Lecture 14- Antimicrobial Resistance (AMR) and Enteric Pathogen Interactions with the Microbiome

Question 1

Antimicrobial Resistance (AMR)

Answer 1

• describes decreased susceptibility of a multitude of microbes to a broad spectrum of single or multiple antibiotics
• widely used in human medicine, agricultural production and food processing
• essential for ensuring human health and the health of our food supply

Question 2

Bactericidal

Answer 2

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

Question 3

Bacterostatic

Answer 3

Inhibit further growth
target PRO synthesis
Macrolides, telithromycin, sulfonamides, tetracycline

Question 4

What are the 5 mechanisms of AMR?

Answer 4

1. Export (specific, non-specific)
2. Destruction (Specific, general)
3. Modification (specific)
4. Altered receptors (specific)
5. Membrane Composition (general)

Question 5

How can AMR be transmitted?

Answer 5

by vertical or horizontal gene transmission

Question 6

how are mutated genes and acquired AR genes spread?

Answer 6

via vertical transmission to offspring during bacterial growth

Question 7

How are mutations caused which leads to AMR?

Answer 7

errors in DNA synthesis, chemical changes include by mutagens, or incorrect repair of damage induced single strand breaks
- spontaneous mutations occur at different rates regardless of the presence of antibiotics

Question 8

Which gene transfer is faster in spreading AMR in an entire ecosystem and why?

Answer 8

Horizontal gene transfer because can be spread across species via conjugation, transformation, and transduction

Question 9

Colistin

Answer 9

• aka polymyxinE
• very old antibiotic
• colistin resistance MCR gene
• gene confers plasmid-mediated resistance to colistin
• MCR capable of horizontal gene transfer

Question 10

Two schools of though for AMR in Foodborne pathogen

Answer 10

1. Food chain propagates AMR infections in humans–> AMR foodborne pathogens are common; AMR in commensal bacteria on food items are very common; the AMR gene pool in food must therefor be very high; very likely that humans are being continuously exposed to AMR genes through the food chain
2. Food chain does not propagate AMR infections in humans–> The actual number of pathogens in food is very small; the actual number of AMR pathogens in food is very small; do any of these genes actually move to organism in the GI tract?

Question 11

Is AMR high in Salmonella?

Answer 11

Yes

Question 12

AMR in Campylobacter

Answer 12

• resistance is detected almost immediately after exposure to the antibiotic
• fluroquinolone resistance in campylobacter is d/t a single chromosomal mutation in the gyrA genes

Question 13

AMR in Listeria monocytogens

Answer 13

• treated with ampicillin and aminoglycodise

- l. monocytogenes is widely distributed in the environment, not problematic in terms of AMR

Question 14

AMR in E.coli

Answer 14

most strains are resistant to antibiotics

Question 15

Enteric Pathogen Interactions with the Microbiome

Answer 15

Bacterial pathogens must interact with the commensal bacterial species that comprise the microbiome
- can occur in food producing animals or human intestine

Question 16

Dysbiosis

Answer 16

bacterial pathogens produce specific PRO that are able to cause a change in the commensal population

Question 17

Listeria monocytogenes listeriolysin (LLS)

Answer 17

bacteriocin highly expressed in intestine that alters the host intestinal microbiota and promotes intestinal colonization
- capable of killing s. aureus and l.lactis which allows l. monocytogenes colonization

Question 18

What are te two phylotypes affected by the expression of LLS?

Answer 18

Alloprevotella and Allobaculum

Question 19

Alloprevotella

Answer 19

includes species that produce butyric acid

Question 20

Allobaculum

Answer 20

include bacterial species that produce acetic acid

- acetic acid prevents l. monocytogenes growth

Question 21

T6SS vibrio cholerae

Answer 21

able to kill e.coli cells but p. aurogenosa cells will in return express another T6SS and kill v. cholerae cells