Antimicrobial Drugs Flashcards
Antibiotic
A product produced by a microorganism which in low concentrations inhibits the growth of other microorganisms
Types of Antibiotics
1- Natural
2-Synthetic
3-Semisynthetic
Importance of Antibiotics
Easily treats illnesses
The ideal Drug
1- Inexpensive
2- Selective toxicity
3- Favourable pharmacokinetics
4- Readily Available
5- Nontoxic
6- Little ressistant
Sources of antimicrobial Agents
1- Chemically synthesised
2-Soil
3- Water
4-molecular manipulation
Bacteriostatic
Inhibits the growth of organisms
Bactericidal
Kills organisms
MIC stands for
minimum Inhibitory concentration
MBC stands for
Minimum Bactericidal Concentration
Minimum Inhibitory Concentration
The lowest concentration that` inhibits the growth of organisms
Minimum Bactericidal Concentration
The lowest concentration that kills 99.9% of the population
The decision to use a bactericidal or a bacteriostatic drug depends on:
the type of infection
Ultimate elimination of the organisms depends on:
- specific antibodies
2.host phagocytic activity
Antimicrobial Spectrum
Range of activity on antimicrobial against bacteria
Broad spectrum antimicrobial drug
inhibits a wide variety of gram +ve and gram -ve bacteria
Narrow spectrum antimicrobial drugs
inhibits a limited variety of bacteris
Types of combining drugs
1 Synergistic
2.Antagonistic
Synergistic
action of one drug enhances the activity of another
Antagonistic
Action of one drug interferes with action of another
Adverse effects
- Toxic Effects
- Suppression of normal flora
- Allergic reactions
Mechanisms of action of antibacterial drugs
- Inhibit cell wall synthesis
- Inhibit protein synthesis
- Inhibit nucleic acid synthesis
- Injury to plasma membrane
- Inhibits synthesis of essential metabolites
inhibition of cell wall synthesis include
β-lactam drugs
β-lactam drugs
- irreversibly inhibit enzymes involved in the final steps of cell wall synthesis
- these enzymes mediate the formation of peptide bridges between adjacent stands of peptidoglycan
- Drug binds to enzymes inhibiting enzymatic activity
- Some bacteria produces β-lactamase enzyme which breaks critical β-lactam
ring
β-lactam drugs include
- Cephalosporins
- Penicillins
- Carbapenems
4.monobactams
Cephalosporins
β-lactam antibiotic derived from the fungus acremonium
Given oral, IV,IM
1960
1st Generation Cephalosporins
Cefalexin
Cefazolin
Cefradnie
1970
2nd Generation cephaolosporins
Cefaclor
Cefuroxime
cefoxtin
1980
3rd Generation cephalosporins
ceftazidime
ceftitriaxone
cefditoren
cefdinir
1990
4th Generation Cephalosporins
Cefeprime
Cefepirome
5th Generation Cephalosporin
Ceftaroline
ceftobiprole
fosamil
Penicillinase resistant drugs
1.Oxcacillin
2.Cloxacillin
3.Amoxcacillin
4.Carbencillin
5.Piperacillin
6.Ticercillin
7.Monobactam
Oxacillin , Cloxacillin are used against
gram+ve bacteria
Amoxcacillin is
broad spectrum
Carbenicillin ,ticarcillin ,pipercillin
gra -ve bacteria
monobactam
gram-ve bacteria
Non β-lactam drugs that inhibit cell wall synthesis
1.polypeptides
*bacteriacin
2. glycopeptides
*vancomycin
Inhibition of protein synthesis
- Targets the ribososmes of bacteria
Three types of protein synthesis drugs
1.tertacyclines
2.aminoglycosides
3.macrolides
tetracyclines
binds to 30S
blocking attachment of tRNA
Aminoglycosides
Binds to 30S
causes it to distrot and malfunction
Macrolides
binds to 50S
prevents contiuation of protein synthesis
Inhibition of nucleic acid synthesis
Quinolones
floroquinolones
*Norfloxacin
*ciprofloxin
*levofolaxin
Injury to plasma membrane
leads to leakage of cellualr content
includes :
colistin
Inhibits synthesis of essential metabolites
Sulfonamide drugs
useful against UTIs
How do bacteria become resistant
- Genetic :
Spontaneous mutation
Gene transfer - Non Genetic :
Intrinsic resistance`
Mechanisms of resistance
1.Production of enzmye that destroys the drug
2.slow or prevent drug from entering the cell
3.alter target of the drug
4.alter their metabolic activity
5.pump antimicrobial drug out of the cell before it can act.
Determination of drug determination
clinical parameters
laboratories parameters
Drug efficiency can be measured by tests:
1.Kirby Bauer method
2.Broth dilution test
3. E test
