Neisseria and Bacteriodes Flashcards
• Gram− diplococci
• Lipooligosaccharide (vs. LPS): lack O antigen extensions
• common oral flora and other mucous membranes
• pathogens: N.gonorrhoeae and N.meningitidis
Host: only humans
Neisseria
What are the virulence factors of N. gonorrhoeae
phase variation and antigenic variation of pilin genes
vaccination is not possible.
t/f: there is no capsule for N. gonorrhoeae
true
ØPilE single chromosomal copy of pilin structural gene
ØStrains contain 10-15 copies of PilE variants lacking promoter and 5 -end of gene called PilS genes
ØPilS genes recombine with PilE creating unlimited antigenic variants of PilE
ØResult is that antigenic structure of pilus protein is constantly changing
Pathogenesis of Gonorrhea
In Neisseriae: Slipped Strand Mispairing resulting from presence of multiple identical repeated sequences at 5 -end of gene. Replication errors due to strand misalignment creates reading frame errors. Often, premature stops, but also results in ON/OFF switch.
Phase Variation:
on/off switch for surface protein expression
Multiple Opa (Colony Opacity) protein copies scattered across genome; Slipped strand mispairing results in frequent variation in Opa protein expression or complete absence of Opa
Phase Variation:
on/off switch for surface protein expression
Ø Phase Variation: on/off switch
Ø E. coli and other Gm- rods simple inversion
of promoter
Pathogenesis of Gonorrhea
Pili mediate bacterial attachment to non-ciliated epithelia
Virulence Factors of N. gonorrhoeae
bacteria proliferate and shed into secretions;
Virulence Factors of N. gonorrhoeae
secreted IgA protease
Virulence Factors of N. gonorrhoeae
Serum-resistant virulent strains cause disseminated gonococcal infections:
• Strains lack Opa proteins (colony opacity proteins = outer-membrane proteins)
Neutrophils unable to engulf bacteria lacking Opa proteins.
• Sialic acid on LOS (Lipidoligosaccharide of outer membrane) binds complement
regulatory proteins, prevents complement-based phagocytosis.
Virulence Factors of N. gonorrhoeae
What is the virulent function of secreted IgA Protease?
Usefulness of cleaving IgA: Coating of bacteria with IgA Fab fragments (does not activate complement and also blocks binding by other IgG and IgM)
addition of sialic acid to lipoligosaccharide inhibits complement fixation
Virulence Factors of N. gonorrhoeae
Sexual transmission - urogenital infections
Gonorrheal Diseases
in men, urethral pus secretion
leukocytes with many gonococci
urethritis
in women, frequently some urination
sensitivity but no other symptoms
cervicitis
t/f: Gonorrheal Diseases are Frequently (almost) asymptomatic
true
o destructive eye infection, acquired during birth
o Application of erythromycin ointment into both
eyes of newborns is mandatory in many states and is considered standard neonatal care
Opthalmia Neonatorum
as a result of Gonorrheal Diseases
Initial infection of cervix, fallopian tubes and vaginal wall glands can lead to PID (15-30%):
o gonococci enter abdominal cavity, cause liver disease
o tissue scarring causes fallopian tube abnormalities which lead to ectopic pregnancies and sterility
§ Pelvic Inflammatory Disease (PID) in women
as a result of Gonorrheal Diseases
_____ ____ can cause Urethral and testicular tubule scarring, resulting from epididymitis, leads to sterility
and increased urethral infections by other microbes
Gonorrheal Diseases
without apparent genital infection, ____ ____ ____ causes skin lesions, suppurative arthritis of a major joint, heart valve destruction.
Disseminated Gonococcal Infection
t/f: Little or no protective immunity (pilin variability!) is observed after recovery from an infection with
N.gonorrhoeae.
true
What are the factors of Neisseria meningitidis that affect intravascualar survival?
Capsule: protects against complement-mediated bacteriolysis and phagocytosis
Acquisition of iron from transferrin
t/f: Neisseria meningitidis can cross the blood brain barrier and multiply in the subarachnoid space
true
