The document discusses various classes of antibiotics including their spectrum of activity, mechanisms of action, and examples. It describes narrow and broad-spectrum antibiotics, and whether they are bacteriostatic or bactericidal. The main classes covered are beta-lactams like penicillins and cephalosporins, macrolides, quinolones, tetracyclines, aminoglycosides, chloramphenicol, and sulfonamides. It provides details on their mechanisms of inhibiting cell wall synthesis, protein synthesis, or nucleic acid synthesis. Examples of commonly used antibiotics in different species are given along with typical dosage ranges.

1. Prepared by
Dr MuhammadAshiq Toor
DVM , B s c (Zoology)
Islamia University of Bahawal Pur (IUB) (2010 – 2015)
+92-344-499-7375
+92-300-364-2402

2. Antibiotics
Class wise , Spectrum , Bacterial activity ,
MOA & dose rates.

3. The Spectrum of Antimicrobial Activity
Narrow spectrum (limited spectrum)
 Antimicrobials effective against a (limited spectrum)
of microbial types.
 A drug effective on G+ve or G-ve bacteria.
Broad spectrum (extended spectrum)
 Antimicrobials effective against a (extended spectrum) wide
variety of microbial types .
 A drug effective against both G+ve & G-ve bacteria .

4. Broad spectrum
Some examples of broad-spectrum antibiotics include :
 Penicillin
 Cephalosporin
 Tetracycline
 Ciprofloxacin
 Levofloxacin
These drugs work on both G+ve & G-ve organisms.

5. Narrow Spectrum
Vancomycin
Azithromycin
Clarithromycin
Clindamycin
Clindamycin + Benzoyl Peroxide
Erythromycin

6. No antibiotic is effective against all microbes

7. The Action of Antimicrobial Drugs
Bacteriocidal
 Kill microbes directly
Bacteriostatic
 Prevent microbes from growing

8. Bacteriostatic vs Bactericidal
Bacteriocidal antibiotics
Kill the target bacteria. These drugs include :
 Penicillins
 Cephalosporins
 Carbapenems
 Aminoglycosides
 Fluoroquinolones
 Nitroimidazoles

9. Bacteriostatic antibiotics
Slow down bacterial growth & allowing the host immune
system to fight the bacteria. These drugs include :
 Macrolides
 Tetracyclines
 Sulfonamides
 Clindamycin
 Chloramphenicol

10. Mechanisms of Antibiotics Action
1- Inhibition of Cell Wall Synthesis
2- Injuring the Plasma Membrane
3- Inhibition of Protein Synthesis
4- Inhibition of Nucleic Acid Synthesis
5- Inhibiting the Synthesis of Essential Metabolites

11. The Action of Antimicrobial Drugs

12. Mechanisms of Antibiotics Action Dihydrofolate

13. Mechanisms of Action:
inhibit the last step in the peptidoglycan
synthesis of the cell wall
1. inhibition of transpeptidase
 enzymes
2. activation of penicillin binding
 proteins (PBPs)
3. activation of autolysins
 (murein hydrolases)

15. Protein Synthesis

16. Inhibition of Protein Synthesis by antibiotics

17. Inhibition of Protein Synthesis by
Antibiotics
Figure 20.4

19. Inhibition of Cell Wall Synthesis
Transpeptidases, Carboxypeptidases &
Transglycosylases
Penicillin-binding proteins (PBPs(
β-Lactam antibiotics: generally are bacteriocidal agents

20. 1- Beta-Lactam Antibiotics :
 Penicillins
 Cephalosporins
2- Glycopeptides :
 Vancomycin
3- Lipopeptides :
 Daptomycin
4- Polypeptides :
 Bacitracin
Inhibition of Cell Wall Synthesis

21. 1- Aminopenicillins: Ampicillin, Amoxicillin
Ampicillin was limited primarily to Escherichia & Proteus
species .
2- Carboxypenicillins: Carbenicillin, Ticarcillin
Are effective against a broader range of G-ve bacteria i.e
Klebsiella, Enterobacter, & Pseudomonas species .
Broad-spectrum penicillins

22. Clavulanic acid, Sulbactam, Tazobactam
(ampicillin, amoxicillin, ticarcillin, piperacillin)
Amoxicillin/clavulanic acid (Co-amoxiclav)
Ampicillin/sulbactam (Sultamicillin)

23. Cephalosporins
More stable to β-lactamase hydrolysis

24. Antimicrobial spectrum of cephalosporins
Generation of
cephalosporin
s
Active towards
Gram-positive
bacteria
Gram-negative
bacteria
І +++ +/-
ІІ ++ +
ІІІ + +++
ІV ++ +++

25. CEPHALOSPORINS
CLASSIFICATION
A. First Generation
 1. Cephaloridine-Loridine, Ceporan
 2. Cephalothin-Keflin
 3. Cephalexin-Keflex, Ceporex
 4. Cefazolin-Cefacidal
 5. Cephradine-Velosef
 6. Cepharpirin-Cefadyl
 7. Cephadroxil-Doricef, Cefamox

26. Second Generation
1. Cefaclor-Ceclor
2. Cefoxitin – Mefoxin
3. Cefuroxime – Zinacef, Zinnat
4. Cefonicid – Monocid
5. Cefotetan - Cefotan
6. Cefamdandole – Mandol
7. Cefprozil – Cefzil
8. Loracarbef – Lorabid
9. Cefmetazole – Zefazone
10. Ceforanide

27. Third Generation
 1. Cefotaxime – Claforan
 2. Cefoperazone – Cefobid
 3. Moxolactam – Moxam
 4. Ceftizoxime – Cefizox
 5. Ceftriaxone – Rocephin
 6. Ceftazidime – Fortum
 7. Cefotiam – Ceradolan
 8. Cefixime – Suprax
 9. Cefetamet – Globocef
 10. Cefpodoxime – Vantin
 11. Ceftibuten – Cedax
 12. Cefdinir –Omnicef
 13. Cefditoren

28. Fourth Generation
1. Cefepime – Maxipime
2. Cefpirome – Cefrom

29. Broad-spectrum antibiotics
 Active against virtually all organisms
Imipenem, Meropenem, Ertapenem
Carbapenems

30. Narrow-spectrum antibiotics
 Are active only against aerobic & G-ve bacteria
Aztreonam
Monobactams

31.  Damage cytoplasmic membrane and inhibit RNA transcription
 The treatment of skin infections
 Used in creams, ointments, sprays
Polypeptides: Bacitracin

32.  Bactericidal
 Bind irreversibly to ribosomal proteins
Misreading of the messenger RNA (mRNA)
Premature release of the ribosome from mRNA
 Streptomycin, Neomycin, Kanamycin, & Tobramycin
Streptomyces species
 Gentamicin & Sisomicin
Micromonospora species
 Amikacin from kanamycin
Aminoglycosides

33.  Broad-spectrum
 Bacteriostatic
 Tetracycline, Doxycycline, Chlorotetracycline
 Binding reversibly to the 30S
 Blocking the binding of aminoacyl-tRNA
 Chlamydia, Mycoplasma, Rickettsia
Tetracyclines

34. Chloramphenicol
 Broad spectrum
 Bacteriostatic
 Blocking peptide elongation
 Typhoid fever

35.  Broad spectrum
 Bacteriostatic
Reversible binding to the 50S rRNA
Erythromycin, Azithromycin, Clarithromycin
Macrolides

36. Inhibition of Nucleic Acid Synthesis
1- Quinolones
2- Rifampin
3- Metronidazole

37.  Synthetic
 Inhibit bacterial DNA gyrases (II) or topoisomerases (IV)
Nalidixic acid
Fluoroquinolones:
Ciprofloxacin Levofloxacin Enrofloxacin
Quinolones

38.  Reduction of its nitro group by bacterial nitroreductase
 Producing cytotoxic compounds that disrupt the host DNA
 Anaerobic bacterial infections (B. fragilis)
Metronidazole

39. Antimetabolites
Sulfonamides
 Preventing the synthesis of the folic acid
 Compete with para-amino-benzoic acid (PABA)

40. Trimethoprim
 Blocks the conversion of dihydrofolate to tetrahydrofolate
 Inhibiting dihydrofolate reductase
 Trimethoprim + sulfamethoxazole: Synergistic combination
 Treatment of acute and chronic urinary tract infections
Antimetabolites

41. S
No Group name Spectrum Activity Examples MOA
1. Beta Lectum Broad spectrum bactericidal Penicillins
Cephalosporins
Inhibit cell wall synthesis
2. Macrolids Narrow spectrum (G +ve) bacteriostatic Azithromycin
Clarithromycin
Erythromycin
30s rRNA block
3. Quinolones Broad spectrum bactericidal Ciprofloxacin
Levofloxacin
Gatifloxacin
Inhibit bacterial DNA gyrases
4. Tetracycline Broad spectrum bacteriostatic Tetracycline,
Doxycycline,
Minocycline
30s rRNA block
5. Aminoglycosides Narrow spectrum (G - ve) Bactericidal Streptomycin,
Neomycin,
Kanamycin, &
Tobramycin
30s rRNA block

42. S
No Group name Spectrum Activity Examples MOA
6. Chloramphenicals Broad spectrum Bacteriostatic Florphenicol
Achlor
Chloromycetin
Binding reversibly to the peptidyl
transferase (50S)
7. Cephalosporins Broad spectrum bactericidal Inhibition of cell wall synthesis
First-generation Narrow-spectrum
(G +ve)
bactericidal Cefazolin
Cephalothin
Cephradine
Second generation expanded-
spectrum (G -ve)
bactericidal Cefamandole,
Cefaclor,
Cefuroxime
Third generation broad-spectrum
Noscomial
diseases
bactericidal Cefixime,
Cefoperazone
Ceftriaxone

43. Fourth
generation
broad-spectrum
Covers
pseudomonal
infections
bactericidal Cefepime,
Cefpirome
Fifth generation Used to treat MRSA bactericidal Ceftobiprole,
Ceftaroline

44. Dose rates of Antibiotics

45. Macrolids
Erythromycin Cattle 8–15 mg/kg, IM, sid-bid
Cat 15 mg/kg, PO, tid
Foals 25 mg/kg, IM, tid
Tylosin Cattle 10–20 mg/kg, IM, sid-bid
Pigs 10 mg/kg, IM, sid-bid
7–10 mg/kg, PO, tid
Cats 10 mg/kg, IM, bid

46. Quinolone
Nalidixic acid Cats, dogs 3 mg/kg, PO, qid
Enrofloxacin Cats 5 mg/kg, PO, sid-bid
Dogs 5–20 mg/kg, PO, sid-bid
2.5 mg/kg, SC, once then PO
Beef cattle (not veal or dairy) 7.5–12.5 mg/kg, SC, once
2.5–5 mg/kg, SC, sid
Pigs 2.5–5 mg/kg, PO or IM, sid
Preruminant calves 2.5–5 mg/kg, PO or SC, sid
Marbofloxacin Cats, dogs 2.75–5.5 mg/kg, PO, sid
Difloxacin Dogs 5–10 mg/kg, PO, sid
Orbifloxacin Cats, dogs 2.5–7.5 mg/kg, PO, sid

47. Tetracycline
Tetracycline Cat , Dog 7 mg/kg, IM, or IV sid-bid
20 mg/kg, PO, tid
OTC Cat , Dog 7 mg/kg, IM or IV , bid
Cattle , sheep ,
pig
5-10 mg/kg, IM or IV, sid-bid
Horse 5 mg/kg, p o bid
Doxy Dog 5 - 10mg/kg, p o sid
Cats 5 mg/kg, IM, sid

48. Aminoglycoside
Gentamicin 6–12 mg/kg, IM or SC, sid
Kanamycin 25–30 mg/kg, IM or SC, sid
Streptomycin 15–25 mg/kg, IM or SC, sid
Amikacin 15–22 mg/kg, IM or SC, sid
Netilmicin 6–12 mg/kg, IM or SC, sid
Neomycin 15 mg/kg, PO, sid-bid
0.5–1 g/quarter,
intramammary, sid

49. Cephalosporin
Dosage, Route, and Frequency
Cephapirin 30 mg/kg, IM or IV, every 4–6 hr
Cefazolin 20–25 mg/kg, IM or IV, tid-qid
Cefpodoxime 8 mg/kg, SC, every 14 days
Cefovecin 5–10 mg/kg, PO sid-bid
Cephalexin 10–30 mg/kg, PO, tid-qid
Cefadroxil 22 mg/kg, PO, bid
Ceftiofur 1.1–2.2 mg/kg, IM, sid

50. Dosages of Sulfonamides
Sulfonamide Species Dosage, Route, and Frequency
Sulfathiazole Horses 66 mg/kg, PO, tid
Cattle, sheep, pigs 66 mg/kg, PO, every 4 hr
Sulfamethazine Cattle 220 mg/kg, PO or IV, sid
Sulfadiazine All 50 mg/kg, PO, bid
Sulfadimethoxine All 55 mg/kg, PO,
Sulfaethoxypyridazine Cattle 55 mg/kg, PO, sid
Pigs 110 mg/kg, PO, sid
Sulfapyridine Cattle 132 mg/kg, PO, bid
Succinylsulfathiazole All 160 mg/kg, PO, bid

51. Examples of antibiotics available in
market

52. Almox-LA:
Composition:
Amoxicilline trihydrate 150mg
Company: Star
Medicine Form: Injectable
Dose Rate: 1m/ 10kg
Availability: 50 ml vial
Price: Rs. 250/=

53. Tylosel:
Composition:
Tylosin Tartarate 200mg
Company: Selmore
Medicine Form: Injectable
Dose Rate: 0.05ml/kg
Availability 50ml vial
Price: Rs. 221/=

54. Genton:
Composition:
Gentamycin Sulphate 100mg
Company: ICI
Medicine Form: Injectable
Dose Rate: 1ml/20kg
Availability 50ml vial
Price: Rs. 275/=

55. Diarex Forte:
Composition
Sulphadiazine 35.5mg
Sulphadimidine 28.4mg
Neomycine Sulphate 1.8mg
Hyoscine Methylbromide 0.04mg
Pectin 7.1mg
Company: zakfas Pharma
Medicine Form: Oral suspension
Dose Rate: 100ml/L.A & 50ml/ S.A
Availability 100ml pack
Price: Rs. 150/=

56. Utinol Tabs:
Composition:
Sulphadiazol 1750mg
Pencilline G 10000i.u
Streptomycine sulphate 50mg
Etinyl estradiol 0.5mg
Company: Star
Medicine Form:Intrauterine passeries
Dose Rate: 4-8/ L.A & 2-4/S.A
Availability 20 passeries per pack

57. DRUGS HALF LIFE ORAL ABS
1.short acting
Sulfacytine
Sulfisoxazole
Sulfamethizole
Short
Short (6 h)
Short (9 h)
Prompt (peaks in
1-4h)
Prompt
Prompt
2. Medium acting
Sulfadiazine
Sulfamethoxazole
Sulfapyridine
Intermediate(10-17h)
Intermediate (10-12h)
No data
Slow (peak in 4-8h)
Slow
Slow
3.Long Acting
Sulfadoxine Long (7-9 days) Intermediate

58. Thank u
STUDY WELL!