Streptococcus and Enterococcus

Question 1

Gram-positive,
non-motile,
catalase-negative,
facultatively anaerobic cocci
that occur in chains or pairs

Answer 1

Streptococci

Question 2

Researchers differentiate species of streptococcus based on

Answer 2

the reactions of antibodies to specific bacterial antigens

Question 3

type of hemolysis of Streptococci

Answer 3

α-β-γ-hemolysis

Question 4

On the basis of hemolysis, streptococci can be divided into 3 groups

Answer 4

• α Hemolytic:
(Partial or green hemolysis),
e.g. Streptococcus viridans, Streptococcus pneumoniae.

• β Hemolytic:
(Complete or yellowish
hemolysis),
e.g. Streptococcus agalactiae and Streptococcus pyogenes.

• γ Hemolytic:
(No hemolysis is seen),
e.g. Enterococci

Question 5

In the medical setting, the most important groups are the

Answer 5

alpha-hemolytic streptococci,
S pneumoniae and Streptococcus viridans group

and the beta-hemolytic streptococci of Lancefield groups A and B

Question 6

Types of streptococcus on blood agar

Answer 6

(1) Group A streptococci (GAS)(Streptococcus pyogenes)
(β- haemolytic)

(2) Group B Streptococcus, Streptococcus agalactiae (β-hemolytic)

(3) α-hemolytic Streptococci,
Streptococcus viridans

(4) α-hemolytic pneumococci (Streptococcus pneumoniae) (Diplococcus)

(5) Group C streptococci (GCS)

(6) Group D streptococci (Enterococcus) γ-hemolytic cocci (non- hemolysis)

Question 7

forms 1-2 mm white colonies

surrounded by large zone of
β- hemolysis after 24 hr on blood agar pate.

Answer 7

Group A streptococci (GAS)(Streptococcus pyogenes)

Question 8

Pathogenic strains of this species often form a capsules

Answer 8

Group A streptococci (GAS)(Streptococcus pyogenes)

Question 9

Strains of streptococcus pyogenes have a number of

Answer 9

structures, enzymes, and toxins that enable them to survive as pathogens in the human body.

Question 10

Two main structural features enable cells of S. pyogens evade phagocytosis:

Answer 10

1- Protein M Virulent
group A streptococcus.

2- Hyaluronic acid capsule.

Question 11

There are many enzymes ( in the Streptococcus pyogenes ) had been identified by researchers:

Answer 11

1) Streptokinase

2) Deoxyribonucleases depolymerize DNA

3) C5a peptidase

4) Hyaluronidase

Question 12

break down blood clot, enabling streptococci cells to spread through infected & damaged tissue

Answer 12

Streptokinase enzyme

Question 13

released from dead cells that reducing the firmness of the pus surrounding the bacteria.

Answer 13

Deoxyribonucleases depolymerize DNA

Question 14

breaks down the complement C5a.

Answer 14

C5a peptidase

Question 15

facilitates the spread of streptococcal cells through tissue by breaking down hyaluronic acid.

Answer 15

Hyaluronidase

Question 16

Group A S. pyogenes secrete three toxins which cause blood capillaries near the surface
to dilate, producing a red rash and shock

Answer 16

1- Erythrogenic toxins

2- Fever-stimulating
pyrogenic-toxin.

3- Pus-producing
pyrogenic-toxin.

Question 17

Group A-Streptococcal diseases:

Answer 17

Cause infections of the upper respiratory tract and invasive infections of the skin and subcutaneous connective tissue

Pharyngitis

Scarlet fever

Streptococcus Toxic Shock Syndrome(STSS).

Necrotizing fasciitis “flesh eating strep”

Rheumatic fever

Glomerulonephritis

Question 18

dissolve blood clot

Answer 18

Streptokinases

Question 19

breaks down hyaluronic acid between cells

Answer 19

Hyaluronidase

Question 20

breaks down DNA released from damaged host cells

Answer 20

Deoxyribonucleases

Question 21

Gram positive,
0.6-1.2 μm in diameter
that divides to form chains

Answer 21

Group B Streptococcus, Streptococcus agalactiae

Question 22

Like group A streptococcus, this coccus (Group BStreptococcus )is also beta-hemolysis,
but it can be distinguished from the S.pyogenes by three qualities

Answer 22

1- It has group specific, polysaccharide cell wall antigens.

2- It forms buttery colonies that are 2-3 mm in diameter and have a small zone of β-hemolysis after24 hr of growth on blood agar.

3- It is bacitracin resistant.

Question 23

Group B Streptococcus, Streptococcus agalactiae produce enzymes:

Answer 23

1. Proteases
2. Hemolysins
3. Deoxyribonuclease
4. Hyaluronidaese

Question 24

enzyme bolize proteins

Answer 24

Proteases

Question 25

enzyme lysis red blood cells

Answer 25

Hemolysins

Question 26

Group B-streptococcus bacteria can colonize:

Answer 26

1. The lower gastrointestinal (GI), genital, and urinary tracts. 2- In adults, primarily follow wound infections. 3. In newborns, cause early-onset disease& late onset disease.

Question 27

α-hemolytic Streptococci, Streptococcus viridans are not part of any Lancefield group.

Answer 27

Because This bacteria lack group-specific carbohydrates

Question 28

This viridans cocci (α-hemolytic Streptococci, Streptococcus viridans ) so called because

Answer 28

of producing a green pigment when grow on blood media.

Question 29

This bacteria (α-hemolytic Streptococci,Streptococcus viridans )inhabit the mouth and cause

Answer 29

dental caries, pharynx, GI tract, genital tract and urinary tract of humans.

Question 30

Streptococcus viridans display alpha- hemolysis. Alpha-hemolysis is also termed incomplete hemolysis or partial hemolysis because

Answer 30

because the cell membranes of the red blood cells are left intact.

Question 31

Lack lancdfield antigens Gram-positive, short chains commonly pairs. Colonies grown for 24 hr are 1-3 mm in diameter, round, mucoid, un-pigmented, and dimpled in the middle because of the death of older cells.

Answer 31

α-hemolytic pneumococci (Streptococcus pneumoniae) (Diplococcus)

Question 32

Pathogenicity of α-hemolytic pneumococci (Streptococcus pneumoniae) (Diplococcus)

Answer 32

1. This diplococcic has polysaccharide capsule, which protects the bacterial cells from digestion after phagocytosis. 2. It secrete IgA protease which destroy IgA antibodies. 3. It secrete pneumolysin which lysis the epithelial cells.

Question 33

α-hemolytic pneumococci (Streptococcus pneumoniae) secrete pneumolysin which lysis the epithelial cells. So Streptococcus pneumonia cause:

Answer 33

1. Pneumococcal pneumonia. 2. Sinusitis and otitis media. 3. Bacteremia & endocarditis. 4. Pneumococcal meningitis.

Question 34

colonies are α-hemolytic on blood agar surface when grown aerobically, and β-hemolytic when grown an-aerobically.

Answer 34

Colonies of S. pnumoniae

Question 35

Not important in human pathogenicity. Gram-positive, in mostly β-hemolytic and facultative anaerobes

Answer 35

Group C streptococci (GCS)

Question 36

Enterococcus, so named because

Answer 36

because all enterococci are spherical & live in the intestinal tract of animals.

Question 37

There are two types of enterococcus

Answer 37

E.faecalis & E.faecium.

Question 38

It is Gram +, un-capsulated bacterial cells, grow at temperatures up to 45°C, at pH 9.6, and in 6.5% NaCl.

Answer 38

Enterococcus

Question 39

genus of rod-shaped, gram-positive, aerobic or (under some conditions) anaerobic bacteria widely found in soil and water.

Answer 39

Bacillus

Question 40

Scientists divide Gram-positive bacilli into:

Answer 40

1- Endospore-forming bacteria such as Bacillus & Clostridium 2- Non endospore-forming bacteria Such as Corynebacterium & Actinomyces

Question 41

Bacillus classified into two major species:

Answer 41

1. Bacillus anthracis cause Anthrax 2. Bacillus cereus cause food poisoning

Question 42

It is Gram + bacilli, in chain have characteristics squared ends endospores are central do not cause bulging.

Answer 42

Bacillus anthracis

Question 43

Pathogenic strains of B. anthracis secrete (anthrax toxin). Anthrax can be deadly even after treatment, because

Answer 43

because antimicrobial drugs do not inactivate accumulated anthrax toxin.

Question 44

The capsule of Bacillus anthracis prevents

Answer 44

effective phagocytosis by white blood cells.

Question 45

Anthrax can be invade human body via one of three routes:

Answer 45

1- Inhalation of spores through respiratory system. 2- Inoculation of spores into the body through a break in the skin. 3- Ingestion of spore through digestive system.

Question 46

On agar media is an aerobe, and facultative anaerobe with temperature 12- 45°C, it is irregularly round colonies, about 2-3 mm in diameter, greyish white

Answer 46

Bacillus anthracis

Question 47

toxin-producing facultatively anaerobic gram-positive bacteria. The bacterium is commonly found in the environment, is often found in soil and vegetation,

Answer 47

Bacillus cereus

Question 48

There are two main types of an intestinal illness caused by B. cereus

Answer 48

One is diarrheal, and one leads more to nausea/vomiting.

Question 49

The pathogenicity of B. cereus, whether intestinal or non-intestinal, is intimately associated with the

Answer 49

production of tissue-destructive exo-enzymes such as hemolysins, phospholipases, and proteases.

Question 50

There are two types of food-borne B. cereus illness.

Answer 50

the first, contaminated food The second type, affected food,