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

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

What’s the difference?

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

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

Neisseria Meningitidis GRAM -

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

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

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

Penicillin

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)

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

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

Classes of antibiotics Beta – Lactam Fluoroquinolones Tetracyclines Sulfanomides

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

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

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

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

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

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

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

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

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

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

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

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

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

Examples: Ear Infections MRSA TB – Tuberculosis Strep throat