Lc 15 Flashcards
What are two species of pathogenic neisseria species?
N.gonorrhoeae and N.meningitis
Explain the type of neisseria and its shape and function
Gram negative diplococci
Kidney bean shaped
Non motile,non spore forming
In what conditions they grow?
-chocolate agar bc they are fastidious and require enriched medium
Primary culture of clinical specimens on selective medium (modified thayer martin agar)
How do we Neisseria species?
-they are both oxidase positive
- gonococcus : glucose agar
Meningococcus: maltose and glucose
- MALDI-TOF : identifies Neisseria bacteria
Explain neisseria species structure and antigens and how they perform immune evasion
Major antigens (pili, outer membrane proteins(Por,Opa), lipooligosaccharide(LOS) )
They disguise
Explain Por’s structure and how they invade host cells
Por: most abundant structural surface protein.
Attach to complement receptor 3(CR3) on cervical epithelial cells in women.
Por is used for serological classification of gonococcci —> two structural classes Por A and Por B is used.
Pili functions in initial attachment to host cells. What receptors do they bind to in host cells?
CD46 on male urogenital epithelial cells
CR3 in female cervical epithelium cells
There are two variations in pili. Explain them
Phase variation : on/ off
Antigenic variation : different gene sequences
What does Opa expression determine?
Colony phenotype: opaque—> Opa expressed
Transparent—> Opa not expressed
How do Opa function?
They attach to host cells. Crucial role in establishment of infection in women
There are two phase changes in Opa. What are they and how do they differ?
Opa+ : cervical isolates
Opa- : isolates obtained during menses
What is the major role of LOS?
Produce inflammatory mediators.
Attach to some female host cells
Sialylated LOS resists serum and attenuates inflammatory response
How do gonorrhea infection of male and female genitalia differ?
Male: acute urethritis
Female : asymptomatic
How do pathogenesis in male genitalia work
-Initial attach to CD46 to male urethral epithelium
-Opa expression (pili +opa) results in closee adhesion between gonococci and host cells
How do pathogenesis in male urethra work?
Gonococcus enters and multiply within epithelial cells and reach the submucosa
Hematogenous(bloodstream infection) occur
Symptomatic infection
How do pathogenesis in female genitalia work?
Pili and Por bind to CR3 on cervical epithelial cells
iC3b deposits on LOS, binds to CR3
Internalization via CR3 doesn’t triggeer inflammatory response
—> asymptomatic infection
What is the main difference structure of n.gonococcus and n.meningitis?
N.meningitidis have polysaccharide capsules
What is the resrvoirs of gonococcal infections?
Extragenital gonorrhea
What are the clinical spectrum and manisfestations?
Urethritis
Rectal
Pharyngeal
Cervicitis
Salpingitis
Disdminated infection
Conjunctivitis
What are the incubation period and symptoms of urethritis
Develop symptoms in 1-6 days,
Urethral discharge and dysuria
erythema and edema
Characteristics of urogenital infection in women
Asymptomatic
Symptoms range from minimal to severe
Incrased vaginal discharge
Dysuria(pain and burning)
What are the symptoms of salpingitis?
Lower abdoman pain, abnormal menses, inflammation of fallopian tube,
Important cause of infertility, ectopic pregnancy
What are some extragenital gonorrhea?
Rectal and pharyngeal
Both asymptomatic and difficult to treat
How do you diagnose gonorrhea
GC diagnosis- nucleic acid amplification test
Gram stain of mald urethral discharge
Culture—> highly sensitive but poorly sensitive to extragenital specimens
How do se treat gonorrhea
Because of antimicronial resistance
Use ceftriaxone
But there are no vaccine
What are the antigens of neisseria meningitidis?
Capsular polysaccharide, Los, pili, OMPs
What is the cause of antigenic diversity ?
Due to interspecies genetic exchange with closely related Neisseria species
What groups cause most serious disease of n.meningitidis?
A,B,C,W,Y
N.meningitis is asymptomatic carriage. How many people carry it and who are most commonly affected?
10-20% , most in adolescents and young adults.
What are the pathogenesis of N.meningitidis?
Attachemeng to oropharynx by pili
Disemination to blood stream—> invasion through blood brain barrier
How do we diagnose meningitidis?
PCR, gram stain of CSF, culture from blood
How do we treat n.meningitidis?
Penicillin G, steroid , antiobiotic , vaccination(MenACWY, MenB)
Why are the recently approved meningococcal vaccines effective against many meningococcal serogroups including serogroup B?
Because the vaccine is protein basesd
