Dr Osama Ma3rof Antibiotics Mob-WhatsApp: 01010343061
Antibiotics simplified
Dr.Osama Ma3rof
Microbiology T.A
Faculty of pharmacy
Mob: 01010343061
https://www.facebook.com/Dr.Osama.Mar3of
أسالكم الدعاء لي و لوالدأي
1
,Dr Osama Ma3rof Antibiotics Mob-WhatsApp: 01010343061
Old definition naturally occurring microbial products which can inhibit or kill
Microorganisms at a very low concentration.
Chemotherapeutic agents: chemical compounds that can inhibit or kill the M.O
Ex. Sulphonamides, Quinolones and Nitofurans
New definition: any agent which can be used to treat systemic infection.
- This agent may be natural, synthetic or semi-synthetic.
General requirements for an antibiotic :
1- It should be able to act on different species of pathogens.
2- It should not have undesirable side effects to the host.
3- Non-toxic.
4- selective to the pathogenic bacteria compared to the host.
N.B → disinfectants have no selectivity
5- Should have high therapeutic index.
6- Easy to use.
7- Inexpensive and easy to be produced.
8- Resistance to it must remain uncommon.
المضادات الحيوية و نزالت البرد
N.B
→ the use of antibiotics against a virus such as flu or the common cold will not treat the condition.
However, there are doctors prescribing antibiotics for people with cold or flu
And this for bacterial secondary infection.
2
,Dr Osama Ma3rof Antibiotics Mob-WhatsApp: 01010343061
Antibiotic classification
The antibiotics can be classified according to :
1- Their mechanism of action e.g. cell wall synthesis inhibitors
2- Their chemical structure e.g. β-lactams, aminoglycosides... etc.
3- Their Effect on microbes cidal or statics.
4- Effect on specific type microbes antibacterial, antifungal, antiviral
Definitions
➢MIC Lowest concentration of antibiotic which .inhibits the growth.
➢MBC Least concentration of antibiotic which kills bacteria.
➢Broad spectrum antibiotic acts on large numbers of G +ve and G –ve bacteria
E.g. Chloramphenicol.
➢Narrow spectrum: antibiotic acts against Gram positive only e.g. Penicillin G
OR Gram negative only e.g. Polymyxin
Some medically important micro organisms
1- S.aureus → the most frequent pathogen of G+ve
Many strains are resistant to antibiotics
Cause → wound infection – pneumonia – food poisoning – urinary tract infection .
2- Pseudomonas aeruginosa → G-ve bacteria
Highly resistant to antibiotics due to their outer membranes
Cause → skin infection – Respiratory tract infection - urinary tract infection
3
, Dr Osama Ma3rof Antibiotics Mob-WhatsApp: 01010343061
Mechanism of action of Antibiotics
Classification of Antibiotics Based on Mechanisms of Action:
Antibiotics which interfere with the cell wall synthesis
►Drugs that inhibit biosynthetic enzymes: → Fosfomycin , Cycloserine
►Drugs that combine with carrier molecules: → Bacitracin.
►Drugs that combine with cell wall substrates: → Vancomycin.
►Drugs that inhibit polymerization and attachment of new peptidoglycan to cell wall:
Penicillins, Cephalosporins, Carbapenems, Monobactams.
Antibiotics which interfere with the cell membrane
►Drugs that disorganize the cytoplasmic membrane: → Polymyxins.
►Drugs that produce pores in membranes: → Gramicidin
Antibiotics which interfere with protein synthesis
►Inhibitors of 30s sub units: Aminoglycosides, Tetracyclines.
►Inhibitors of 50s subunits: Chloramphenicol, Macrolides, and Lincosamides.
Antibiotics that Inhibit Nucleic Acid Synthesis
►Inhibitors of DNA replication: →Quinolones.
►Inhibitors of RNA polymerase: →Rifampicin.
Inhibitors of Folate metabolism
►Inhibitor of pteroic acid synthetase: →Sulfonamides.
►Inhibitor of dihydrofolate reductase: →Trimethoprim.
4
Antibiotics simplified
Dr.Osama Ma3rof
Microbiology T.A
Faculty of pharmacy
Mob: 01010343061
https://www.facebook.com/Dr.Osama.Mar3of
أسالكم الدعاء لي و لوالدأي
1
,Dr Osama Ma3rof Antibiotics Mob-WhatsApp: 01010343061
Old definition naturally occurring microbial products which can inhibit or kill
Microorganisms at a very low concentration.
Chemotherapeutic agents: chemical compounds that can inhibit or kill the M.O
Ex. Sulphonamides, Quinolones and Nitofurans
New definition: any agent which can be used to treat systemic infection.
- This agent may be natural, synthetic or semi-synthetic.
General requirements for an antibiotic :
1- It should be able to act on different species of pathogens.
2- It should not have undesirable side effects to the host.
3- Non-toxic.
4- selective to the pathogenic bacteria compared to the host.
N.B → disinfectants have no selectivity
5- Should have high therapeutic index.
6- Easy to use.
7- Inexpensive and easy to be produced.
8- Resistance to it must remain uncommon.
المضادات الحيوية و نزالت البرد
N.B
→ the use of antibiotics against a virus such as flu or the common cold will not treat the condition.
However, there are doctors prescribing antibiotics for people with cold or flu
And this for bacterial secondary infection.
2
,Dr Osama Ma3rof Antibiotics Mob-WhatsApp: 01010343061
Antibiotic classification
The antibiotics can be classified according to :
1- Their mechanism of action e.g. cell wall synthesis inhibitors
2- Their chemical structure e.g. β-lactams, aminoglycosides... etc.
3- Their Effect on microbes cidal or statics.
4- Effect on specific type microbes antibacterial, antifungal, antiviral
Definitions
➢MIC Lowest concentration of antibiotic which .inhibits the growth.
➢MBC Least concentration of antibiotic which kills bacteria.
➢Broad spectrum antibiotic acts on large numbers of G +ve and G –ve bacteria
E.g. Chloramphenicol.
➢Narrow spectrum: antibiotic acts against Gram positive only e.g. Penicillin G
OR Gram negative only e.g. Polymyxin
Some medically important micro organisms
1- S.aureus → the most frequent pathogen of G+ve
Many strains are resistant to antibiotics
Cause → wound infection – pneumonia – food poisoning – urinary tract infection .
2- Pseudomonas aeruginosa → G-ve bacteria
Highly resistant to antibiotics due to their outer membranes
Cause → skin infection – Respiratory tract infection - urinary tract infection
3
, Dr Osama Ma3rof Antibiotics Mob-WhatsApp: 01010343061
Mechanism of action of Antibiotics
Classification of Antibiotics Based on Mechanisms of Action:
Antibiotics which interfere with the cell wall synthesis
►Drugs that inhibit biosynthetic enzymes: → Fosfomycin , Cycloserine
►Drugs that combine with carrier molecules: → Bacitracin.
►Drugs that combine with cell wall substrates: → Vancomycin.
►Drugs that inhibit polymerization and attachment of new peptidoglycan to cell wall:
Penicillins, Cephalosporins, Carbapenems, Monobactams.
Antibiotics which interfere with the cell membrane
►Drugs that disorganize the cytoplasmic membrane: → Polymyxins.
►Drugs that produce pores in membranes: → Gramicidin
Antibiotics which interfere with protein synthesis
►Inhibitors of 30s sub units: Aminoglycosides, Tetracyclines.
►Inhibitors of 50s subunits: Chloramphenicol, Macrolides, and Lincosamides.
Antibiotics that Inhibit Nucleic Acid Synthesis
►Inhibitors of DNA replication: →Quinolones.
►Inhibitors of RNA polymerase: →Rifampicin.
Inhibitors of Folate metabolism
►Inhibitor of pteroic acid synthetase: →Sulfonamides.
►Inhibitor of dihydrofolate reductase: →Trimethoprim.
4
