Antibiotics by kirby-bauer method Flashcards

1
Q

What is an antimicrobic/antimicrobial agent?

A

any chemical or physical agent that inhibits the growth of a microorganism or kills it

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2
Q

what is a chemotherapeutic drug?

A
  1. antimicrobial agent

2. chemical compounds that are taken internally to ease the symptoms of a disease or to speed the patient’s recovery

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3
Q

what three criteria must a chemotherapeutic drug meet to be considered an antibiotic?

A
  1. its a chemical substance produced by a microorganism
  2. it stops the growth of or kills other microorganisms
  3. it is effective in very small doses.
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4
Q

True or false: antibiotic production by microorganisms is common. If true, where is it most common?

A

True, most common in soil microbes.

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5
Q

What are antibiotics effect against and what are they not effective against

A
  1. effective against bacteria and fungi

2. not effective against viruses

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6
Q

The course of an infection depends upon what?

A

the race between the pathogen’s ability to grow in the host tissue and the tissues ability to capture and destroy that invading pathogen

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7
Q

Purpose of antibiotics?

A

to weaken or kill some of the invading pathogens; hopefully the body’s tissues can then destroy the rest.

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8
Q

what is a chronic infection?

A

its marked by long duration or frequent recurrence ( if pathogen did not go away)

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9
Q

What happens if there is a chronic infection?

A

the pathogen is isolated and an antibiotic it is easily weak to is found for it.

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10
Q

what results with overuse of antibiotics and over prescription of broad-spectrum antibiotics ?

A
  1. risk of increasing antibiotic resistance

2. affecting balance of non-target populations (wiping out important bacteria needed by body)

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11
Q

What happens after isolating the pathogen to determine its susceptible antibiotic?

A

the plates are heavily streaked and antibiotic sensitivity disks are used to determine the antimicrobial activity for each antibiotic.

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12
Q

conditions for the antibiotic disks on the agar surface?

A

they are placed on the agar surface after inoculation and BEFORE incubation.

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13
Q

what happens to the antibiotic disk during incubation?

A

it diffuses from the disk into the agar, creating a concentration gradient such that the greatest concentration is at the edge of the disk

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14
Q

what happens to the cells during the incubation of the plate with the antibiotic discs?

A

it grows confluently to form a thick loawn of microbial growth except where the microorganisms are either killed or stopped from growing by the antibiotic.

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15
Q

What is a zone of inhibition?

A

a clear zone in which there is no microbial growth

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16
Q

How is the effectiveness of the antibiotic preliminarily determed ?

A

its determined by the size of the zone of inhibition

the type of medium used

17
Q

what does the zone of inhibition vary according to?

A

to how easily the antibiotic diffuses through the agar

18
Q

What is special about the kirby-bauer method?

A

it is highly standardized to avoid varying results due to alterations in procedure

19
Q

What agar is used in the kirby-bauer method?

A

only the mueller hinton agar is used

20
Q

what is the components of the mueller hinton agar?

A

it has the same composition as TSA
but is prepared under exacting conditions such that its chemical composition is always the same
pH = 7.2 to 7.4

21
Q

what two things are the size of the zone of inhibition related to?

A
  1. minimum concentration that kills or inhibits that microbe (minimum inhibitory concentration (MIC))
  2. ability of the antibiotic to diffuse through the agar
22
Q

what is MIC

A

This is the lowest concentration of an antimicrobial drug that prevents visible growth of a microorganism after overnight incubation with media.