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Beta-Lactam Antibiotics

Four types

  1. Penicllins         
  2. Cephalosporins
  3. Caxbapenems
  4. Monobactams 


  • Natural
  • Semisynthtic


  1. Parental
    a. IM
    1. Procaine Pencilllin
    2. Benzathzine Penicllin  

b. IV

  1. Benzyl penicllin (Pen. G)
  1. Oral
    a. Penicillin V (Methoxy penicllin) 


  1. Aminopenicllins
    1. Amoxicillin
    2. Ampicllin
  2. Isoxzolyl (Antistaphyloccal-beta-lactamase stable)
    1. Nafcillin                        
    2. Cloxacillin            
    3. Oxacillin               
    4. Dicloxacillin                  
    5. Flucloxacillin
  3. Antipseudomonal
    a. Carboxypenicllins
    1. Ticarcillin              
    2. Carbenicillin

b. Ureidopenicllins

  1. Azlocillin                
  2. Mezlocillin            
  3. Piperacillin
4. Beta-lactamase inhibitors
  1. Sulbactam          
  2. Tazobactam        
  3. Clavulanic acid 


  1. Generation -I
    1. Cephalexin  
    2. Cefadroxil        
    3. Cephalothin                
    4. Cepharidine         
    5. Cefazolin
  2. Generation -II
    1. Cefuroxime          
    2. Cefaclor          
    3. Cefoxitin          
    4. Cefotetan            
    5. Cefmetazole                
    6. Cefprozil        
    7. Cefomandole        
    8. Lorcarbef
  3. Generation -III
    1. Cefexime              
    2. Cefdinir            
    3. Cefpidoxime            
    4. Ceftibuten            
    5. Ceftrioxone          
    6. Cefotaxime        
    7. Cefoperazone          
    8. Ceftazidime
    9. Ceftizoxime          
    10. Moxalactam
  4. Generation -IV
    1. Cefepime              
    2. Cefpirome
  5. Generation -V
    a. Ceftobiprole


  1. Aztreonam


  1. Imepenem           
  2. Meropenem          
  3. Faropenem          
  4. Ertapenem 


  1. Beta-lactams inhibit cell wall synthesis
    i. Bind to PBP; interrupt transpeptidation step


  1. Mutation in PBP (Anti-staphylococcal antibiotics)
  2. Beta-lactamases (Periplasmic space)  

Beta-Lactamases are most commonly classified according to two general schemes:

(AIIMS NOV 2010, MAY 2011, NOV 2011, ALL INDIA 2009,10,11)

  1. Ambler molecular classification scheme.
  2. Bush-Jacoby-Medieros functional classification system.  
  1. The Ambler scheme divides beta-lactamases into four major classes (A to D). The basis of this classification scheme rests upon protein homology (amino acid similarity), and not phenotypic characteristics. beta-lactamases of classes A, C, and D are serine beta-lactamases.
  2. In contrast, the class B enzymes are metallo-beta-lactamases use zinc and calcium ions for its action. SHV and TEM type of resistance are mainly seen in bacteria.
  3. The Bush-Jacoby-Medeiros classification scheme groups beta-lactamases according to functional similarities (substrate and inhibitor profile).
  4. There are four main groups (1 to 4) and multiple subgroups in this system. This classification scheme is of much more immediate relevance to the physician or microbiologist in a diagnostic laboratory because it considers beta-lactamase inhibitors and beta-lactam substrates that are clinically relevant

Class A ESBLs:

  1. Extended-spectrum β-lactamases (ESBLs) A are enzymes which are capable of hydrolyzing penicillins, cephalosporins of the first, second, third, and fourth generations & the monobactam antibiotic aztreonam.
  2. It has also been observed that ESBL-producing bacteria are frequently resistant to other classes of antibiotics such as quinolones, aminoglycosides, and sulfamethoxazole.
  3. Cephamycins (e.g., cefoxitin) or carbapenems (e.g., imipenem, meropenem, and ertapenem) are not affected by these enzymes
  4. The carbapenems (including imipenem, meropenem, and ertapenem) have the most consistent activity against ESBL-producing organisms, given their stability to hydrolysis by ESBLs.
  5. Cephamycins are also stable to the hydrolytic effects of ESBLs. Unfortunately, ESBL-producing organisms may lose outer membrane proteins leading to resistance to the cephamycins not related to beta-lactamase production .
  6. ESBLs are inhibited by β-lactamase inhibitors (clavulanic acid, tazobactam, and sulbactam). 

Class B metallo beta-lactamases.

  1. Class B enzymes are Zn2_-dependent beta -lactamases that demonstrate a hydrolytic mechanism different from that of the serine beta-lactamases of classes A, C, and D .
  2. Organisms producing these enzymes usually exhibit resistance to penicillins, cephalosporins, carbapenems, and the clinically available beta-lactamase inhibitors Interestingly, the hydrolytic profile of MBLs does not typically include aztreonam

Class C serine cephalosporinases

  1. Organisms expressing the AmpC beta -lactamase are typically resistant to penicillins, beta -lactam– beta -lactamase inhibitor combinations, and cephalosporins, including cefoxitin, cefotetan, ceftriaxone, and cefotaxime.
  2. AmpC beta- lactamase producers are resistant to penicillins and cephalosporins including cephamycins and β-lactamase inhibitors.
  3. This property differentiates ESBL A producers from the AmpC β-lactamase producers.
  4. AmpC enzymes poorly hydrolyze cefepime and are inhibited by cloxacillin, oxacillin, and aztreonam. 

Class D serine oxacillinases.

  1. Class D beta -lactamases were initially categorized as “oxacillinases” because of their ability to hydrolyze oxacillin at slow rate.
  2. In bacteria, OXA beta–lactamases can also confer resistance to penicillins, cephalosporins, extended-spectrum cephalosporins (OXA-type ESBLs), and carbapenems (OXA-type carbapenemases).
  3. Generally speaking,OXA enzymes are resistant to inhibition by clavulanate, sulbactam, and tazobactam.
  4. Interestingly, sodium chloride and chelating agents like EDTA inhibits some carbapenem hydrolyzing oxacillinases


  1. Penicllins--- acid labile
  2. Methicllin also acid labile
  3. Methoxy penicllin acid stable
  4. Hal lives of penicllins
    1. Pen G=15-30 mins
    2. Procaine Pen=1 hour
    3. Benzathine pen=12-24 hours
  5. Bile elimination (NO C)
    1. Nafcillin                        
    2. Oxacillin              
    3. Cloxacillin            
    4. Ceftriaxone      
    5. Cefoperazone
  6. Rest of peniclillins
    a. Eliminated by tubular secretion; elimination is interfered by probenacid
  7. Penicillins don’t enter blood brain barrier unless meninges are inflamed
    a. Imepenem enters freely


  1. Penicillin G (DOC)
    1. Group B                        
    2. Group A beta hemolytic streptococci             
    3. Group D (BAD bacteria)                
    4. Tetanus                                
    5. Syphllis        
    6. Yaws                            
    7. Pinta                                    
    8. Anthrax       
    9. Leptospirosis                  
    10. Actinomyecetes                    
    11. Gonorrhea (Resistant)       
    12. Diptheria                      
  2. Amoxycillin
    1. Otitis media
    2. Sinusitis
  3. Ampicillin (DOC)
    1. Enterococcus faecalis
    2. Listeria meningitis
  4. Imepenem (DOC)
    1. Enterobacter infections
    2. Also active in klebsella, psedomonas, staphylococci (not MRSA)
    3. Enters BBB freely
    4. Not a prodrug; given with cilastin (renal dehydropeptidase inhibitor)
    5. Resistance mediated by:
      i. Metalloproteases
  5. Ceftriaxone (DOC)
    1. Typhoid fever
    2. Gonorrhea
    3. Resistant pneumococcal infections
    4. Meningitis
    5. H. Influenza  
  6. Cefazolin (DOC)
    a. Wound infections
  7. Ceftazidime
    a. Most potent antipseudomonal cephalosporine; piperacillin is most potent penicillin
  8. Cefepime
    1. Short acting
    2. Enters CSF
    3. Active against pseudomonas, klebsella, enterobacter, citrobacter, serratia+ resistant bacteria of first 3 generations
    4. Avoided in renal failure
    5. DOC for Phnemonia in ICU
  9. Ceftobiprole
    a. Active against MRSA 


  1. MC-allergic reactions
    a. Minor rashes
    b. Or Anaphylaxis
  2. Supeinfections
  3. Disulfiram like reactions
  4. Thrombocytopenia
  5. Seizures (MC-imepenem)
  6. Serum sickness (Penicillin MC cause)
  7. Jerish-Heximer reaction
    a. Seen in syphilis, gonorrhea
  8. Nafcillin
    a. Neutropenia
  9. Oxacillin
    a. Hepatitis
  10. Cloxacillin
    a. Photosenstivity
  11. Ampicllin
    i. Diarrhea               
    ii. Rashes
  12. Methicillin
    a. Interstitial nephritis
  13. Cephalothin
    a. Injection pain
    b. Penicillin also cause; that is why procaine is added to reduce pain
  14. Cepharidine
    a. Nephrotoxicity
  15. Moxalactam
    a. Hypoprothrombinemia
  16. Cefoperazone
    a. Thrombocytopenia
  17. Ceftazidime
    a. Netropenia

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