L15: Staphylococcus

Question 1

what staphylococci bacteria is coagulase positive ?

Answer 1

S. aureus (common true pathogen)

Question 2

what staphylococci bacteria is coagulase negative ?

Answer 2

S. epidermis
S. saprophyticus

(opportunistic pathogens )

Question 3

describe the arrangement of staphylococcus bacteria .

Answer 3

gram positive bacteria in clusters

Question 4

what is the main site of S. aureus colonization?

Answer 4

the nose

Question 5

what color does a colony of S. aureus give?

Answer 5

golden ( staphyloxonthin carotinoid pigment )

Question 6

S. aureus infections can be both exogeneic and endogenic

Question 7

how is S. aureus transmitted?

Answer 7

direct and indirect contact

inhalation

Question 8

what virulence factor of S. aureus is responsible for prevention of activation of compliment >?

Answer 8

protein A ( binds to Fc portion of IgG)

Question 9

what virulence factor of S. aureus is responsible for Adhesion ?

Answer 9

techoic acid

Question 10

what virulence factor of S. aureus has the ability to induce septic shock ?

Answer 10

Lipoteichoic acid ( by inducing cytokines such as IL-1 and TNF from macrophages

Question 11

how does S. aureus react to the following lab tests :
coagulation test :
catalase test :
lipase test:
novobiocin sensitivity test :

Answer 11

coagulase positive
catalase positive
lipase positive
novobiocin sensitive

Question 12

which extracellular factor (s. aureus ) dissolves fibrin threads in blood clots , allowing bacteria to move freely ?

Answer 12

staphylokinase ( fibronolysin )

Question 13

what toxin is responsible for marked necrosis of skin and hemolysis ?

Answer 13

heamolysins

Question 14

what toxin is responsible for food positioning ?

Answer 14

enterotoxin ( super antigen within GIT that releases large amounts of ILs)

Question 15

what are some examples of s. aureus associated diseases that originate from intoxication ?

Answer 15

food poisoning
toxic shock syndrome
staphylococcal scaled skin syndrome

Question 16

food poisoning:
-recovery within a day or so
-vomiting more than dhiarrea
-from dairy products , meat , and fish
-1-8 hour incubation period

toxic shock syndrome :
-fever , HYPoTENTION
-sun burn like skin
-involves at least 3 of the following organs : liver , kidney , blood , muscle , CNS , GIT

staphylococci scaled skin syndrome :
-serous fluid exudates
-loss of hair and nails
-recovery with 7-10 days
-occurs in young children

Answer 16

:D

Question 17

90% Of S. aureus are resistant to___

Answer 17

most penicillin’s since they contain beta lactamase

Question 18

S. aureus undergoes penicillin binding proteins alterations , which is another reason why they can resist penicillin . what gene codes for these alterations ?

Answer 18

mecA

Question 19

what technique is used to detect carriers of S. aureus ?

Answer 19

nasal swab

Question 20

what organism is most commonly transferred through infected catheters and prosthetic implants?

Answer 20

S. epidermis

major cause of sepsis in neonates or patients doing dialysis

Question 21

what’s the most common bacteria to cause cerebrospinal fluid shunt infection ?

Answer 21

S. epidermis

Question 22

what Staphylococcus bacteria mostly affects sexually active young women ?

Answer 22

S.saprophticus : causes UTI

Question 23

which staphyloccocal bacteria is resistant to novobiocin ?

Answer 23

S. saprophiticus

Answer 24

,