Microbiology Theory

Question 1

The layer that differentiate gram positive from gram negetive bacteria

Answer 1

Peptidoglycan

Question 2

What does peptedioglycan composed of?

Answer 2

Lipoteichoic acid

Wall teichoic acid

Question 3

What are the shapes of bacteria and give an example for each?

Answer 3

Spherical- staphylococcus auerus
Rods(bacilli) -Escherishia coli
Spiral- Treponame pallidum

Question 4

Some features of staphylococcus auerus

Answer 4

Facultative anaerobic
Gram positive
Coccal bacterium
Haemolysis on blood agar plates

Question 5

Reproduction in S. Auerus

Answer 5

Asexually , binary fission

Question 6

Staphylococcus are facultative anaerobes, describe

Answer 6

With presence of oxygen the respire

With absence of oxygen they ferment

Question 7

The catalase test in staphylococus is ………….

Answer 7

Positive

2H2O2———-> O2 + 2H2O2

Question 8

List some tests to differentiate between staphylococcus species

Answer 8

1- coagulase test
2- novobiocin resistance
3- biochemical tests

Question 9

Describe the colonies of S.aureus

Answer 9

Large, round, golden yellow colonies with haemolysis on blood agar plate

Question 10

The color of gram positive bacteria is…………. Why?

Answer 10

Purple due to the peptidoglycan layer

Question 11

Species of staphylococcus

Answer 11

1- staphylococcus aureus
2- staphylococcus saprophyticus
3- staphylococcus epidermidis

Question 12

Some diseases caused by S.aureus as an opportunistic pathogen:

Answer 12

1- skin, hair follicle infections- furuncles
2- pneumonia
3- Wound infections
4- bacteremia-sepsis

Question 13

Some diseases caused by S.aureus as a toxin producing strain:

Answer 13

1- food poisoning
2- scalded skin syndrome
3- staphylococcal toxic shock

Question 14

Why it’s dangerous if the S.aureus entered the blood?

Answer 14

Because it will become a systemic infection and infect all organs

Question 15

List some localized infections caused by Staphylococcus Aureus

Answer 15

Scalded skin syndrome, food poisoning, impetigo, pimples, boils

Question 16

List some systemic infections caused by Staphylococcus Aureus

Answer 16

Toxic shock syndrome, pneumonia

Question 17

According to how deep S.aureus get deep through a cut , what are its classes?

Answer 17

1- skin,soft tissue infections

2- invasive infections

Question 18

What are some skin, soft tissue infections caused by Staphylococcus Aureus?

Answer 18

Impetigo, cellulitis

Question 19

What are some invasive infections caused by Staphylococcus Aureus?

Answer 19

• septicemia (blood poisoning)
• septic arthritis( joint infections)
• endocarditis ( infection of the heart lining)

Question 20

The symptoms of skin , soft tissue infections

Answer 20

-boils , which are painful filled pumps over or under skin leads to impetigo which is crust on skin or cellulitis , which cause redness pain and swelling for skin or underlying tissues

Question 21

Who have the higher chance to get an invasive infection caused by Staphylococcus?

Answer 21

People who having dialysis, or have weak immune system due to HIV or getting immunosuppressant

Question 22

Describe the colonies morphology of staphylococcus on blood agar

Answer 22

Creamy to golden color
Medium to large
Show double zone of haemolysis particularly when refrigerated

Question 23

How can you differentiate bet staphylococcus aureus and other staph species?

Answer 23

Haemolysis 
Coagulase test ( clumping factor )

Question 24

What are the result of coagulase test for different staph species?

Answer 24

Positive for staphylococcus aureus

Negative for staphylococcus saprophyticus and staphylococcus epidermidis

Question 25

Treatments of staphylococcus aureus

Answer 25

1- broad host range antibacterial “quinolones”
2- topical creams for skin infections
3- if beta-lactam resistant “MRSA-methicillin resistant staph aureus “ vancomycin is used

Question 26

If the body has deep infection

What are the requirements?

Answer 26

1- higher dosage of antibacterial
2- IV route
3- prolonged treatments
4- debridements and drainage could be used.

Question 27

Describe the colony of staphylococcus epidermidis

Answer 27

Small to medium colonies

Question 28

What are some diseases caused by Staphylococcus epidermidis

Answer 28

Septicemia and endocarditis

Question 29

Staphylococcus epidermidis are…………..

Answer 29

Common normal flora / occasionally opportunistic for hospitalized patients ( in dwelling catheters) , gets commonly on implanted( heart valves, catheters

Question 30

Coagulase test for staph epidermidis is …………

Answer 30

Negative

Question 31

Novobiocin suspcetibility test for staphylococcus epidermidis

Answer 31

Sensitive

Question 32

Staphylococcus epidermidis are resistant to most of antibacterial, how they are treated?

Answer 32

Give vancomycin and rifamipicin

Question 33

Staphylococcus saprophyticus is a ……………..infection
a- respiratory tract 
b- urinary tract 
c- gastrointestinal tract 
d- blood stream

Answer 33

b- urinary tract

Question 34

The result of coagulase test of staph saprophyticus

Answer 34

Negative

Question 35

The novobiocin susceptibility test for staph saprophyticus is

Answer 35

Resistant

Question 36

The colonies morphology for staphylococcus saprophyticus is ……

Answer 36

Medium such as other coagulase negative staphylococcus species

Question 37

The MAS ( mannitol salt agar ) test result for staphylococcus aureus is ……..

Answer 37

Positive turns yellow

Question 38

What is the substance which determines the coagulase result?

Answer 38

Fibrinogen——> fibrin

Question 39

Streptococcus are typed according to:

Answer 39

1- surface carbohydrates: A to U

2- haemolysis profile: alpha , beta and gamma haemolysis

Question 40

…………….is a type of beta haemolysis streptococci

Answer 40

Streptococcus pyogenes