antibiotics in the food supply

Question 1

AMR

Answer 1

• 80% of antibiotics used in Canada are used in agriculture
• Teixobactin: newest antibiotic
• Antibiotics used in food-producing animals help select for the presence of antibiotic resistance genes and antibiotic resistant bacteria
• when manure is spread in soil and onto crops they mix with the environment
• current manure precessing are ineffective at removing AMR bac
• if vegetables are eaten raw, you may be consuming several AMR bac

Question 2

Bacteriocidal antibiotics

Answer 2

• kill the bacterial cell
• target key cell structures (biosynthesis of the cell wall or DNA)
• B-lactam antibiotics family (aminoglycosides, quinolones )

Question 3

Bacteriostatic antibiotics

Answer 3

inhibit further growth

• target protein synthesis
• macrolides, tetracycline, sulfonamides

Question 4

Impact of the food chain on AMR

Answer 4

• Antimicrobials are used in food production to treat infected animals, prevent infection, and promote growth in animals
• In organic farming (no antimicrobials) higher presence of pathogens
• EU banned the use of antibiotics for growth promotion
• prevalence of AMR is linked to widespread use

Question 5

2 schools of thought? AMR in the food chain

Answer 5

1. The Food chain propagates AMR infections in humans:
   - AMR foodborne pathogens are common
   - AMR in commensal bacteria on food items are very common
   - AMR genepool in food must therefore be very high
   - likely that humans are bein continuously exposed to AMR genes through the food chain
2. The food chain does not propagate AMR infections in humans
   - the actual number of pathogens in foods is very small
   - the actual number of AMR pathogens in food is very small
   - Do any of these genes actually move to organisms in the GI tract?

Question 6

Development of AMR in bacteria

Answer 6

• AMR aquired via HGT and VGT
• mutation: mutagens, incorrect repair of double-stranded breaks
• antibiotics selects for resistant individuals and sublethal levels of antibiotics increase reactive oxygen species with increase the rate of mutation

Question 7

HGT and VGT

Answer 7

• HGT: mediates the spread of AMR by mobile genetic elements (plasmids, transposons)
• transfer via conjugation, transformation, transduction
• VGT is very slow: mutations must accumulate and cells must divide
• HGT is rapid

Question 8

mechanisms of AMR

Answer 8

• export
• destruction
• modification
• altered receptors
• membrane compostition

Question 9

colistin

Answer 9

• polymyxin E
• old antibiotic not used in humans due to kidney toxicity
• used in emergency situations as a last resort
• mcr-1 gene was discovered in 2011, and is capable of HGT. detected in 30 countries

Question 10

methods of detecting AMR

Answer 10

disk diffusion, MIC test strips, Sensititre MIC plates

Question 11

disk diffusion test

Answer 11

• agar diffusion test, kirby-bauer test: test of the sensitivity of bacteria to a specific antibiotic
• uses antibiotic disks, which are placed on agar containing a lawn of bacteria
• incubate
• zone of inhibition forms and is measured
• diameter is compared to a database of zone standards
• bacteria are susceptible, intermediately susceptible, or resistant

Question 12

MIC test strips

Answer 12

• minimal inhibitory concentration: the lowest concentration of a drug at which no visible growth occurs
• have a predifined and dried antibiotic concentration gradient
• where the ellipse meets the strip, the MIC can be determined

Question 13

Sensititre MIC plate

Answer 13

• 96-well plates with lyophilized antibiotics to determine the MIC to a variety of antibiotics
• dilutions of bacteria with a usable carbon source were inoculated into each well of the plate