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Microbiology > Kaul - Gram+ And Gram- Cocci > Flashcards

Kaul - Gram+ And Gram- Cocci Flashcards

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Biology 101 flashcards
1
Q

Virulence factors of staph aureus

A

Cytotoxins - Hemolysins and Leukocidins (PVL)
Super antigen toxins - TSST-1, enterotoxin, exfoliatin
Protein A, Microcapsule, Adhesins
Invasins

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2
Q

How do the Staph Aureus super antigens work?

A

They non-specifically crosslink MHC to TCR –> activates T cells that shouldn’t be activated–> overproduction of cytokines

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3
Q

What does Protein A do?

A

Anti-opsonin effect by binding Fc region of antibodies

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4
Q

Most common clinical presentations of Steph aureus infections

A

Skin and Soft tissue infections (SSTIs)
- furuncles, carbuncles, impetigo, cellulitis

Osteomyelitis, septic arthritis, Pnemonia, and acute endocarditis

Toxinoses - Toxic Shock syndrome (TSST-1), food poisoning (enterotoxin), and scalded skin syndrome (exfoliatin)

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5
Q

Staph epidermis

A
  • produces cell surface polysaccharide “slime” that adheres to bioprosthetic materials.
  • major component of normal skin flora
  • cause wound infections throug broken skin
  • frequently involve in catheter infections, medical device infections, and IV live infections
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6
Q

Staph saprophyticus

A
  • normal vaginal flora
  • causes UTI, cystitis in women
  • resistant to novobiocin
  • sensitive to penicillin G
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7
Q

Between strep and staph which are in clusters and which are in chains

A 
Staph = clusters
Strep = chains
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8
Q

Between strep and staph which is catalase positive?

A

Staph

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9
Q

Of the staphs, which are coagulase positive and which negative?

A

Aureus = positive

Epidermidis and saprophyticus = negative

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10
Q

What are two ways you can distinguish strep organisms from each other?

A

Hemolysis pattern and lancefield group

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11
Q

Lancefield group

A

Based on antigenic cell wall polysaccharide called C-substance

  • groups A-U
  • tested in a slide agglutination assay
  • common ones are A, B, D, and none
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12
Q

What is the breakdown of which strep is in which lancefield group and which hemolysis pattern?

A

Strep Pyogenes - Group A strep and beta hemolysis

Strep agalactiae - Group B strep, beta hemolysis

Strep neumo and Virdans group - no lancefield group and alpha hemolysis

Strep bovis - group D lancefield group and gamma hemolysis

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13
Q

Strep Pyogenes virulence factors

A

M protein - inhibits complement
Strepyolysin O and S - lyses RBCs
Streptokinase

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14
Q

Clinical manifestations of Strep Pyogenes (Group A Strep)

A
  • Sore throat, pharyngitis, scarlet fever
  • skin infections - impetigo, cellulitis, necrotizing fasciitis
  • toxic shock syndrome

Post infection - rheumatic fever - myocarditis, arthritis, chorea, fever (JONES)
- acute glomerulonephritis

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15
Q

How is strep Pyogenes (GAS) spread?

A

Contact, droplets, food - it usually inhabits the nasopharynx, throat, and sometimes skin.

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16
Q

Strep agalactiae

A

Group B strep

  • female reproductive tract
  • causes neonatal sepsis
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17
Q

WHat test can be done to seperate strep Pyogenes from strep agalactiae?

A

Bacitracin

  • Pyogenes = bacitracin sensitive
  • agalactiae - bacitracin resistant
18
Q

Virdans group strep

A

Live in the oral cavity

  • usually not invasive but dental or oral surgical procedures facilitate entrance into the bloodstream
  • causes dental cavities
  • causes subacute endocarditis
19
Q

What does strep Pneumo look like under microscope

A

Lancet shaped cells arranged in chains

20
Q

Strep Pneumo virulence factors

A
  • polysaccharide capsule that prevents phagocytosis. It is antigenic
21
Q

Where is strep Pneumo usually found?

A

Nasopharynx - so infections are usually endogenous

22
Q

Clinical manifestations of strep Pneumo

A

Meningitis, Otitis media, pneumonia, Sepsis

23
Q

What tests can differentiate between strep Pneumo and strep Virdans?

A

Optochin test - Pneumo is optochin sensitive

Bile acids - Pneumo is bile sensitive

Quellung - strep Pneumo has a capsule so it will have a border around it.

24
Q

Strep Pneumo treatment

A

Cephalosporins such as ceftriaxone or cefotaxamine

25
Q

Strep Pneumo vaccine

A

Adults take PPV, which is a 23-valent polysaccharide for adults 65 and up or high risk people over 2

Children take PCV13 - given to children under 5 and immunocomprimised adults over 65

26
Q

Strep Boviss

A

Component of gastrointestinal flora

  • can grow on bile but not in NaCl
  • gamma or sometimes alpha hemolysis
  • Group D strep
27
Q

Enterococci

A

Considered a Group D antigen

  • gamma hemolysis (or sometimes alpha and even less sometimes beta)
  • E. faecalis and E. Faecium are most summon types
  • component of GI floria
  • opportunistic infections that leads to endocarditis and bacteremia/sepsi
  • also causes binary tract infections and urinary tract infections
28
Q

What is a frequent resistance for enterococci?

A

Vancomycin

- called VRE

29
Q

How to identify enterococci?

A

They grow on bile salts and also grow in NaCl

30
Q

Treatment for enterococci?

A

Ampicillin + Gentamycin/Penicllin +streptomycin

Vancomycin

Linezolid for VRE

31
Q

Neisseria

A 
Gram negative
Diplococci
Often seen with PMNs
IgA protease is virulence factor
Pilli demonstrates phase variation
32
Q

N. Gonorrhoeae

A 
Unencapsulated
Pili
Opa
LOS
IgA protease
Require iron, so they express proteins that can extract iron from host iron proteins such as transferrin and lactoferrin.
33
Q

Clinical manifestations of N. Gonorrhoeae

A

Genitourinary infections - PID, urethritis
Ophthalmia neonatorum
Septic arthritis

34
Q

Diagnosis of N. Gonorrhoeae

A

Gram stain from specimen or smear
Culture - must be cultured on Thayer-Martin medium, which suppresses normal flora.
- oxidase positive
NAATs

35
Q

Treatment for N. Gonorrhoeae

A

IM ceftriaxone

- also give athromycin or doxycycline to cover possible concomitant chlamydia

36
Q

N. Meningitidis virulence factors

A 
Antigenic capsule
Pilli
LOS
Opa
IgA protease
Iron extraction system
37
Q

Where is N. Meningitidis usually carried?

A

Nasopharynx

38
Q

Clinical manifestation of meningitidis

A

Petechial rash
Headache
Stiff neck
Sensitivity to light
Septic shock (LOS)
Disseminated intravascular coagulation (DIC)
Adrenal collapse (Waterhouse-Friedrichsen Syndrome)

39
Q

Treatment for meningococcus

A

Ceftriaxone/cefotaxime

Prophylactic rifampin treatment for family members and close contact persons

40
Q

Clinical diagnosis of meningitis

A

Gram stain CSF, blood, skin or nasopharyngeal samples

  • oxidase positive
  • culture for differentiation
  • meningitidis ferments maltose whereas Gonorrhoeae doesn’t
  • you can do a rapid latex agglutination test to test for capsular antigen

Microbiology (14 decks)

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