Lecture 14 Flashcards
What is the traditional definition of an antibiotic and why is this flawed?
The traditional definition of an antibiotic is a substance produced by a microorganism which is effective in killing or inhibiting other microorganisms
This definition is flawed as many modern day antibiotics are either modified in the lab or completely made in the lab
What are the three classes of antibiotics with regards to their production?
Synthetic, Semisynthetic, organic
What tends to be the term utilized for these modern day antibiotics that are entirely synthesized?
Antimicrobial agent, anti-fungal agent etc.
What modern, entirely synthesized agents are never called antibiotics?
Antiviral agents
What are the desirable qualities in an antibiotic?
Kill or inhibit bacterial growth
No damage caused to host or allergic reaction created
Stable storage
Remains specific tissue long enough to help host
Quickly kills pathogens to reduce changes of antibiotic resistance developing
What is the antibacterial spectrum?
The range of activity against bacteria
Give an example of a narrow spectrum antibiotic
Vancomycin which only effects gram positive bacteria
Give an example of a broad spectrum antibiotic
Ampicillin or tetracycline which is effective against both gram positive and gram negative bacteria
What is bacteriostatic activity?
The level of antimicrobial acitvity that inhibits pathogen growth allowing the immune system to overcome the infection
What is bactericidal activity?
The level of antimicrobial technology that kills the pathogen
What is an antibiotic combination and what is its purpose?
Broaden the antibiotic spectrum and to allow for the ability to kill any of the microbes that have mutated quickly resulting in the ability to kill an resistant organisms that emerge, can also be used to treat polymicrobial infections
What is antibiotic synergism?
When two antibiotics combine to enhance antimicrobial activity
What is antibiotic antagonism?
When two antibiotics interfere with each other resulting in less antimicrobial activity than that of the most active drug
What is the minimum inhibitory concentration?
The minimum concentration of the antibiotic required to inhibit growth of the pathogen
What is the minimum bactericidal concentration?
The minimum concentration required to kill the pathogen
What are the two ways of calculating the minimum inhibitory concentration?
- Lawn agar plate with antibiotic discs, the concentration can be calculated from the diameter
- Use of a dilution series
What is a dilution series?
A series of broth cultures with the same concentration of bacteria, treated with different antibiotic concentrations, the results of the broth culture growth can be then be used to determine the minimum inhibitory concentration and the minimum anti bactericidal concentration
What is an antibacteriogram?
A lawn agar with antibiotic discs
What are the 5 main targets of anti biotics?
Cell wall Synthesis, DNA replication, RNA synthesis, Antimetabolites, Protein Synthesis
What are the two different types of antibiotics that target cell wall synthesis?
Beta Lactam antibiotics and glycopeptides
What are beta lactam antibiotics?
Bacteriacidal antibiotics which inhibit peptidyl transferase such as penecillin, amoxycillin and ampicillin
How are gram negative bacteria made susceptible to beta lactam anti biotics?
Penecillins are altered in the lab to produce compounds such as amoxycillin which can pass through membrane pores on the bacterial outermembrane
What are Glycopeptides?
Bactericidal compounds such as vancomycin which binds to the monomers of peptidoglycan preventing their polymerisation
What are antibiotics that target RNA transcription?
Rifamycins which bind to bacterial RNA polymerase causing a change in the conformation of the active site preventing RNA transcription
Bactericidal compounds used against mycobacteria
What are the antiobiotics that target DNA replication?
Quinones and fluoroquinones which bind to topoisomerases preventing DNA replication as they prevent supercoiling, acting as bactericidal agents
What is the difference between fluoroquinones and quinones?
Fluorquniones are more active and are typically used due to antibiotic reistances
What are the antibiotics that target antimetabolites?
Sulfonamides are bacteriostatic compounds which prevents parabenzoic acid from being converted to tetrahydrofolic acid which prevents the formation of nucleic acids as this is a required co-factor
What are the antibiotics that target protein synthesis?
Antibiotics that target the large ans small (50S and 30s) components of the bacterial ribosome
What antibiotics target the 30S ribosome unit?
Aminoglycosides and tetracyclines
How to aminogylcosides target protein synthesis?
Freeze the 30S complex resulting in the misreading of mRNA causing nonsense proteins, is a bacteriocidal compound affective agains gram negative bacteria, synergistic with penecillins
How do tetracyclines inhibit protein synthesis?
Inhibits the binding of amino acyl-tRNA to accceptor site, broad spectrum, bacteriostatic compounds which are typically not used for children
What antibiotics bind to the 50S subunit?
Macrolides, Lincosamides and Chloramphenicol
How do Macrolides work?
inhibit translocation of tRNA from A to P site, bacteriostatic and act against gram positives
How do Lincosamides work?
inhibit peptidyl transferase activity, bacteriostatic broad spectrum compounds
How do Chloramphenicols work?
Broad spectrum, bacteiostatic which is rarely used due to strong side effects
What are the 4 antibiotic resistant mechanisms?
Exclusion of antibiotic from site of action,
New or modified antibiotic insensitive target,
Efflux pump for the removal of antibiotics,
Enzymatic modification or degradation of the antibiotic
What are the two major forms of resistance?
Non-genetic and genetic
How does an organism gain genetic antibiotic resistance?
Transformation, transduction or conjugation
