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Microbiology > Unit 8 > Flashcards

Unit 8 Flashcards

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1
Q

What are antimicrobials

A

Chemicals that inhibit the growth or kill microorganisms

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2
Q

What are the terms antimicrobials are the umbrella term for? What are each specific to?

A

Antibiotics: specific to bacteria

Antivirals: specific to viruses

Antifungals: specific to fungi

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3
Q

Describe the 5 mechanisms of action antibiotics take on bacteria cells

A 
Acting on or altering: 
Cell wall
Cell membrane
Ribosomes 
Metabolic enzymes
DNA replication
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4
Q

Describe how drugs may affect cell wall synthesis in a gram positive cell

A

Gram positive cells have a rigid cell wall to prevent lysis, certain antibiotics block proper cell wall synthesis to make them more susceptible to lysis

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5
Q

True or false

Drugs that affect cell wall synthesis only work on cells that are in the process of growing

A

True

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6
Q

Describe how beta-lactam antibiotics work

A

Drug class that affect cell wall synthesis

Includes; penicillins and cephalosporins

These drugs contain a beta lactam ring that binds to and blocks the enzyme transpeptidase from working (this enzyme produces peptide cross links between the peptidoglycan layers)

results in a weak cell wall

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7
Q

Describe how beta-lactam antibiotic resistance works

A

An enzyme found on plasmids; beta-lactamase, is the main mechanism of resistance to beta lactam drugs

This enzyme cleaves the beta-lactam ring so the drug can no longer bind to transpeptidase

The gene for this enzyme on plasmids is Very easily spread to progeny and other bacteria

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8
Q

Describe what happens to the cell membrane when certain drugs insert into the plasma membrane

A

The drug acts like a detergent and disrupts lipid layers of the cell membrane

It creates openings/pores that allow cytoplasms too leak out

Increases the ability of other drugs to enter the cells

These drugs kill the bacteria

Ex. Ploymixins, amnioglycosides

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9
Q

Describe the ways certain drugs block ribosome function

A

Blocking protein synthesis by;

1) binding to the ribosome and blocking its function
2) binding to the tRNA so amino acids cannot be transported to the ribosome

Bacteria will either stop growing or die

Classes of drugs: aminoglycosides, macrolides, lincosamides, tetracyclines, chloramphenicol, florfenicol

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10
Q

What is aminoglycoside’s mechanism of action when it comes to blocking ribosome function?

A

Causes the mRNA to be misread when building proteins

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11
Q

Describe the ways antibiotics block metabolic enzymes

A

Some bind to the active site of critical enzymes in order to block function

Others bind to the critical enzyme cofactors/coenzymes/substrates so that the compounds are no longer available for metabolism

Stops growth, not as good for killing

Drug classes; sulphonamides, anti-metabolites

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12
Q

Describe how antibiotics block DNA synthesis

A

The antibiotic binds to the DNA or the enzymes involved in DNA replication

This either:

1) physically blocks the replication process
2) cause non-viable mutations to occur during DNA replication

Bacteria will die without replicating

Drug class: fluoroquinolones

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13
Q

What are bacteriostatic drugs

A

Slows replication rate of bacteria at the proper dose (stasis: stopping)

Allows the immune system to clear the bacteria more effectively

Animal must have a functioning immune system in order for these drugs to be successful

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14
Q

What are bacteriocidal drugs

A

Killing bacteria

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15
Q

True or false

Bacteriocidal and bacteriostatic drugs will always work in the way they are meant to on all bacteria

A

False

May have different effects in different bacteria

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16
Q

What is MIC

A

Minimum inhibitory concentration

Lowest concentration of an antibiotic that will completely inhibit growth of specific bacteria in VITRO

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17
Q

What is in vitro

A

Outside the living body in an artificial environment (petri dish)

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18
Q

What is MBC

A

Minimum bacteriocidal concentration

Lowest concentration of an antibiotic that will kill specific bacteria

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19
Q

True or false

MIC or MBC must reach the site of infection in order to be effective

A

True

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20
Q

What does effectiveness of a drug depend on

A

Dose (mg/kg)
Route of administration
Frequency of dosing

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21
Q

What does failure to achieve at least MIC result in

A

Failure to treat infection

Increased risk of drug resistance

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22
Q

What is the antibiotic spectrum

A

The range of bacteria for which the drug is effective

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23
Q

What is a NARROW spectrum antibiotic

A

Antibiotics only work on either gram positive OR gram negative bacteria

Considered more specific

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24
Q

What is a BROAD spectrum antibiotic

A

Antibiotics works on both gram positive and gram negative bacteria (no necessarily all)

Considered less specific

25
Q

What are the characteristics of “first choice” antibiotics in ANY situation

A

Bacteriocidal
Narrow spectrum (broad is bad)
Least side effects to the patient

26
Q

Why are antibiotics used? Give 4 reasons for antibiotics used in vet medicine

A

Used to control bacteria in or on the body

1) therapeutic use
2) prophylaxis
3) metaphylaxis
4) growth promoter

27
Q

Describe how antibiotics used in a therapeutic manner

A

Used to treat bacterial causes of infection that are occurring currently in the animal

28
Q

What is the gold standard method of therapeutic antibiotic use

A

Requires identifying bacterial agent of the disease and selecting the right drug for it

Includes: culture and identifications tests to determine genus at minimum, and antimicrobial testing for best drugs

29
Q

What are the limitations if you use the gold standards when choosing antibiotics

A

Time and money for testing

30
Q

If you use the gold standards, you are least like to cause

A

Drug resistance

31
Q

What is the Kirby Bauer Test

A

Standard test for antibiotic sensitivity and resistance

32
Q

Describe how you do the Kirby Bauer test

A

Bacteria is cultured on solid media

Discs containing different antibiotics are placed on the media

Drugs that are effective against the bacteria will prevent any bacterial growth around the disc

33
Q

Describe reporting for the Kirby Bauer test

A

Sensitive (S): inhibits growth at therapeutic dose (recommended)

Intermediate (I): inhibits growth if dose is higher than recommended

Resistant (R): no inhibition, dose to inhibit bacteria cannot be achieved because it may be toxic to the patient.

34
Q

How are antibiotics used in prophylaxis

Give an example

A

Using antibiotics to PREVENT an infection that might occur (preventative treatment) can be very effective

Ex. Giving an antibiotic before an intestinal surgery to prevent the development of an infection

35
Q

True or false

Using antibiotics in a prophylaxis manner gives leeway for less aseptic technique in surgeries

A

FALSE

36
Q

How are antibiotics used in metaphylaxis

Who is this commonly used in

A

The timely MASS medication of a group of animals to eliminate or minimize an expected outbreak of a disease (group prophylaxis)

Common in cattle, swine and poultry

37
Q

How are antibiotics used as growth promoters

Give an example

A

Addition of antibiotics to feed or water to mass medicate a group of animals in order to increase feed efficiency (used in sub-therapeutic doses)

Common in poultry, also used in swine and beef

Ex. Low levels of tetracycline in water enhance growth rates in chickens

Very controversial

38
Q

Why is using antibiotics as a growth promoter controversial

A

Because it increases the risk of antimicrobial resistance

39
Q

What is antimicrobial resistance

A

The acquired ability of microorganisms to survive despite the presence of therapeutic concentrations of a chemical that is normally lethal

Applies to bacteria, viruses, fungi, parasites and insects

40
Q

What are the 3 major mechanisms of antimicrobial resistance

A

Spontaneous mutation of target proteins so the drug cannot bind

Acquiring plasmids that contain resistance genes

Cross resistance due to acquiring the drug efflux pump

41
Q

Describe how spontaneous mutation results in antimicrobial resistance

A

Bacteria have extremely fast generation times so change due to spontaneous mutations can occur rapidly

Most common change is to the target proteins so the drug can no longer bind and work against it

42
Q

Describe the 3 methods of plasmid based antimicrobial resistance and give an example

A

The plasmid genes can contain

1) an altered enzyme that the drug can’t bind to
2) an enzyme that breaks down drugs
3) transporter that prevents drug entry or that removes the drug once inside the cell

Once bacteria have this plasmid, it is passed to all progeny cells and can be transferred to adjacent bacteria which is why AMR is spread so rapidly

Ex. Beta-lactamase gene is a form of plasmid based resistance

43
Q

How do bacteria have antimicrobial resistance via a drug efflux pump

A

Bacteria acquire a new transporter gene that pumps drugs out of the bacteria cell

Pump found in the cell membrane, when drugs enter the cell the pump immediately removes it. It is able to pump out many different classes of drugs

44
Q

The drug efflux pump initially develops against one drug, but then provides resistance to other drugs, this is called

A

Cross Resistance

45
Q

Describe Fluoroquinolone antibiotics

A

A class of antibiotics that block replications of bacterial DNA

One of the newest classes introduced in the 1980s

It is bacteriocidal, relatively safe and broad spectrum

46
Q

What happens when bacteria are exposed to fluoroquinolone antibiotics

A

Bacteria have a very high risk of developing mutations that result in the drug efflux pump

47
Q

Describe the fluoroquinolone antibiotics importance

What has been deemed about this drug

A

Category 1: very high importance according to WHO and Health Canada

Intended for use in hospital under strict supervision for the treatment of multi-resistant strains of bacteria

Only to be used when there is no other option due to increased risk of creating cross resistance

48
Q

What are the intended uses of fluoroquinolone antibiotics in human medicine

A

Hospital acquired infections

For other severe infections only if there is proven resistance to other antibiotic classes

49
Q

What are the approved uses of fluoroquinolone antibiotics in vet medicine

A

Bovine respiratory disease

Dogs/cats: topical ear medications, treating UTIs, wounds, abscesses

Used to be allowed to be used in poultry feed but no longer allowed since resistance issues emerged

50
Q

What are Super Bugs

A

Bacteria that are resistant to multiple classes of antibiotics

These have limited treatment options And often concern both humans and animals (zoonotic)

Nosocomial, highly virulent and have multi-drug resistance

51
Q

What are ESKAPE pathogens

A

A list of superbugs that are nosocomial, highly virulent and have multi-drug resistance

Enterococcus faecium, staphylococcus aureus, klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, enteribacter sp. , E. coli and Clostridioides difficile

52
Q

What are the top three concerns with antibiotic resistance

A

1) costs of treatments (more/longer hospital stays, expensive drugs)
2) costs in human health (zoonotic diseases, resistant diseases (E.Coli, staphylococcus, streptococcus, mycobacterium Tb, results in prolonged illness/hospitalization/can’t work or treat)
3) will we run out of antibiotics (special antibiotics are reserved only for human medicine or treating resistant strains, drug development is expensive and will not often be used in vet med)

53
Q

What are 7 risk factors for antimicrobial resistance

A

1) bacteria exposed to sub-therapeutic levels of drug
2) selecting bacteriostatic drugs
3) selecting broad spectrum drugs when the target pop has a lower MIC/MBC
4) incomplete treatment; not all target bacteria were removed
5) inappropriate fluoroquinolone use
6) if bacteria comes from a hospital setting (risks of being previously exposed)
7) increased exposure to different antibiotics

54
Q

As long as a drug is present, there is selective pressure for the resistant strain to

A

Flourish

55
Q

What are some reasons identified by WHO that increases antimicrobial resistance

A

1) resistant organisms being transferred from animals to humans (meat, diary, manure, overuse in livestock)
2) treating without identifying bacteria causing disease (using antivirals for bacteria)
3) lack of sensitivity testing
4) using broad spectrum
5) not completing full course of meds (some bacteria remain and become resistant)
6) ground water contamination from urine/feces from treated livestock
7) inappropriate disposal of antibiotics
8) overuse of antibacterial cleaning products

56
Q

True or false
Antibiotic classes such as sulphonamides, tetracyclines, beta-lactam and aminoglycosides are used in livestock and human medicine

A

True

57
Q

What are some ways to increase antibiotic effectiveness and avoid resistance?

A

1) identify what type of pathogen is causing disease and then identify which specific pathogen it is (viral/bacterial/fungal)
2) identify which antibiotic(s) it is susceptible to and which it is resistant to
3) select the susceptible antibiotic with the narrowest spectrum
4) use drug as intended (dose, indication, frequency, duration)
5) treat until infection is resolved

58
Q

True or false

As of 2018, all antibiotics of human relevance can only be acquired by prescription only

A

True

59
Q

Describe the 4 categories of importance of antibiotics

A

Category 1) very high importance -resistant cases

Category 2) high importance -variety of cases

Category 3) medium importance -topicals, very common

Category 4) low importance -not used in people

Microbiology (12 decks)

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