Neisseria species
Gram-negative cocci
Typically in pairs resembling kidney beans (diplococci)
All important neisseriae are oxidase-positive
Outer membranes contain lipooligosaccharides (LOS) rather than
lipopolysaccharides
Thus, their endotoxins have few repeating sugar units.
Growth is inhibited by toxic trace metals and fatty acids cultured on
heated blood (chocolate) agar
2 primary neisseriae are distinguished:
N. meningitidis ferments glucose and maltose both
N. gonorrhoeae ferments glucose, not maltose
1. N. meningitidis (meningococcus)
a. Primarily enters through respiratory tract
b. Causes meningitis and meningococcemia
c. Most important virulence factor prominent polysaccharide
capsule
d. 13 serologic groups; types A, B, C, Y and W-135 cause most
infections.
e. Capsule induces protective antibodies. It is utilized as key
immunogen in vaccines
f. Produces an IgA protease cleaves secretory IgA organism
attachment to upper respiratory tract membranes.
2. N. gonorrhoeae (Gonococcus)
a. Enters via genital tract
b. Causes gonorrhea, neonatal conjunctivitis, pelvic inflammatory
disease.
c. Lack of polysaccharide capsule no available vaccine
d. Relies on pili, which mediate attachment to human mucosal
surfaces.
e. Strains without pili are nonpathogenic
f. Pili exhibit antigenic variation, allowing pathogen to evade
host immune response.
g. Secretes IgA protease and utilizes endotoxins (LOS) and
membrane proteins for pathogenesis
h. Smears show gram negative diplococci located in patient’s
neutrophils(males).
, Transmission and pathogenesis
1. N. meningitidis
a. Humans are the only natural hosts
b. Transmitted from person to person via airborne respiratory
droplets.
c. First colonize nasopharynx, become part of transient flora.
d. Most infected become chronic asymptomatic carriers.
e. Bacteria can enter bloodstream through nasopharynx to
spread to meninges or joints, or disseminate throughout the
body (meningococcemia)
f. 3 virulence factors
i. Polysaccharide capsule
1. Most important virulence factor
2. Resist phagocytosis by neutrophils
ii. Endotoxin (lipooligosaccharide, LOS)
1. Unlike lipopolysaccharide of enteric bacteria,
Neisseria endotoxin contains few repeating sugar
units
2. LOS is responsible for pathophysiologic changes like
fever, shock and disseminated intravascular
coagulation
iii. IgA protease
1. Cleaves secretory IgA
2. Bacteria evades local immune defenses
3. Attaches to upper respiratory tract membranes.
g. Late acting components deficiency (C6-9) increased risk of
meningococcal bacteremia.
2. N. gonorrhoeae:
a. Infects only humans
b. Highly sensitive to dehydration and cool conditions
c. Transmitted exclusively by intimate sexual contact or vertically to
newborns.
d. Infects
i. Vagina
ii. Cervix
iii. Urethra
e. Pathogenesis is driven by
i. Pili and adherence
1. Lacks polysaccharide capsule
Gram-negative cocci
Typically in pairs resembling kidney beans (diplococci)
All important neisseriae are oxidase-positive
Outer membranes contain lipooligosaccharides (LOS) rather than
lipopolysaccharides
Thus, their endotoxins have few repeating sugar units.
Growth is inhibited by toxic trace metals and fatty acids cultured on
heated blood (chocolate) agar
2 primary neisseriae are distinguished:
N. meningitidis ferments glucose and maltose both
N. gonorrhoeae ferments glucose, not maltose
1. N. meningitidis (meningococcus)
a. Primarily enters through respiratory tract
b. Causes meningitis and meningococcemia
c. Most important virulence factor prominent polysaccharide
capsule
d. 13 serologic groups; types A, B, C, Y and W-135 cause most
infections.
e. Capsule induces protective antibodies. It is utilized as key
immunogen in vaccines
f. Produces an IgA protease cleaves secretory IgA organism
attachment to upper respiratory tract membranes.
2. N. gonorrhoeae (Gonococcus)
a. Enters via genital tract
b. Causes gonorrhea, neonatal conjunctivitis, pelvic inflammatory
disease.
c. Lack of polysaccharide capsule no available vaccine
d. Relies on pili, which mediate attachment to human mucosal
surfaces.
e. Strains without pili are nonpathogenic
f. Pili exhibit antigenic variation, allowing pathogen to evade
host immune response.
g. Secretes IgA protease and utilizes endotoxins (LOS) and
membrane proteins for pathogenesis
h. Smears show gram negative diplococci located in patient’s
neutrophils(males).
, Transmission and pathogenesis
1. N. meningitidis
a. Humans are the only natural hosts
b. Transmitted from person to person via airborne respiratory
droplets.
c. First colonize nasopharynx, become part of transient flora.
d. Most infected become chronic asymptomatic carriers.
e. Bacteria can enter bloodstream through nasopharynx to
spread to meninges or joints, or disseminate throughout the
body (meningococcemia)
f. 3 virulence factors
i. Polysaccharide capsule
1. Most important virulence factor
2. Resist phagocytosis by neutrophils
ii. Endotoxin (lipooligosaccharide, LOS)
1. Unlike lipopolysaccharide of enteric bacteria,
Neisseria endotoxin contains few repeating sugar
units
2. LOS is responsible for pathophysiologic changes like
fever, shock and disseminated intravascular
coagulation
iii. IgA protease
1. Cleaves secretory IgA
2. Bacteria evades local immune defenses
3. Attaches to upper respiratory tract membranes.
g. Late acting components deficiency (C6-9) increased risk of
meningococcal bacteremia.
2. N. gonorrhoeae:
a. Infects only humans
b. Highly sensitive to dehydration and cool conditions
c. Transmitted exclusively by intimate sexual contact or vertically to
newborns.
d. Infects
i. Vagina
ii. Cervix
iii. Urethra
e. Pathogenesis is driven by
i. Pili and adherence
1. Lacks polysaccharide capsule
