Kaul - Gram+ And Gram- Cocci

Question 1

Virulence factors of staph aureus

Answer 1

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

Question 2

How do the Staph Aureus super antigens work?

Answer 2

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

Question 3

What does Protein A do?

Answer 3

Anti-opsonin effect by binding Fc region of antibodies

Question 4

Most common clinical presentations of Steph aureus infections

Answer 4

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)

Question 5

Staph epidermis

Answer 5

• 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

Question 6

Staph saprophyticus

Answer 6

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

Question 7

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

Answer 7

Staph = clusters
Strep = chains

Question 8

Between strep and staph which is catalase positive?

Answer 8

Staph

Question 9

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

Answer 9

Aureus = positive

Epidermidis and saprophyticus = negative

Question 10

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

Answer 10

Hemolysis pattern and lancefield group

Question 11

Lancefield group

Answer 11

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

Question 12

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

Answer 12

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

Question 13

Strep Pyogenes virulence factors

Answer 13

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

Question 14

Clinical manifestations of Strep Pyogenes (Group A Strep)

Answer 14

• 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

Question 15

How is strep Pyogenes (GAS) spread?

Answer 15

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

Question 16

Strep agalactiae

Answer 16

Group B strep

• female reproductive tract
• causes neonatal sepsis

Question 17

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

Answer 17

Bacitracin

• Pyogenes = bacitracin sensitive
• agalactiae - bacitracin resistant

Question 18

Virdans group strep

Answer 18

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

Question 19

What does strep Pneumo look like under microscope

Answer 19

Lancet shaped cells arranged in chains

Question 20

Strep Pneumo virulence factors

Answer 20

• polysaccharide capsule that prevents phagocytosis. It is antigenic

Question 21

Where is strep Pneumo usually found?

Answer 21

Nasopharynx - so infections are usually endogenous

Question 22

Clinical manifestations of strep Pneumo

Answer 22

Meningitis, Otitis media, pneumonia, Sepsis

Question 23

What tests can differentiate between strep Pneumo and strep Virdans?

Answer 23

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.

Question 24

Strep Pneumo treatment

Answer 24

Cephalosporins such as ceftriaxone or cefotaxamine

Question 25

Strep Pneumo vaccine

Answer 25

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

Question 26

Strep Boviss

Answer 26

Component of gastrointestinal flora - can grow on bile but not in NaCl - gamma or sometimes alpha hemolysis - Group D strep

Question 27

Enterococci

Answer 27

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

Question 28

What is a frequent resistance for enterococci?

Answer 28

Vancomycin | - called VRE

Question 29

How to identify enterococci?

Answer 29

They grow on bile salts and also grow in NaCl

Question 30

Treatment for enterococci?

Answer 30

Ampicillin + Gentamycin/Penicllin +streptomycin Vancomycin Linezolid for VRE

Question 31

Neisseria

Answer 31

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

Question 32

N. Gonorrhoeae

Answer 32

``` 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. ```

Question 33

Clinical manifestations of N. Gonorrhoeae

Answer 33

Genitourinary infections - PID, urethritis Ophthalmia neonatorum Septic arthritis

Question 34

Diagnosis of N. Gonorrhoeae

Answer 34

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

Question 35

Treatment for N. Gonorrhoeae

Answer 35

IM ceftriaxone | - also give athromycin or doxycycline to cover possible concomitant chlamydia

Question 36

N. Meningitidis virulence factors

Answer 36

``` Antigenic capsule Pilli LOS Opa IgA protease Iron extraction system ```

Question 37

Where is N. Meningitidis usually carried?

Answer 37

Nasopharynx

Question 38

Clinical manifestation of meningitidis

Answer 38

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

Question 39

Treatment for meningococcus

Answer 39

Ceftriaxone/cefotaxime | Prophylactic rifampin treatment for family members and close contact persons

Question 40

Clinical diagnosis of meningitis

Answer 40

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