Gram Negative Bacteria Flashcards

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1
Q

Structure of gram negative?

How does it evade immune system?

A

Two membrane - outer membrane connected LPS layer
Outer layer - major LSP antigen
LPS and capsule help immune evasion

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2
Q

What are the surface antigens?

A
KOH P 
K antigen - capsule
O antigen - outer membrane lipopolysaccharide
H antigen - flagellum 
Peptidoglycan
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3
Q

Structure cell envelope - outside in?

A

Capsule –> LPS –> porin –> OM –> periplasm –> peptidoglycan –> inner membrane

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4
Q

Give example of medically important gram negative spp

A

Neisseria - meningitis and gonnorhoea
Haemophilius Influenza - meningitis and pneumonia
Pseudomonas aeruginosa - burn pt and lung infection CF pt

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5
Q

What is neisseria? - how do they grown and what would you culture them on?

A

Gram negative diplococci

Grow fastidiously on chocolate agar

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6
Q

What is N. Meningitidis

A

Infection of CSF and meninges caused by commensal carry in nasopharynx
Capsular

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7
Q

What is N. Gonnorhoea

A

STI, genital and oral infection

Lipooligosaccharide capsule often sialyated

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8
Q

Explain serogrouping on N. Meningitis

Which serogroup comprised 90% diagnosis?

A

Dependent on polysaccharide capsular antigen
Serotype: A, B, C, Y, W135
Serotype B = 90% cases

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9
Q

Pathogenesis of N. Meningitis

A

Spread to subarachnoid space or via nasopharyngeal mucosa to blood
IgA proteases for serum resistance

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10
Q

Where is highest occurrence of meningitis

A

Sub-saharan Africa in ‘meningitis belt’

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11
Q

Diagnosis meningitis?

A
CSF - many PMNLs and presence of bacteria
Blood culture (choc agar) - sugar fermentation test - +ve glucose and maltose, oxidase positive
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12
Q

Tx meningitis?

A

Penicillin and cefotaxime

Followed by eradicative tx or rifampicin or ciprofloxacin (often w/ corticosteroid)

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13
Q

What is haemophilus influenza?

A

Gram -ve cocco-bacilli

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14
Q

Pathogenesis of h. influenza and main virulence factor?

A

6 capsular type - a–>f

Avoidance c3b binding, IgA proteases, fimbriae adhesion

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15
Q

Diagnosis h. influenza?

A

Sputum, throat swab, blood culture (choc agar)

Haemophili require factor X (haemin) and factor V (NAD/ NADH) growth

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16
Q

Tx h.influenza

A

Cefotaxime

Chemoprophylaxis for contacts - rifampicin

17
Q

What is pseudomonas aeruginosa?

A

Gram -ve motile aerobic rod

18
Q

Characteristic diagnosis p.aeurginosa?

A

Green spreading colonies with grapes smell

19
Q

Virulence of pseudomonas aeruginosa?

A

Extracellular proteases which break down tissue

20
Q

Complication of pseudomonas aeruginosa?

A

Septicemia

21
Q

What are the ESKAPE pathogens

A

Most antibiotic resistant pathogens - highest risk in hospital and clinical setting

E (+ve) - enterococcus faecium 
S (+ve) - staph aureus 
K (-ve) -klebsiella pneumoniae 
A (-ve) - acinetobacter 
P (-ve) - pseudomonas
E (-ve) - enterobacter