Lab 13

Question 1

What genera produce gram positive pathogenic cocci that cause abscesses, impetigo, furuncles, carbuncle, osteomyelitis, and fatal septicemia

Answer 1

Staphylococcus and Streptococcus

Question 2

Staphylococcus species are

Answer 2

Gram positive, spherical, arranged in clusters, facultative anaerobes

Question 3

The 2 groups of pathogenic cocci are known as

Answer 3

Pyogenic or pus forming cocci

Question 4

Where are Staphylococcus species found

Answer 4

On normal flora of skin and nasal membranes

Question 5

Nonpathogenic species of Staphylococcus are

Answer 5

1. S.epidermidis
2. Normal flora of skin, respiratory, and gastrointestinal tract
3. Non pigmented white colonies, non hemolytic, Coagulase negative, can grow in Mannitol but are non fermenters
4. Noninvasive staphylococcus

Question 6

Pathogenic species of Staphylococcus are

Answer 6

1. S.aureus
2. Hemolytic, Coagulase positive, pigmented yellow, able to ferment Mannitol with acid production.
3. Can be found in nares and axillae
4. Food poisoning, abscesses in all parts of the body–>can be fatal

Question 7

What is the pathogenicity of Staphylococcus dependent on

Answer 7

The ability of the strain to make extracellular toxins, enzymes, and state of health if the host

Question 8

What is Coagulase

Answer 8

A bacterial enzyme that coagulats blood. The enzyme coagulated fibrinogen, a plasma protein found in animal blood, and converts it into fibrin. This cause it to form threads, producing a clot.

Question 9

How does coagulase help bacteria

Answer 9

The clot protects it by isolating it from the hosts defenses and immune system, such as phagocytosis.

Question 10

What causes Staphylococcal diseases

Answer 10

1. The direct infection and colonization if this bacteria. It has the ability to form capsules which make it more virulent. This allows for adherence and can evade phagocytosis. It can stimulate a superantigenic reaction of the immune system
2. Production of toxins

Question 11

What is a superantigenic response

Answer 11

When the host’s body produces antigens that stimulate a storm of cytokines that function as mediators to control the breach of invading microorganisms. The immune response so big that it causes damage to nearby cells.

Question 12

What diseases are caused by Staphylococcus

Answer 12

1. Methicillin resistant staphylococcus aureus; hospital acquired and community acquired infections
2. Skin and soft tissue infections, pneumonia, endocarditis, osteomyelitis
3. Food poisoning, cellulitis, scalded shock syndrome, toxic syndrome

Question 13

Streptococcus species are

Answer 13

Gram positive, cocci, in chains, catalase negative, exhibit various hemolysis patterns, microaerophiles and capnophiles

Question 14

Where are streptococcus species normally found

Answer 14

Normal flora of these are found in the throat, mouth, nose, and intestines. They are also widely distributed in nature.

Question 15

What diseases are pathogenic species of streptococcus associated with

Answer 15

1. Strep throat, pharyngitis, scarlet fever, cellulitis, erysipelas, impetigo
2. Bacterial pneumonia, puerperal fever, rheumatic fever, acute glomerulinephritis
3. Meningitis, neonatal sepsis
4. Invasive forms include necrotizing fasciitis, myositis, Streptococcal toxic shock syndrome
5. Vaginitis, UTIs, skin infections, endocarditis
6. Entercoccus–> UTIs and biliary tract infections

Question 16

What are Entercoccus species resistant to that other streptococcus species are not

Answer 16

Bike salts and other salts

Question 17

How do you differentiate between streptococcus and staphylococcus species

Answer 17

With the catalase test. Streptococcus species are catalase negative while Staphylococcus are catalase positive

Question 18

How are streptococcus differentiated from other streptococcus species

Answer 18

By the reaction produced on blood agar

Question 19

B- hemolysis , example of bacteria

Answer 19

1. Streptolysins completely lys the blood cells

2. Streptococcus pyogenes

Question 20

a- hemolysis , example of bacteria

Answer 20

1. Partial lysing of blood cells and produce a greenish hue on BAP
2. S.mitis or S.pneumonia

Question 21

y- hemolysis , example of bacteria

Answer 21

1. Do not lyse blood cells and produce no hemolysis

2. Entercoccus faecalis

Question 22

How are Streptococci classified

Answer 22

Based on serological antigen reactions and grouped into groups A through R

Question 23

What do groups A-D of streptococcus species show

Answer 23

B- hemolysis

Question 24

Group A of Streptococcus species are sensitive to

Answer 24

Bacitracin

Question 25

What is Streptococcus pneumonia sensitive to

Answer 25

Optochin antibiotic

Question 26

What is the purpose, positive and negative reaction, type of media, substrate, reagent indicator, end product of gram stain

Answer 26

1. To establish gram type, size, shape, and arrangement 2. G+--> purple: LARGE amounts of peptidoglycan and NO lipopolysaccharide, G negative-->pink: SMALL amounts of peptidoglycan and, characteristically, lipopolysaccharide (LPS). 3. Reagent: crystal violet (+), safranin(-)

Question 27

What is the purpose, positive and negative reaction, type of media, substrate, reagent indicator, end product of Mannitol Salt agar

Answer 27

1. Selective and differential. Selective for Staphylococcus (halophiles). Differentiates from pathogenic Mannitol fermenters, non pathogenic do not ferment Mannitol 2. Positive-->growth, Negative--> no growth and For fermentation + turn yellow, - turn red 3. 7.5% salt concentration, sugar Mannitol agar 4. pH indicator: phenol red

Question 28

What streptococcus species is resistant to high concentrations of salt

Answer 28

Enterococci

Question 29

What streptococcus species are in Group D? How are they differentiated from other streptococcus species ?

Answer 29

1. Enterococci, also referred to as the fecal group of streptococci 2. By a positive reaction in Bile Esculin agar and salt broth

Question 30

Neisseria are gram type? How are they differentiated from other cocci? What are the 2 major pathogens?

Answer 30

1. Gram negative diplococci 2. Positive oxidase reaction 3. N.meningitis, N.gonorrhea

Question 31

What is the purpose, positive and negative reaction, type of media, substrate, reagent indicator, end product of TSA

Answer 31

1. Tryticase Soy agar is a general purpose medium and allows most bacteria to grow 2. One can double check the growth on this medium and compare it to selective/differential medium to ensure good growth of colonies and to observe true morphology of colonies 3. Cannot determine or differentiate genus or species type

Question 32

What is the purpose, positive and negative reaction, type of media, substrate, reagent indicator, end product of oxidase test

Answer 32

1. Differentiation of bacteria 2. Detects oxidase enzyme. Oxidase performs the final step in electron transport, reducing oxygen to water. Enterobacteriaceae (-)do not reduce oxygen with this enzyme. Neisseria (+)do. 3. Colorless reagent--> oxidase paper 4. Can use general purpose media for growth of bacteria and test while in log stage 5. The chemical in the presence of oxygen and an oxidase enzyme will form a colored compound--> black or purple (after 20 sec)

Question 33

When testing for oxidase, why should a metal loop be avoided

Answer 33

Iron in loop can interfere with reaction and give a false positive

Question 34

How do you differentiate Neisseria species from streptococcus or staphylococcus

Answer 34

Gram stain, they are gram negative diplococci

Question 35

What is the purpose, positive and negative reaction, type of media, substrate, reagent indicator, end product of catalase test

Answer 35

1. Catalase is an enzyme that detoxifies hydrogen peroxide, a byproduct of respiration. It does this by breaking hydrogen peroxide into water and oxygen 2. Glob of bacteria is placed on slide 3. Reagent--> Hydrogen peroxide 4. Positive--> bubbles 5. Streptococcus are catalase negative and Staphylococcus are catalase positive

Question 36

What is the purpose, positive and negative reaction, type of media, substrate, reagent indicator, end product of salt broth test

Answer 36

1. It is a selective medium which tests the ability of an organism to survive in a salt-rich environment. 2. The salt tolerance test is performed using Tryptic Soy Broth with added sodium chloride (regular table salt) to create an overall salt concentration of 6.5%. 3. Positive--> turbidity 4. Possible Entercoccus species or halophile if positive, if negative it is possibly other species of streptococci

Question 37

What is the purpose, positive and negative reaction, type of media, substrate, reagent indicator, end product of bile esculin test

Answer 37

1. Selective and differential medium which is presumptively used to identify Enterococci and group D Streptococci based on the ability of an organism to hydrolyze esculin. 2. Contains bile salts to inhibit the growth of other gram positive organisms other than Enterococci and group D Streptococci. It contains sodium azide to inhibit the growth of gram negative organisms. 3. Esculin in medium is hydrolyzed and causes a reaction: esculin >glucose and esculetin and ferric citrate--> brownish black color--> positive, no color change--> negative

Question 38

What is the purpose, positive and negative reaction, type of media, substrate, reagent indicator, end product of blood agar plates

Answer 38

1. To differentiate between diffent species of streptococcus and enriched in that the sheeps blood has growth factors that allow fastidious bacteria to grow that may not normally grow on general purpose media. 2. It contains sheep blood that can be lysed by certain bacteria that possess hemolytic enzymes. Different species contain different classes of hemolysins. 3. alpha- partial hemolysis, beta- complete hemolysis, gamma- no hemolysis

Question 39

What is the purpose, positive and negative reaction, type of media, substrate, reagent indicator, end product of Coagulase test

Answer 39

1. Differentiate between organisms that produce enzyme to coagulate blood 2. Sterile plastic tube 3.Emulsify several colonies in 0.5 mL of rabbit plasma (with EDTA) to give a milky suspension. Incubate tube at 35°-37°C in ambient air for 4 hours.Check for clot formation--> positive 4. Pathogenic invasive species of Staphylococcus are Coagulase positive Nonpathogenic noninvasive Staphylococcus species are Coagulase negative

Question 40

Mannitol broth

Answer 40

1. Differentiate fermenting bacteria from non fermenting 2. Mannitol/sugar in broth 3. Positive yellow 4. Negative pink