, infectiousness
A
- Pathogenesis:
- Secondary syphilis is systemic
- Manifestations
- 6 weeks after initial chancre heals
- Localized or diffuse mucocutaneous lesions
- Rash, lymphadenopathy, condyloma lata, bacteremia, alopecia
- 30% untreated develop tertiary syphilis
- Diagnostic tests
- Specimens in darkfield microscopy or direct fluorescence Ab (DFA-TP)
- Infectiousness
- Organisms can be located in condylomata
- Also transmissible by blood
15
Q
Latent syphilis: manifestations, diagnostic tests, infectiousness
A
- Manifestations:
- Asymptomatic
- Can relapse to stage 2
- Diagnostic test:
- Serologic testing, FTA
- Infectiousness
- Noninfectious except in pregnant women transmitting it to their fetuses
16
Q
Tertiary syphilis: pathogenesis, manifestations, diagnostic tests, infectiousness
A
- Pathogenesis:
- Lesions caused by immune mediated destruction of tissues
- Manifestations
- Develops over 6-40 years
- Neurologic, gummatous, or cardiovascular
- 25% die
- Diagnostic tests:
- Serologic testing, FTA
- Infectiousness:
- Non-infectious
17
Q
Tertiary syphilis complications
A
- Neurologic syphilis:
- Common
- Can be asymptomatic
- Subacute meningitis with predominance of lymphocytes
- Meningovascular syphilis
- Tabes dorsalis
- General paresis of insane
- Associated with Argyll Robertson pupil - reactive to accomodation but not to light
- Gummatous syphilis:
- Rare
- Granulomatous lesions that eventually fibrose
- Often located in skin and bone
- Cardiovascular syphilis
- Rare
- Aortic aneurysm
- Aortic insufficiency
- CAD
- Dissection
18
Q
Diagnosis of syphilis: primary or secondary
A
- Darkfield examination: drop of tissue fluid or exudate placed on slide –> examined with light
- Still used for diagnosis of primary syphilis because Ab-based tests may not yet be positive (takes about 2 weeks for person to develop Abs against Ag)
- Immunofluorescence: detection of T. pallidum from specimens using fluorescein-labeled anti-treponema serum
