This document provides a comprehensive overview of antibiotics, including their definitions, history, classification, mechanisms of action, and therapeutic applications. It discusses various antibiotic types such as sulfonamides, penicillins, cephalosporins, and their use in treating infections, while also addressing antibiotic resistance and public health impacts. Key information regarding dosages, adverse effects, and specific agents useful for orofacial infections is also included.

1. DR. DIPLINA BARMAN 1

2.  DEFINITION OF ANTIBIOTICS
 HISTORY
CLASSIFICATION OF ANTIBIOTICS
 MECHANISM OF ACTION
 PRINICIPLE OF ANTIBIOTIC THERAPY
 CHOICE OF AN ANTIMICROBIAL AGENTS
 COMBINED USE OF ANTIMICROBIAL AGENTS
 ANTIBIOTICS USEFUL FOR OROFACIAL INFECTIONS
 PROPHYLACTIC ANTIBIOTICS
ANTIBIOTIC RESISTANCE
PUBLIC HEALTH SIGNIFICANCE OF ANTIBIOTICS
SUMMARY
CONCLUSION
REFERENCES
CONTEN
TS
2

3. What is Antibiotic?
•Substances produced by microorganisms,
• Selectively suppress the growth , kill other microorganisms at very low
concentrations.
•‘Chemotherapeutic agent’ - synthetic compounds,
•Antimicrobial agent (AMA) - synthetic + naturally obtained drugs that
attenuate microorganisms. 3

4. 4

5. HISTORY
Period of empirical use
• 16th 17th century AD
• Use of mouldy curd by
Chinese on boils,
chaulmoogra oil by the
Hindus on leprosy ,
cinchona bark for fevers
etc.
Ehrlich’s phase of dyes
and organometallic
compounds (1890–1935)
• Ehrlich tried methylene
blue, trypan red, etc
• He developed the
arsenicals— atoxyl for
sleeping sickness,
arsphenamine in 1906 and
neoarsphenamine in 1909
for syphilis.
• He coined the term
‘chemotherapy’.
The modern era of
chemotherapy
• Domagk in 1935
demonstrated therapeutic
effect of Prontosil, a
sulfonamide dye, in
pyogenic infection
5

6. 1877 - Pasteur demonstrated Phenomenon of antibiosis.
1929 – Fleming - Penicillium mould - destroy Staphylococcus on the
culture plate. He named penicillin but could not purify it.
1941 - Chain and Florey found out the clinical use of penicillin.
1944 -Waksman and his colleagues discovered Streptomycin.
6

7. CLASSIFICATION OF ANTIBIOTICS
Chemical
structure
Mechanism
of action
Type of organism
against which they
are active
Spectrum
of activity
Type of
action
Source
7

8. 1.Sulfonamides and related drugs: Sulfadiazine, Sulfones— Dapsone (DDS),
Paraaminosalicylic acid (PAS).
2. Diaminopyrimidines: Trimethoprim, Pyrimethamine.
3. Quinolones: Nalidixic acid, Norfloxacin, Ciprofloxacin, etc.
4.β-lactam antibiotics: Penicillins, Cephalosporins, Monobactams.
5. Tetracyclines: Oxytetracycline, Doxycycline, etc.
6. Nitrobenzene derivative: Chloramphenicol.
7. Aminoglycosides: Streptomycin, Gentamicin, Neomycin, etc.
8. Macrolide antibiotics: Erythromycin, Clarithromycin, Azithromycin, etc.
8
A. Chemical structure

9. 9. Lincosamide antibiotics: Lincomycin, Clindamycin.
10. Polypeptide antibiotics: Polymyxin-B, Bacitracin.
11. Glycopeptides: Vancomycin
12. Oxazolidinone: Linezolid.
13. Nitrofuran derivatives: Nitrofurantoin.
14. Nitroimidazoles: Metronidazole, Tinidazole.
15. Nicotinic acid derivatives: Isoniazid, Pyrazinamide.
16. Polyene antibiotics: Nystatin, Amphotericin-B.
17. Azole derivatives: Miconazole, Clotrimazole, Ketoconazole, Fluconazole
18. Others: Rifampin, Viomycin, Ethambutol, Thiacetazone, Griseofulvin.
9

10. 1. Inhibit cell wall synthesis: Penicillins, Cephalosporins, Vancomycin,
Bacitracin.
2. Cause leakage from cell membranes: Polypeptides—Polymyxins, Bacitracin ,
Polyenes—Amphotericin B, Nystatin.
3. Inhibit protein synthesis: Tetracyclines, Chloramphenicol, Erythromycin,
Clindamycin.
4. Cause misreading of m-RNA code and affect permeability:
Aminoglycosides— Streptomycin, Gentamicin, etc.
10
B. Mechanism of action

11. 5. Inhibit DNA gyrase: Fluoroquinolones— Ciprofloxacin.
6. Interfere with DNA function: Rifampicin, Metronidazole.
7. Interfere with DNA synthesis: Acyclovir, Zidovudine.
8.Interfere with intermediary metabolism: Sulfonamides, Sulfones,
Trimethoprim, Pyrimethamine, Ethambutol.
11

12. 1. Antibacterial: Penicillins, Aminoglycosides, Erythromycin, etc.
2. Antifungal: Griseofulvin, Amphotericin B, Ketoconazole, etc.
3. Antiviral: Acyclovir, Amantadine, Zidovudine, etc.
4. Antiprotozoal: Chloroquine, Pyrimethamine, Metronidazole, etc
5. Antihelmintic: Mebendazole, Niclosamide, Diethyl carbamazine, etc.
12
C. Type of organisms against which primarily active :

13. D. Spectrum of activity
Narrow spectrum
• Penicillin G
• Streptomycin
• Erythromycin
Broad spectrum
•Tetracyclines
•Chloramphenicol
13

14. SULFONAMIDES
•First antimicrobial agents (AMAs)
•Effective against pyogenic bacterial infections.
•Primarily bacteriostatic - gram positive , gram negative bacteria.
•Used in combination with trimethoprim (as cotrimoxazole) or
pyrimethamine (for malaria).
Doses and Uses
•Sulfadiazine : 0.5 g QID to 2 g TDS-
meningitis
•Sulfadoxine: used in combination with
pyrimethamine for malaria.
Adverse effects
Nausea, vomiting and epigastric pain.
Crystalluria is dose related but
infrequent now.
Hypersensitivity : 2–5% patients.
14

15. COTRIMOXAZOLE
•Sulfamethoxazole + trimethoprim - 20 : 1.
•Individually-bacteriostatic
•Combination-Bacteriocidal.
•Uses: tonsillitis, pharyngitis, sinusitis, otitis media.
•Orodental infections,
•Patients allergic to β-lactam antibiotics.
•Dose : 80 mg trimethoprim + 400 mg
sulfamethoxazole tab BD for 2 days then 1 BD. Eg.
Septran.
Mechanism of action
15

16. FLUOROQUINOLONES
• Active against : gram positive cocci ,
anaerobes.
• Mechanism of action :
Inhibit the enzyme bacterial DNA
gyrase which nicks double-stranded
DNA, introduces negative supercoils
and then reseals the nicked ends.
16

17. CIPROFLOXACIN
•Most potent first generation FQ.
•Rapid bactericidal activity.
•β-lactam and aminoglycoside
resistant bacteria.
•Contraindicated during pregnancy.
Eg. CIPLOX 250, 500, 750 mg tab
17
Uses:
•Urinary tract infection,
typhoid fever.
•Ciprofloxacin +
metronidazole = refractory
mixed infections like
periodontitis.

18. Norfloxacin
•Less potent than ciprofloxacin.
•Primarily used for urinary and genital tract infections.
•NORFLOX 200, 400, 800 mg tab.
Ofloxacin
•Intermediate between ciprofloxacin and norfloxacin.
•Suited for orodental infections as it is active against certain anaerobes.
•ZANOCIN 100, 200, 400 mg tab. 18

19. METRONIDAZOLE
•Broad spectrum antiprotozoal drug.
•Selectively toxic to anaerobic microorganisms.
Pharmacokinetics
•completely absorbed from the
small intestines.
•metabolized in liver primarily
by oxidation
•excreted in urine
Adverse effects
•Most common : anorexia, nausea, bitter or metallic taste.
•Less frequent side effects are—headache, glossitis, dryness of mouth,
•Contraindicated in the first trimester of pregnancy.
FLAGYL, METROGYL, METRON, 200, 400 mg tab. 19
NITROIMIDAZOLES
Bacteriostatic

20. 20

21. USES
•Dose : 200–400 mg TDS.
•ANUG (in combination with either penicillin V, amoxicillin, erythromycin
or tetracycline).
•Periodontitis, pericoronitis, acute apical infections and some endodontic
infections also respond well to metronidazole given for 5–7 days.
•Amoebic infection.
21

22. Ornidazole
•Activity similar to metronidazole, but it is slowly metabolized for
amoebiasis, anaerobic infections.
•ORNIDA 500 mg tab, 125 mg/5 ml suspension.
22

23. Beta-Lactam Antibiotics
•Antibiotics having a β-lactam ring.
•penicillins and cephalosporins.
•most commonly used antibiotics in dentistry.
•Mechanism of action—inhibition of synthesis of
the bacterial peptidoglycan cell wall.
Bacterial cell wall synthesis
23

24. 24

25. PENICILLINS
•First antibiotic - 1941.
•Originally obtained from the fungus
Penicillium notatum, but presently from P. chrysogenum.
•Consists of fused thiazolidine and β-lactam rings to which side chains
are attached through an amide linkage.
25

26. 1.Natural
penicillins :
Penicillin G
(Benzyl penicillin)
2.Semisynthetic
penicillins:
Methicillin, Cloxacillin
a. Acid-resistant
alternative to penicillin G:
Phenoxymethyl penicillin
(Penicillin V).
b. Penicillinase - resistant
penicillins : Methicillin,
Cloxacillin.
c. Extended spectrum
penicillins :
i) Aminopenicillins:
Ampicillin, Amoxicillin.
ii) Carboxypenicillins:
Carbenicillin.
iii) Ureidopenicillins:
Piperacillin.
26

27. PENICILLIN-G (BENZYL PENICILLIN)
•Narrow spectrum
•Activity is limited primarily to gram-positive bacteria and few others.
•Streptococci , pneumococci gram-positive bacilli and spirochetes are highly
sensitive.
•Many bacteria are inherently insensitive to PnG .
•Acquired resistance through production of penicillinase.
27

28. Adverse effects:
•Pain at i.m. injection site, nausea
on oral ingestion.
•In large doses, toxicity to the
brain may be manifested as
mental confusion, muscular
twitchings.
•Hypersensitivity.
Uses:
•Dental infections like those caused as a
sequelae of carious lesions and are
caused by both aerobic and anaerobic
bacteria.
•Periodontal abcess , periapical abscess
, pericoronitis , acute suppurative
pulpitis , ANUG , cellulitis etc.
•Pharyngitis, tonsillitis, otitis media etc.
28

29. SEMISYNTHETIC PENICILLINS
•Produced by chemically combining specific side chains (in place of benzyl side chain of PnG)
or by incorporating specific precursors in the mould cultures.
•Eg. Procaine penicillin and Benzathine penicillin are salts of PnG and not semisynthetic
penicillins.
•The aim of producing semisynthetic penicillins has been to overcome the shortcomings
of PnG, which are:
1. Poor oral efficacy.
2. Susceptibility to penicillinase.
3. Narrow spectrum of activity.
4. Hypersensitivity reactions 29

30. Phenoxymethyl penicillin (Penicillin V)
•Acid stable.
•Better oral absorption.
•Plasma t½ is 30–60 min.
•Antibacterial spectrum is similar to penicillin G but it is about 1/5 as active
against Neisseria, other gram-negative bacteria and anaerobes.
•Dose: 250–500 mg, children 125–250 mg; given 6 hourly.
30

31. PENICILLINASE-RESISTANT PENICILLINS
•Have side chains that protect the β-lactam ring from attack by staphylococcal
penicillinase.
Methicillin
•It is highly penicillinase resistant but not acid resistant—must be injected.
Cloxacillin
•Highly penicillinase as well as acid resistant.
•More active than methicillin against penicillinase producing Staphylococcus.
31

32. Semisynthetic penicillins active against gram-negative bacilli.
Ampicillin
•Active against all organisms sensitive to PnG.
•More active than PnG for Strep. viridans and enterococci (therefore better suited
for dental infections).
•Dose: 0.5–2 g oral/i.m./i.v. depending on severity of infection, every 6 hours;
children 25–50 mg/kg/day.
32
EXTENDED SPECTRUM PENICILLINS

33. USES:
1. Urinary tract infections
2. Respiratory tract infections
3. Meningitis
4. Subacute bacterial endocarditis: preferred over PnG.
Adverse effects:
Diarrhoea is frequent after oral administration of ampicillin
Interactions:
Hydrocortisone inactivates ampicillin if mixed in the i.v. solution.
33

34. •Close congener of ampicillin.
•Oral absorption is better.
•Incidence of diarrhoea is lower.
•One of the most frequently used antibiotics for treatment of dental infections
250–500 mg TDS given for 5 days.
•Prophylaxis of local wound infection , distant infection (endocarditis)
following dental surgery in susceptible patients.
•Dose: 0.25–1 g TDS oral/i.m. 34
AMOXICILLIN

35. •Family of enzymes produced by many gram-positive and gram-negative
bacteria that inactivate β-lactam antibiotics by opening the β-lactam ring.
•Eg.: clavulanic acid, sulbactam and tazobactam.
•Obtained from Streptomyces clavuligerus.
•Permeates the outer layers of the cell wall of gram negative
bacteria and inhibits the periplasmically located β-lactamase. 35
BETA-LACTAMASE INHIBITORS
Clavulanic acid

36. •Addition of clavulanic acid re-establishes the activity of
amoxicillin against β-lactamase producing resistant Staph. Aureus.
•Skin and soft tissue infections, dental infections.
•Eg. AUGMENTIN, Amoxicillin 250 mg + clavulanic acid 125 mg
tab; 1–2 tab TDS, severe infections 4 tabs 6 hourly.
36
USES:

37. CEPHALOSPORINS
•Group of semisynthetic antibiotics.
•Obtained from a fungus Cephalosporium.
•Mechanism of action : Bactericidal action.
•Chemically related to penicillins; the nucleus consists of a β-lactam ring fused to
a dihydrothiazine ring.
37

38. Classification of Cephalosporins
First generation Second generation Third generation Fourth generation
More active against
gram positive
organism
More selective against
gram positive and
gram negative
organisms
Highly active against
gram negative
organisms
Similar antibacterial
activity as that of
third generation but
highly resistent to
beta lactamases
Parenteral-
Cephalothin
Cefazolin
Cephaloridine
Oral-
Cephalexin
Cephadine
Cefadroxil
Parenteral-
Cefuroxim
Cefoxitin
Oral-
Cefaclor
Cefuroxim axetal
Parenteral-
Cefotaxim
Ceftizoxime
Ceftraxone
Cefoperazone
Oral-
Cefexime
Parenteral-
Cefepime
Cefiperome
38

39. 39

40. FIRST GENERATION CEPHALOSPORINS
•1960 , high activity against gram-positive but weaker against gram-negative
bacteria.
Cefazolin
•PnG sensitive organisms, i.e. streptococci , meningococci, C. diphtheriae,
H.influenzae etc.
•Preferred parenteral first generation cephalosporin, especially for surgical
prophylaxis.
•Dose: 0.25 g 8 hourly (mild cases), 1 g 6 hourly (severe cases) i.m. or i.v.
40

41. Cephalexin
•Orally effective.
•Used in dentistry as an alternative to amoxicillin.
•Dose: 0.25–1 g 6–8 hourly (children 25–100 mg/kg/day).
Cefadroxil
•Close congener of cephalexin.
•Good tissue penetration including that in alveolar bone (tooth socket)
•Exerts more sustained action at the site of infection.
•Dose: 0.5–1 g BD. DROXYL 0.5, 1 g tab, 41

42. Third generation Cephalosporins
Activity against gram-negative Enterobacteriaceae; some inhibit Pseudomonas
as well.
Cefotaxime:
• 3rd generation
• anaerobic & some gram positive bacteria
• meningitis (gram negative bacilli),
• life threatning /hospital aquired infections.
• septicaemias and infections in immunocompromised patients.
42

43. TETRACYCLINE
• Broad spectrum antibiotic.
• Primarily bacteriostatic.
• Inhibit protein synthesis by binding
to 30S ribosomes in susceptible organism.
• Tetracyclines have chelating property.
43
ADMINISTRATION
•Orally taken ½ hr before or 2 hr after food
•Not recommended by i.m. route.
PRECAUTIONS:
1. Should not be used during pregnancy, lactation and in children.
2. Should be avoided in patients on diuretics.
3. Should be used cautiously in renal or hepatic insufficiency.
4. Should not mix injectable tetracyclines with penicillin.
BROAD SPECTRUM ANTIBIOTICS

44. •Epigastric pain, nausea, vomiting and diarrhoea.
•Acute hepatic necrosis in pregnant women.
•Risk of kidney damage.
•Brown discolouration, ill-formed teeth, more susceptible to caries.
•Tetracyclines given between 3 months and 6 years of age affect the crown of
permanent anterior dentition.
•Given during late pregnancy or childhood, tetracyclines can cause temporary
suppression of bone growth.
44
ADVERSE EFFECTS:

45. General medical uses:
The drug of first choice in:
(a) Atypical pneumonia due to
Mycoplasma pneumoniae
(b) Cholera
(c) Brucellosis.
(d) Relapsing fever due to Borrelia
recurrentis.
(g) Rickettsial infections: typhus , Q fever,
etc.
Uses in Orodental conditions :
a) Periodontal inflammation
b) Chronic periodontitis
c) Juvenile periodontitis
45

46. •Broad-spectrum antibiotic.
•Gram-positive and negative bacteria, rickettsiae, chlamydia, mycoplasma etc.
•Inhibits bacterial protein synthesis.
•Attaches to the 50S ribosome and hinder the access of aminoacyl-tRNA to the
acceptor site for amino acid incorporation.
•Primarily bacteriostatic , high concentrations - cidal effect.
•Rapidly and completely absorbed after oral ingestion.
•Oral administration —as capsules; 250–500 mg 6 hourly
46
CHLORAMPHENICOL

47. Adverse effects
1. Bone marrow depression
2. Hypersensitivity reactions
Rashes, fever etc
3. Irritative effects Nausea,
vomiting, diarrhoea, pain on
injection.
4. Superinfections
5. Gray baby syndrome : at
high doses (~100 mg/kg)
USES
•No indication in dentistry despite
its broad-spectrum antimicrobial
action.
•Enteric fever
•Meningitis
•As second choice drug
(a) to tetracyclines for brucellosis,
cholera,
rickettsial and chlamydial infections.
(b) to erythromycin for whooping
cough
47

48. MACROLIDE ANTIBIOTICS
•Antibiotics having a macrocyclic lactone ring with attached sugars..
ERYTHROMYCIN
•Isolated from Streptomyces erythreus.
•Widely employed, mainly as an alternative to penicillin.
•Narrow spectrum.
•Active against gram-positive and a few gram-negative organisms.
Mechanism of Action
Erythromycin is bacteriostatic at low concentration but cidal at high
concentrations. Erythromycin acts by inhibiting bacterial protein synthesis. It
combines with 50S ribosome subunit and interferes with ‘translocation’. 48

49. Uses :
Second choice drug to penicillins for:
•Periodontal/ periapical abscesses
•Necrotizing ulcerative gingivitis
•Postextraction infections
•Cellulitis, etc.
In patients allergic to penicillins, or those with penicillin resistant
infections.
49

50. AZITHROMYCIN
•Has an expanded spectrum.
•Improved pharmacokinetics.
•Better tolerability and drug interaction profiles.
•More active than other macrolides against H. influenzae, and certain
anaerobes like Peptostreptococcus, few Clostridia.
•Better activity against oral spirochetes and gram negative anaerobes.
•Can be used in orodental infections in place of erythromycin.
•Dose: 500 mg once daily 1 hour before or 2 hours after food.
50
NEWER MACROLIDES

51. CLINDAMYCIN
•Dental infections - anaerobic bacteria.
•Patients resistant to penicilin.
•Dentoalveolar abscesses , bone infections caused by Staphylococci or
Bacteroides.
•Alternative antibiotic for prophylaxis of endocarditis due to postextraction
bacteraemia in patients with damaged heart valves or other risk factors.
•Dose: 150–300 mg QID oral; 200–600 mg i.v. 8 hourly.
51

52. AMINOGLYCOSIDES
 Broad spectrum of action
 Rapid bactericidal effect
 Inhibitors of Protein Synthesis
Systemic aminoglycosides
•Streptomycin
•Amikacin
•Gentamicin
•Kanamycin
•Tobramycin
Topical aminoglycosides
•Neomycin
•Framycetin
USES
• Gram-positives, except Streptococus and
Enterococcus.
• Combine with aminoglycoside (Gentamicin or
Streptomycin) & penicillin, ampicillin or
vancomycin produces a synergistic bactericidal
effect.
• In serious infection, with beta-lactams or
fluoroquinolones.
• Gram-negative nosocomial infections
52

53. TOXICITIES
•Ototoxicity
-Cochlear damage
-Vestibulaar damage
•Nephrotoxicity
•Neuromuscular blockade
53

54. Polyenes: Amphotericin B (AMB), Nystatin,
AMPHOTERICIN B (AMB)
•Combine with ergosterol present in fungal cell membrane, and create micropores
through which ions, amino acids and other water-soluble substances move out.
•Candida albicans, Histoplasma capsulatum,, aspergillus etc.
•Not absorbed orally, excretion occurs slowly both in urine and bile.
•Uses: can be used topically for oral, vaginal and cutaneous candidiasis
54
ANTIFUNGAL DRUGS

55. NYSTATIN
•Used only locally.
•In dentistry, topically applied nystatin is the 2nd choice drug to clotrimazole for oral thrush,
denture stomatitis, antibiotic associated stomatitis, corticosteroid associated oral candidiasis
and mucocutaneous candidiasis of lips, etc
•1 mg tablet is placed in the mouth to dissolve slowly 4 times a day, or it can be crushed and
suspended in glycerine for application on the lesions.
•Bitter foul taste and nausea are the side effects.
55

56. •To determine the severity of infection.
•To evaluate state of patient’s host defense mechanisms.
•To determine whether patient should be treated by general dentist or
specialist.
•To treat infection surgically.
•To support the patient medically.
•Choose and prescribe appropriate antibiotic.
•Proper antibiotic administration.
•Monitoring the patient.
56
PRINCIPLES OF ANTIBIOTIC THERAPY

57. CHOICE OF AN ANTIMICROBIAL AGENT
• Age
• Renal and hepatic function
• Local factors
• Drug allergy
• Impaired host defence
• Pregnancy
1.Patient factors
• Spectrum of activity
• Type of activity
• Sensitivity of the organism
• Relative toxicity
• Pharmacokinetic profile
3.Drug factors
2.Organism related
considerations
57

58. Age :
•Larger doses of chloramphenicol - grey baby syndrome.
•Sulfonamides displace bilirubin from protein binding sites—can cause
kernicterus in the neonate.
•The t½ of aminoglycosides is prolonged in the elderly and they are more
prone to develop VIII nerve toxicity.
•Tetracyclines accumulate in the developing teeth and bone —discolour and
weaken them— are contraindicated below the age of 6 years.
58

59. Renal and hepatic function
59

60. Local factors :
(a)Presence of pus and secretions
(b)Presence of necrotic material or foreign body
(c)Haematomas foster bacterial growth
(d)Lowering of pH at site of infection
Drug allergy :
•Erythromycin or Clindamycin are the alternative drugs for
dental infection in patients allergic to penicillin
60

61. Impaired host defence :
•Pyogenic infections occur readily in neutropenic patients; while if cell-
mediated immunity is impaired (e.g. AIDS), infections by low-grade pathogens
and intracellular organisms abound.
•In an individual with normal host defence, a bacteriostatic AMA may achieve
cure; while intensive therapy with cidal drugs is imperative in those with
impaired host defence.
61

62. Pregnancy
Safe drugs
> Penicillins
> Cephalosporins
> Erythromycin
Contraindicated
> Tetracyclines
> Aminoglycosides
> Fluoroquinolones
> Cotrimoxazole
> Chloramphenicol
> Sulfonamides
62

63. Genetic factors:
•Sulfonamides, chloramphenicol and fluoroquinolones are likely to produce
haemolysis in G-6PD deficient patient.
Organism-related considerations
Antibiotic susceptibility test
Disc diffusion test
63

64. Minimum inhibitory concentration (MIC)
•The lowest concentration of an antibiotic which prevents visible growth of a
bacterium determined.
•Done in microwell culture plates using serial dilutions of the antibiotic.
•For treatment purposes, the dosage of antibiotic given should yield a peak
body fluid concentration 3-5 times higher than the MIC or MIC x 4 = dosage to
obtain peak achievable concentration.
64

65. Broth dilution methods showing MIC and MBC
Minimum bactericidal concentration (MBC)
•MBC is the concentration of the antibiotic which kills 99.9% of the bacteria.
65

66. DRUG FACTORS
1. Spectrum of activity:
•For definitive therapy → a narrow spectrum drug is preferred.
•For empirical therapy → often a broad-spectrum drug is preferred.
2. Type of activity:
•A bactericidal antibiotic may be preferred over bacteriostatic.
•Acute infections generally resolve faster with bactericidal than with
bacteriostatic drugs 66

67. 3. Relative toxicity:
• Obviously, a less toxic antibiotic is preferred, e.g. a β-lactam over an
aminoglycoside or erythromycin over clindamycin.
4. Pharmacokinetic profile:
• A drug, which penetrates better and attains higher concentration, is likely
to be more effective.
67

68. COMBINED USE OF ANTIMICROBIALS
More than one AMAs are frequently used concurrently. The objectives of using
antimicrobial combinations are:
1. To achieve synergism:
Eg.:
1. combination of a β-lactamase inhibitor clavulanic acid or sulbactam with amoxicillin or ampicillin for β-
lactamase producing H. influenzae.
2. Penicillin/ampicillin + streptomycin/gentamicin for enterococcal SABE.
3. Penicillin + sulfonamide for actinomycosis
68

69. 2. To reduce severity or incidence of adverse effects.
3. To prevent emergence of resistance.
4. To broaden the spectrum of antimicrobial action.
a) Treatment of mixed infection
b) Initial treatment of severe infections
69

70. Disadvantages of antimicrobial combinations
1. They foster a casual rather than rational outlook in the diagnosis of
infections and choice of AMA.
2. Increased incidence and variety of adverse effects.
• Toxicity of one agent may be enhanced by another, e.g. vancomycin
tobramycin and gentamicin + cephalothin produce exaggerated kidney
failure.
3. Increased chances of superinfections.
4. Higher cost of therapy.
70

71. PROPHYLACTIC USE OF ANTIMICROBIALS
Refers to the use of AMAs for preventing the setting in of an infection or suppressing
contacted infection before it becomes clinically manifest.
Antimicrobial prophylaxis in dentistry
This is warranted for two distinct purposes viz.
(a) prevention of local wound infection
(b) prevention of distant infection (e.g. bacterial endocarditis) in predisposed patients
following dental procedures.
71

72. Prophylaxis of dental wound infection
•Clear risk of wound infection.
•Simple extractions and minor periodontal procedures does not require.
•Incidence of postoperative infection is higher when oral surgery had lasted 2 hours or more
eg. prosthesis insertion into the bone or soft tissue, such as dental implants and extensive
reconstructive surgeries.
•All orodental procedures which disturb/ damage mucosa including extractions, scaling, etc.
need to be covered by prophylaxis in diabetics, corticosteroid recipients and other
immunocompromised subjects
72

73. 73

74. PROPHYLAXIS OF DISTANT INFECTION
• Gentamicin 120 mg (2 mg/kg) i.m./i.v. may be given just before the dental
procedure in addition to amoxicillin (or its substitute) and another dose of
amoxicillin 500 mg (12.5 mg/kg) be repeated 6 hours after the procedure.
• If patient is allergic to penicillin :
vancomycin 1 g (20 mg/kg) i.v. over 2 hours + gentamicin 120 mg (2 mg/kg)
i.m./i.v. just before the procedure.
74

75. FAILURE OF ANTIMICROBIAL THERAPY
1. Improper selection of drug, dose, route or duration of treatment.
2. Treatment begun too late.
3. Failure to take necessary adjuvant measures, e.g. drainage of abscesses.
4.Poor host defence—as in leukaemias, neutropenia and other causes; especially
if bacteriostatic AMA is used.
5. Infecting organism present behind barriers, such as vegetation on heart valves
(in SABE), inside the eyeball, blood-brain barrier.
75

76. 1. Penicillins.
2. Cephalosporins.
3. Erythromycins.
4. Clindamycin and Lincomycin.
5. Metronidazole.
6. Aminoglycosides.
7. Fluoro quinolones – ciprofloxacin.
8. Sulfonamides and trimethoprim
76
ANTIBIOTICS USEFUL FOR OROFACIAL INFECTIONS:

77. AHA RECOMMENDATIONS
PROPHYLAXIS
RECOMMENDED:
1.Extractions
2.Periodontal surgery
3.Implants placement
4.Endodontic surgery
5.Subgingival antibiotic fiber
strips
6.Intraligamentary LA
injections.
NOT RECOMMENDED:
1.Restorative dentistry
2.LA injections
3.Intracanal endodontic
treatment
4.post-op suture removal
5.Oral radiographs
77

78. Odontogenic infection, oral and maxillofacial implications
•Initial stage- Aerobic bacteria invade.
•Severe infection- Aerobic and anaerobic bacteria invade.
•Advanced stage- anaerobic infection.
Pericoronitis :
•Acute pericoronitis, if severe, may require antibiotic therapy.
•Treatment - debridement, drainage of the site,
penicillin 500 mg qid,
amoxacillin 500mg qid,
clindamycin 300mg qid
Dento Alveolar Abscess:
Penicillin is the drug of choice
78

79. Soft tissue wounds :
•open for six hours or more, (considered infected,)
•if primary closure is elected, a delayed primary closure is preffered.
•delayed technique cannot be utilized,-antibiotic support is helpful.
•early primary closure -amoxicillin with clavulanic acid
Chronic inflammatory periodontal diseases :
•TOPICAL MEASURES - Tetracyclins, metronidazole 250mg tid, , penicillins500mg qid,
cephalosporins.
ANUG
Topical measures with systemic antibiotic penicillin, metronidazle 400mg qid, 79

80. For hospitalalized/ when inta-venous therapy is indicated-
Aqueous penicillin, 2 million Units IV Q6h, metronidazole 500mg q6h for 4 - 6 weeks
OR
Ampicillin/sulbactum 1.5 to 3.0 gm IV q6h for 2 days then amoxacillin/clavulanate
(augmentin)875, 125.mg PO bd for 4 to 6 weeks.
For out patient treatment
penicillin V 2gm + metronidazole 500mg q8h for 2 to 4 weeks after last sequestrum removal
and patient with out symptons.
OR
cefoxitin 1 gm q8h IV OR IM
cephalexin 500mg q6h PO for 2 to 4 weeks
OR
clindamycin 600, 900mg q6h IV then clindamycin 300, 450 mg PO.
Antibiotic regimen for osteomyelitis
80

81. Regimen for fracture
•therapeutic doses for 10 to 14 days.
•should begin as early as possible after diagnosis.
Pre-operatively
penicillin 2 million units or cefazolin 0.5 gm-1.5 gm 12 hr [25- 50 mg/kg].
Post-operatively
Penicillin 500mg 6 hr [30-40 mg /kg]
Cephalexin 500mg 6 hr [25- 50 mg/kg]
In suspected intra-cranial contamination-
Pre-operatively- naficillin 2-6 gm 6hr+ gentamycin 3-5mg/kg 8 hr
Post-operatrively- cephalexin 500mg 6 hr[25-50 mg/kg] 81

82. 82

83. 83

84. 84
ANTIBIOTIC RESISTANCE Resistance arises through one of three mechanisms:
 natural resistance in certain types of bacteria,
genetic mutation,
one species acquiring resistance from another.

85. 85
PUBLC HEALTH IMPORTANCE OF THE ANTIBIOTICS
Limited supportive care provided by health
professionals.
Difficulty in treating various infections
Antibiotic Resistance – Economic burden to the
healthcare system.
Increased prevalence of resistant and multi-resistant bacterial strains
An overview of antimicrobial resistance and its public health significance, Brazilian journal of Microbiology 45, 1, 1-

86. 86
S
U
M
M
A
R
Y
DEFINITION OF ANTIBIOTICS
HISTORY
CLASSIFICATION OF ANTIBIOTICS
COMBINED USE OF ANTIMICROBIAL AGENTS
ANTIBIOTICS USEFUL FOR OROFACIAL INFECTIONS
PROPHYLACTIC ANTIBIOTICS
ANTIBIOTIC RESISTANCE
PUBLIC HEALTH SIGNIFICANCE OF ANTIBIOTICS

87. Antibiotics are used to treat infections and are also responsible for making
them more difficult to treat because of their misuses and development of
resistance.
The only way to keep antibiotics useful is to use them appropriately and
judiciously.
CONCLUSIONS
87

88.  THE PHARMACOLOGIC BASIS OF THERAPEUTICS GOODMAN & GILMAN 11THED
 ESSENTIALS OF MEDICAL PHARMACOLOGY
K.D.TRIPATHI 5TH ED
 TEXTBOOK OF PHARMACOLOGY - TOPAZIAN
 TEXTBOOK OF MUCROBIOLOGY- C. P. BAVEJA 3RD ED.
 BURKET’S ORAL MEDICINE, 12TH ED
 SYMPOSIUM ON ANTIMICROBIAL THERAPY, GENERAL PRINCIPLES OF ANTIMICROBIAL
THERAPY
 AN OVERVIEW OF ANTIMICROBIAL RESISTANCE AND ITS PUBLIC HEALTH
SIGNIFICANCE, BRAZILIAN JOURNAL OF MICROBIOLOGY 45, 1, 1-5(2014)
REFERENCES
88

89. 89