Bacte Staph

Question 1

What type of bacteria are Staphylococci?

Answer 1

Gram-positive cocci

They are spherical (0.5-1.5um) and can appear singly, in pairs, or in clusters.

Question 2

What is the catalase test result for Staphylococci?

Answer 2

Catalase-positive

This differentiates them from Streptococci.

Question 3

What are the typical colony characteristics of Staphylococcus aureus?

Answer 3

Medium to large; smooth, entire, slightly raised, opaque; creamy yellow/golden yellow color

Most colonies are beta-hemolytic.

Question 4

What is the principal virulence factor of Staphylococcus aureus?

Answer 4

Coagulase/Staphylocoagulase

It allows spontaneous blood clotting.

Question 5

What type of media can Staphylococcus aureus be cultivated in?

Answer 5

7.5% to 10% NaCl (halophilic)

This concentration allows for its growth.

Question 6

What is the role of Protein A in Staphylococcus aureus?

Answer 6

Immunologically active substance found in the cell wall

It is antiphagocytic and competes with neutrophils for opsonins.

Question 7

What are the types of enterotoxins produced by Staphylococcus aureus?

Answer 7

Serologically grouped into A, B, C, D, E, G, H, I, J

A, B, D are associated with food poisoning.

Question 8

What does Toxic Shock Syndrome Toxin-1 (TSST-1) cause?

Answer 8

Menstruating-associated toxic shock syndrome

It is absorbed through the vaginal mucosa.

Question 9

What does exfoliative toxin A and B cause?

Answer 9

Scalded Skin Syndrome (SSS)

It destroys the stratum granulosum of the skin.

Question 10

What is the predominant hemolysin produced by Staphylococcus aureus?

Answer 10

Alpha hemolysin

It destroys RBCs, platelets, and macrophages.

Question 11

What is Methicillin-resistant Staphylococcus aureus (MRSA)?

Answer 11

A strain of S. aureus resistant to methicillin and other antibiotics

Resistance is due to an altered penicillin-binding protein (PBP2a).

Question 12

What does the Mannitol Salt Agar indicate if it turns yellow?

Answer 12

The organism utilizes mannitol as a source of energy

This is a semi-confirmatory test for S. aureus.

Question 13

What are the two types of coagulase tests?

Answer 13

Slide coagulase test and tube coagulase test

The slide test shows cell-bound coagulase; the tube test detects both bound and free coagulase.

Question 14

What distinguishes Staphylococcus epidermidis from Staphylococcus saprophyticus?

Answer 14

S. saprophyticus is the most common cause of UTI in young sexually active females

S. epidermidis is an indigenous microbiota of the skin.

Question 15

What is the significance of Baird-Parker medium?

Answer 15

For isolation of staphylococci from food specimens, environment, and cosmetic products

It is a selective medium.

Question 16

What is the modified oxidase test used for?

Answer 16

To differentiate Micrococcus from Staphylococcus

Micrococcus is positive; Staphylococcus is negative.

Question 17

What is the result of the catalase test for Staphylococcus?

Answer 17

Positive result shows effervescence/bubble formation

A negative result shows no bubble formation.

Question 18

What is the clinical significance of Staphylococcus lugdunensis?

Answer 18

More virulent than other coagulase-negative Staphylococci

It is associated with infective endocarditis and septic shock.

Question 19

Fill in the blank: Staphylococcus aureus is primarily responsible for infections when it enters a normally sterile site due to __________.

Answer 19

Trauma or abrasion of the skin, or mucosal surfaces.

Question 20

True or False: Staphylococcus is facultatively anaerobic.

Answer 20

True

Except for some species that may be strictly anaerobic.

Question 21

What does the lysostaphin susceptibility test differentiate?

Answer 21

Micrococcus (susceptible) from Staphylococcus (resistant)

Lysostaphin can lyse staphylococci.