Neisseria and Related Gram Negative Organisms Flashcards
Who gets meningitis?
Kids 6mo - 2 yr. People in conditions of overcrowding (college). Splenectomy.
Where is neisseria meningitidis found normally?
In the nasopharynx of healthy people
When does neisseria meningitidis cause a life-threatening infection?
When it reaches the bloodstream/CNS.
How is meningococcus spread?
Through respiratory droplets.
Virulence factors of N. meningitidis
IgA protease. Pili to attach to respiratory epithelium. OPA and OPC proteins lead to engulfment by respiratory cells. Polysaccharide capsule. MOST IMPORTANTLY: Lipooligosaccharide, an endotoxin that triggers sepsis.
How does menigococcus get to the subarachnoid space?
Respiratory droplets, pass through respiratory mucosa, into blood, passes through blood-brain barrier into CSF in subarachnoid space, multiplies there.
Classic sign of meningococcemia?
Rash with petechia/purpura. The rash does not blanch.
What bacteria have LPS, which have LOS?
LPS = E. coli, klebsiella. LOS = n.meningitidis
Why is LPS/LOS dangerous?
When the organism dies, LPS/LOS is released and causes a huge inflammatory response.
N. Meningitidis serogroups
Determined by polysaccharide capsule, 13 in total, most important are A, C, Y, W-135.
Conjugate vaccine vs polysaccharide vaccine
Sugars are not very immunogenic, will only induce IgM response. Conjugated to a protein, however, the polysaccharide will induce an IgG response.
How to treat neisseria meningitidis?
Unique because its one of the few gram negative organisms that are susceptible to penicillin. It does not produce a beta-lactamase, so cephalosporins are more commonly used.
What to give when suspected meningitis but no organism visible on the gram stain?
Give ceftriaxone, vancomycin (in case of resistance), and ampicillin (for listeria).
What does N. meningitidis look like under a microscope?
Gram negative diplococci.
Listeria monocytogenes appearance under microscope?
Gram positive rod. With tumbling end over end movement.
Can listeria cause meningitis?
Yup, can spread from gastrointestinal tract to meninges.
Who gets listeria induced meningitis?
Infants and the elderly, pregnant women and the immunocompromised.
Chemoprophylaxis for meningitis?
Yes, give Rifampin to close contacts.
Neisseria Gonorrhoeae appearance
Gram negative diplococci
Differences between gonococcus and meningococcus
N. Gonorrhoeae does not have a true LPS capsule, only uses glucose. Meningococcus uses maltose.
Virulence factors for N. gonorrhoeae?
Pili on outer membrane assists in binding to mucosal surfaces.
What other infections can gonorrhoeae cause?
Pelvic inflammatory disease, eye infections
How to treat N. gonorrhoeae?
Has beta lactamase activity, increasing resistance to fluoroquinolones. Cephalosporins are the mainstay of therapy
What is assumed with a gonorrhoeae infection
Co-infection w/ chlymydia, so need to give doxycycline/macrolide too.
Haemophilus Influenzae Appearance on slides and plates
Small gram negative rods. Growth on chocolate agar with factor V and X. Also grows in satellite colonies next to staph aureus. CAPSULE!
V factor, X factor
NAD secreted by staph aureus, X = intracellular heme, released by S.Aureus.
Vaccinate for H. Influenzae?
Yes, HiB vaccine is a capsular polysaccharide conjugated to proteins.
Haemophilus Ducreyii
Sexually transmitted, painful ulcer with enlarged tender lymph nodes.
Appearance of Haemophilus Ducreyii on slide
School of fish!
Moraxella catarrhalis appearance
Small gram negative diplococci.
How to distinguish moraxella catarrhalis?
Aerobic and catalase positive.
What does Moraxella catarrhalis cause?
Otitis, sinusitis, and pneumonia, especially in patients with emphysema.
Bordetella Pertussis appearance
Gram negative coccobacillus
Classic virulence factor of B. Pertussis?
AB toxin
3 phases of whooping cough?
Catarrhal - flu-like, non productive cough, lasts 2 weeks.
Paroxysmal - Bursts of coughing followed by whooping inspiration.
Convalescence- paroxysms improve gradually, can recur.
How to detect gonorrhea?
DNA amplification.
