Beta lactam antibiotics like penicillins, cephalosporins, carbapenems, and monobactams contain a beta-lactam ring. They are bactericidal and work by inhibiting bacterial cell wall synthesis. Penicillins are further divided into narrow and extended spectrum types. Common side effects include hypersensitivity reactions and diarrhea. Beta lactamase inhibitors are often combined with antibiotics to overcome resistance from beta lactamase producing bacteria. Each class of beta lactam antibiotic has varying spectra of activity and therapeutic uses depending on whether they are effective against gram-positive, gram-negative, anaerobic, and multidrug resistant bacteria.

1. Beta lactam antibiotics

2. β LACTAM ANTIBIOTICS
Have a β-lactam ring in their structure
•Penicillins
•Cephalosporins
•Carbapenems
•Monobactams
all are bactericidal

3. PENICILLINS
Mechanism of Action
• Bind to penicillin binding proteins on the cytoplasmic
membrane and Inhibit the enzyme transpeptidase that is
essential for the bacterial cell wall rigidity.
• This results in the formation of bacteria with weak cell wall
& undergo lysis.
Mechanism of Resistance:
• Beta lactamase (penicillinase) enzyme produced by the
bacteria inactivate penicillins (most common cause)

4. PENICILLINS
A. Narrow Spectrum Penicillins
Penicillinase sensitive (Natural Penicillins)
• Benzyl penicillin (Penicillin-G )
• Benzathine penicillin
• Penicillin V (oral)
Penicillinase Resistant (Antistaphylococcal penicillins)
• Methicillin
• Nafcillin
• Cloxacillin
B. Extended Spectrum Penicillins
Penicillinase sensitive
 Aminopenicillins
• Ampicillin,
• Amoxycillin,
 Antipseudomonial penicillins
• Ticarcillin
• Pipercillin

5. ANTIMICROBIAL SPECTRUM & USES
BENZYLPENICLLIN (Penicillin G):
• Infections caused by Streptococcus pyogenes
(pharyngitis, otitis media, oral infections) Streptococcus
pneumoniae (pneumonia)
• Enterococcus ( bacterial endocarditis) –synergistic when
combined with gentamicin
• Actinomycetes israelii ( Actinomycosis) Bacillus anthracis
(Anthrax)
• Clostridium tetani, (tetanus) Cl. Perfringes ( Gas
gangrene), Bacteroides oropharyngeal strains, Treponema
pallidum (syphillis)

6. BENZATHINE PENICILLIN
• Prophylaxis against reinfection with β haemolytic
streptococcal pharyngitis (Rheumatic fever)
PENICILLIN V
• Used in Oropharyngeal infections
CLOXACILLIN, NAFCILLIN (Antistaphylococcal )
• Used in Staphylococcal infections like
osteomyelitis, septicaemia, endocarditis
• Dental uses : Endodontic
infections, Periodontitis, Gingivitis, Odontogenic
infections, Periodontal abscess, Acute necrotizing ulcerative
gingivitis.

7. EXTENDED SPECTRUM PENICILLINS
AMOXYCILLIN & AMPICILLIN
• Amoxycillin is better absorbed orally and food does not interfere
with its absorption.
• Diarrhea & rash is more common with ampicillin and rare with
amoxycillin
• Ampicillin ( four times daily) Amoxicillin ( thrice daily)
• Their antibacterial activity is enhanced if used in combination with
beta lactamase inhibitors
USES
• H influenzae (pneumonia, otitis media, sinusitis)
• E. coli (UTI)
• Enterococcal infections
• Oropharyngeal infections
• Helicobacter pyroli eradication in peptic ulcer.

8. Antipseudomonal penicillins
• TICARCILLIN & PIPERACILLIN
• Pseudomonal infections it is combined with Clavulanic acid
Adverse effects of Penicillins
Hypersensitivity reaction
• Mild urticarial skin rash to a serious anaphylactic shock (
severe hypotension, bronchospasm & laryngeal edema)
Maculopapular rash - Ampicillin
Diarrhea , pseudomembranous colitis- Ampicillin
Interstitial Nephritis : Methicillin

9. BETA LACTAMASE INHIBITORS
• β lactamase inhibitors are drugs that inhibit β-lactamases -
enzymes produced by bacteria that inactivate the β-lactam
antibiotics.
• Drugs are Clavulanic acid, Sulbactam
• Clavulanic acid is combined with Amoxycillin
• Sulbactam is combined with Ampicillin
Uses:
• Effective against β lactamase producing bacteria eg Strep.
Pneumoniae , H influenzae (otitis media, sinusitis, orofacial
infections)
• Neisseria gonorrhoeae (gonorrhoea)
• Anaerobes ( Intra abdominal abscess)

10. CEPHALOSPORINS
I Generation – Active against Gm+ve,(staphylo & streptococci)
but a moderate effect on Gm-ve bacteria ( klebsiella & E coli) .
• Cephalexin, Cefadroxil
II Generation- Resistant to beta-lactamase, active against almost
all Gm-ve bacilli—
• Cefaclor , Cefprozil
III Generation- More active than either of two generations against
certain Gm-ve bacteria-
• Ceftibuten and Cefixime
IV Generation - More resistant to some beta-lactamase
producing species.
• Cefepime

11. Therapeutic uses of Cephalosporins
I Generation Cephalosporins :
• Infections caused by G +ve cocci such as, Staphyl aureus,
strepto pneumoniae, strepto pyogenes, Anaerobic streptococci.
II Generation Cephalosporins:
• Strepto pneumoniae, strepto pyogenes, Neisseria gonorrhoeae,
E coli, H influenzae, Klebsiella pneumoniae. Infections caused
by anaerobes Bacteroides fragilis & H influenza
III Generation Cephalosporins :
• Neiseria gonorrhoeae, E coli, Salmonella, H influenzae,
Proteus & Pseudomonas aeruginosa, penicillin resistant
pneumococci

12. Adverse effects of Cephalosporins
• Hypersensitivity reactions – Less compared to Penicillins
• Superinfection:
• Pseudomembranous enterocolitis
• Diarrhoea
• Hypoprothrombinemia (Bleeding)

13. Carbapenems
Imipenem &Meropenem
• Effective against Gm+ve, Gm-ve including
pseudomonas, anaerobes & β lactamase producing
organisms.
Uses
• Mixed aerobic & anaerobic infections
• Penicillin resistant pneumococci
• Enterobacter infections
• Pseudomonal infections
Adv effects
• Vomiting, diarrhoea, Seizures

14. Monobactams
Eg: Aztreonam
• Resistant to β-lactamases & active against pseudomonas
• No activity against G+ve or anaerobes.
• Uses:
• Patients allergic to penicillins
• Pseudomonal and other Gm-ve infections .