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41 Cards in this Set

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What diseases are caused by Neisseria gonorrhoeae
Urethritis, cervicitis, proctitis, pharyngitis, conjunctivitis, epididymitis, endometritis, salpingitis, pelvic inflammatory disease, perihepatitis, bartholinitis, disseminated gonococcal infection
What are the general characteristics of Neisseriaceae
Gram negative diplococci, oxidase positive, nonmotile. Require iron and 2-8% CO2 for growth
Naturally competent for DNA transformations
How is Neisseria gonorrhoeae transmitted
Viral contact between mucosal surfaces and infected tissue or secretion. Non-sexual transmission is rare
ID50 for men is 10^3
Attack rate from infected persons is 20-50%
What is the clinical spectrum of Neisseria gonorrhoeae
Asymptomatic infection
Rectal infection
Pharyngeal infection
Ophthalmia neonatorum
Localized dissemination in the reproductive tract
Disseminated gonococcal infection (DGI)
Describe urethritis caused by Neisseria gonorrhoeae
Males and females. Frequent, urgent and painful urination and yellow mucopurulent discharge containing neutrophils and gram-negative diplococci
Describe cervicitis caused by Neisseria gonorrhoeae
Inflammation of the endocervical canal with mucopurulent discharge. Infection of paracervical glands, Bartholin's glands resulting in abscesses. Presents as vulvovaginitis rather than cervicitis in pre-adolescent girls and hysterectomized women
Describe rectal infection from Neisseria gonorrhoea
Usually asymptomatic, but may have tenesmus, discharge or pain on defecation
Describe pharyngeal infection from Neisseria gonorhoeae
Usually asymptomatic, but may have very sore throat. From orogenital sex. In patients with gonorrhea, gonococcal pharyngitis is found
Describe Ophthalmia neonatorum caused by Neisseria gonorhoeae
Acute purulent conjunctivitis in the newborn which was once a common cause on blindness in the US
Describe localized dissemination in the reproductive tract caused by Neisseria gonorrhoeae
Males: Epididymitis, prostitis. Can lead to infertility
Females: Endometritis, salpingitis, pelvic inflammatory disease. Damage to the fallopian tubes during salpingitis can cause post-infection complications like chronic pelvic pain, infertility, and ectopic pregnancy. Dissemination into the peritoneum from the fallopian tubes can lead to perihepatitis (Curtis-Fitx-Hugh syndrome)
Describe disseminated gonococcal infection (DGI) caused by Neisseria gonorrhoeae
Hematogenous spread with a predilection for skin and joints, resulting in dermatitis and arthritis. Dermatitis manifests as hemorrhagic papular lesions. Gonococcal arthritis is the leading cause of septic arthritis in young adults and usually involves the large joints. DGI can cause endocarditis or meningitis
What is the pathogenesis of Neisseria gonorrhoeae
Upon entry into the lower urogenital tract, gonocci adhere to epithelial cells via colonization pili. Invasion of epithelial cells also occurs. Vigorous inflammatory response can occur. Discharge contains neutrophils, exfoliated epithelial cells and diplococci
What is the connection between gonorrhea in females and hormonal status
Gonococcal Disseminated gonococcal infection and Pelvic inflammatory disease tend to occur during or shortly after menses; women are more heavily colonized in the proliferative stage
How does pH of the lower female genital tract affect gonorrhea
Neisseria gonorrhoeae is sensitive to low pH. The occurrence of vulvovaginitis in prepubescent and post-hysterectomy females rather that cervicitis may be due to the higher vaginal pH in these females
How does the onset of menstrual blood affect gonorrhea
Ascension to the upper reproductive tract may be facilitated by the reflux of menstrual blood. High amounts of iron bound to hemoglobin may stimulate gonococcal growth or up-regulate virulence genes
In the fallopian tubes, what do gonococci specifically adhere to
Nonciliated epithelial cells. Damage to columnar epithelial cells and ciliated cells is mediated by gonococcal lipooligosaccharide (LOS) and peptidoglycan fragments
Disseminated gonococcal infections (DGI) is associated with what types of strains
Those that express porins that bind to complement regulatory proteins C4 binding protein (C4bp) and factor H (fH). Binding to these will cause down-regulation of complement activation, and decrease complement-mediated killing
What types of gonococcal strains are epidemiologically associated with DGI
Strains that contain the porin serotypes that bind C4bp and fH. Strains that express serum-sensitive porin types are associated with localized mucosal infections
What allows the gonococcus to evade the immune response or provide functionally different phenotypes
Antigenically and phase variable surface proteins, such as pili, opacity proteins, and lipooligosaccharide
Why might repeated gonococcal infection be common
The antigenically variable nature of the gonococcal surface
Define phase variation in gonococci
The ability to turn the expression of a gene on or off; can be reversible or nonreversible, depending on the mechanism
What two variations provide for the variable nature of gonococcal surfaces
Antigenic variation and phase variation
What is the major subunit of gonococcal pili
The antigenically variable protein called pilin. Antigenic variation of pilin is probably a major mechanism by which the gonococcus evades the immune response
What does the pili (fimbriae) of gonococci do
Mediates adherence to epithelial cells and spermatozoa
What is the probable function of Opacity (Opa) proteins in Neisseria gonorrhoeae
Mediate adherence to, and invasion of, epithelial cells and non-opsonic uptake by neutrophils
What are opacity (Opa) proteins in gonococci
Family of variable outer membrane proteins (up to 12 of them). Each individual Opa protein undergoes phase variation via a frame shift mechanism
What does Neisseria sp express instead of the lipopolysaccharide found in enteric gram negative bacteria
Lipooligosaccharide (LOS) (short carbohydrate chains)
How does gonococcal LOS undergo phase and antigenic variation
Via frameshift mechanisms that occur in glycosyltransferase genes. The gonococcus also produces a sialyltransferase that catalyzes the addition of host sialic acid residues to its LOS
What is the significance of sialylated LOS
Gonococci with sialylated LOS are more resistant to complement-mediated lysis due to this capsule-like modification
What are three less common gonococcal virulence factors
Iron-binding proteins: response to low iron. Compete with human transferrin, hemoglobin and lactoferrin
IgA1 protease: cleaves IgA1
P.I. protein-major porin: serological classification only
Why is Neisseria gonorhoeae able to persist during periods of intense inflammation
It has multiple mechanisms by which it evades complement-mediated and phagocytic killing
What is the epidemiology of Neisseria gonorrhoeae
High incidence; Regional differences in the US; high incidence in adolescents; more common in men; frequent in African Americans
How is laboratory diagnosis of Neisseria gonorrhoeae made
Males: Gram stain of urethral discharge. Look for gramneg diplococci within neutrophils. PCR if asymptomatic
Females: PCR of urine or cervical discharge. Also rectal swabs
How is Neisseria gonorrhoeae cultured
Chocolate agar; modified Thayer Martin or Martin Lewis agar
For gonococcal infections in children, what must be considered
Sexual abuse. Genital, anal, and pharyngeal cultures should be obtained from all patients before antibiotic therapy is initiated
Why is penicillin no longer the first choice for Neisseria gonorrhoeae
Penicillinase-producing N. gonorrhoeae carry penicillinase on a small plasmid, probably acquired from H. ducreyi.
Penicillin resistance due to altered penicillin-binding proteins can also occur and is chromosomally encoded
What is tetracycline resistance in Neisseria gonorrhoeae due to
Insertion of a transposon carrying the tetM gene into the large conjugative plasmid. Can join with the penicillinase-producing plasmid
What is the antibiotic of choice against Neisseria gonorrhoeae
Ceftriaxone. Fluoroquinolones (ciprofloxacin and ofloxacin) are usually effective too
When treating for Neisseria gonorrhoeae, what else should be treated for
Chlyamidia trachomatis, since coinfection is common. Use doxycycline
How should gonococcal conjunctivitis be treated
With erythromycin or tetracyclin ophthalmic ointment or silver nitrate drops
Why is there no vaccine for Neisseria gonorrhoeae
Unlike most serogroups of N. meningitidis, the gonococcus lacks a capsule to which a protective immune response can be induced