Presentation antibiotics

1. Maninder Kaur
Intern
Antibiotics
in Oral and
Maxillofacial
Surgery

2. INTRODUCTION
ANTIBIOTIC TERMINOLOGY
DEFINITION: SUBSTANCES DERIVED FROM
MICROORGANISMS WHICH SUPPRESS THE GROWTH / KILL
THE MICROORGANISMS AT A VERY LOW CONCENTRATION
OR
A CHEMICAL SUBSTANCE PRODUCED BY
MICROORGANISMS HAVING THE PROPERTY OF INHIBITING
THE GROWTH OF OR DESTROYING OTHER
MICROORGANISMS IN HIGH DILUTION
CHEMOTHERAPY :TREATMENT OF SYSTEMIC INFECTIONS
WITH SPECIFIC DRUGS THAT SELECTIVELY SUPPRESS THE
INFECTING MICROORGANISM WITHOUT SIGNIFICANTLY
AFFECTING THE HOST.

3. HISTORY
⦿ (A) The period of emperical use South American Indians used
the bark of the cinchona tree to extract quinine to control malaria
and mercury was known to cure syphilis in the late
1400's,‘mouldy curd’ by Chinese on boils, mercury by
Paracelsus (16th century) for syphilis, Cinchona bark (17th
century) for fevers.
⦿ (B) Ehrlich’s phase of dyes & organometallic compounds (1890-
1935): methylene blue, tryptan red, etc.
He coined the term ‘Chemotherapy’

4. HISTORY
⦿ (C) The Modern Era of chemotherapy was ushered in by
Domagk in 1935 by demonstrating the therapeutic effect of
prontosil , a sulfonamide dye in pyogenic infection.
Other pioneers in the field of antibiotics were Louis Pasteur,
Alexander Fleming, Chain Florey , Waksman.
All received Nobel prizes for their discoveries.

5. CLASSIFICATION
BASED ON TYPE OF ORGANISM THEY ACT
UPON:
1. Antibacterial –
2. Antifungal -
3. Antiviral-
4. Antiprotozoal-
penicillin
amino glycosides
erythromycin
griseofulvin
amphotericin
ketoconazole
acyclovir
amantidine
zidovudine
metronidazole
chloroquine

6. - Macrolide antibiotics
○ Erythromycin, Roxithromycin, Azithromycin etc
⚫ Polypeptide antibiotics
○ Polymyxin – B, colistin, Bacitracin, Tyrothricin etc
⚫ Glycopeptides
○ Vancomycin, Teicoplamin
⚫ Oxazolidinase
○ Linezolid
⚫ Nitrofuran derivatives
○ Nitrofurantoin, Furazolidine
⚫ Nitroimidazoles
○ Metronidazole, Tinidazole
⚫ Polyene antibiotics
○ Nystatin, Amphotericin – B, Hamycin
⚫ Azole derivatives
○ Miconazole, clotrimazole, ketoconazole, fluconazole

7. CLASSIFICATION
(v) TYPE OFACTION:
13
Primarily Bacteriostatic Primarily
Bactericidal
Sulfonamides Penicillins , Cephalosporins,
Tetracyclines Aminoglycosides,
Chloramphenicol Vancomycin,
Erythromycin Ciprofloxacin, Isoniazid ,
Ethambutol Rifampin, Cotrimoxazole,

8. SOURCE
⦿ Fungi
⚫Penicillin, Cephalosporin, Griseofulvin.
⦿ Bacteria
⚫Polymyxin B, Colistin, Bacitracin, Tyrothricin
Aztreonam.
⦿ Actinomycetes
⚫Aminoglycosides, Tetracyclines, Chloramphenicol,
Macrolides, Polyenes.

9. PRINCIPLES OF ANTIBIOTIC THERAPY
PRINCIPLE 1: TO DETERMINE THE SEVERITY OF
INFECTION
PRINCIPLE 2: TO EVALUATE STATE OF
PATIENT’S HOST DEFENSE MECHANISMS
PRINCIPLE 3:TO DETERMINE WHETHER
PATIENT SHOULD BE TREATED BY GENERAL
DENTIST OR SPECIALIST
PRINCIPLE 4:TO TREAT INFECTION
SURGICALLY

10. PRINCIPLE 5 :TO SUPPORT THE PATIENT MEDICALLY
PRINCIPLE 6 : CHOOSE AND PRESCRIBE
APPROPRIATE ANTIBIOTIC
PRINCIPLE 7 : PROPER ANTIBIOTIC
ADMINISTRATION
PRINCIPLE 8 :MONITORING THE PATIENT

11. PRINCIPLES FOR CHOOSING APPROPRIATE
ANTIBIOTIC
(I) IDENTIFICATION OF THE CAUSATIVE
ORGANISM:-
⦿ Scientifically - laboratory
⦿ Emperically – knowledge of
the pathogenesis & clinical
presentation.
⦿ Initial emperical therapy
instituted with a fair degree of reliability.

12. PRINCIPLES FOR CHOOSING APPROPRIATE
ANTIBIOTIC
⦿ Typical odontogenic infection is caused by a mixture of aerobic
& anaerobic bacteria (70%)
⦿ Aerobic bacteria – 5% (gm positive cocci)
⦿ Pure anaerobic bacteria – 25% (gm positive cocci – 30% & gm
negative rods – 50%)
⦿ All are sensitive to penicillin & penicillin like drugs, but
Fusobacterium frequently resistant to erythromycin (apprx. 50%)

13. PRINCIPLES FOR CHOOSING APPROPRIATE
ANTIBIOTIC
Pathobiology of mixed odontogenic infection:-
Entry of organisms
(aerobic)
Effects underlying
tissues
Cellulitis develops Condtion resolves on
treatment
Hypoxic acidotic condition
Tissue destruction and
abscess formation
(anaerobic)
Production of
enzymes and toxins

14. PRINCIPLES FOR CHOOSING
APPROPRIATE ANTIBIOTIC
CULTURES SHOULD BE PERFORMED:-
1. Pt. with an infection has compromised host defenses
2. Received appropriate treatment for 3 days without
improvement
3. Postoperative wound infection
4. Recurrent infection
5. Actinomycosis is suspected, or
6. Osteomyelitis is present

15. PRINCIPLES FOR CHOOSING
APPROPRIATE ANTIBIOTIC
(II) DETERMINATION OF ANTIBIOTIC
SENSITIVITY:-
⦿ Not responded to initial antibiotic therapy or a postoperative
wound infection – causative agent identified & the antibiotic
sensitivity determined.

16. DISK DIFFUSION METHOD
RATIONALE :
⦿ Antibiotics diffuse into the agar and inhibit the growth
of sensitive bacteria in a semicircular zone around the disc.
⦿ When the resistance to a given agent is present, the zone
radius will be reduced or these will be no zone at all.

17. Advantages :
⦿ Simple to perform
⦿ Inexpensive
⦿ Provides data within 18 to 24 hours
Disadvantages :
⦿ It is only semi quantitative and is not useful for
many flow growing or fastidious organisms.
⦿ It has not been adequately standardized for
anaerobic bacteria.

18. PRINCIPLES FOR CHOOSING APPROPRIATE
ANTIBIOTIC
⦿ The result of these studies provide the information needed to
prescribe the most appropriate antibiotic.
⦿ Penicillin is excellent for treatment of streptococcusinfection & is
good to excellent for the major anaerobes of odontogenic
infections.
⦿ Erythromycin - Streptococcus,Peptostreptococcus & Prevotella
but is ineffective against Fusobacterium.

19. PRINCIPLES FOR CHOOSING APPROPRIATE
ANTIBIOTIC
⦿ Clindamycin – streptococcus& major anaerobic groups.
⦿ Cephalexin – moderately active against streptococcus& is good to
excellent against anaerobes.
⦿ Metronidazole – no activity against streptococcusbut has
excellent activity against anaerobes.

20. PRINCIPLES FOR CHOOSING APPROPRIATE
ANTIBIOTIC
(III) USE OF A SPECIFIC, NARROW SPECTRUM
ANTIBIOTIC:-
Advantages -
⦿ less chances of developing resistant organisms.
E.g. streptococcussensitive to penicillin , cephalosporin and
tetracycline.
⦿ Minimizes the risk of super infections.
E.g. moniliasis and gram negative pneumonias

21. PRINCIPLES FOR CHOOSING APPROPRIATE
ANTIBIOTIC
(IV) USE OF THE LEAST TOXIC ANTIBIOTIC:-
⦿ Equally effective but less toxic drugs have to be used.
E.g. bacteria causing odontogenic infection susceptible to both
penicillin and chloramphenicol.
⦿ More toxicity present with the latter drug.

22. PRINCIPLES FOR CHOOSING APPROPRIATE
ANTIBIOTIC
(V) PATIENT DRUG HISTORY:-
⦿ Previous allergic reactions
⦿ Previous toxic reactions
⦿ Allergy rate to penicillin - 5 %
⦿ Cross sensitivity Penicillins and cephalosporins.
⦿ Toxic reactions - identify the drug and precise reaction
⦿ Likely to happen again.

23. PRINCIPLES FOR CHOOSING APPROPRIATE
ANTIBIOTIC
(Pharmacologic factors in antibiotic selection)
(VI) USE OF A BACTERICIDAL RATHER THAN A
BACTERIOSTATIC DRUG:-
Advantages:
1. Less reliance on the host resistance
2. killing of the bacteria by the antibiotic itself
3. Faster results
4. Greater flexibility with dosage intervals.
⦿Used especially when the host defenses are low.

24. PRINCIPLES FOR CHOOSING APPROPRIATE
ANTIBIOTIC
(VII) USE OF THE ANTIBIOTIC WITH A
PROVEN H/O SUCCESS:-
⦿Critical observation of the clinical effectiveness over a prolonged
period -----assessment of
⦿ Frequency of treatment success and failures
⦿Frequency of adverse reactions
⦿Frequency of side effects
⦿Standards for use

25. PRINCIPLES FOR CHOOSING APPROPRIATE
ANTIBIOTIC
(VIII) COST OF THE ANTIBIOTIC:-
⦿ Difficult to place a price tag on health.
⦿ In some situations, more expensive antibiotic is the drug of
choice.
⦿ In other situations, there may be a substantial difference in price
for drugs of equal efficacy.
⦿ Surgeon should consider the cost of the antibiotic prescribed.

26. PRINCIPLES FOR CHOOSING APPROPRIATE
ANTIBIOTIC
(IX) ENCOURAGE PATIENT COMPLIANCE:-
⦿ Dosage interval that encourages compliance
OD 80%
BID 69%
TID 59%
QID 35%
⦿ Non-compliant start feeling better
3-5 days
>7 days
50%
20%
⦿ Antibiotic that would have the highest compliance would be the
drug given OD for 4 or 5 days.

27. Indications for use of
antibiotics
⦿ Rapidly progressive swelling
⦿ Diffuse swelling
⦿ Compromised host defenses
⦿ Involvement of facial spaces
⦿ Severe pericoronitis
⦿ Osteomyelitis

28. Use of antibiotics is not
necessary
⦿ Chronic well localized abscess
⦿ Minor vestibular abscess
⦿ Dry socket
⦿ Mild pericoronitis

29. INDICATIONS OF EMPIRICAL
ANTIBIOTIC THERAPY :
⦿ The site and feature of the infection have been
well defined.
⦿ The circumstances leading to the infection are
well known.
⦿ Organisms that most commonly cause such
infections.

30. EMPIRIC ANTIBIOTIC TREATMENT
Early infection (first 3 days of symptoms and mildly
immunocompromised)
⦿ Penicillin
⦿ Clindamycin
⦿ Cephalexin
Late infection (After 3 days of symptoms or moderately to severely
immunocompomised)
⦿ Clindamycin
⦿ Revicillin and metranidazole.
⦿ Ampicillin and sulbactam.
⦿ Cephalosporin (first or second generation).
-Mild, moderate and severe compromised based on CD4 / viral
loads, glycemic control, and the degree of alcoholic related disease.

31. 7)PROPER ANTIBIOTIC ADMINISTRATION
⦿ Proper dose.
⦿ Proper time interval.
⦿ Proper route of administration.
⦿ Combination antibiotic therapy.
⦿ It is indicated in few situations like in:
⚫ Situations of life threatening situations of unknown cause.
⚫ To increase the bactericidal effect of a specific organism.
⚫ Prevention of the rapid emergence of resistant bacteria.
- Empiric therapy of certain odontogenic infections like when the
infection progresses to the lateral and retropharyngeal spaces and
caused by aerobes and anaerobes.

32. PRINCIPLES OF ANTIBIOTIC DOSING
⦿ GOAL :
1. To aid the body’s defenses to clear the
tissues of microbial pathogen by achieving
antibiotic levels in the infected area to or greater
than the MIC

33. ANTIBIOTIC DOSING VARIABLES
⦿ PHARMACOKINETIC FACTORS
Diffusion to the site of action
1.Tissue pH.
2.Lipid and water solubility
3.Plasma protein binding
⦿ INOCULUM EFFECT- It is defined as a laboratory
phenomenon that results in significantly increased MIC
required of an antibiotic. When the number of inoculated
organisms increases. It generally occurs in case b-lactum
antibiotics and b-lactamase producing bacteria
(review of infectious diseases vol.2 number.3 may- june 1989)
⦿ SURFACE AREA TO VOLUME RATIO

34. Lipophilic antibiotics
Tetracyclines,macrolides,fluoroquinolones
Pass better through tissue barriers
Effective against intracellular pathogens
Drug depot within macrophages

35. Hydrophilic antibiotics
Beta-lactams,vancomycin,aminoglycosides
Confined to ECF
Poor diffusion through capillaries

36. PLASMA PROTEIN BINDING
Limited plasma protein binding
Diffuse easily through capillary walls
and
other barriers

37. PRINCIPLES OF ANTIBIOTIC THERAPEUTIC DOSE
(I) PROPER DOSE:-
⦿ Dose – 3 to 4 times the MIC
for e.g. penicillinase producing staphylococcus -
MIC 6 µg/ ml , plasma level - 18µg /ml
⦿ Administration of doses above this level – increases the
likelihood of toxicity & is wasteful.
⦿ Sub therapeutic levels - mask the infection ,recurrence.
51

38. DRUG DOSE CALCULATION
⦿ BASED ON BODY SURFACE AREA
Individual dose = BSA[m2] x adult dose
1.7
⦿ BASED ON BODY WEIGHT
Individual dose = BW[kg] x average
70 adult dose

39. IN PEDIATRICS
YOUNG’S FORMULA :
CHILD DOSE = Age x adult dose
Age + 12
DILLING’S FORMULA :
CHILD DOSE = Age x adult dose
20

40. NEONATES AND INFANTS
⦿ Greater percentage of body weight
compared with body water
Greater volume of distribution
Increased serum half lives
⦿ Reduced gastric emptying
⦿ Reduced plasma protein binding
⦿ Reduced GFR

41. ELDERLY
⦿ Reduced host defenses
⦿ Underlying illness
⦿ Reduced total body water
⦿ Lean body mass
⦿ Reduced cardiac output
⦿ Reduced gastric emptying time
⦿ Decreased renal function

42. ⦿ LOADING DOSE; This is a single or few
quickly repeated doses given in the beginning to
attain target concentration capacity.
⦿ MAINTAINANCE DOSE: This is the dose
repeated at specific interval after attainment of
target cycles per second

43. ANTIBIOTIC LOADING DOSES
longer
⦿ INDICATIONS :
1. The half-life of the antibiotic is
than 3-hours.
2. A delay of longer than 12-hours to
achieve therapeutic blood levels is unacceptable.
Because most acute orofacial infections
begin and peak rapidly

44. DURATION OF ANTIBIOTIC DOSING
⦿ The ideal antibiotic duration is the shortest
time that will prevent both clinical and
microbiological relapse.
Clinical improvement of the patient
Remission of infection.

45. PRINCIPLES OF ANTIBIOTIC THERAPEUTIC DOSE
(II) Proper time interval:-
⦿ Established plasma t 1/2 – one half of the absorbed dose is
excreted.
⦿ Usual dosage interval for therapeutic use of antibiotics - Four
times the half life.
E.g. cefazolin t 1/2 - 2 hours.

46. PRINCIPLES OF ANTIBIOTIC THERAPEUTIC DOSE
(III) Proper route of administration:-
⦿In some infections , only the parenteral route produces necessary
serum level of antibiotic
For e.g. Penicillin V oral - 2 gm
Plasma level - 4 µG/ mL
⦿Oral route - variable absorption.
⦿Serious well established infection - parenteral route

47. PRINCIPLES OF ANTIBIOTIC THERAPEUTIC DOSE
(IV) Consistency in Route of Administration:-
⦿After initial response , immediate discontinuation of parenteral
route - Recurrence
⦿Maintenance of peak blood levels of antibiotic for an adequate
period is important – max. tissue penetration & effective
bactericidal action.
⦿After the 5th day of parenteral administration, the blood levels
achievable with oral administration are usually sufficient.

48. PRINCIPLES OF ANTIBIOTIC THERAPEUTIC DOSE
(V) Combination Antibiotic therapy:-
⦿ Life threatening sepsis of unknown cause
⦿ Increased bactericidal effect against a specific µorg is desired.
E.g. treatment of infections caused by enterococcus
⦿ Prevention of rapid emergence of resistant bacteria
E.g. tuberculosis
⦿ Empiric treatment of certain odontogenic infections
E.g. Penicillin G & Metronidazole

49. COMBINATION ANTIBIOTIC THERAPY
Combination therapy with two or more antibiotics is
used in special cases:
⦿ Prevent the emergence of resistant strains
⦿ To treat emergency cases during the period when
an etiological diagnosis is still in progress
⦿ To take advantage of antibiotic synergism

50. ADVANTAGES vs DISADVANTAGES
⦿ Broad antibacterial
spectrum
⦿ Reduced dose for each
agent.
⦿ Antibiotic synergism
⦿ Decreased adverse drug
reactions
⦿ Greater likelihood of
adverse reactions
⦿ Antibiotic antagonism
⦿ Increased financial costs
⦿ Greater microbial
resistance
⦿ Resistance genes
⦿ Increased risk of
superinfection

51. SYNERGISTIC ANTIBIOTIC
COMBINATION
⦿ Cell wall inhibitors and aminoglycosides
⦿ Beta-lactams with beta-lactamase inhibitors
⦿ Beta-lactams that act on different PBPs
⦿ Sulfonamides and trimethoprim

52. PRINCIPLES OF ANTIBIOTIC THERAPEUTIC DOSE
⦿ Should be avoided when not specifically indicated.
⦿ Usual result – broad spectrum exposure that leads to depression
of the normal host flora & inc opportunity for resistant bacteria
to emerge.
⦿ For routine infections, the disadvantages of combination therapy
outweigh the advantages.
67

53. POSTANTIBIOTIC EFFECTS
⦿ Is the persistent supression of microbial growth
after short time exposure to an antimicrobial
agent.
⦿ MECHANISM :
Is the time necessary to recover from
sublethal structural and metabolic alterations that
prevents resumption of bacterial regrowth.

54. FACTORS INFLUENCING PAE
⦿ The particular organism
⦿ Inoculum size
⦿ Growth medium
⦿ Organism growth phase
⦿ Mechanism of action of antibiotic
⦿ Duration of exposure to the drug

55. ANTIBIOTIC SIDE EFFECTS
Side effects are unwanted but often unavoidable
pharmacodynamic effects that occur at therapeutic doses.
1) HAEMATOLOGIC EFFECTS
a) Leucopenia and thrombocytopenia: Beta lactams
sulfonamides(Cotrimazole)
b) Anaemia: Beta lactam- Autoimmune anaemia
Cotrimazole- Folate deficiency- Megaloblastic anaemia
Chloramphenicol- Aplastic anaemia.
c) Platelet dysfunction: Anti pseudomonal penicillins- Impaired
platelet aggregation.
d) Clinical bleeding: Moxalactam- Interferes with vit.K depended
clotting factor synthesis.
Trovafloxacin- Increases prothrombin time.

56. 2) HYPERSENSITIVITY EFFECTS
Drug fever: 10-15% of unexplained fever in hospitalized patients.
Beta lactams, Sufonamides.
Drug rashes: Itching, urticaria, maculo popular rashes.
Beta lactams, sulfonamides.
Anaphylactic reactions: Beta lactams, rare in Sulfonamides.
Serum sickness: Develops 2 weeks after exposure- Beta lactams.
Photosensitivity reactions: Tetracycline, Sparfloxacin
Rare with Doxycyclin, minocycline
Drug induced Systemic Lupus Erythematosus(SLE):
Minocyclin, Isoniazide, Nitrofurantoin, Griseiofulvin.

57. 3) NEUROLOGIC EFFECTS
a) Encephalopathy: Trovafloxacin- Mental
confusion
Clarithromycin
b) Seizures: Ciprofloxocin, Imipenem,
Trovafloxacin.
It depends on seizure threshold of patient.
c) Neuromuscular blockade: Aminoglycosides
d) Peripheral neuropathy: Isoniazide, Griseiofulvin
e) Muscular tremors and myalgias: Trovafloxacin
f) Ototoxicity: Aminoglycisides, Parenteral
Erythromycin
g) Blindness: Ethambutol, Chloroquine.

58. 4) PULMONARY EFFECTS
a) Acute pulmonary reactions: Rifampicin- Flu like illness.
Nitrofurantoin: Varying degrees of respiratory
Insufficiency, Pleural effusion.
b) Chronic pulmonary reaction: Nitrofurantoin-
Pulmonary fibrosis.
5) CARDIAC EFFECTS
a) Ventricular arrhythmias: Erythromycin
b) Hypotension: Trovafloxacin, Amphotericin-B

59. 6) GASTROINTESTINAL EFFECTS
a)Nausea and vomiting
Clarithromycin,Amoxicillin/Clavulanate,Azithromycin,
Doxicycline,Minocycline.
b) Non-clostridium difficile diarrhea:
Macrolides,Ampicillin, Trovafloxacin
c)Cl. Difficile diarrhoea
Beta lactums, Quinolones
d)Anti pancreatitis
Trovafloxacin.

60. 7)HEPATIC SIDE EFFECTS
a) drug induced hepatitis
-Isoniazide- elevates serum transaminas,
Trovafloxacin,Oxacillin
b) Cholestasis
-Erythromycin,Nitrofurantoin
c) Hepatic necrosis
-PAS, Ketoconazole or Trovafloxacin
8)NEPHROTOXIC SIDE EFFECTS
a) Nephrotoxicity
Aminoglycosides-Tubular toxicity.
Tetracyclines, Polymyxin –B
b) Interstitial nephritis
Beta lactamase therapy.

61. ANTIBIOTIC RESISTANCE
⦿ The organisms continue to multiply even in the
presence of antibiotic.
⦿ Resistance to an antimicrobial can arise
(1) Mutation in the gene that
determines sensitivity/resistance to the agent or
(2) Acquisition of
extrachromosomal DNA (plasmid) carrying a
resistance gene.
(3) Bacteriophages.
(4) Mosaic genes
Mutation: random, undirected, heritable variation caused
by an alteration in the nucleotide sequence at some
point of the DNA of the cell

62. CROSS RESISTANCE
Single mechanisms confers resistance to
multiple antimicrobial agents
MULTIPLE RESISTANCE
Multiple mechanisms
Cross resistance - closely related antimicrobial
agents
Multiple resistance - unrelated antimicrobial
agents.

63. MISUSE OF ANTIBIOTICS
⦿ 1) Treatment of untreatable infections
⦿ 2) Therapy of fever of unknown origin
⦿ 3) Improper dosage
⦿ 4) Inappropriate reliance on
chemotherapy alone
⦿ 5) Lack of adequate bacteriological
information

64. DEVELOPMENT OF DRUG RESISTANCE
⦿ Refers to unresponsiveness of a microorganism to an AMA
⦿ Natural Resistance
⦿ Acquired Resistance
.

65. DEVELOPMENT OF DRUG RESISTANCE
⦿ Single step mutation
E.g. Enterococci to Streptomycin, E.coli & Staphylococci
to rifampin
⦿ Multistep mutation
E.g. resistance to erythromycin, tetracyclines &
chloramphenicol by many organisms.

66. DEVELOPMENT OF DRUG RESISTANCE
⦿ Gene Transfer:- from organism to another can occur by,
(i) Conjugation:-
E.g. Chloramphenicol – typhoidbacilli,
Streptomycin – E.coli, Penicillin – Haemophilus & Gonococci
(ii) Transduction:-
E.g. Penicillin, Erythromycin & Chloramphenicol
(iii) Transformation:-
E.g. pneumococcal resistance to Penicillin G

67. PRINCIPLES OF PROPHYLACTIC ANTIBIOTIC
It is the use of antibiotics before, during, or after a
diagnostic, therapeutic, or surgical procedure to
prevent infectious complications.
ADVANTAGES:
1.Prevention of infection.
2.Decrease patient morbidity and mortality.
3.Decrease hospital stay.
4.Decreased medical cost.
5.Decreased total antibiotic usage.
6.Decrease numbers of resistant bacteria – because of
short term course.

68. DISADVANTAGES
⦿ No reduction of infection.
⦿ Development of increased number of
resistant bacteria.
⦿ Delay in onset of infection.
⦿ Adverse effect on surgical technique

69. THE PRINCIPLES FOR
PROPHYLACTIC ANTIBIOTICS
⦿ Increased risk of significant bacterial contamination
and a high incidence of infection.
⦿ Organism must be known.
⦿ Antibiotic susceptibility must be known.
⦿ To be effective and to minimize adverse effects the
antibiotic must be in the tissue at the time of
contamination (operation) and it must be continued
for not more than 4 hours after cessation of
contamination.
⦿ Four times the MIC of the causative organisms.
⦿ Timing the antibiotic correctly.
⦿ Shortest effective antibiotic exposure.

70. PRINCIPLE 1: PROCEDURE SHOULD HAVE
A SIGNIFICANT RISK OF INFECTION
1.Bacterial inoculum of sufficient size
2.Extensive and prolonged surgery
3.Insertion or presence of foreign body
4.Depressed host resistance

72. PRINCIPLE 2: TO CHOOSE CORRECT
ANTIBIOTIC
1.Effective against the most likely organism
2.Narrow spectrum antibiotic
3.Least toxic antibiotic
4.Bactericidal antibiotic

73. PRINCIPLE 3: ANTIBIOTIC PLASMA
LEVEL MUST BE HIGH
⦿ To ensure diffusion of antibiotic into all fluid and
tissue components
⦿ USUAL RECCOMENDED DOSE: Two times
the usual therapeutic dose

74. PRINCIPLE 4: TO TIME ANTIBIOTIC
ADMINISTRATION CORRECTLY
⦿ Antibiotic must be administered before the
surgery begins
Prolonged surgery
Additional antibiotic is required
Intraoperative dose intervals should be one half
the usual therapeutic dose interval

75. PRINCIPLE 5: USE OF SHORTEST EFFECTIVE
ANTIBIOTIC EXPOSURE
⦿ Continued antibiotic administration - no benefit once the
surgical procedure is complete
⦿ Hence the final dose of the antibiotic - after surgical
operation
Procedure lasts for Short procedure
more than two hours
2nd dose of antibiotic is
required
Single preop dose is
adequate

76. CONDITIONS CONSIDERD FOR ANTIBIOTIC
PROPHYLAXIS
⦿ Antibiotic prophylaxis recommended :
High risk condition
1.Prosthetic cardiac valves
2.Bioprosthetic valves
3.Previous bacterial endocarditis
4.Complex congenital CHD
Moderate risk condition
1.Acquired valvular dysfunction
2.Hypertrophic cardiomyopathy
3.Other congenital cardiac malformation

77. ANTIBIOTIC PROPHYLAXIS NOT
RECOMMENDED
⦿ LOW RISK CONDITION:
1.Isolated atrial septal defect
2. Previous coronary artery bypass
graft surgery.
3. Mitral valve prolapse without
valvular regurgitation
4. Cardiac pacemakers and
defibrillators
5. Previous rheumatic fever without
valvular regurgitation

78. 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