Flashcards in Lecture 3 - Antibiotics & Resistance Deck (36):
For inanimate objects
nontoxic, for living tissues (hand san)
antimicrobials from bacteria and fungi exploited by humans
How was penicillin discovered
Was on a plate withs staph, and no growth around the penicillin
Best way to kill bacteria
When are antibiotics absolutely required?
Surgery and essentially all forms of medicine
2 problems for antibiotics
No profit, less interest. Resistance always occurs
What are the 2 fates of antibiotics
Kill the bacteria or stunt the growth
Minimum inhibitory concentration - how much antibiotic is needed to stop growth
How do we test MIC
Various test tubes with varying conc and the bacteria. Which everyone shows a visible change is the MIC. NEW: strips used on plate with different antibiotics, as the strip moves towards to centre concentrate increases. Measure conc where growth of bacteria stops
5 Antibiotic Targets
- cell wall synthesis
- protein synthesis
- DNA/RNA synthesis
- folate synthesis
- changes in cell membrane
How is cell wall synthesis stopped?
- Using B-lactam rings that will bind to penicillin binding proteins (PBP) and will stop the cross linking
How does bacteria counteract b-lactam
Production of b-lactamase which destroys the lactam ring and thus no binding to peptide
What is used when penicillin resistance occurs?
Methicillin, can't be cleaved by lactamase
How does the bacteria counteract methicillin?
Makes different Protein Binding Penicillin which won't bind lactam or methicillin
What is the main job of Vancomycin
Stops cell wall synthesis for gram positives (can't get through the outer membrane of g-)
How does vancomycin work?
Binds the terminal d-ala-d-ala and stops transcription
How does bacteria counteract vancomycin?
Changes terminal end to d-ala-d-lac so that vancomycin cannot bind
What is the target for protein synthesis inhibition?
What is used to inhibit folic acid synthesis
Trimethoprim and sulfonamides
Where is Folic Acid obtained from
Humans - diet, Bacteria - must synthesize on won
What is used to inhibit DNA/RNA synthesis?
Fluoroquinolones which stop the coiling, and Rifampicin which stop RNA polymerase from working
What is used to alter the cell membrane?
Polymyxin B, binds to LPS and disrupts the membrane
What is horizontal transfer?
The gain of new genes from another organisms
What are the 3 methods of horizontal gene transfer?
Transformation - floating dna
Transduction - bacteriophage
Conjugation - direct passing of plasmid
What does enterococci infect?
The GI tract
What type of pathogen is Enterococci
UTI, Surgical infections and endocarditis
VRE stands for
Vancomycin resistant enterocci
G-, nosocomial, very resistant to all antibiotics
G-, nosocomial, pneumonia, highly resistnat
G+ rod shapped, forms endospores
Clastridium difficile (C. diff) causes
pseudomembranous colitis - antibiotic caused diarrhea
How is C. diff transmitted?
Via the focal oral route