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
For ____ ______ Symptoms start like a mild cold, progress to throbbing headache, fever, stiffness in
neck and back, nausea and vomiting, deafness and coma.
Shock and death (100% if untreated) may occur within 24 hours, but frequently is slower so that effective treatment can be given (<10% death in treated cases).
Neisseria meningitidis
Obstruction of release of increased fluid pressure (due to PMN attempts at
eradication: pus and clotting) impairs brain, causes paralysis of motor nerves and coma. Loss of blood supply to brain is one of the frequent symptoms just prior to death
Neisseria meningitidis
LOS/endotoxin release from blood-circulating meningococci (which have a high tendency to auto-lyse and thus spread LOS widely) causes shock.
Neisseria meningitidis
T/F: with Neisseria meningitidis, small local skin hemorrhages are observed: Localized loss of vascular integrity: effect of inflammatory cytokines release induced by endotoxin activation of macrophages.
this is contrary to other meningitis-causing infections.
true
blood spots, bruising, and discoloration of skin from coagulation in small blood vessels
Purpura fulminans
Purpura fulminans is seen in what bacterial infection?
Neisseria meningitidis
______ _____ Can progress to disseminated intravascular coagulation: blood clots throughout the circulatory system resulting in blockages and excessive bleeding elsewhere (clotting factors depleted)
Purpura fulminans
Ø Large capsule
Ø IgA protease
Ø Pili
Ø Shedding of lots of Endotoxin shock
Vi rulence Factors of N.meningitidis
What is the virulent role of the large capsule in neisseria meningitidis
Ø Large capsule leads to disseminated intravascular coagulation (DIC)
Some virulent strains have capsules with sialic acid on LOS (like N.gonorrhea): reduces phagocytosis further
What are the two effective vaccinations against capsular polysaccharides?
MenACWY Vaccine
MenB vaccine
CDC recommended since 2005 Protection from 4 major disease-causing strains: A, C, W135 and Y (serotyping: 12 antigenic groups)
MenACWY Vaccine
– approved in 2014 & also recommended B capsule poly-sialic acid; Andy Marso’s case involved serogroup B bacteria. European MenB vaccine was used in outbreaks at Princeton and UC Santa Barbara in 2013-2014
MenB vaccine
t/f: Mandatory vaccination for neisseria meningitidis for students living in dorms
in many states, military recruits, and jail inmates
true
Neisseria meningitidis is gram __
negative
Virulence factors:
- pili
- Ag-variation
- OPA IgA protease endotoxin/ LOS
Clinical Features:
- gonorhea pelvic inflammatory disease
- arthritis
Epidemiology:
- sexual transmission
- asymptomatic carrier
Neisseria Gonorrhae
Virulence factors:
- polysaccarhide capsule
- entoxin/ LOS
- Pili
- IgA protease
Clinical Features:
- meningitis
- meningococcemia
Prevention:
-MenACWY & MenB vaccines
Epidemiology:
- asymptomatic carrier
- aerosol transmission
- children/young adult
Neisseria meningitidis
Gram− bacteria of the human colon/oral cavity
- Strict anaerobes
- Commensals
- Opportunistic pathogens
Bacteroidales
G-
- most frequently isolated from clinical specimens of abscesses caused by intestinal bacteria
- most oxygen-resistant Bacteroides
Bacteroides fragilis
Ø Superoxide dismutase - detoxifies oxygen radicals
Ø Catalase - breaks down hydrogen peroxide
Allows survival in well oxygenated peritoneal cavity
Also helps bacteria resisting killing by phagocytosis
Ø Polysaccharide capsule
Virulence Factors of Bacteroidales
______ Disease is caused when bacteria are introduced into deep tissues
- peritonitis - rupture of infected appendix/diverticulum
- pulmonary abscess - aspiration of oropharyngeal bacteria
Bacteroidales
T/F: Bacteroides fragilis is one component in these diseases
polymicrobial diseases
true
start with acute inflammation
progress to formation of localized abscesses
biphasic-
____ ____ changes as disease progresses
100’s of different species in inoculum few species in abscess
bacterial composition
- perforation of intestine/spillage of intestinal fluid
- neutrophils mobilized
- surviving bacteria resistant to phagocytosis
(B. fragilis has a capsule) - oxygen-sensitive bacteria are killed
(peritoneal cavity well-oxygenated) - facultative anaerobes grow first (E. coli)
- some strict anaerobes survive
- site becomes anaerobic
- surviving strict anaerobes become predominant
Course of disease for Bacteroidales
treat _____ with Surgery and antibiotic combinations (target aerobes and anaerobes)
Bacteroidales
