Beta-lactam antibiotics include penicillins, cephalosporins, carbapenems, and monobactams. They work by inhibiting bacterial cell wall synthesis through binding to penicillin-binding proteins. Penicillins are further classified into natural, semisynthetic, and extended spectrum categories. Semisynthetic penicillins like amoxicillin have better oral absorption. Beta-lactamase inhibitors are often combined with antibiotics to prevent bacterial inactivation of the drug. Cephalosporins have a wider spectrum than penicillins and are classified in generations based on their antimicrobial activity. Carbapenems and monobactams also inhibit cell wall synthesis but have even broader

1. BETA
LACTAM
ANTIBIOTICS

2. Antibiotic
An antibiotic is an agent that either kills or
inhibits the growth of a micro organism.

3. Tetracyclines
Spectinomycins
Sulphonamides
Macrolides
Chloramphenicol
Trimethoprim
Penicillins
Cephalosporins
Monobactams
Carbapenems
Fluoroquinolones
Glycopeptides
CLASSIFICATION OF
ANTIBIOTICS
(Based on mode of action)
BACTERIOSTATIC
ANTIBIOTICS
BACTERICIDAL
ANTIBIOTICS

4. CLASSIFICATION OF
ANTIBIOTICS
(Based on structural similarities)
Beta Lactams
Penicillins
Cephalosporins
Monobactams
Carbapenems
Fluoroquinolones
Macrolides
Tetracyclines
Aminoglycosides

5. Antibiotics: Mode of action
Inhibitors of DNA synthesis
Inhibitors of bacterial protein synthesis
Inhibitors of bacterial cell wall synthesis
Interference with metabolism
Impairment of nucleic acids

6. Bacterial cell structure
Gram positive more susceptible than gram negative

7.  Peptidoglycan layer is composed of alternating units of N-acetyl
glucosamine(NAGA) and N-acetyl muramic acid(NAMA)
 NAGA and NAMA are crosslinked by a class of transpeptidases
known as penicillin binding proteins (PBPs)
 Interfering with this cross linking disrupts the cell wall synthesis.
 POINT TO REMEMBER :

8. Beta Lactam antibiotics
• Contains a beta lactam ring in their molecular structure.
• Nitrogen is attached to the beta carbon relative to the carbonyl ring and
hence the name.

9. Classification of beta lactam antibiotics
 Penicillins
 Cephalosporins
 Carbapenems
 Monobactams
 B lactamase inhibitors

10. Mechanism of action
 The beta lactam antibiotics bind to Penicillin Binding
proteins(PBPs). ( transpeptidase , other enzymes and related
proteins )
 PBPs are unable to crosslink peptidoglycan chains.
 Bacteria is unable to synthesize a stable cell wall.
 Hence, the bacteria is lysed.

11. Penicillins
 Sir Alexander Fleming discovered penicillin from penicillium
notatum
 Now obtained from Penicillium chrysogenum for therapeutic
use

12. Classification of penicillins
A)NATURAL
1. Regular - Penicillin G (Benzyl penicillin)
2. Repository – Procaine penicillin
Benzathine penicillin
B) SEMISYNTHETIC
1. Acid resistant – Penicillin V
2. Penicillinase resistant – cloxacillin, methicillin, dicloxacillin, nafcillin
3. Aminopenicillins – ampicillin, bacampicillin, amoxicillin
4. Antipseudomonal –
i) Carboxypenicillins – carbenicillin, ticarcillin
ii) Ureidopenicillins – mezlocillin, piperacillin
3 & 4 are EXTENDED SPECTRUM PENICILLINS

13. Natural penicillins
 Penicillin G (Benzyl penicillin), Procaine penicillin, Benzathine penicillin
 Acid labile – given parenterally (IM/IV)

14. Uses
 Pneumococcal infections
 Streptococcal infections
 Meningococcal infections
 Staphylococcal infections
 Syphilis
 Diphtheria
 Actinomycosis
 Tetanus & gas gangrene
 Prophylaxis uses : Rheumatic fever, Gonorrhoea, Syphilis

15. Adverse effects
 Hypersensitivity – skin rash, urticaria, pruritus, bronchospasm, fever,
anaphylaxis
 hence intradermal skin injection test dose is a must before administration.
 Other than the rare event of anaphylaxis penicillins are one of the safest
antibiotics
 Local pain at injection site
 CNS : confusion,convulsions,coma
 Suprainfections

16. ANAPHYLATIC SHOCK TREATMENT
 DRUG OF CHOICE : )
 dose : 0.2 - 0.5 ml of 1: 1000 solution S.C ( if mild )
 50 - 100 ug of 1: 10,000 solution I.V ( if severe )
 corticosteroid : hydrocortisone
 others : antihistaminic , iv fluids , oxygen therapy , dopamine.

17. Semisynthetic penicillins
1.Acid resistant – Penicillin V
Use : Streptococcal pharyngitis, sinusitis and trench mouth.
2.Penicillinase resistant – cloxacillin, methicillin, oxacillin, nafcillin
Use : Staphylococcal infections ,treatment of human bites .

18. Aminopenicillins – ampicillin, bacampicillin, amoxicillin
Use :
1. Respiratory tract infections- bronchitis, sinusitis, otitis media
2. Urinary tract infections
3. Meningitis
4. Typhoid
5. Septicaemia
6. Bacillary dysentery
7. Bacillary endocarditis

19. Amoxicillin vs Ampicillin
 Amoxicillin is better absorbed orally
 Food does not interfere with its absorption
 Attains high blood levels after oral administration
 Diarrhoea is rare
 Longer acting than ampicillin (given thrice daily)
 Does not reduce the effectiveness of oral contraceptives.

20. Antipseudomonal penicillins
i) Carboxypenicillins – carbenicillin, ticarcillin
ii) Ureidopenicillins – azlocillin, mezlocillin, piperacillin
Use:
Pseudomonas, Klebsiella, Proteus infections
Adverse effects: Carbenicillin causes edema and CCF, bleeding

21. Beta lactamase inhibitors
 Beta lactamases are enzymes produced by bacteria which open up
the beta lactam ring and inactivates the beta lactam antibiotics.
 Beta lactamase inhibitors bind to and inactivates beta lactamases
thereby preventing destruction of beta lactam antibiotics.
 Clavulanic acid
 Sulbactam
 Tazobactam

22. Combinations
 Clavulanic acid + amoxicillin – oral/IV
 Clavulanic acid + ticarcillin – IV
 Sulbactam + ampicillin – IV
 Tazobactam + piperacillin – IV
Use:
Cellulitis, diabetic foot, skin & soft tissue infections, respiratory &
genitourinary infections, mixed aerobic-anaerobic & nosocomial
infections

23. Cephalosporins
 Semisynthetic antibiotics
 Wider spectrum of activity
 Mechanism of action similar to penicillins i.e. inhibits bacterial
cell wall synthesis
 Bactericidal

24. Classification
 First generation - effective against gram positive organisms
 Second generation - more active against gram negative
organisms
 Third generation - effective against gram negative organisms
and anaerobes
 Fourth generation - gram positive and gram negative
organisms
 Fifth generation – MRSA and gram negative organisms

27.  first and second generation cephalosporins are used as
substitutes to penicillins in those who have mild allergic reaction to
penicillin
 NOT IN THOSE WITH SEVERE REACTIONS LIKE
ANAPHYLAXIS/ ANGIOEDEMA .
 Used as a first line empirical therapy along with aminoglycosides
in treatment of bacteremia / septicemia.
 Cefoxitin , cefotetan ( both 2 nd generation )are used in anaerobic
infections.

28. CEFTRIAXONE : THIRD GENERATION
 ITS a third generation cephalosporin
 highly resistant to beta lactamases.
 good activity against gram positive and negative organisms,
moderate against psuedomonas .
 has the longest half life amongst beta lactam antibioitics ( 8 hrs )
 enters csf when meninges are inflammed , hence used in treatment
of meningitis .
 other uses : complicated UTI ,abdominal sepsis, chancroid

29. FOURTH GENERATION
 Similar to third generation but more resistant to beta
lactamases .
 active against enterobacteriacea ( gram negative ) and
psuedomonas resistant to group 3
 examples cefepime , cefpirome
 given parenterally .

30. Uses
 Gram negative infections- urinary, respiratory and soft tissue
infections
 Surgical prophylaxis
 Gonorrhoea
 Meningitis
 Mixed aerobic-anaerobic infections
 Typhoid
 Nosocomial infections

31. Adverse effects
 Hypersensitivity reactions-skin rash, fever, serum sickness,
anaphylaxis
 Nephrotoxicity
 Diarrhoea
 Bleeding
 Low WBC count
 Pain at injection site

32. Carbapenems :
imipenem, meropenem, ertapenem, doripenem, faropenem
 Spectrum : gram positive, gram negative and anaerobic
organisms.
 Mechanism of action: inhibits bacterial cell wall synthesis
 Uses : UTI, respiratory, skin, bone, soft tissue, intra abdominal
and gynecological infections
 only FAROPENEM IS ORALLY ACTIVE , hence can be given
orally . rest are given IV parenterally.

33. IMIPENEM
 BACTERICIDAL
 broad spectrum beta lactam antibiotic
 effective against gram positive , enterobacteriacea , psuedomonas
, anaerobes ( like clostridia difficile).
 rapidly hydrolysed by enzyme dehydropeptidase in renal tubules.
 hence combined with cilastin that reversibly blocks this enzyme
and protects imipenem .
 not absorbed from GIT , given parenterally .

34. Monobactam:
aztreonam
 Single beta lactam ring
 Effective against gram negative organisms but not against gram
positive and anaerobes.
 spectrum similar to aminoglycosides,hence used as a reserve drug in
treating gram -ve infections in those whom aminoglycosides are
contraindicated .
 MoA : inhibits bacterial cell wall synthesis ( bactericidal )
 Given parenterally
 Uses : nosocomial pseudomonas infections and other gram negative
infections

35. ANTIPSEUDOMONAL ANTIBIOTICS
Pneumonic : BLAQ Pseudomonas
 Beta Lactam antibiotics :
 Penicillins : i) Carboxypenicillins – carbenicillin, ticarcillin
ii) Ureidopenicillins – azlocillin, mezlocillin, piperacillin
 Cephalosporins : Ceftazidime, cefoperazone, cefepime, cefpirome
 Carbapenem : imipenem, meropenem, doripenem
 Monobactam : aztreonam
 Aminoglycosides
 Quinolones
 Polypeptides

36. THANK YOU