Antibiotics and Penicillin Quiz

Course Information

• Course code: MICR20010
• Course title: Agricultural Microbiology
• Instructor: Dr. Tadhg Ó Cróinín

Exam Schedule

• Practical Exam: November 22nd, 2-3 PM. 30 multiple-choice questions (MCQs) over 1 hour. Focuses on practical material (manual and online). Worth 15% of the final grade.
• Final Exam: December 12th, 9:30-11:30 PM. Confirm time on official schedule. 60 MCQs over 2 hours. Questions will cover lecture material. Worth 70% of the final grade.
• Practice materials for both exams are available on Brightspace.

Remaining Lectures

• Lecture 10: Microorganisms and Disease
• Lecture 11: The Immune System
• Lecture 12: Pathogenic Bacteria
• Lecture 13: Pathogenic Fungi and Viruses
• Lecture 14: Antibiotic Resistant Microorganisms
• Lecture 15: Microbiology in the Food Industry - The Fungi
• Lecture 16: Microbiology in the Food Industry - Fermentations
• Lecture 17: The Nitrogen Cycle

Antibiotic Discovery and Resistance

• What are Antibiotics?
  • Compounds produced by microorganisms.
  • Kill or inhibit the growth of other microorganisms.
  • Approximately 70% are produced by Streptomyces bacteria
  • Penicillin was first and produced by Penicillium notatum
  • Approximately 8000 known antibiotics.
• Discovery of Penicillin:
  • 192: Alexander Fleming discovered that the bacterium Staphylococcus aureus failed to grow in areas contaminated by Penicillium notatum.
  • 1940: Howard Florey and Ernst Chain purified penicillin, injected into mice, and initiated human trials.
  • 1942: Pfizer achieved mass production of Penicillin using deep-tank fermentation techniques.
  • 1950: Penicillin was available orally to the public without a prescription.
  • 1945: Nobel Prize in Physiology & Medicine jointly awarded to Fleming, Florey, and Chain for the discovery of Penicillin.

Antibiotic Producing Organisms

(Table 30.2)

• Various microorganisms, including bacteria (e.g., Bacillus licheniformis, Streptomyces species), fungi (e.g., Cephalosporium spp., Penicillium griseofulvin), and actinomycetes, produce antibiotics.

Development of Penicillin Strains

• The original Penicillium mould (notatum) produced much less penicillin (less than 10 units per mL of broth) in 1943.
• A new strain, Penicillium chrysogenum, produced 100 times more penicillin.
• Strain improvement continued over the next 30 years.

Industrial Evolution of Penicillin Production

• Various methods and developments in penicillin production are detailed, showing increases in yield over time.

Drug Discovery

• A method of initial strain screening is described.

Check Antibiotic Spectrum

• A method of determining antibiotic efficiency on different microorganisms
• Streaking a sample of suspected antibiotic-producing microorganisms and testing for the zone of growth and inhibition.

Disk-Diffusion Method

• Use of the Disk-Diffusion Method for identifying effective antibiotics.

Testing a Strain - Examples

• Staphylococcus albus
• Micrococcus luteus

The Action of Antimicrobial Drugs

• Bactericidal: Directly kills microbes.
• Bacteriostatic: Prevents microbes from growing.

Effects of Drug Combinations

• Synergism: Combined drug effect is greater than individual drug effects. Example: Combination of penicillin with potassium clavulanate (inhibitor of penicillinase). This combination with broad-spectrum penicillin - amoxicillin is Augmentin.
• Antagonism: Combined drug effect is less than individual drug effects.

Synergism between Two Different Antibiotics

• Demonstrated visually by the effect of two different antibiotics on the growth of specific microorganisms.
• Shows antibiotic synergy, resulting in a larger zone of inhibition.

The Action of Antimicrobial Drugs: Mechanism of Action

• Cell wall synthesis
• Protein synthesis inhibition
• Nucleic acid replication inhibition
• Plasma membrane injury
• Essential metabolite synthesis inhibition

Inhibitors of Cell Wall Synthesis - example: Penicillin

• Naturally occurring penicillins.

• Semisynthetic penicillins (improved from natural forms, overcoming weaknesses).

• Extended-spectrum penicillins (effective against a broader range of bacteria).

• Penicillin G (requires injection).

• Penicillin V (taken orally).

However...

• A cartoon about bacteria developing resistance to penicillins.

Antibiotic Resistance

• Misuse of antibiotics selects for resistant mutants.

• Includes factors like outdated antibiotics, using them inappropriately, or not completing a full course.

• Using antibiotics in animal feed.

Antibiotics and Animal Feed

• Data shows a correlation of increasing resistance to antibiotics in poultry by use in animal feed over time.

Resistance to Penicillin

• Gene for beta-lactamase (an enzyme that breaks down penicillin) carried by plasmids.
• Methicillin introduced, relatively resistant to beta-lactamases.
• Methicillin-resistant Staphylococcus aureus (MRSA) is a consequence

The Evolution of Drug-Resistant Bacteria

• Staphylococcus aureus (commonly found on people).
• MRSA (methicillin-resistant S. aureus) is a serious pathogen.
• S. aureus resistance to penicillin emerged within two years of its widespread use.
• Resistance to methicillin emerged shortly after its widespread use.

Methicillin

• Methicillin mechanism for inhibiting bacteria.
• Different protein used by MRSA strains.
• MRSA strains' higher survival rate compared to non-resistant S. aureus strains when exposed to methicillin.
• Current resistance to multiple drugs in the MRSA strain.

Resistance Mechanisms

• Mechanisms of resistance to antibiotics: Blocking entry, inactivation of enzymes (eg: beta lactamases), altering the target molecule, and efflux.

Finding new Antibiotics

• Teixobactin, a new discovery, signals a new antibiotic class.
• Importance in finding new ways to combat resistance.
• Exploring new environments for discovering new antibiotics.

Next Time:

• Microbiology in the food industry, Part 1: The Fungi