Module 6: Section 2B

Question 1

Pre-antibiotic era

Answer 1

• Use of antibiotics evolved from Lister’s work
• He used an antiseptic carbolic acid, to try and prevent sepsis after surgery

Question 2

Sulfa drugs

Answer 2

• Ehrlich launched the field of chemotherapy by discovering a dye that was active against the parasite caused Sleeping Sickness
• Domagk discovered a dye that could protect mice from streptococci and staphylococci infections without harming them
• This dye was metabolized to sulfanilamide (sulpha drugs)

Question 3

Penicillin

Answer 3

• First naturally occurring antibiotic
• Fleming later “rediscovered” penicillin but stopped his research when he couldn’t prove in vivo activity
• Florey and Chain later purified penicillin and conducted successful human trials

Question 4

Streptomycin

Answer 4

• Waksman’s team discovered streptomycin from Streptomyces griseus after screening 10,000 soil microbes
• By 1953, other Streptomyces species produced major antibiotics like chloramphenicol, neomycin, and tetracycline, launching the “Antibiotic Era”

Question 5

End of the Antibiotic Era

Answer 5

Antibiotic resistance is rising fast, making many antibiotics less effective and leading experts to predict we may be nearing the end of the “Antibiotic Era.”

Question 6

Actinobacteria

Answer 6

• Important group of microbes concerning medicine, agriculture and food production
• Streptomyces is the best studied Actinobacteria because of its role as a producer of antibiotics

Question 7

How does Streptomyces produce antibiotics?

Answer 7

• Antibiotics such as streptomycin (made by S. griseus) are secondary metabolites that prevent competing bacteria from using nutrients around the hyphae
• Streptomyces hyphae secrete many enzymes into the soil to break down insoluble organic polymers (like cellulose and chitin) into sugars they take back into the organism

Question 8

How does Streptomyces protect itself from it’s own antibiotics?

Answer 8

• Streptomyces encodes genes for enzymes to protect themselves against the antibiotics they produce
• These genes get passed from microbe to microbe by horizontal gene transfer

Question 9

Origin of Antibiotics & Resistance

Answer 9

• Most antibiotics come from soil microbes like Streptomyces
• These microbes protect themselves by making resistance enzymes
• The resistance genes spread by HGT, reducing antibiotic effectiveness over time

Question 10

Solution preparation - vaccine testing

Answer 10

• Vaccine must first be manipulated into a form that can be injected or ingested
• Once done, the material must be suspended in a solution that can be used for testing

Question 11

Preclinical trials - Vaccine testing

Answer 11

• Vaccine solution is first tested in cell culture and animal models to determine its overall toxicity
• An animal model will give information about whether or not protective antibodies are made

Question 12

Clinical trials - Vaccine testing

Answer 12

• This is the phase of testing in humans
• The first 2 phases test for the type and strength of the immune response
• This phase tests wether or not the vaccine is actually protective

Question 13

Microbes used to produce medicinal prodcucts

Answer 13

• Bacteria make a great platform for the synthesis of products used to treat humans
• Because of how easy they are to grow and how many tools have been developed for genetic engineering

Question 14

Production of human insulin

Answer 14

• One of the most well-established bacterial synthesis platforms is for the production of human insulin
• Initially cloned around 1976
• The approval to sell recombinant human insulin in the USA was not granted until 1986

Question 15

Production of human insulin - Step 1

Answer 15

Initial process of insulin manufacture is the insertion of synthetic DNA coding for A and B chains of insulin into two plasmids

Question 16

Production of human insulin - Step 2

Answer 16

Next step is to insert the two plasmids separately into Escherichia coli.

Question 17

Production of human insulin - Step 3

Answer 17

The A and B chains are then purified from the two bacterial cultures

Question 18

Production of human insulin - Step 4

Answer 18

Finally, the purified A and B chains are recombined to produce the full insulin molecule

Question 19

Microbes used for indicators of safety

Answer 19

• Another use of microbes to protect human health is as biomarkers
• Certain microbes are commonly used as ‘sentinels’ to indicate the safety of food and water

Question 20

What indicator is commonly used to measure water safety in sewage treatment?

Answer 20

• Fecal coliforms (often E. coli) are measured because they normally live in the human intestine, grow in aerobic & anaerobic conditions, and are common in sewage
• The test is culture-based, so bacteria must be alive for accurate results

Question 21

Microbes and food safety

Answer 21

• O157:H7 strain of E. coli has been associated with several outbreaks in recent years
• It is an enterohemorrhagic strain that causes blood diarrhea and hemolytic ureic syndrome, sometimes leading to death

Question 22

Microbes as Food Safety Indicators

Answer 22

• Canadian Food Inspection Agency (CFIA) uses E. coli to check overall food hygiene and safety in production facilities
• CFIA tests foods with high contamination risk to assess general cleanliness and safety
• CFIA also routinely tests and recalls foods due to microbiological contamination

Question 23

Listeria monocytogenes

Answer 23

• One of the most virulent food borne pathogens
• It colonizes the GI tract and can then invade the host by crossing the intestinal epithelial barrier and infecting macrophages
• It can then be transported through the blood, causing a system,ic infection as well as meningitis in young patients

Question 24

Official scientific definition of probiotics

Answer 24

Live microorganisms that when administered in adequate amounts confer a health benefit on the host

Question 25

The problem about the definition of a probiotic

Answer 25

No legal definition of a probiotic exists, which allows the marketing of products labeled as "probiotics" that do not meet the fundamental criteria in the scientific definition

Question 26

What is a prebiotic?

Answer 26

A non digestible food ingredient that beneficially affects the host by selectively stimulating the growth and/or activity of bacteria in the colon and thus improving health

Question 27

Probiotic Lactobacillus sp - Step 1

Answer 27

- L. rhamnosus GG secretes 2 proteins - p40 and p75 have been shown to confer a protective effect

Question 28

Probiotic Lactobacillus sp - Step 2

Answer 28

- These proteins interact with and activate a host cell surface receptor called EGFR - Activation of EGFR initiates signalling through 2 different pathways

Question 29

Probiotic Lactobacillus sp - Step 3

Answer 29

One pathway, by up regulating expression of a group of genes via AP1 binding to their promoters, helps to protect and repair tight junctions

Question 30

Probiotic Lactobacillus sp - Step 4

Answer 30

- Second signalling pathway results in up regulation of a different set of genes - These gene products block signals telling the epithelial cells to die - This helps to prevent holes in the epithelial barrier

Question 31

Probiotic consortium strategy

Answer 31

- Researchers at U of Guelph + Queen’s developed a 33-microbe mixture of gut commensals with negligible antibiotic resistance to manipulate the gut microbiome - These microbes are easy to culture and chosen to help improve gut health

Question 32

Benefits of the 33-microbe mixture

Answer 32

Used to restore gut flora in C. difficile infections and shown to protect the GI tract in a mouse model of colitis