1. Bacteria and Antibiotics
Mrs. Stewart
Medical Interventions
Central Magnet School
Bacteria and Antibiotics

2. 2 Classes of Bacteria Thin layer of peptidoglycan
Gram (-)
Gram (+)
Thin layer of peptidoglycan
Lipopolysaccharides (endotoxins)
Stain red
Thick layer of peptidoglycan
Stain blueish - purple

3. What’s the difference?

5. Gram Stain Bacteria are stained with two stains:
Crystal Violet stain (blue/purple)
Fuchsin counterstain (red)
Gram –
Red
LPS cell wall prohibits peptidoglycan layer from absorbing crystal violet stain (absorbs counter stain)
Gram +
Blueish-purple
Peptidoglycan layer absorbs the crystal violet stain

6. Think – Pair – Share
What cellular components do some bacterial cells have that make them powerful pathogens? Explain.

7. Neisseria Meningitidis
GRAM -

8. How do we treat bacterial infections?
Antibiotics are drugs used to treat infections caused by bacteria.
Antibiotic - A substance produced by or derived from a microorganism and able in dilute solution to inhibit or kill another microorganism

9. History of Antibiotics
1928- Alexander Fleming
Accidentally discovered penicillin
Left lab untidy for a month and went on vacation
Came back and found a fungus growing in one of his bacterial cultures. Fungus was inhibiting the bacteria.
Fungus = penicillium notatum
Later named: penicillin

10. Gangrene and Sepsis - WWI
Gangrene – wound infections that lead to many amputations or sepsis
Sepsis – bacterial infection in blood stream – leads to organ system failures

11. Penicillin

12. Where Do Antibiotics Come From?
The early antibiotics = natural products of other microorganisms (fungi or other bacteria)
Now = created synthetically (chemically altering existing natural products)

13. Which antibiotic is prescribed?
Depends on the bacteria
Gram + OR
Gram -

14. How Do Antibiotics Work?
Bactericidal – Kills the bacteria
Bacteriostatic – inhibits growth & reproduction
* The body’s natural defenses can usually take it from there

15. Classes of antibiotics
Beta – Lactam
Fluoroquinolones
Tetracyclines
Sulfanomides

16. Beta – Lactam
Disrupt the synthesis of peptidoglycan thereby inhibiting cell wall synthesis & damaging cell wall integrity
Broad spectrum (can work against + or -)
Bactericidal
Example: Penicillins

17. Think – Pair – Share
Why are penicillins often more effective against gram positive than gram negative bacteria?

18. Fluoroquinolones
Inhibit topoisomerase enzymes which prohibit DNA replication and protein synthesis
Broad spectrum – effective against + and -

19. Tetracyclines
Bind the 30s ribosomal subunit, blocking the attachment of tRNA, thereby inhibiting protein synthesis
Broad spectrum – effective against + and -

20. Sulfa (sulfonamides) 1st class of antibiotics ever used
Structurally similar to PABA – a substance that the bacteria use to synthesize folate (folic acid)
Inhibits the synthesis of folic acid (Folate)
folate is necessary for DNA synthesis
No DNA synthesis (replication) = No cell division

21. Think – Pair – Share
Why is it important to understand the structure of a bacterial cell when developing an antibiotic?

22. Think – Pair – Share
What class of antibiotics would you prescribe for Sue? Explain.

23. When are antibiotics prescribed?
Bacterial infections only
Antibiotics target bacteria and a few parasites.

24. Why don’t antibiotics work on viruses?
They do not share the same structures
Viruses consist of a hereditary material (DNA or RNA) surrounded by a protein coat or fatty envelope.
They do not have any organelles – they hijack host cells to produce more DNA/RNA or proteins

25. What type of infection is it?
Antibiotics are not effective against viruses.
Most colds and sore throats are caused by viruses

26. Think – Pair – Share
How do antibiotics function without harming the surrounding human cells?

27. Should we take antibiotics if we are unsure what the pathogen is?NO
That leads to antibiotic resistance due to overuse

28. How does overuse lead to resistance?
There are more bacterial cells in/on your body than there are human cells
Antibiotics will target all susceptible bacteria – not just the spot of infection
All bacteria living within your body will either die (susceptible) or will live (resistant)
Survival of the fittest

29. Examples:
Ear Infections
MRSA
TB – Tuberculosis
Strep throat