study guide

Question 1

What is the Kirby-Bauer test used for?

Answer 1

to determine which antibiotics a specific bacterium is most susceptible or resistant to

Question 2

What is meant by the term resistant?

Answer 2

Antibiotics will have no effect on bacteria growth; they don’t work

Question 3

What is meant by the term susceptible?

Answer 3

Antibiotics work; bacteria is sensitive to antibiotics

Question 4

What is a zone of inhibition?

Answer 4

Area of no growth

Question 5

Why must a chart be used to read the results?

Answer 5

every antibiotic has different diameters in which they show they are effective

Question 6

Given the information on a chart, be able to determine an antibiotics effectiveness

Disk potency: _____________________________
Resistant: _____________________________
Intermediate: _______________________
Susceptibility: __________________
PG. 34

Answer 6

1) measurement of antibiotic strength
2) the ability of the microbe to grow in the presence of antibiotics
3) bacteria falls short of resistance
4) antibiotics work

Question 7

What is an antibiotic?

Answer 7

Substances that kill or prevent the growth of bacteria

Question 8

What is the difference between broad spectrum and narrow spectrum? Why would one be used over the other?

Answer 8

Broad spectrum kills a large range of things while narrow spectrum targets a specific thing. We would use broad spectrum if we don’t know what is causing the disease. Narrow is when we have a good indicator as to what is causing disease

Question 9

What is the difference between bacteriostatic and bactericidal?

Answer 9

Bacteriostatic: slows/stops bacteria growth
Bactericidal: kills bacteria

Question 10

What is a disinfectant?

Answer 10

Chemical substances that kill or inhibit the growth of microorganisms.

Question 11

How did we determine which disinfectant worked best?

Answer 11

seeing which disinfectant produced the largest zone of inhibition

Question 12

What effect does pH have on bacterial growth?

Answer 12

• different bacterial species grow best in different pH ranges. Each bacteria has it’s own set of cardinal pH’s (minimum growth pH, Maximum growth pH, and optimum pH). Bacteria grows best in their optimum pH. If the pH falls below the minimum tolerable pH or rises above the maximum tolerable pH, the bacterium is unable to produce energy and enzymes may become ineffective.
• If the pH falls below the minimum tolerable pH or rises above the maximum tolerable pH, the bacterium is unable to produce energy and enzymes may become ineffective.

Question 13

What are the terms applied to bacteria at different pH ranges?

pH below 5.5 = _____________
pH 5.5 – 8.5 = _____________
pH above 8.5 = ____________

Answer 13

1) acidiophiles
2) neutrophiles
3) alkaliphiles

Question 14

What effect does temperature have on bacterial growth?

Answer 14

• At optimum temperature, bacteria will show its highest growth rate. Below the minimum temperature and above the maximum temperature, the bacterium will not survive.
• Temperature increases or decreases the rate at which the bacteria replicate

Question 15

What is meant by the term optimum temperature?

Answer 15

Optimum temperature: bacteria shows highest growth rate

Question 16

What is meant by the term cardinal temperatures?

Answer 16

Cardinal temperatures: optimum, minimum, maximum temperatures

Question 17

What are the terms applied to bacteria at different growth temperatures?

Grow <20˚C = _________________
Grow in freezing but can grow >30˚C = ____________
Grow in moderate temp. (15˚C – 45˚C) = ___________
Grow in warmer temp. (>40˚C) = ______________
Grow 65˚C – 110˚C = _________________

Answer 17

1) psychrophiles
2) psychrotrophs
3) mesophiles
4) thermophiles
5) extreme thermophiles

Question 18

What is aerotolerance?

Answer 18

Refers to the ability of an organism to live & grow in the presence of oxygen

Question 19

How can aerotolerance be tested?

Answer 19

• Uses a fluid thioglycollate medium (ON TEST): contains an oxygen gradient ranging from anaerobic at the bottom of the tube to aerobic at the top of the tube
• The chemical resazurin is included in the media to indicate the presence of oxygen by producing a pink coloration where oxygen is present

Question 20

What are the terms applied to each type of aerotolerance?

Answer 20

• Obligate aerobes : require O2
• Facultative anaerobes : will grow with or without O2, but grow better with O2
• Aerotolerant anaerobes : do not require O2 but are not harmed by it, spread throughout tube
• Obligate anaerobes : cannot grow in the presence of O2

1= obligate aerobe, 2= obligate anaerobe 3= facultative anaerobes 5= aerotolerant

Question 21

What test did we use to differentiate staphs from streps?

Answer 21

Catalase test

• Simple and immediate
• Identifies organisms that possess the enzyme catalase, which breaks down hydrogen peroxide into water and gaseous oxygen
  
  • Staph = catalase-positive; bubbles form
  • Strep = no catalase; no bubbles

Question 22

What are other ways that could have differentiated these two?

What specific tests/stains would help you differentiate?

Answer 22

1) By their morphology. Staphylococcus forms clusters of grape like shapes. While Streptococcus forms chains of “pearl necklaces.”
2) catalase, gram stain, simple stain,

Question 23

What tests were used on the staphs?

1. _____________: uses rabbit plasma tubes

to identify if a bacteria is _______________ by identifying the presence of the enzyme coagulase. Coagulase is an enzyme used by S. aureus to cause_________________________. WHICH acts as a mechanism of envading the hosts’ immune system.

Answer 23

1) Coagulase
2) staphlococcus aureus
3) the formation of blood plasma clots around themselves

Question 24

What tests were used on the staphs?

2. __________: Uses DNAse plate

• Another method of differentiating between forms of Staphylococci
• Only ________________ produces the enzyme DNase
• _________________ in host cell
• DNase agar is __________ but presence of enzyme (DNAse) will leave a clearing around bacterial growth

Answer 24

1) DNAse
2) Staphylococcus aureus
3) Breaks down DNA
4) green

Question 25

What tests were used on the staphs? 3. \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_: Uses MSA plate * Selective for all Staphylococci * _________ inhibits growth of most other organisms, but staphylococcus does very well in this high salt environment * Differentiates between \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ * pH indicator phenol red in the agar will turn ________ as fermentation decreases the pH of the media. (phenol red is yellow below pH 6.8, red at pH 7.4 to 8.4, and pink above pH 8.4) * Selective → high salt only selects \_\_\_\_\_\_\_\_\_\_\_\_\_ * Differential → yellow means \_\_\_\_\_\_\_\_\_\_\_\_\_\_, hence differentiates staph aureus from the different staphs (which don’t ferment mannitol)

Answer 25

1) Mannitol Salt Agar (MSA) 2) 7.5% salt 3) mannitol-fermenting pathogenic Staphylococci and non-mannitol fermenting Staphylococci 4) yellow 5) staphylococcus to grow 6) it ferments mannitol

Question 26

What tests were used on the staphs? 4. \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_: uses blood agar plate * Novobiocin is an \_\_\_\_\_\_\_\_\_\_\_\_ * This test will differentiate __________ from other Staphylococci * S. saprophyticus is resistant to novobiocin, while ___________ and _________ are susceptible * If there is a zone of inhibition, not S. Saprophyticus bacteria

Answer 26

1) Novobiocin Sensitivity Test 2) antibiotic 3) Staphylococcus saprophyticus 4) S. aureus 5) S. epidermis

Question 27

If there What is hemolysis? What are the different types? What is each one doing? And what does each look like?

Answer 27

* An enzyme that destroys or partially destroys red blood cells * Beta-hemolytic streptococci completely hydrolyze (breakdown with water) red blood cells * Alpha-hemolytic streptococci partially hydrolyze red blood cells * Gamma-hemolytic (or Non-hemolytic) are not hemolytic at all and do not affect the red blood cells * Beta – Bad (complete breakdown of RBC); Alpha – almost as bad (partial breakdown); Gamma - good (no breakdown) * β (Beta): clearing around colonies, yellow; * ἇ (alpha): appears as a green coloration; * Ɣ (gamma): will not produce a color change in the media just growth in colonies.

Question 28

For all of the staph and strep tests: \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_: uses blood agar plate * Objective is to identify _________________ based on its susceptibility to the antibiotic bacitracin. * The test is useful in differentiating the beta-hemolytic group A strep (Streptococcus pyogenes is bacitracin susceptible) from other beta-hemolytic streptococci. Streptococcus pyogenes is Bacitracin __________ while most others are resistant

Answer 28

1) Bacitracin Sensitivity 2) streptococcus pyogenes 3) sensitive

Question 29

For all of the staph and strep tests: 6. \_\_\_\_\_\_\_\_\_\_\_\_\_: uses bile esculin plate * Selects for Group D Streptococci and Enterococci * Media contains bile, which allows the growth of Group D Strepto/Enterococci, but inhibits others * Differentiates between Group D Strepto/Enterococci and non-Group D’s * Group D Strepto/Enterococci can hydrolyze esculin into glucose and esculetin. * The glucose is used for _______________ and the esculetin reacts with iron salts in the media to form a black precipitate which verifies presence of a Group D Strepto/Enterococci.

Answer 29

1) Bile Esculin Test 2)

Question 30

Life cycle of… Plasmodium:

Answer 30

mosquito takes blood & injects sporozoites --\> sporozoites infect liver cells --\> turn into schizonts --\> rupture and release merozoites --\> after initial replication in the liver (exo-erythrocytic schizogony), the parasites undergo asexual multiplication in the erythrocytes (erythricytic schizogony) --\> merozoites infect red blood cells --\> the ring stage trophozoites mature into schizonts, which rupture releasing merozoites --\> some parasites differentiate into sexual erythrocytic stages (gametocytes) --\> blood stage parasites are responsible for the clinical manifestations of the disease.

Question 31

**Life cycle of…** Plasmodium:

Answer 31

The gametocytes, male (microgametocytes) and female (macrogametocytes), are ingested by an Anopheles mosquito during a blood meal --\> parasites’ multiplication in the mosquito is known as the sporogonic cycle --\> while in the mosquito’s stomach, the microgametes penetrate the macrogametes generating zygotes --\> the zygotes in turn become motile and elongated (ookinetes) --\> which invade the midgut wall of the mosquito where they develop into oocysts --\> the oocysts grow, rupture, and release sporozoites --\> which make their way to the mosquito’s salivary glands. Inoculation of the sporozoites into a new human host perpetuates the malaria life cycle.

Question 32

**Life cycle of…** Trypanosoma:

Answer 32

triatomine bug takes a blood meal (passes metacyclic trypomastigotes in feces, trypomastigotes enter bite wound or mucosal membranes such as the conjunctiva) --\> common triatomine vector species for trypanosomiasis belong to the genera Triatoma, Rhodnius, and Panstrongylus. Inside the host, the trypomastigotes invade cells near the site of inoculation, where they differentiate into intracellular amastigotes --\> amastigotes multiply by binary fission --\> and differentiate into trypomastigotes, and then are released into the circulation as bloodstream trypomastigotes --\> Trypomastigotes infect cells from a variety of tissues and transform them into intracellular amastigotes in new infection sites. Clinical manifestations can result from this infective cycle. The bloodstream trpomastigotes do not replicate (different from the African trypanosomes). Replication resumes only when the parasite enters another cell or are ingested by another vector. The “kissing” bug becomes infected by feeding on human or animal blood that contains circulating parasites. --\> the ingested trypomastigotes transform into epimastigotes in the vector’s midgut --\> the parasites multiply and differentiate in the midgut --\> and differentiate into infective metacyclic trypomastigotes in the hindgut.

Question 33

What are the neglected parasitic infections in the US? Why have these been targeted?

Answer 33

Neglected parasitic infections in the U.S…. 1. Chagas disease (trypanosomiasis) 2. Neurocysticerosis (by taenia solium) 3. Toxocariasis 4. Toxoplasmosis 5. Trichomoniasis * Targeted because people are unaware they have the infection and they can lead to serious consequences

Question 34

Infections in which humans are… Dead end host: \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ Part of life cycle: \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_

Answer 34

1) Naegleria, Toxocariasis, Toxoplasmosis 2) Giardiasis, Malaria, Trypanosomiasis, Taeniasis, Trichomoniasis