Lecture 11 BIOL 533 1
Neisseriaceae
BIOL 533
Lecture 11
Medical Microbiology
Lecture 11 BIOL 533 2
Comparison of Meningococcus
and Gonococcus
? Pathobiology
? Similarities,
– Both diploccocci
– Share about 80% DNA
– Neither makes exotoxin; both make endotoxin
– Both are relatively good colonizers
? Other species colonize mucous membranes and
skin,and rarely cause disease
Lecture 11 BIOL 533 3
Comparison of Meningococcus
and Gonococcus
? Differences,
– Gonococcus causes gonorrhea
? Localized inflammation (usually in urethra) and is
very rarely fatal
– Meningococcus causes meningitis and other
diseases
? Systemic and life-threatening disease
Lecture 11 BIOL 533 4
Comparison of Meningococcus
and Gonococcus
? Why are diseases so different?
? Presence in normal flora
– 10% healthy people colonized by
meningococcus in posterior pharynx
– Gonococcus not present
Lecture 11 BIOL 533 5
Comparison of Meningococcus
and Gonococcus
? Penetration of mucous membranes
– Mechanism similar for the two organisms
– Penetrate different mucous membranes
columnar epithelial cells
? Meningococcus—nasopharnyx
? Gonococcus—fallopian tubes
Lecture 11 BIOL 533 6
Comparison of Meningococcus
and Gonococcus
? Survival against host defenses
– Gonococcus killed in bloodstream
– Meningococcus grows extremely fast in
bloodstream,reaching very high blood titers
? Reason,large capsule and outer membrane
proteins
Lecture 11 BIOL 533 7
Comparison of Meningococcus
and Gonococcus
? Signs and symptoms of two diseases
– Gonococcus (highly invasive) cause symptoms
frequently,but sites are localized
? Production of pus and pain during urination
? Sequellae depending on location
– Inflammation of fallopian tubes
– Pelvic inflammatory disease
? May result in scarring,leading to infertility and
ectopic pregnancy
Lecture 11 BIOL 533 8
Comparison of Meningococcus
and Gonococcus
? Signs and symptoms
– Meningococcus (highly serum-resistant )-
causes septicemia with multiple organ
involvement,including CNS
– Damage caused by
? Disseminated intravascular coagulation (DIC),
accompanied by shock,fever,and other responses
? Due to large amount of endotoxin in blood,tissues
? Due to ability of meningococcus to thrive in blood
Lecture 11 BIOL 533 9
Neisseria meningitidis
? Morphology
– Encapulated Gram— diplococci
? Colonization
– Asymptomatically in nasopharnyx of healthy
individuals
Lecture 11 BIOL 533 10
Neisseria meningitidis
? Microbial physiology and structure
– Colony morphology
? Form transparent,non-pigmented,non-hemolytic
colonies on chocolate blood agar in 5% CO2
– Capsule indicated by large mucoid colonies
– Physiology
? Oxidase+
? Acid production from glucose and maltose,but not
sucrose or lactose
? Several serotypes known
Lecture 11 BIOL 533 11
Neisseria meningitidis
? Causes of pathogenesis
– Ability to colonize nasopharnyx due to
presence of pili
– Ability to resist host defenses and spread due
to presence of capsule
– Expression of toxic effects due to presence of
endotoxin
Lecture 11 BIOL 533 12
Neisseria meningitidis
? Disease process
– Attach to specific receptors on non-ciliated
cells of nasopharnyx
? Pili—mutants have decreased cell binding ability
– Organisms internalized into phagocytic
vesicles by endocytosis
? After 18-24 hours,found in sub-epithelial tissue
space
Lecture 11 BIOL 533 13
Neisseria meningitidis
? Tissue damage
– Type of damage
? Endothelial damage
? Inflammation of blood vessel walls
? Thrombosis
? Disseminated intravascular coagulation
– Mechanism (endotoxin)
? Continuous production of excess membrane
fragments that contain LPS
Lecture 11 BIOL 533 14
Neisseria meningitidis
? Epidemiology
– Transmitted by respiratory secretions to
people living in close contact
– Incidence during Spring
– Susceptibility
? Children <5 years old
? Older individuals infected during epidemics
? Maternal Ab protection for first 6 months
Lecture 11 BIOL 533 15
Neisseria meningitidis
? Syndromes
– Meningitis
? Symptoms,headache and fever (young children—
fever and vomiting)
? Mortality
– Untreated,100%
– Treated,<15% when antibiotics administered promptly
? Incidence of neurological problems is low
Lecture 11 BIOL 533 16
Neisseria meningitidis
? Syndromes
– Meningococcemia (with or without meningitis)
? Life-threatening,with mortality of 25%,even
when promptly treated
? Pathology
– Thrombosis of blood vessels
– Multiorgan involvement
– Small skin lesions on trunk and lower extremities (may
form larger hemorrhagic lesions
– May progress to completely debilitating DIC with shock
(destruction of adrenal gland)
Lecture 11 BIOL 533 17
Neisseria meningitidis
? Syndromes
– Milder septicemia (chronic)—persist for days
or weeks
? Symptoms,low-grade fever,arthritis,skin lesions
? Response to antibiotics normally excellent
Lecture 11 BIOL 533 18
Neisseria meningitidis
? Laboratory diagnosis
– Blood and cerebrospinal fluid (especially
inside neutrophils)
? Treatment
– Penicillin (resistant strains rarely seen)
– Chloramphenicol,ceftriaxone,cefotaxine
Lecture 11 BIOL 533 19
Neisseria meningitidis
? Prevention and control (high-risk groups)
– Use of prophylactic antibiotics
? Penicillin not effective in eliminating carrier state
? Antibiotics of choice,
– Sulfonamide
– Rifampin,for sulfonamide-resistant strains
– Sulfadiazine
Lecture 11 BIOL 533 20
Neisseria meningitidis
? Prevention and control (high-risk groups)
– Vaccine
? Polyvalent given to children older than 2 years
? Effective against all but Group B (not
immunogenic)
? Group B—most important
Lecture 11 BIOL 533 21
Neisseria gonorrhoeae
? Third most commonly sexually transmitted
disease in USA
? Microbial physiology and structure
– Morphology
? Cell—small Gram— diplococci
? Colony—grow on chocolate agar,Thayer-Martin
agar,and Martin-Lewis agar
? Inhibited by fatty acids and trace metals
Lecture 11 BIOL 533 22
Neisseria gonorrhoeae
? Physiology
– Susceptible to dessication—require 5% CO2
– Colony types (T1-T5)
? T1 and T2 virulent; others are not
? Identification,
– Colony morphology
– Presence of cytochrome oxidase
– Strict oxidative metabolism of glucose,but not other
carbohydrates
Lecture 11 BIOL 533 23
Neisseria gonorrhoeae
? Structure of cell
– Endotoxin—resembles meningococcus
? Contain lipid A and core polysaccharide,but no
strain-specific 0 side chain
? Released into extracellular space like
meningococcus
Lecture 11 BIOL 533 24
Neisseria gonorrhoeae
? Pathogenesis
– Encounter and entry
? Only present in humans; not present in
environment or other animals
? Both men and women can be asymptomatic
(normally women)—important to trace and treat
contacts
– Doesn’t colonize vagina in post-pubescent girls
? Attaches to columnar epithelium not squamous
epithelium
? Can colonize throat and rectum
Lecture 11 BIOL 533 25
Neisseria gonorrhoeae
? Pathogenesis
– Process
? Introduced into vagina or urethral mucosa of
penis—attach to surface of epithelial cells and
multiply
– Attach to unidentified specific receptors by pili (also
prevent phagocytosis)
– Protein II—once cells brought close enough by pili,
adherence to cell occurs (also called OPA)
Lecture 11 BIOL 533 26
Neisseria gonorrhoeae
? Pathogenesis
– Process
? Localization due to method of introduction,not
tissue preference
– Gonococcal pharyngitis (oral-genital sex)
– Gonococcal proctitis (anal intercourse)
Lecture 11 BIOL 533 27
Neisseria gonorrhoeae
? Spread and multiplication
– Once attach to non-ciliated cells,multiply
rapidly and spread up urethra (male) or
through cervix (female)
? Are not motile; aided external mechanisms
– Eddy current in mucus
– Attached to spermatozoa
? Protected from IgA by IgA protease
Lecture 11 BIOL 533 28
Neisseria gonorrhoeae
? Spread and multiplication
– Invasion
? Once attach,microvilli extend and embrace
organisms
? Internalized by endocytosis into ―nonprofessional
phagocytes‖ and transported in cell by phagocytic
vesicles
– Coalesce to form larger vesicles—gonococci multiply
– Sheltered from Ab and professional phagocytes
Lecture 11 BIOL 533 29
Neisseria gonorrhoeae
? Spread and multiplication
– Invasion
? After internalization,transported to base of non-
ciliated cells
– Vacuoles fuse with basement membrane and discharge
contents into subepithelial connective tissue
– Either cause local damage or enter blood vessels and
cause disseminated disease
Lecture 11 BIOL 533 30
Neisseria gonorrhoeae
? Survival in bloodstream
– Most strains killed by antibodies
? Target surface proteins and LPS
– Resistant strains cause disseminated disease
? Distinguising characteristics
– More sensitive to penicillin
– Have specific nutritional requirements
– Attachment sialic acid to CHO portion LOS; blocks
complement of activation and binding to other surface
proteins
Lecture 11 BIOL 533 31
Neisseria gonorrhoeae
? Survival in bloodstream
– Women tend to have disseminated disease
affecting joints
? Toxic products spread in blood from local site
(Murein—arthritis)
Lecture 11 BIOL 533 32
Neisseria gonorrhoeae
? Damage
– Ciliated cells—done by endotoxin and
fragments of murein (muramyl monomers,
same as Bordetella pertussis)
? Studied most in fallopian organ culture
? Ciliary mechanism important for transporting egg
from ovary to uterus and for clearing bacteria from
mucosal surface
– After damage,fallopian tube susceptible to bacteria from
vaginal flora that ascend through the cervix and uterus
Lecture 11 BIOL 533 33
Neisseria gonorrhoeae
? Damage
– Submucosal connective tissue,due to
inflammatory response
? Male urethra—leads to local symtoms (pain on
urination and pus discharge)
– Other diseases cause by other pathogens have some of
the same symptoms
– Pain is more intense and urethral discharge is more
copious,thicker,and greenish-yellow
Lecture 11 BIOL 533 34
Neisseria gonorrhoeae
? Outcome of infection
– Males—symptoms usually subside in several
weeks,even without treatment
? Repeated infections,in untreated,can lead to
scarring and stricture of urethra
– Relatively unusual,because males usually seek treatment
Lecture 11 BIOL 533 35
Neisseria gonorrhoeae
? Outcome of infection
– Females—local urogenital infection frequently
asymptomatic
? Complications yield symptoms
? Sequellae of fallopian tube damage
– Ectopic pregnancy,recurrent PID by other organisms,
chronic pelvic pain,and infertility due to blockage or
damage to tubes
? Can lead to death of woman and her unborn child
Lecture 11 BIOL 533 36
Neisseria gonorrhoeae
? Prompt treatment for either gender
decreases chances of disseminated
disease
? Epidemiology,sexual transmission
– Males—20% after intercourse
– Females—50% after intercourse
Lecture 11 BIOL 533 37
Neisseria gonorrhoeae
? Diagnosis
– Gram— intracellular diplococci in vaginal,
cervical,or urethral specimens is suggestive;
start antibiotic therapy
– Important to culture for confirmation
– Biochemical tests
? Oxidase+
? Oxidize glucose,not maltose nor sucrose
Lecture 11 BIOL 533 38
Neisseria gonorrhoeae
? Treatment
– Used to be massive doses of penicillin
– Now,If ?-lactamase resistant (plasmid; same
as Haemophilus influenzae); cephalosporin,
cefriaxone-IM
– Resistance to penicillin,tetracycline,
aminoglycosides (chromosomal; change in cell
surface)—susceptibility test
– Single dose oral therapy
Lecture 11 BIOL 533 39
Neisseria gonorrhoeae
? Treatment
– Single dose oral therapy,ciprofloxacin;
cifixime
? Resistance increasing
– If complicated by Chlamydia,doxycycline;
azithromycin
Lecture 11 BIOL 533 40
Studying Disease and
Development of Vaccine
? No optimal animal model yields symptoms
– Use human volunteers
– Other models,
? Injected bacteria in chamber on back of mouse to
study systemic spread
? Cultured mammalian cell lines to study adherence
and invasion
? Fallopian tube segment (organ culture) to study
effects of infection on Fallopian tubes
Lecture 11 BIOL 533 41
Studying Disease and
Development of Vaccine
? Phase variation,
– Expression of Ag
? Antigenic variation,
– Expression of different copies
? High frequency processes
Lecture 11 BIOL 533 42
Antigenic Variation and
Phase Variation
? Reassortment and recombination of
repeated genes
? Pili antigenic variation
– 1 pil E (pilin expression locus) complete
structural gene yields pilin
– Chromosome also contains 10-15 copies of
other variant-pilus genes
? All truncated at 5’ end lack promoter and
sequences coding for N-terminal protein
Lecture 11 BIOL 533 43
Antigenic Variation and
Phase Variation
? Pil S (silent) non-functional
? Homologous recombination bet pil S and
pil E
– Can also have recombination of small portion
pil S yields hybrid
– Pil S always acts as donor; never altered
themselves; transforming molecule
? Phase variation,expression on or off at
high frequency
Lecture 11 BIOL 533 44
Antigenic Variation and
Phase Variation
? Mechanisms
– Site-specific inversion of segment with a
promoter
– Type 1 fimbriae E,coli; Salmonella flagellar
types
– Pili expression of other Gram—
– On,transcription of fim A gene take place
– Off,other direction
Lecture 11 BIOL 533 45
Antigenic Variation and
Phase Variation
? Short nucleotide repeats at 5’ end of
genes
– Can be gained or lost due to strand
misalignment during replication and repair
– Disrupt translational reading frame
Lecture 11 BIOL 533 46
Antigenic Variation and
Phase Variation
? Expression Opa proteins (protein II)
– Copies of complete opa genes (each encode
different Ag varients)
– Each gene copy has repeats of sequence
CTCTT within 5’ end
– Gain or loss alters reading frame,protein
made or not
Lecture 11 BIOL 533 47
Antigenic Variation and
Phase Variation
? Similar mechanism controls expression of
other surface proteins
? Affects expression of biosynthetic genes
for LPS yielding structural variability
Lecture 11 BIOL 533 48
Lecture 11
? Questions?
? Comments?
? Assignments..,