Chapter 8: Gram-negative Bacteria: Neisseria Flashcards
Neisseria - morphology?
cocci in pairs (diplococci)
each coccus is shaped like a kidney bean, and the concave sides face each other, so the diplococcus looks like a small donut
Neisseria - Gram-stain?
Gram-negative
What are the two families of Gram-negative diplococci?
Neisseria
Moraxella (in the greater family of Neisseriaceae)
Which 2 species of Neisseria cause disease in humans?
Neisseria meningitidis
N. gonorrhoeae
Gram-negative kidney-shaped diplococci?
Neisseria
Neisseria meningitidis - Gram stain?
Gram-negative
Neisseria meningitidis - morphology?
kidney bean shaped diplococci with concave sides facing each other, forming the appearance of a donut
Neisseria meningitidis - metabolism?
facultative anaerobe (or aerobic)
What bacteria is aka meningococcus?
Neisseria meningitidis
Neisseria meningitidis - encapsulated?
polysaccharide capsule
What virulence factors does Neisseria meningitidis exhibit? (5)
1) polysaccharide capsule - 13 serotypes
2) endotoxin (LPS)
3) IgA1 protease
4) have unique proteins that can extract iron from transferrin, lactoferrin, and hemoglobin
5) Pili: adherence
What is the purpose of Neisseria meningitidis polysaccharide capsule?
antiphagocytic (as long as the human host doesn’t have specific antibodies to opsonize the bacterium)
What effect does endotoxin/LPS released by Neisseria meningitidis into the blood have on the blood?
hemorrhage (blood vessel destruction) and sepsis
What effect does endotoxin/LPS released by Neisseria meningitidis into the blood have on the skin?
petechiae (petechial ash): tiny round red dots of hemorrhage on the skin
What effect does endotoxin/LPS released by Neisseria meningitidis into the blood have on the internal organs when disease progresses? What is this syndrome called?
hemorrhage of adrenal glands (Waterhouse-Friderichsen syndrome)
What is the purpose of Neisseria meningitidis pili?
allow attachment to human nasopharyngeal cell, and undergo antigenic variation to avoid attack by the immune system
Does everyone with Neisseria meningitidis nasopharyngeal infection become symptomatic?
No, 5% are asymptomatic (carriers) and develop anti-meningococcal antibodies
What groups are at high risk of becoming infected with Neisseria meningitidis? (3)
1) infants aged 6 months to 2 years
2) army recruits
3) college freshmen
How is Neisseria meningitidis transmitted?
via respiratory droplets
How do patients with invasive Neisseria meningitidis infection present? (3)
1) bacterial meningitis: stiff neck, headache, fever, chills
2) petechial rash: tiny round red dots of hemorrhage in the skin due to release of endotoxin (vascular necrosis and inflammation)
(3) sepsis
Which bacteria are responsible for most neonatal meningitis (<3mos)?
1) Group B streptococcus
2) Listeria monocytogenes
3) E. coli
Which bacteria are responsible for meningitis in older children (after maternal antibodies passively given to fetus wane and before new antibodies develop)?
1) Haemophilus influenzae
2) Neisseria meningitidis
What causes the petechiae observed with Neisseria meningitidis infection?
release of LPS endotoxin from the meningococcus, causing vascular necrosis, and inflammatory reaction, and hemorrhage into the surrounding skin
What is Waterhouse-Friderichsen syndrome?
Fulminant meningococcemia (N. meningitidis septic shock) - bilateral hemorrhage into the adrenal glands occurs, causing renal insufficiency. Abrupt onset of hypotension and tachycardia, along with rapidly enlarging petechial skin lesions. DIC and coma may develop. Death can occur rapidly (6-8 hours).
What is the classic special medium for culturing Neisseria meningitidis?
Thayer-Martin (or VPN) media
“to connect to Neisseria, please use your VPN client”
What is Thayer-Martin (VPN) media? (defn and components)
essentially chocolate agar with antibiotics
1) Vancomycin inhibits gram-positive organisms
2) Polymyxin inhibits gram-negative organisms except Neisseria
3) Nystatin inhibits fungi
What is chocolate agar?
blood agar that has been heated so it turns brown
What is the classic special medium for culturing Neisseria gonorrhoeae?
Thayer-Martin (or VPN) media
“to connect to Neisseria, please use your VPN client”
Thayer-Martin (VPN) media can culture which organisms?
The Neisserias (2):
Neisseria meningitidis
Neisseria gonorrhoeae
Neisseria meningitidis - maltose metabolism?
yes, able to metabolize maltose
MeninGitidis ferment maltose and glucose
Neisseria gonorrhoeae - maltose metabolism?
no, not able to metabolize maltose
Gonorrhoeae ferment Glucose
Neisseria meningitidis - glucose metabolism?
yes, can metabolize glucose
MeninGitidis ferment maltose and glucose
Neisseria gonnorhoeae - glucose metabolism?
yes, can metabolize glucose
Gonorrhoeae ferment Glucose
How can you differentiate among the different species of Neisseria in the lab?
Neisseria meningitidis can ferment (produce acid) from maltose metabolism; Neisseria gonorrhoeae cannot.
What is the treatment for Neisseria meningitidis meningococcemia/meningitis? (2)
1) penicillin G
2) ceftriaxone (3rd generation cephalosporin)
What is the treatment for close contacts of a Neisseria meningitidis infected patient? (3)
Prophylaxis:
1) rifampin
2) ciprofloxacin
3) ceftriaxone
Is there a vaccine for Neisseria meningitidis?
yes!
What is the vaccine for Neisseria meningitidis composed of?
purified capsular polysaccharides from certain strains (groups A, C, Y, and W135) - TYPE B IS NOT COVERED (does not induce immunity)
Meningitis is usually caused by which capsule serogroups of Neisseria meningitidis?
A, B, C
epidemics are usually type B
Which capsule serogroup of Neisseria meningitidis is not covered by the vaccine?
B
How many capsule serogroups are there for Neisseria meningitidis?
13
A, B, C, D, E, H, I, K, L, X, Y, Z, W-135
(F, G, J are not included!)
What are the problems with the current Neisseria meningitidis vaccines?
1) Do not induce sufficient immunity in children <2
2) Duration of immunity in adults is only 2-4 years
Does Neisseria meningitis produce exotoxins?
no
What are the symptoms of Neisseria meningitidis meningitis? (5)
1) fever
2) stiff neck (nuchal rigidity)
3) vomiting
4) lethargy or altered mental status
5) petechial rash
What are the symptoms of Neisseria meningitidis septicemia (meningococcemia)? (4)
1) fever
2) petechial rash
3) hypotension
4) fulminant meningococcemia (Waterhouse-Friderichsen syndrome): hemorrhage of the adrenal glands along with hyptension and the petechial rash
Neisseria gonorrhoeae - Gram stain?
Gram-negative
Neisseria gonorrhoeae - morphology?
kidney bean shaped diplococci with concave sides facing each other, forming the appearance of a donut
How is Neisseria meningitidis infection diagnosed?
smear and culture from blood and CSF
Neisseria gonorrhoeae - metabolism?
facultative anaerobe (or aerobic)
Neisseria gonorrhoeae - encapsulated?
no capsule
What virulence factors does Neisseria gonorrhoeae exhibit? (5)
1) endotoxin (LPS)
2) IgA1 protease
3) have unique proteins that can extract iron from transferrin, lactoferrin, and hemoglobin
4) Pili: adherence, antigenic variation, antiphagocytic
5) outer membrane proteins (porins and Opa proteins): invasion into epithelial cells
What are the functions of Neisseria gonorrhoeae pili? (3)
1) adherence to host cells
2) prevent phagocytosis: adhere so closely to host cells that macrophages or neutrophils are unable to attack
3) antigenic variation - genes encoding pili undergo multiple recombinations
What is the function of Neisseria gonorrhoeae outer membrane proteins (PorA and PorB, formerly called protein I)?
promote invasion into epithelial cells
What is the function of Neisseria gonohorroea Opa proteins?
another class of outer membrane proteins (other than PorA and PorB (protein I)) that promote adherence and invasion into epithelial clels. - so named because their expression results in opaque colonies
How does Neisseria gonorrhoeae cause systemic infection?
- Pili, porins, and Opa proteins allow to the gonococci to bind to a Fallopian tube non-ciliated epithelial cell.
- Gonococcal endotoxin (LPS) then destroys the cilia on neighboring cells.
- The gonococcus is then taken up by endocytosis, transported in the endocytic vacuoles where it multiples, and is released into the subepithelial space where it can cause more systemic infection.
Does Neisseria meninigitidis secrete exotoxins?
NO
Does Neisseria gonorrhoeae secrete exotoxins?
No
How does Neisseria gonorrhoeae infection present in men?
urethritis - inflammation of the urethra (gonococci penetrates the mucuous membranes of the urethra)
-some men will remain asymptomatic
How does Neisseria gonorrhoeae infection present in women?
cervical infection (columnar epitheliam), which becomes reddened and friable, with a purulent exudate - which can progress to pelvic inflammatory disease PID. -a large percentage of women are asymptomatic
What is PID?
pelvic inflammatory disease - “pus in dere”
-infection of the uterus (endometritis), fallopian tubes (salpingitis), and/or ovaries (oophoritis)
Define endometritis.
infection of the uterus (as in PID)
What is infection of the uterus called?
endometritis
Define salpingitis.
infection of the Fallopian tubes (as in PID)
What is infection of the Fallopian tubes called?
salpingitis
Define oophorotis.
infection of the ovaries (as in PID)
What is infection of the ovaries called?
oophorotis
How does PID present? (4)
1) fever
2) lower abdominal pain
3) abnormal menstrual bleeding
4) cervical motion tenderness
Differential for:
1) fever
2) lower abdominal pain
3) abnormal menstrual bleeding
4) cervical motion tenderness
PID (pelvic inflammatory disease)
Why do over 50% of cases of PID occur within one week of the onset of menstruation?
Menstruation allows the bacteria (Neisseria gonorrhoeae or Chlamydia trachomatis) to spread from the cervix to the upper genital tract
What are complications of PID?
1) sterility - from scarring of the Fallopian tubes (which occludes the lumen and prevents sperm from reaching the ovulated egg)
2) ectopic pregnancy - scarring of the Fallopian tubes causes resistance to normal egg transit down the tubes.
3) abscesses - in Fallopian tubes, ovaries, or peritoneum.
4) peritonitis - bacteria may spread from ovaries and Fallopian tubes to infect the peritoneal fluid
5) peri-hepatitis (Fitz-Hug-Curtis syndrome) - infection of the capsule that surrounds the liver
What are the 2 major causes of PID?
Neisseria gonorrhoeae
Chlamydia trachomatis
What is Fitz-Hugh-Curtis syndrome?
peri-hepatitis - infection by Neisseria gonorrhoeae or Chlamydia trachomatis of the capsule that surrounds the liver. A patient will complain of right upper quadrant pain and tenderness. Complication of PID.
How does Neisseria gonorrhoeae infection present in both men and women? (2)
1) Gonococcal bacteremia
2) Septic arthritis
How does the gonococcal bacteremia of Neisseria gonorrhoeae typically present?
Rarely, it can invade the bloodstream.
Manifestations include fever, joint pains, and skin lesions (which usually erupt on the extremities).
Pericarditis, endocarditis, and meningitis are rare but serious complications of a disseminated infection.
How does the septic arthritis of Neisseria gonorrhoeae infection typically present?
Acute onset of fever occurs along with pain and swelling of 1-2 joints.
Progressive destruction of the joint will occur without prompt antibiotic therapy.
Gram stain and culture of synovial fluid (increased WBCs) reveals Gram-negative diplococci within the WBCs.
-Is the most common kind of septic arthritis in young, sexually active individuals.
What is the most common cause of septic arthritis in young, sexually active individuals?
Neisseria gonorrhoeae
How is Neisseria gonorrhoeae transmitted?
- Transmission of body fluids among sexually active adults and teens.
- During birth as the baby passes through the vaginal canal.
How does Neisseria gonorrhoeae present in infants, when transmitted during vaginal delivery?
ophthalmia neonatorum (neonatal conjunctivitis) - an eye infection usually occurs on the first or second day of life and can damage the cornea, causing blindness.
Define ophthalmia neonatorum.
(neonatal conjunctivitis) - an eye infection usually occurs on the first or second day of life and can damage the cornea, causing blindness.
Neisseria gonorrhoeae or Chlamydia eye infections.
In culture, how do you distinguish Neisseria gonorrhoeae from normal Gram-negative diplococci flora of the vaginal tract?
Thayer-Martin VPN media
Is there a vaccine for Neisseria gonorrhoeae?
No!
There is a vaccine for Neisseria (meningitidis, gonorrhoeae, both).
Neisseria meningitidis only.
There is no vaccine for Neisseria gonorrhoeae.
What is the treatment for ophthalmia neonatorum (neonatal conjunctivitis)?
erythromycin eyedrops (effective against both Neisseria gonorrhoeae and Chlamydia trachomatis)
What is the treatment for gonococcal disease?
Ceftriaxone 250mg IM
and Azithromycin 1g orally, or doxycycline, for possible chlamydia co-infection
Moraxella (Brnhamella) catarrhalis - Gram stain?
Gram-negative
Moraxella (Branhamella) catarrhalis - morphology?
diplococci
Neisseria family
Moraxella (Branhamella) catarrhalis - reservoir?
part of normal human respiratory flora
What major diseases does Moraxella (Branhamella) catarrhalis cause? (3)
1) otitis media
2) respiratory infection in patients with COPD or in the elderly
3) COPD exacerbations
What 3 main bacteria cause otitis media?
1) Streptococcus pneumoniae (30% of cases)
2) Haemophilus influenzae (25% of cases)
3) Moraxella catarrhalis (15-20%)
Where does Kingella kingae frequently colonize?
throats of young children
What diseases can Kingella kingae cause?
1) septic arthritis in children
2) osteomyelitis in children
3) endocarditis of native and prosthetic valves in adults and children
What slow growing Gram-negative pathogens cause endocarditis?
HACEK group of bacteria:
1) Haemophilus
2) Actinobacillus
3) Cardiobacterium
4) Eikenella
5) Kingella
Kingella kingae - Gram stain?
Gram-negative
Kingella kingae - morphology?
diplococci
Neisseria family
