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Medical Microbiology > Neisseria and Related Gram Negative Organisms > Flashcards

Neisseria and Related Gram Negative Organisms Flashcards

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USMLE® Step 1 flashcards Biology 101 flashcards
1
Q

Who gets meningitis?

A

Kids 6mo - 2 yr. People in conditions of overcrowding (college). Splenectomy.

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2
Q

Where is neisseria meningitidis found normally?

A

In the nasopharynx of healthy people

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3
Q

When does neisseria meningitidis cause a life-threatening infection?

A

When it reaches the bloodstream/CNS.

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4
Q

How is meningococcus spread?

A

Through respiratory droplets.

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5
Q

Virulence factors of N. meningitidis

A

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.

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6
Q

How does menigococcus get to the subarachnoid space?

A

Respiratory droplets, pass through respiratory mucosa, into blood, passes through blood-brain barrier into CSF in subarachnoid space, multiplies there.

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7
Q

Classic sign of meningococcemia?

A

Rash with petechia/purpura. The rash does not blanch.

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8
Q

What bacteria have LPS, which have LOS?

A

LPS = E. coli, klebsiella. LOS = n.meningitidis

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9
Q

Why is LPS/LOS dangerous?

A

When the organism dies, LPS/LOS is released and causes a huge inflammatory response.

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10
Q

N. Meningitidis serogroups

A

Determined by polysaccharide capsule, 13 in total, most important are A, C, Y, W-135.

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11
Q

Conjugate vaccine vs polysaccharide vaccine

A

Sugars are not very immunogenic, will only induce IgM response. Conjugated to a protein, however, the polysaccharide will induce an IgG response.

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12
Q

How to treat neisseria meningitidis?

A

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.

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13
Q

What to give when suspected meningitis but no organism visible on the gram stain?

A

Give ceftriaxone, vancomycin (in case of resistance), and ampicillin (for listeria).

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14
Q

What does N. meningitidis look like under a microscope?

A

Gram negative diplococci.

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15
Q

Listeria monocytogenes appearance under microscope?

A

Gram positive rod. With tumbling end over end movement.

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16
Q

Can listeria cause meningitis?

A

Yup, can spread from gastrointestinal tract to meninges.

17
Q

Who gets listeria induced meningitis?

A

Infants and the elderly, pregnant women and the immunocompromised.

18
Q

Chemoprophylaxis for meningitis?

A

Yes, give Rifampin to close contacts.

19
Q

Neisseria Gonorrhoeae appearance

A

Gram negative diplococci

20
Q

Differences between gonococcus and meningococcus

A

N. Gonorrhoeae does not have a true LPS capsule, only uses glucose. Meningococcus uses maltose.

21
Q

Virulence factors for N. gonorrhoeae?

A

Pili on outer membrane assists in binding to mucosal surfaces.

22
Q

What other infections can gonorrhoeae cause?

A

Pelvic inflammatory disease, eye infections

23
Q

How to treat N. gonorrhoeae?

A

Has beta lactamase activity, increasing resistance to fluoroquinolones. Cephalosporins are the mainstay of therapy

24
Q

What is assumed with a gonorrhoeae infection

A

Co-infection w/ chlymydia, so need to give doxycycline/macrolide too.

25
Q

Haemophilus Influenzae Appearance on slides and plates

A

Small gram negative rods. Growth on chocolate agar with factor V and X. Also grows in satellite colonies next to staph aureus. CAPSULE!

26
Q

V factor, X factor

A

NAD secreted by staph aureus, X = intracellular heme, released by S.Aureus.

27
Q

Vaccinate for H. Influenzae?

A

Yes, HiB vaccine is a capsular polysaccharide conjugated to proteins.

28
Q

Haemophilus Ducreyii

A

Sexually transmitted, painful ulcer with enlarged tender lymph nodes.

29
Q

Appearance of Haemophilus Ducreyii on slide

A

School of fish!

30
Q

Moraxella catarrhalis appearance

A

Small gram negative diplococci.

31
Q

How to distinguish moraxella catarrhalis?

A

Aerobic and catalase positive.

32
Q

What does Moraxella catarrhalis cause?

A

Otitis, sinusitis, and pneumonia, especially in patients with emphysema.

33
Q

Bordetella Pertussis appearance

A

Gram negative coccobacillus

34
Q

Classic virulence factor of B. Pertussis?

A

AB toxin

35
Q

3 phases of whooping cough?

A

Catarrhal - flu-like, non productive cough, lasts 2 weeks.
Paroxysmal - Bursts of coughing followed by whooping inspiration.
Convalescence- paroxysms improve gradually, can recur.

36
Q

How to detect gonorrhea?

A

DNA amplification.

Medical Microbiology (29 decks)

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