Classes of antibiotics
β-Lactams
- Include penicillin, the first antibiotic discovered, by Alexander Fleming in 1928
- All β-lactams contain a lactam ring, and include pencillins such as amoxicillin and
cephalosporins
- These antibiotics work by interfering with the synthesis of peptidoglycan, an important
component of bacterial cell walls, and because of this are mainly effective against gram-
negative bacteria
- Bacteria can develop resistance to β-lactams through a variety of routes, including the
production of enzymes which break down the lactam ring (β-lactamases)
- In the NHS, pencillins are the most heavily prescribed antibiotics, with amoxicillin being the
most common
- Examples: Pencillins such as Amoxicillin and Flucloxacillin, Cephalosporins such as
Cefalexin
Sulfonamides
- The sulfonamide Prontosil was the first commercially available antibiotic, developed in
1932
- Sulfonamides are able to act on both gram-negative and gram-positive bacteria as they do
not kill bacteria directly, but inhibit bacterial synthesis of the B vitamin folate, thus
preventing growth and reproduction
- Presently, sulfonamides are rarely used, due to bacterial resistance and also the concern of
unwanted side effects including hepatotoxicity
- Examples: Prontosil, Sulfanilamide, Sulfadiazine and Sulfisoxazole
Aminoglycosides
- Aminoglycosides inhibit the synthesis of proteins in bacteria, eventually leading to cell
death
- These are only effective against certain types of gram-negative bacteria, and some gram
positive bacteria
- This class of antibiotics is not absorbed during direction, so must be injected
- In the treatment of tuberculosis, Streptomycin was the first found to be effective, however
due to toxicity issues, aminoglycosides are rarely used at present
- Examples: Streptomycin, Neomycin, Kanamycin and Paromomycin
β-Lactams
- Include penicillin, the first antibiotic discovered, by Alexander Fleming in 1928
- All β-lactams contain a lactam ring, and include pencillins such as amoxicillin and
cephalosporins
- These antibiotics work by interfering with the synthesis of peptidoglycan, an important
component of bacterial cell walls, and because of this are mainly effective against gram-
negative bacteria
- Bacteria can develop resistance to β-lactams through a variety of routes, including the
production of enzymes which break down the lactam ring (β-lactamases)
- In the NHS, pencillins are the most heavily prescribed antibiotics, with amoxicillin being the
most common
- Examples: Pencillins such as Amoxicillin and Flucloxacillin, Cephalosporins such as
Cefalexin
Sulfonamides
- The sulfonamide Prontosil was the first commercially available antibiotic, developed in
1932
- Sulfonamides are able to act on both gram-negative and gram-positive bacteria as they do
not kill bacteria directly, but inhibit bacterial synthesis of the B vitamin folate, thus
preventing growth and reproduction
- Presently, sulfonamides are rarely used, due to bacterial resistance and also the concern of
unwanted side effects including hepatotoxicity
- Examples: Prontosil, Sulfanilamide, Sulfadiazine and Sulfisoxazole
Aminoglycosides
- Aminoglycosides inhibit the synthesis of proteins in bacteria, eventually leading to cell
death
- These are only effective against certain types of gram-negative bacteria, and some gram
positive bacteria
- This class of antibiotics is not absorbed during direction, so must be injected
- In the treatment of tuberculosis, Streptomycin was the first found to be effective, however
due to toxicity issues, aminoglycosides are rarely used at present
- Examples: Streptomycin, Neomycin, Kanamycin and Paromomycin
