Bacteria Growth and Identification

Question 1

Why is it important to understand differences between host and bacterial cells?

Answer 1

ecological plaque hypothesis- describes the interaction between bacteria and the environment- important for insight into disease process.

Question 2

Why is pili an important structure that sits on the surface of bacteria?

Answer 2

The oral bacteria can use these structures to adhere to other bacteria and tooth structures- can be antiphagocytic

Question 3

What can bacteria growth kinetics tell us?

Answer 3

After time bacteria growth is exponential, and starts with 1 (doubling time of 20 min) after 8 hours you will have 16,777,216. Bacteria under right conditions can grow massivley

Question 4

What is an example of selective agar and non selective agar?

Answer 4

non selective- blood agar
selective- mannitol salt agar

Question 5

describe different atmospheric bacterial growth conditions

Answer 5

Aerobic = Oxygen
Capnophilic = Carbon dioxide
Facultative = With & without oxygen
Microaerophilic = require small amounts of oxygen
Anaerobic = without oxygen

Question 6

What phase does bacteria go in after a lag phase (after it has acclimatised)?

Answer 6

Logarithmic phase

Question 7

What do the different stages in bacterial growth kinetics have a impact on?

Answer 7

the pharmacodynamics of antibiotics

Question 8

What are features of non selective blood agras?

Answer 8

will grow many different bacteria
helps to provide a broad overview

Question 9

following an oral swab what agar plate would you tend to swab?

Answer 9

selective and non selective

Question 10

What is the starting point for a gram stain?

Answer 10

is that we try to get a pure colony of the bacteria on to the agar- when we have the colony a gram stain is attempted

Question 11

what are 4 dies used to try and identify bacteria in a gram stain reaction?

Answer 11

crystal violet, lugols iodine, acetone (decolourise it), red dye (counter stain)

Question 12

What is the importance of the gram stain reaction?

Answer 12

gives us an insight into some bacteria physiology linked to cell wall, this gives insight into classification and disease, and what type of antibiotic is needed

Question 13

what colour do gram positive bacteria stain

Answer 13

purple- large and thick peptidoglycan that sticks to the stain

Question 14

Gram negatrive bacteria

Answer 14

peptidoglycan layre is very thin, the gram stain does attach- counter stain red/pink allowing us to see

Question 15

What is the difference between endotoxin and exotoxins?

Answer 15

exotoxins- generally proteins produced inside the cell then excreted out- both gram pos and neg
endotoxins- this comprises fragments of the bacteria cell walls- gram negavtive bacteria usually

Question 16

what is another name for endotoxins?

Answer 16

lipopolysaccharide- causes symptoms of systemic diseases

Question 17

endotoxins such as lipopolysaccharide can cause what?

Answer 17

sepsis

Question 18

describe Gram stain shape- 1)cocci 2)strep 3)stafla 4) bacilli 5) spiral

Answer 18

cocci- round/ football shaped bacteria- pos and neg
strep- in chains not a direct shape but usually occurs with another such as streptococci
stafla- in clumps (not dircet) staflacocci
4- bacilli- cigar shaped rice/ rod- both neg and pos
5- spiral bacteria can cause acute ulcerative gingivitis- not good with gram stain

Question 19

Describe the gram stain of pus?

Answer 19

helps make provisional diagnosis
gram positive in chains- helps guide a empirical antibiotic treatment

Question 20

Gram positive cocci in chains are known as?

Answer 20

streptococci

Question 21

what is a disease caused by streptococci?

Answer 21

dental caries

Question 22

whats an example of a gram positive baciili infection?

Answer 22

clostridium tetinii

Question 23

Give an example of gram negative cocci

Answer 23

neisseria meningitidis -meningitis

Question 24

give an example of gram negative bacilli

Answer 24

black permanent anaerobe- prevotella intermedia- periodontal disease

Question 25

What is a pathogen?

Answer 25

an organism which can invade the body and cause disease, such an organism is described as pathogenic

Question 26

What are the two different types of s. aureus?

Answer 26

Methicillin Sensitive S. Aureus
Methicillin Resistant S. Aureus MRSA

Question 27

What is meant by colonization?

Answer 27

the precense of micro- organisms in or on host, with growth and multiplication, but without any overt clinical expression at the time the micro organism is isolated- no antibiotics used

Question 28

MRSA is transmitted easily in dental practice T or F?

Answer 28

true

Question 29

What is meant by infection?

Answer 29

invasion of the body by pathogenic microbes and the reaction of the tissues to their presence and to the toxins generated by them