Antibiotics Flashcards
What are the different types of antimicrobial agents?
- Bacteriostatic
- Bactericidal
- Bacteriolytic
What is a bacteriostatic agent?
stops growth of bacteria
What is a bactericidal agent?
kills the cells of bacteria
What is a bacteriolytic agent?
causes cell to be lysed
What does a bacteriostatic graph look like relating to the total cell count and viable cell count?
Directly proportional increase until introduction of agent where the total cell count and viable cell count becomes stationary
What does a bactericidal graph look like relating to the total cell count and viable cell count?
Directly proportional increase until introduction of agent.
Total count becomes stationary
Viable cell count decreases
What does a bacteriolytic graph look like relating to the total cell count and viable cell count?
Directly proportional increase until introduction of agent.
Both lines decreases
What is a total cell count?
Cells of all both dead and alive
What is a viable cell count?
Cells of only living
What are the majority of antibiotics structures based on?
Against bacteria structure or cellular processes
Why is there a resistance to antibiotics?
Massive selective pressure from bacteria to evolve
What do quinolones target?
DNA gyrase
What is DNA gyrase?
Protein involved in unwinding DNA
What is the use of antibiotics having quinolones?
Protein will not be able to replicate, therefor cannot reproduce
What do you call an antibiotic if it cannot synthesis a new wall?
Bacteriolytic
What is another name for antibiotics?
Antimicrobials
Are all antibiotics synthesis in the lab?
No, they can be naturally occurring
What do you call a modification of natural antibiotics?
Semi-synthetic antibiotics
What do the brackets at the end of bacterial species represent?
Endospore forming bacteria
What does a bacterial species with a (A) at the end mean?
Actinomyces
What does a bacterial species with a (F) at the end mean?
Fungi
Give an example fo naturally occurring antibiotics?
Aminoglycosides
Macrolides
Tetracyclines
What are aminoglycosides?
Antibiotics that contain amino sugars bonded by glycosidic linkage
What are examples of aminoglycosides antibiotics?
Kanamycin
Neomycin
Amikacin
What do aminoglycosides inhibit?
Ribosome function
Are aminoglycosides commonly used?
No
What are aminoglycosides considered to be?
A reserve antibiotic fo when other antibiotics fail
What are macrolides?
Contains lactone rings bonded to sugars
What is does the macrolide target?
50s subunit of ribosome
What is an example of macrolide?
Erythromycin
What are tetracyclines?
Contains four rings
What is the use of tetracyclines?
- Widespread medical use in human/animals
- Inhibition of protein synthesis
- Inhibits function of 30S ribosomal subunits
What is the name for naturally occurring penicillin?
Benzylpenicillin
Is benzylpenicillin antibiotic against Gram-positive or Gram-negative bacteria?
Gram-poistive
How is natural penicillin modified?
By the R-group
What are the different semi-synthetic penicillin’s?
- Methicillin
- Oxacillin
- Ampicillin
What do quinolones bind to?
the A subunit of DNA gyrase (A2B2)
What does modification of naturally occurring bacterial allow?
Targeting of a range of bacteria
What is penicillin involved in targeting?
Peptidoglycan synthesis
What type of antibiotic agent is aminoglycosides?
Bacteriostatic
What type of antibiotic agent is Macrolides?
Bacteriostatic
What type of antibiotic agent is tetracyclines?
Bacteriostatic
Is antibiotics more used in human or agriculture?
Agriculture
What type of antibiotic is must frequently used?
Penicillin
What group of antibiotic is the most important?
Beta-Lactam antibiotics
What antibiotics does the group of Beta-Lactam antibodies include?
- Penicillins
- Cephalosporins
- Cephamycins
How discovered penicillin?
Alexander Fleming
What is penicillin primary effective against?
Gram-positive bacteria
What type of penicillin is effective against Gram-negative bacteria
Synthetic forms of Penicillins
What do pencilling target?
Cell wall synthesis
How many antibiotics discovered are clinically useful?
Less than 1%
What are three different types of inhibitions that antibiotics do again bacteria?
- Transcription inhibition
- Translation inhibition
- Cell wall biosynthesis inhibitors
Give examples of transcription inhibitors antibiotics:
- Actinomycin
- Rifampin
How do transcription inhibitors antibiotics work?
Interfere with gene expression
How does actinomycin work as a transcription inhibitor?
- Inhibits transcription
- Binding tightly to double stranded DNA at G-C base pairs
- Binding prevents DNA strand from unwinding
- Blocks RNA polymerase
Why does actinomycin have a limited application in medicine?
Lacks specificity and produces toxicity
How does rifampin work as a transcription inhibitor?
-Binds to RNA polymerase
How does bacteria become resistant to rifampin?
Mutation in gene for B subunit of RNA polymerase
What is rifampin effective against?
Mycobacteria and other Gram-positive bacteria
How do translation inhibitors antibiotics work?
Disrupting ribosome
What are examples of translation inhibitor antibiotics?
- Aminoglycoside streptomycin
- Tetracycline
- Chloramphenicol
- Puromycin
- Macrolide
How does amino glycoside streptomycin work as a translation inhibitor?
- Binds irreversibly to 30s ribosomal subunits
- Inhibits translation intiation
- Also misread information of mRNA
- Non functional protein
What are glycoside streptomycin effective against?
aerobic gram-negative rods and some Gram-positive organisms
How does amino tetracycline work as a translation inhibitor?
- Binds reversibly to 30S ribosomal subunit
- Prevents incoming aminoacyl-tRNAs from binding to A site of ribosome
What was the first broad-spectrum antibiotics?
Tetracycline
What does tetracycline inhibit?
Most Gram-negative and Gram-positive
What is the must important antibiotics in medicine?
Tetracycline
How does Chloramphenicol work as a translation inhibitor?
-Binds reversibly to 50S ribosome subunit and inhibit formation of peptide bonds between amino acids
What does Chloramphenicol work on?
Gram-negative/positive
What is a problem with Chloramphenicol?
Toxic - some patients taking antibiotics develop potential fatal conditions of aplastic anemia
How does puromycin work as a translation inhibitor?
- Binds to A site of 50S ribosomal subunit
- Mimics structure of aminoacyl-tRNA
- Forms peptide bond in P site
- Complex leaves ribosome prematurely terminating translation
Does puromycin inhibit protein synthesis in all organism?
Yes
How does macrolide work as a translation inhibitor?
- Binds to 50s ribosomal subunit and inhibits protein synthesis
- Occurs during transfer of peptidyl-tRNA from A site to P site
- Antibiotics blocks polypeptide transfer
- Halts translocation
When do you use macrolide?
When some is allergic to penicillin
What are antibiotic examples of cell wall biosynthesis inhibitors?
-B-lactam group
Is penicillin G in B-lactam group?
Yes
What structural components do B-lactam group have?
B lactam ring
Is penicillin G a natural or synthetic antibiotic?
Natural antibiotic
How do semi-synthetic penicillins differ?
N-acyl groups
How does penicillin G work?
- Disrupts formation of new cell wall during bacterial growth
- Prevents transpetidase enzyme from catalysing the glycol chains via binding to enzyme
- Glycan chain will lack cross link and be weak
- Cells lyse under extreme somatic pressure
What is a famous antibiotics?
Vancomycin
How does vancomycin work?
Inhibits cell wall biosynthesis
Does vancomycin have a poor or good bioavailability?
Poor bioavailability
What antibiotic do you use to treat C. difficile?
Vancomycin
What is the role of transpeptidase enzyme?
Catalyse a link between glycan chains
How do you measure antibacterial activity?
- Inoculate plate with a liquid culture of a test organism
- Discs containing antimicrobial agents are places on surface
- Incubate for 24-48 hours
- If organisms show susceptibility to some against = indicate inhibition of bacterial growth around discs (zone of inhibition)
What has almost all pathogenic microbes acquired resistance to?
Chemotherapeutic agents
How can resistance be minimised?
Using antibiotics correctly and only when needed
What are the 5 antibiotic resistance categories?
- Organisms lacks structure the antibiotics inhibits
- Organisms is impermeable to antibiotic
- Organisms can inactivate the antibiotic
- Organisms may modify the target of the antibiotic
- Organisms may be able to pump out the antibiotic
What do most drug-resistant bacteria isolate from patients contain?
Drug-resistance genes located on R plasmids
What selects for the spread of R plasmids?
Use of antibiotics in medicine, veterinary and agriculture
What do R plasmids contain?
- Resistance transfer facto - enables conjugation
- Genes conferring resistance
