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Food Microbiology > Antibiotics in the Food Supply > Flashcards

Antibiotics in the Food Supply Flashcards

1
Q

What are the main applications of antimicrobials? Of these, which is the main use in Canada?

A

Agriculture, human medicine, food processing

agriculture uses 80% of antibiotics in Canada!

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2
Q

What is “AMR?”

A

Antimicrobial resistance

decreased susceptibility of multiple microbes to a broad spectrum of single/multiple antibiotics

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3
Q

What was the earliest type of antibiotics, and when was this discovered?

A

Sulfonamides (1930s)

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4
Q

what are the latest type of antibiotics?

A

Teixobactin (2015)

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5
Q

Name the main types of antibiotics in the 1940s:

A

aminoglycosides

beta-lactams

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6
Q

Name the main antibiotics in the 1950s:

A

chloroamphenicol
tetracycline
glycopeptides
macrolides

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7
Q

Name the main antibiotics in the 1960s:

A

streptogramins
quinolones
lincosamides

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8
Q

Name an antibiotic from the 1970s:

A

Trimethoprim

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9
Q

Name the antibiotics from the 2000s:

A

Cycliclipopeptides

oxazolidinones

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10
Q

How can agricultural use of antibiotics affect human health?

A

use in animals -> selects for presence of ARGs (antibiotic resistance genes) and ARBs (antibiotics resistant bacteria)

manure -> environment (gain more ARG and ARB) -> vegetables -> consumed
(genes for resistance have entered body)

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11
Q

True/False: antibiotics used for agriculture are different from those used for human medicine

A

False; same compounds

*except chloramphenicol (only human)

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12
Q

What are the mechanisms behind antibiotics?

A

inhibit protein synth (aminoglycosides, chloroamphenicol, macrolides, tetracyclines)
inhibit cell wall synth (beta-lactams, polypeptides)
inhibit DNA synth (fluoroquinones)
inhibit folic acid synth (sulfonamides)

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13
Q

The main purposes of antibiotics in agriculture:

A

prevent disease
treat disease
growth promotion

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14
Q

antibiotics can be classified as ___ or ____. Describe each category.

A

bacteriocidal: (kills) - target key structures (cell wall, DNA)

Bacteriostatic: (inhibit growth) - target nonessential process (protein synth)

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15
Q

Give examples of bacteriocidal vs bacteriostatic antibiotics:

A

bacteriocidal: b-lactams, aminoglycosides, quinolones
bacteriostatic: macrolides, telithromycin, sulfonamides, tetracycline

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16
Q

True/False: the EU bans the use of antibiotics for agriculture

A

False; banned for GROWTH PROMOTION (can still use therapeutically)

17
Q

Did the Denmark ban on antibiotics in agriculture have positive outcomes?

A

Human health: no, incidence of Salmonella and Campylobacter infections stayed the same

But: reduced numbers of virginiamycin-resistant enterococcus in chicken

18
Q

In ____ farming, there are no antimicrobials used. What outcomes does this have?

A

organic

higher prevalence of salmonella, toxoplasma, campylobacter

19
Q

True/False: antibiotics are also used on plants

A

True (sprayed) - but difficult to know numbers (not kept track of)

20
Q

What are common antibiotics used on plants?

A

oxytetracycline, streptomycin

21
Q

What antibiotics are used in aquaculture?

A

sulfadimethoxine, ormetoprim, sulfamerizine, oxytetracycline

22
Q

What is an issue concerning antibiotics with imported food?

A

other countries have different regulations; imported food may contain antibiotic residues

23
Q

What evidence suggests that antibiotics in the food chain can lead to AMR infections in humans?

A

AMR Foodbourne pathogens are common

AMR in commensal bacteria on food is very common

AMR genepool in food is high

humans continuously exposed to AMR genes through food chain

24
Q

What evidence suggests that antibiotics in the food chain DO NOT lead to AMR infections in humans?

A

actual # of pathogens in food is small

actual # of AMR pathogens is very, very small

No evidence that genes actually move to organisms in GI tract

25
Q

How do bacteria develop/transmit AMR?

A

mutated genes (error in DNA synth, induced by mutagens, or incorrect repair) - occurs spontaneously at 10^-6 to 10^-10 bp/generation

passed on VERTICALLY (mother-daughter), or HORIZONTALLY (gene transmission)

26
Q

What mechanism spreads AMR very rapidly? How does it happen?

A

Horizontal gene transfer (HGT)

mobile genetic elements (plasmids, transposons, integrons)
-> transfer by conjugation, transformation, transdution

27
Q

True/False: HGT is limited to within a species

A

False

can spread across species, genera, and entire ecosystems

28
Q

What are the mechanisms of AMR? Are they specific or general?

A 
export (specific or nonspecific)
destruction (specific or general)
Modification (specific)
Altered receptors (specific)
membrane composition (general)
29
Q

What is an old antibiotic not commonly used, and why has it come back into prevalence?

A

Colistin (polymyxin E) - not used due to kidney toxicity

increase in AMR -> use as last-resort in multi-drug resistant Pseudomonas aeruginosa, K. pneumoniae, Acinetobacter

30
Q

What is the significance of the mcr-1 gene?

A

discovered in E. coli from pig (China) - gives plasmid-mediated resistance to colistin (last-resort antibiotic)

has been found in E. coli, Salmonella, K. pneumonia, enterobacter, in 30 countries!

31
Q

What methods are used to detect AMR?

A

Disk diffusion
MIC test strips
Sensititre MIC plate
Gene testing

32
Q

Describe the Kirby-Bauer test:

A

place antibiotic infused disks on agar inoculated with lawn of bacteria -> incubate -> observe for zone of inhibition -> measure and compare to database of zone standards (susceptible, mod. susceptible, resistant)

33
Q

What factors affect the zone size in the Kirby-Bauer test?

A

effectiveness of antibiotic

diffusion rate of antibiotic

34
Q

How do MIC test strips work?

A

strip infused with antibiotics (in a concentration gradient) -> place on bacteria lawn on agar -> observe for growth (elliptical shape; as conc decreases along strip, bacteria will grow closer)
strip contains markings indicating conc., MIC is concentration at which bacteria can touch strip

35
Q

What are sensititre MIC plates?

A

96 well plates, different antibiotics per row
Add dilutions of bacteria + usable carbon source in each well
Incubate -> measure with plate-reader to determine MIC

36
Q

What is an important tool to help with genetic methods for testing AMR?

A

Comprehansive Antibiotic Resistance Database

take whole genome sequence, compare

Food Microbiology (21 decks)

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