Control of Pathogenic Bacteria

Bacteria spread in various ways:

1. moisture droplets in the air

2. dust

3. direct contact

4. fecal contamination

5. animal bites

6. wounds

April 21, 2023

Aseptic Techniques

(in addition to body’s own defence mechanisms)

• To prevent infection we use: autoclaves: sterilization of surgical equipment by extreme heat

protective clothing: masks, gowns, gloves

antiseptics: chemicals that kill bacteria (ex: alcohol, Lysol, etc)

air filtration: in operating rooms

extermination: kill animals that are carrying the disease

April 21, 2023

Treatment of Active Infections (kill bacteria inside host)

problem: find a medication that kills bacteria, but won’t kill the host cells

solution: antibiotics most important discovery of the last century

attack bacterial cell walls causing bacteria to die

not dangerous to humans or other animals no cell walls

April 21, 2023

Discovery of Penicillin

• discovered by Alexander Fleming (1929)

• cultured bacteria on agar

• mould contaminated his plates

aspergillus penicillium

April 21, 2023

Discovery of Penicillin

bacterial colonies growing on agar

petri dish with nutrient agar

zone of inhibition (no growth)

mould colony

April 21, 2023

Discovery of Penicillin

• observed a zone of inhibition: (no bacterial growth) around the mould colony

conclusion: mould produces a chemical (antibiotic) that kills bacteria

i.e. discovered penicillin

April 21, 2023

Antibiotics

• since the discovery of penicillin, many antibiotics have been discovered

• some ( > 2500) produced naturally by microorganisms• others synthetically

April 21, 2023

Antibiotics

• researchers must continue to find new antibiotics because:

different species of bacteria have different cell walls, therefore need different antibiotics to destroy them

bacteria evolve very quickly - mutate

if only one bacterium becomes resistant…..

i. they reproduce asexually (binary fission) so quickly(~ every 20 minutes - 7h → 1x106 bacteria)

ii. can pass on antibiotic resistance to other species through sexual reproduction

April 21, 2023

Antibiotic Resistance

• Antibiotic resistance develops from genetic variations within a bacterial population

• After first exposure to an antibiotic: Weaker strains of bacteria are killed Stronger antibiotic resistant strains survive and pass

their resistance to the next generation

FROM WHAT WE KNOW WHY SHOULD YOU ALWAYS TAKE ANTIBIOTICS FOR THE FULL LENGTH OF TIME?

April 21, 2023

Homework

• Page 127 # 1, 2, 4, 7