The document discusses penicillins and cephalosporins, which are classes of beta-lactam antibiotics. It describes their discovery and mechanisms of action, inhibiting bacterial cell wall synthesis. It categorizes different generations and types of penicillins and cephalosporins based on their spectra of activity against gram-positive and gram-negative bacteria. It also addresses bacterial resistance, proper use, side effects, and alternatives like macrolides when patients exhibit penicillin allergies.

1. Penicillins & Cephalosporins
know the basics
Dr.T.V.Rao MD
Dr.T.V.Rao MD
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2. Beginning of Antibiotics with
Discovery of Penicillin
• The discovery of
penicillin has been
attributed to Scottish
scientist Alexander
Fleming in 1928 and the
development of
penicillin for use as a
medicine is attributed
to the Australian Nobel
Laureate Howard
Walter Florey.
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3. Antibacterial agents
• Antibacterials/antimicrobial drugs - Substances that
inhibit the growth of or kill bacteria or other
microorganisms (microscopic organisms =
bacteria, viruses, fungi, protozoa)
• Bacteriostatic = Inhibits growth of bacteria
• Bactericidal = Kills bacteria
• Peaks & Troughs = Serum antibacterial levels for drugs w/
a narrow therapeutic index
- Too high = drug toxicity (Peak - 1 hr. after drug infused)
- Too low = therapeutic range (Trough - before dose)
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4. Uses of Antimicrobial Agents
• Antimicrobial agents are widely
employed to cure bacterial diseases
• Definition of Antibiotic – Antibiotics are
substances that are derived from a
various species of microorganisms and
are capable of inhibiting the growth of
other microorganism even in small
concentrations.
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5. Antibacterials
• Mechanism of Action:
1. Inhibition of cell wall synthesis - Bactericidal
2. Alteration in membrane permeability - ‘Cidal’
or ‘Static’
3. Inhibition protein synthesis - ‘Cidal’ or ‘Static’
4. Inhibition of bacterial RNA & DNA - Inhibits
synthesis of RNA & DNA
5. Interferes with metabolism in the cell - ‘Static’
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6. Antibacterial Drugs
• Drugs 1. Penetrate bacterial cell wall in sufficient
concentrations
2. Affinity to the binding sites on the bacterial
cell:
- Time drug remains at binding sites =
effect
- Time controlled by pharmacokinetics
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7. Antibacterials
• Pharmacodynamics - Concentration at site or exposure time for drug plays an
important role in bacteria eradication
- Duration of time for use of antibacterial varies according
to type of pathogen, site of infection & condition of host
- With some severe infections - continuous infusion more
effective than intermittent
- Body defense & drugs work together to stop infectious
process
- Effect = drug & host’s defense mechanisms
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8. Effects of concentrated drug dosing
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9. Antibacterials
• Bacterial Resistance - result naturally or may be
acquired
* Natural (inherent) = w/o previous exposure to antibiotic
ie. pseudomonas resistant to Penicillin G
* Acquired = prior exposure to antibacterial
ie. staph aureus was sensitive to PCN G, now it’s not
• Nosocomial infections - infections acquired while
clients are in the hosp. Many are mutant strains resistant
to many Antibacterials
Prolonged hospital stay
• Antibacterial resistance occurs when antibiotics are used
frequently
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10. Antibacterials
• Culture & Sensitivity - Blood test done to determine
effect drugs have on a specific organism
Culture = organisms responsible
Sensitivity = what antibiotic will work best
• Narrow & Broad Spectrum
Narrow - primarily effective against 1 type of organism
Broad - effective against both gram + & gram - organisms
* Used before isolating organism through C & S
* Not as effective as narrow spectrum against those
single organisms
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11. Antibacterials
Penicillins (PCN)
• From mold genus Penicillium - ‘miracle drug’ from
WWII
• A beta-lactum structure (beta-lactum ring) interferes
w/ bacterial cell wall synthesis by inhibiting the
bacterial enzyme necessary for cell division &
synthesis
• Bacteria die of cell lysis (breakdown)
• Both ‘static’ & ‘cidal’ in nature
• Mainly referred to as beta-lactum antibiotics
(enzymes produced by bacteria that can inactivate
PCN - Penicillinase = beta-lactamases which attack
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PCN

12. Penicillins and Cephalosporins
• Penicillin and cephalosporins act inhibiting Trans
peptidases, the enzyme catalyzes the final linking
step in synthesis of peptidoglycan.
• Due to this reason Penicillin in bactericidal for
growing bacteria since new peptidoglycan is
synthesized at that stage only.
• In nongrwoing cells penicillin is inactive
• An intact beta – lactum is essential for antibacterial
activity of penicillins
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13. Antibacterials
Penicillins
• Natural Penicillins
Penicillin G, Penicillin V, Procaine, Bicillin
- Good gram +, fair gram - , good
anaerobic
- PCN G = more effective IV or IM, but
painful d/t aqueous solution
- PCN V = PO; peak 2 - 4 hrs
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14. Classification of Penicillins
• Natural
Benzyl penicillin
Phenoxymethyl penicillin v
Semi synthetic and pencillase resistant
1 Methicillin
2 Nefcillin
3 Cloxacillin
4 Oxacillin
5 Floxacillin
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15. Antibacterials
Penicillins
• Aminopenicillins (Broad Spectrum)
Amoxicillin (Amoxil), Ampicillin
(Omnipen), Bacampicillin HCL (Spectrobid)
- Gram + & Gram - Costlier
- Inactivated by beta-lactamases = ineffective
against Staphylococcus aureus (staph. A)
- Amoxicillin = most prescribed PCN derivative
for adults & children
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16. Antibacterials
Penicillins
• Penicillinase - Resistant Penicillins
Methicillin (Staphcillin), Nafcillin
(Unipen), Oxacillin (Bactocil)
- Used to treat penicillinase-producing
Staph A.
- Gram + , not effective against Gram - IV & PO
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17. Antibacterials
Penicillins
• Extended - Spectrum Penicillins
Carbenicillin
(PO), Mezlocillin, Piperacillin, Ticarcillin, T
icarcillin-clavulanate (Timentin) - IM & IV
- Broad spectrum - good gram (-), fair
gram (+)
- Good against Pseudomonas aeruginosa
- Not penicillinase resistant
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18. Antibacterials
Penicillins
• SE & adverse reactions of Penicillins
1. Hypersensitivity - mild or severe
Mild = rash, pruritus, & hives - Rx w/ antihistamines
Severe = anaphylactic shock - occurs w/ in 20 min. - Rx w/
epinephrine
2. Super infection - secondary infection when normal
microbial flora of the body disturbed during antibiotic Rx
Mouth, resp. tract, GI, GU or skin - usually fungus
3. Organ toxicity - esp. liver & kidneys where drugs
metabolized & excreted (aminoglycosides)
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19. CEPHALOSPORINS
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20. Most commonly used Antibiotics
Cephalosporins
• Beta-lactam antibiotics are among the
most commonly prescribed
drugs, grouped together based upon a
shared structural feature, the betalactam ring. Cephalosporins cover a
broad range of organisms, are generally
well-tolerated, and are easy to
administer; thus, these agents are
frequently used beta-lactam drugs
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21. Antibacterials
Cephalosporins
• From a fungus Cephalosperium acremonium
- Gram (+) & gram (-)
- Resistant to beta - lactamase
- Bactericidal - action similar to PCN’s
- 4 groups (generations) - each effective against
a broader spectrum of bacteria
- about 10% of people allergic to PCN also to
allergic to cephalosporins
- Action - inhibits bacterial cell wall synthesis
- IM & IV - onset = almost immediate
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22. Antibacterials
Cephalosporins
• 1st Generation Cephalosporins - cefadroxil
(Duricef) & cephalexin (Keflex) - PO; Cefazolin
(Ancef) & cephalothin (Keflin) - IM
- Gram (+), & gram (-)
- Esp. used for skin/skin structure
infections
- Keflin used for resp, GI, GU, bone, &
joint infections
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23. Antibacterial
Cephalosporins
• 2nd Generation Cephalosporins cefaclor (ceclor) - PO, cefoxitin
(Mefoxin), cefuroxime
(Zinacef), cefotetan (Cefotan) - IM & IV
- Gram (+), slightly boarder gram (-)
effect than 1st generation
- for harder to treat infections
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24. Antibacterials
Cephalosporins
• 3rd Generation Cephalosporins cefotaxime (Claforan), ceftazidime
(Fortaz), ceftriaxone (Rocephin), cefixime
(Suprax) - IM or IV
- More effective against gram (-), less
effective against gram (+)
- for harder yet to treat infections
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25. 4th Generation Cephalosporins
• 4th Generation Cephalosporins cefepime (Maxipime) - IV or IM
• - Resistant to most betalactamase bacteria
• - greater gram (+) coverage than
3rd generation
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26. 5th Generation Cephalosporins
• Ceftaroline is a novel fifth-generation
cephalosporin, which exhibits broadspectrum activity against Gram-positive
bacteria, including MRSA and
extensively-resistant strains, such as
Vancomycin-intermediate S. aureus
(VISA), heteroresistant VISA (hVISA), and
Vancomycin-resistant S. aureus (VRSA)
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27. Why 5th Generation Cephalosporins
• Microbial resistance has reached alarming
levels, threatening to outpace the ability to counter
with more potent antimicrobial agents. In
particular, methicillin-resistant Staphylococcus aureus
(MRSA) has become a leading cause of skin and softtissue infections and PVL-positive strains have been
associated with necrotizing pneumonia. Increasing
reports of growing resistance to glycopeptide have
been noted, further limiting the efficacy of standard
antibiotics, such as Vancomycin.
• A need for newer Antibiotics is growing need
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28. ceftaroline is effective in
•
In addition to being an exciting new
agent in the anti-MRSA
armamentarium, ceftaroline provides
efficacy against many respiratory
pathogens including Streptococcus
pneumoniae, Haemophilus
influenza, and Moraxella catarrhalis.
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29. - Antibacterials
Macrolides, Lincosamide, Vancomycin
• All differ in structure, but similar spectrums of antibiotic
effectiveness to PCN
• Used as PCN substitutes, esp. w/ people allergic to PCN
• Erythromycin frequently prescribed if hypersensitive to
PCN
• Macrolides - Erythromycin, Azithromycin
(Zithromaz), Clarithromycin (Biaxin) - PO/IV, Dirithromycin
(Dynabac) - PO - Broad spectrum of activity
- Low to mod dose = bacteriostatic
- high doses = bactericidal
SE = GI disturbances, Allergic rxns = Hepatotoxicity
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30. Antibacterials
Lincosamide
• Clindamycin (Cleosin), Lincomycin
(Lincorex) - PO, IM, IV
- Inhibit bacterial protein synthesis
- ‘Static’ & ‘cidal’ actions depending on drug
dosage
- effective against most gram (+), no gram (-)
- Clindamycin more effective than lincomycin
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31. Antibacterials
Vancomycin
• Glycopeptide bactericidal antibiotic - IV
- Use: Drug resistant Staph A., cardiac surgery prophylaxis for clients w/ PCN allergies
- SE = Ototoxicity - damage to auditory branch
of 8th cranial nerve permanent hearing loss
or loss of balance & Nephrotoxicity
- Serum Vancomycin levels drawn to minimize
toxic effects
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32. Antibacterials
Vancomycin
• Glycopeptide bactericidal antibiotic - IV
- Use: Drug resistant Staph A., cardiac surgery prophylaxis for clients w/ PCN allergies
- SE = Ototoxicity - damage to auditory branch
of 8th cranial nerve permanent hearing loss
or loss of balance & Nephrotoxicity
- Serum Vancomycin levels drawn to minimize
toxic effects
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33. • Programme Created by Dr.T.V.Rao MD for
Medical and Paramedical Students in the
Developing World
• Email
• doctortvrao@gmail.com
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