Staphylococcus

Question 1

Staphylococcus (Characteristics)

Answer 1

• Gram positive, cocci, non motile
• Pairs; short chains; clusters
• Facultative anaerobes; diversity

Question 2

Staphyle:
Coccus:

Answer 2

Staphyle: bunch of grapes
Coccus: a grain or berry

Question 3

Indigenous Bacteria

Answer 3

Establish residence on surface tissue or alimentary tract; especially the anterior nares

Question 4

Staphylococci are part of the ______ ______

Answer 4

Natural flora

Question 5

There are >__ species of Staphylococcus

Answer 5

20

Question 6

Coagulase

Answer 6

A biochemical test that differentiates S. aureus from other Staph - contributes to the clotting of plasma

Question 7

Coagulase converts ______ to ______

Answer 7

Fibrinogen to Fibrin

Question 8

How do we differentiate Staphylococcus and Streptococcus (both gram positive)

Answer 8

Catalase produced by staphylococcus under aerobic conditions

Question 9

Multiple _______ ______ assist establishing a staphylococcus infection

Answer 9

extracellular factors

Question 10

Protein A

Answer 10

Unique to S. Aureus

- Major protein component of cell wall that is covalently bound to peptidoglycan

Question 11

IgG effects on Protein A

Answer 11

• With IgG molecules bound in the “wrong” orientation (om relation to normal antibody function), the IgG disrupts opsonization and phagocytosis of bacteria

Question 12

Toxins produced by S. aureus (4)

Answer 12

1) Hemolysins
2) Leukotoxins
3) Enterotoxins (superantigens) - toxic shock syndrome
4) Exfoliative toxins

Question 13

Hemolysins

Answer 13

Red blood cell membrane damaging proteins

- Contribute to pathogenicity by producing tissue damage after the establishment of a focus infection

Question 14

Leukotoxin

Answer 14

A two protein toxin, attacks polymorphonuclear leukocytes and macrophage

Question 15

Enterotoxins

Answer 15

Large family of Staphylococcus toxins, superantigens

Question 16

Enterotoxins
Function:
Source:
Symptoms:

Answer 16

Function: Cause diarrhea and emesis
Source: S. aureus contaminated foods
Symptoms: Within 2-6 hours of ingestion
- Cramping, nausea, vomiting, diarrhea

Question 17

Enterotoxins are _____-stable

Answer 17

heat

Question 18

TSST

Answer 18

Toxic shock syndrome toxin

Question 19

Enterotoxins and TSST bind directly to ______ and ______ independent of antigen

Answer 19

MHC class II; TCR

Question 20

Enterotoxins and TSST: method of toxicity

Answer 20

Massive cytokine production yields systemic toxicity of host/ Suppression of the adaptive immune response

Question 21

Exfoliative toxin

Answer 21

2 forms ETA/ETB - proteases

Stimulate lysis of the intercellular attachment between cells of the epidermis

Question 22

Staphylococcus Epidemiology

Answer 22

Staphylococcus are a normal component of human indigenous flora and are carried asymptomatically at several body sites, especially anterior nares

Question 23

Staphylococcus Transmission

Answer 23

Direct contact by the hands is the most important route of transmission

Question 24

Staphylococcus Infection

Answer 24

• Typically localized
• Intact skin major barrier to infection
• Skin primary sites of infection

Question 25

Appearances of Staphylococcus infectio``````n

Answer 25

``` Folliculitis Boil Impetigo Scalded skin syndrome Pneumonia ```

Question 26

Treatment of S. Aureus infections

Answer 26

- Adequate drainage of wound - Removal of foreign objects - Antibiotic Therapy - Methicillin - Vancomycin

Question 27

Methicillin Resistant S. Aureus (MRSA)

Answer 27

MR of SA is due to the selection of SA with mutations within the Penicillin Binding Proteins that have low affinity for penicillin

Question 28

PBP

Answer 28

Penicillin Binding Proteins

Question 29

Vancomycin Resistance

Answer 29

- SA strain resistant to intermediate, but clinically significant levels of vancomycin VIrSA - Typically in MRSA - patients with prolonged vancomycin therapy, up to 18 wks, selects for VIrSA - VIrSA resistance due to changes in cell wall

Question 30

MICs for Vancomycin

Answer 30

SA vancomycin - susceptible: 0.5 - 2µg/ml SA vancomycin - intermediate (VIrSA): 4-8 µg/ml SA vancomycin - resistant (VRSA): >16 µg/ml

Question 31

HA-MRSA vs. CA-MRSA

Answer 31

HA-MRSA infection is easily contracted in hospital settings | CA-MRSA infection spreads through those living in close contact, such as military barracks, dormitories and gyms

Question 32

S. Epidermis

Answer 32

Low virulence - Hospital acquired - contamination of surgical site binds to plastics - Treatment, problem multi-drug resistant use antibiogram

Question 33

S. Saprophyticus

Answer 33

Urinary tract infections selectively binds to cells of the urinary tract - Does not posses any virulence factors found in SA