Antibiotic Resistance in Bacteria
Electron Micrograph of E. Coli
Diseases Caused by Bacteria
1928 1 2 Fleming 3 discovers penicillin the first antibiotic.
Some Clinically Important Antibiotics Antibiotic Producer Organism Activity Site Or Mode Of Action Ampicillin Penicillium Gram-negative and Grampositive bacteria. Cell wall synthesis Penicillin Penicillium chrysogenum Gram-positive bacteria Cell wall synthesis Cephalosporin Cephalosporium acremonium Broad spectrum Cell wall synthesis Bacitracin Bacillus subtilis Gram-positive bacteria Cell wall synthesis Polymyxin B Bacillus polymyxa Gram-negative bacteria Cell membrane Chloramphenicol synthetic Broad spectrum Protein synthesis Erythromycin Streptomyces erythreus Gram-positive bacteria Protein synthesis Streptomycin Streptomyces griseus Gram-negative bacteria Protein synthesis Tetracycline Streptomyces rimosus Broad spectrum Protein synthesis Vancomycin Streptomyces orientalis Gram-positive bacteria Protein synthesis Gentamicin Micromonospora purpurea Broad spectrum Protein synthesis
What is an antibiotic? An antibiotic is a natural substance secreted by one microorganism that will kill or inhibit growth and reproduction of other microorganisms.
Antibiotics Affect Bacterial processes of growth and Reproduction Inhibit cell wall formation Disrupting cell membrane function Preventing DNA replication Inhibiting Transcription Inhibiting Translation or Protein Synthesis
A Typical Bacteria Cell
Penicillin Targets the cell walls of bacteria inhibits the cross-linking, of the peptidoglycan chains. halts cell wall expansion. causing cell lysis
Ampicillin Member of penicillin family Gram +/- Inhibits cell wall synthesis
Antibiotics that Affect the Cell Wall Fosfomycin Bacitracin Penicillin amoxicillin ampicillin cephalosporin Vancomycin
Plasma Membrane
Antibiotics that affect the cell membrane: Polymyxin B
DNA Replication
Antibiotics that affect DNA Replication: Sulfonamides Prontosil
Transcription
Translation Protein Synthesis
Tetracyclines Broad spectrum Inhibit bacterial protein synthesis Blocks trna attachment to ribosome
Chloramphenicol Similar to tetracycline Synthetic Inhibits protein synthesis by attaching to the ribosome Interferes with peptide bond formation between amino acids
Kirby-Bauer Test Antibiotic Susceptibility of Bacteria qualitative test of inhibition
Kirby-Bauer Test Streptomycin (S10) penicillin (P10) Tetracycline (TE30) chloramphenicol (C30) Staphylococcus aureus
Kirby-Bauer Test Streptomycin (S10) penicillin (P10) Tetracycline (TE30) chloramphenicol (C30) Escherichia coli
Antibiotic-Sensitivity Testing
Antibiotic Resistance Staphylococcus Aureus Vancomycin 1996 Japan
Amp Resistant E. Coli
How do bacteria become resistant? Antibacterial lotions, Soaps and Sprays Leave only resistant bacteria
How do bacteria become resistant? Decreased transport of the antibiotic into the cell membrane. Production of enzymes that destroy the inhibitory capacity of the antibiotic Modification of the antibiotic binding site so that the drug no longer binds to the target. Production of alternate molecules that can replace those disrupted by the antibiotic.
Plasmids
CONJUGATION THE PROCESS OF EXCHANGING GENETIC MATERIAL THROUGH CELL- TO-CELL CONTACT
TRANSFORMATION THE PROCESS BY WHICH BACTERIA CELLS PICK UP AND INCORPORATE DNA FROM DEAD BACTERIA CELLS. THEY TAKE UP DNA FROM DEAD CELLS OF THE SAME OR A CLOSELY RELATED SPECIES
divide each Petri Dish into 4 sections on the bottom of the plate. Label one section as no antibiotic. Label three sections with the antibiotics to be tested ampicillin penicillin tetracycline
On one plate spread out 200 µl of the E. coli # 1 liquid culture.
On the other plate spread out 100 µl of the E. coli # 2 liquid culture.
On each section of the plates put the correct antibiotic treated disc.
Place the plates at 37 C overnight.
Results
Results