1. Beta – Lactam Antibiotics
Prof. R. K. Dixit
Pharmacology and Therapeutics
K. G. M. U. Lucknow

2. Objectives
After completion of this lecture you will be able to understand
What are betalactam antimicrobials
Mechanism of action
Types of Penicillin, Uses, ADRs
Classification of Cephalosporin, Uses, ADRs
Members of Carbapenem and Monobactam, Uses, ADRs

3. Penicillins Cephalosporins Carbapenems Monobactams
Have Beta-lactam ring
Important groups are (PCcM) Paracetamol
Penicillins
Cephalosporins
Carbapenems
Monobactams

4. Raw material for other penicillin
Broken by Amidase enzyme
Active material
Raw material for other penicillin
Broken by Betalactamase enzyme
Inactive
Responsible for hypersensitivity

5. Active material
Raw material for other penicillin
Inactive (Major Determinant)
Responsible for hypersensitivity

6. Beta Lactamase inhibitor (Claulanic acid and Sulbactam)
Penicillin
Cephalosporins
Monobactam
Carbapenem
Beta Lactamase inhibitor (Claulanic acid and Sulbactam)
Suicide Inhibitors
Beta Lactamase

9. Penicillin First antibiotic to be used clinically in 1941
One of the least toxic antibiotic even today
Obtained from
Penicillium notatum (Early)
Penicillium chrysogenum (Now, Better Yield)
Scientists- Fleming – Chain – Florey
Original Penicillin –
Penicillin G, Benzyl Penicillin ( R is Benzyl (CH2C6H5) )

10. Chemistry Penicillin nucleus consists of Thiazolidine ring (Ring A)-
Sulphur containing with COOH (Carboxyl group),
Beta lactam ring (Ring B) – (Broken by Betalactamase)
Side chain is attached at position – 6- (NHCOR)
Side chains attached through amide linkage. (Broken by Amidase)

11. Beta Lactam ring is broken by –
Penicillinase (Beta Lactamase), and by gastric acid.
Resultant Product is Penicilloic acid with
No anti-bacterial activity but
Acts as antigenic determinant (Major determinant)
Penicillins are available as
Na+ or K+ salts .
Amine salts such as Procaine and Benzathine Penicillin.

12. Penicilloic acid is any of several acids which are obtained from the penicillins by the hydrolytic opening of the lactam ring (as by the action of a beta-lactamase). 
A thiazolidinedicarboxylic acid obtained via hydrolysis of the β-lactam ring of a penicillin
Hypersensitivity is the most important adverse effect of the penicillins.
The major antigenic determinant of penicillin hypersensitivity is its metabolite, penicilloic acid, which reacts with proteins and serves as a hapten to cause an immune reaction.

13. -Broken down by Amidase = (Removes Side Chain)
Natural Penicillin –
-Broken down by Amidase = (Removes Side Chain)
Penicillin – side chain =
6- Amino-Penicillanic acid (6-APA)
Active moiety
Has intact Betalactam ring (B)
With NH2 group at position 6 joined to thiazolidine ring.

14. 6-APA is basic raw material
Large amount of 6-APA are produced from culture of P. chrysogenum. (Fungal Amidase hydrolyze side chain at position-6.)
6-APA is basic raw material
Different types of penicillin are obtained by attaching different groups at position -6.
6-APA + other side chains =
Different types of semi synthetic Penicillins (Different Pk and Pd)

15. Sodium or Potassium salts
More stable (Stability decreases after making solution)
Natural Penicillin is
Benzyl penicillin or Penicillin G (PnG) and it is
Thermo and Acid labile

16. Penicillin Units One unit of Sodium Benzyl Penicillin = 0.6µg Or
One mega unit = 0.6 gram
One gram = 1.6 million units

18. MOA Bacteria are unique Don’t have osmotic regulating mechanism
Cell wall controls osmotic changes.
Cell wall is composed of
Peptidoglycans
Cross linked by peptide chains.
NAM – NAG ( N-acetyl muramic acid and N- acetyl glucosamine)
Cross linked by a Pentaglycine cross bridge
(Extending from the L-lysine residue of one peptide chain to the D-alanine residue of another peptide chain).

19. Cross bridging is transpeptidation reaction.
Transpeptidase and related proteins (Penicillin Binding Proteins) are used for making cross linkage.
Cross linking provides stability, strength.

20. β-Lactams inhibit Transpeptidase leading to Damage of cross linking
Weakening of cell wall
Swelling of cell due to Endosmosis
Bacterial membrane bursts
Bacterial lysis
Additional mechanism –
Activation of autolysing enzymes
(Murein Hydrolase and Autolysins)
More lethal during active multiplication

21. Betalactam Antibiotics

22. Penicillin Binding Proteins are of three types
PBP-1- involved in peptidoglycan synthesis during elongation
PBP-2- is carboxypeptidase. It hydrolyses the terminal D-ala residue present on the adjacent pentapeptide chain to promote further cross linking at that site. Its inhibition leads to spherical cells (Instead of rod shaped bacilli)
PBP-3 is endopeptidase. It splits cross linking involved in septum formation during cell division. (Inhibition leads to filamentation wherein cells cannot separate from one another during cell division.)

23. Bactericidal activity of penicillin is more against Gram positive
Bactericidal activity of penicillin is more against Gram positive. (Difference in organization of cell wall)
In gram positive
Thick layer of Peptidoglycans and teichoic acid (a polyol phosphate polymer) surrounds the membrane.
Peptidoglycans layer is easily accessible to Beta lactam antibiotics
In gram negative
Two membranes are present. (The cytoplasmic membrane and an outer membrane with thin layer of Peptidoglycans sandwiched between the two).
The outer membrane consists of lipopolysaccharides with narrow porin channels which function as a barrier to permeability of antibiotics

24. Aminoglycosides addition is synergistic
Penicillins which are hydrophilic in nature (Ampicillin and Amoxicillin) can diffuse through porin channels and show activity against negative.
Pseudomonas lacks porins due to which even Ampicillin and amoxicillin can’t act against them.
Aminoglycosides addition is synergistic

25. Why selective against bacteria ( and different types of bacteria)
Peptidoglycans cell wall is unique to bacteria.
In gram positive cell wall is entirely made by Peptidoglycans with extensive cross linking ( More effective in +ve)
In gram negative cell wall consists of lipoprotein and Peptidoglycans with less cross linking ( Less effective in –ve)
Penicillin binds with PBPs and every organism has different proteins with different affinity for penicillin.
Gram negative bacteria have porins of specific proteins located in outer membrane. Permeability of different beta-lactam antibiotics through these channels differs leading to variable action.

26. Resistance against Penicillin
Natural
Target enzymes and PBPs are deeply located (Lipoprotein barrier in –ve)
PBPs of organisms have low affinity for penicillin
Acquired
Production of Penicillinase (Beta-Lactamase) enzyme, (>300 subtypes). Common organisms producing Beta-Lactamase are
Staphylococcus
Bacillus subtilis
Gonococci
E. coli
Enterococci
Haemophilus influenza
Loss or alteration of Porin channels in gram negative
Modification of penicillin binding proteins (PBPs)- having low affinity .
Activation of antibiotic efflux mechanism- Some gram negative bacteria

27. Adverse effects General
Hypersensitivity reactions (including Anaphylaxis)
More with procaine penicillin,
Intradermal Skin sensitivity test
Major Determinant (Penicilloyl moiety in terms of amount) is responsible for hypersensitivity other than anaphylaxis
Minor determinants( Penicillamine and Penicillenate) are responsible for anaphylaxis.
The Penicilloyl moiety or major determinant results from reaction of beta-lactam ring with endogenous proteins. The Beta lactam ring spontaneously opens in the body forming a hapten-protein complex, the most abundant but not necessarily most immunogenic.

28. Hypersensitivity testing

29. Super infections (Ampicillin)
Nephrotoxicity (Methicillin causing interstitial nephritis)
Increase in Prothrombin time leading to bleeding
Jarisch -Herxheimer Reaction-
Common in secondary syphilis,
Release of Spirochetal lytic products (Heat stable proteins, endotoxins)
Characterized by fever, myalgia, exacerbation of lesions,
Usually occurs within 2 hours of first dose
Treatment- NSAIDs and Corticosteroids
Also in Borelliosis, Leptospirosis, and Brucelosis
Adolf Jarisch an Austrian and Karl Herxheimer a German dermatologist

30. Jarisch Herxheimer Reaction
Due to release of heat-stable proteins from spirochetes and the reaction.
Typically, the death of bacteria and the associated release of endotoxins or lipoproteins occurs faster than the body can remove the substances.
Usually manifests within two hours of the first dose and usually self limiting
Fever, chills, rigor, hypotension, tachycardia, hyperventilation, vasodilatation with flushing, myalgia 
Exacerbation of skin lesions.
Classically associated with penicillin treatment of syphilis.
Also in borreliosis (Lyme disease and tick-borne relapsing fever), leptospirosis, Q fever, bartonellosis (including cat scratch disease), brucellosis,
Increase in inflammatory cytokines during the period of exacerbation, including tumor necrosis factor alpha, interleukin-6 and 8
Prophylaxis and treatment with an anti-inflammatory agent and Corticosteroids
Jarisch and Herxheimer (Dermatologists) observed in syphilis treated with mercury.  
Observed in 50% of patients with primary and 90% of with secondary syphilis.
Both Adolf Jarisch an Austrian dermatologist, and Karl Herxheimer a German dermatologist, are credited with the discovery of the Jarisch–Herxheimer reaction. Both Jarisch and Herxheimer observed reactions in patients with syphilis treated with mercury.

31. Jarisch Herxheimer Reaction

32. Drug Interactions Penicillin with Aminoglycosides-
With Tetracyclines, Chloramphenicol, Erythromycin-
Antagonism
Penicillin with Aminoglycosides-
Synergism.
Penicillin and Aminoglycosides or Penicillin and hydrocortisone in same syringe –
Inactivate each other (Pharmaceutical)
Ampicillin with Allopurinol –
High incidence of non-urticarial maculopapular rashes
Penicillin with Probenecid
Prolongs action of penicillin by decreasing tubular secretion

33. Uses General , Plus Prophylaxis- Rheumatic fever
SABE (Streptococcal viridans)
Gonorrhea
Syphilis-
1.2 MU of Procaine penicillin for 12 days or
2.4 MU of Benzathine Penicillin
Leptospirosis (Weil’s Disease)
Actinomycosis, Listriosis, Lyme Disease, Anthrax, Rat bite fever, Erysipeloid, Gingivostomatitis
Diphtheria
Tetanus
Gas gangrene (Clostridium pefringens (welchii)
Prophylaxis-
Rheumatic fever, SABE,
Agranulocytosis

34. Thanks