1. ANTIBIOTICS IN ORAL AND MAXILLOFACIAL SURGERY
AIM: The aim of this seminar is to discuss various antibiotics and their use in
oral and maxillofacial surgery.
INTRODUCTION: Antibiotics are regarded as miracle drugs. They are our
most effective weapons against infectious diseases brought about by
microorganisms like bacteria, fungi and parasites. In the past treating the
bacterial infections was very difficult. In fact before the discovery of
antibiotics, many patients contracting bacterial infections never made it out of
hospital beds alive. This is why discovery of antibiotics was one of the most
important health advances in human history. Antibiotics have a well
documented efficacy in the trearment of established infections and as
prophylactic agents in medically compromised patients.
DEFINITION: Antibiotic is a chemical substance produced from microorganisms
have the property of inhibiting the growth of other microorganismsin high
dilution.
HISTORY: PAUL ERHLICH(1854-1915) an organic chemist observed that
methylene blue specifically killed and stained certain bacterial cells and
reasoned that chemical might be produced that could unite with and destroy
parasitic agents of disease without injuring the host cells. First accidentally
discovered in 1928 by ALEXANDER FLEMING when a dish in which he was
growing staphylococcus bacteria became contaminated with pencillium mould
was destroying bacteria. This substance was later named PENICILLIN. In 1944
WALKSMAN isolated streptomycin from streptomyces griseus in culture from
chicken throat.
MODE OF ACTION: Antibiotics act on four targets
1. Cell wall
2. Cytoplasmic membrane
3. Ribosomes
4. RNA molecules involved in transcription of genetic information.

2. CLASSIFICATION:
Antibiotics are broadly classified in to
 Bactericidal antibiotics- they kill bacteria
 Bacteriostatic antibiotics- they inhibit bacterial proliferation.
Based on their mechanism of action antibiotics are classified as
I) Inhibit cell wall synthesis: penicillins, cephalosporins, vancomycin,
bacitracin, cycloserine.
II) Damage of cell membrane causing leakage of cell contents:
polymixins, amphoterecin B, nystatin.
III) Bind to ribosomes and inhibit protein synthesis: chloramphenicol,
tetracyclines, erythromycin, clindamycin, aminoglycosides.
IV) Inhibit DNA gyrase: fluoroquinolones.
V) Inhibit DNA function: rifampicin.
VI) Inhibit DNA synthesis: acyclovir, zidovudine.
VII) Interefere with metabolism: sulfonamides, trimethoprim.
ANTIBIOTICS ANTIBACTERIAL
SPECTRUM
DOSE ROUTE OF
ADMINISTRATION
Fluoroquinolones Gram negative
and gram
positive and
anaerobic
organisms.
1) Norfloxacin 400mg
BD
Oral
2) Ciprofloxacin 250-
750mg
BD
Oral
3) Pefloxacin 400mg
BD
400mg
12hrly
Oral
IV
4) Ofloxacin 200-
400mg
OD
200-
Oral
IV

3. 400mg
12-24
hrly
5) Lomyfloxacin 400mg
OD
Oral
6) Sparfloxacin 200-
400mg
OD
Oral
ANTIBIOTICS ANTI
BACTERIAL
SPECTRUM
DOSE ROUTE OF
ADMINISTRATION
Penicillins Narrow
antibiotic
spectrum
effective
against gram
positive
organisms
1) Sodium penicillin G 0.5-5MU
4-6hrs
IV/IM
2) Procaine penicillin
G
0.5-1MU
12-24 hrs
IM
3) Benzathine
penicillin G
1.2-2.4
MU 3-4
WKS
DEEP IM
SEMISYNTHETIC
PENICILLINS
1) Dicloxacillin 200-
500mg
QID
Oral
2) Naficillin 1-2 gms
4-6hrs
IV
3) Ampicillin 250mg or
1 gm qid
Oral
4) Ampicillin and
salbactum
1gm and
0.5gm 6-
8hrly
IV
5) Amoxicillin 250-
500mg
tid
Oral

4. 6) Amoxicillin and
clauvlanic acid
250mg
and 125
mg tid
Oral
7) Piperacillin 3-4 gms
4-6hrly
IV
8) Ticarcillin 3gms 4-
6hrly
IV
CEPHALOSPORINS
First generation Have wider
activity than
penicillin. Gram
positive
resistent to
penicillin
1) Cephalothin 1-2gms
6hrly
IV
2) Cephalozin 0.5-1gm
6hrly
IM/IV
3) Cephalexin 0.25-1gm
qid
Oral
4) Cefadroxil 0.5-1gm
bid
Oral
Second generation Gram negative
resistent to
beta
lactamases
1) Cefuroxime 0.75-
1.5gm
8hrly
IM/IV
2) Cefumandole 0.5 -2gms
4-8 hrly
IM/IV
3) Cefuroxime 0.25-
0.5gm bd
Oral
4) Cefaclor 0.25-
0.5gm
Oral
Third generation Highly resistent
to beta
lactamases.
Effective
against gram

5. negative
organisms
1) Cefotaxime 1-2gms
8hrly
IM/IV
2) Ceftriaxone 1-2gms
od
IM/IV
3) Cefperazone 1-2gms 8-
12hrly
IM/IV
Fourth generation Serious gram
negative
infections
1) Cefipime 1-2gms
12hrly
IV
Broad spectrum
antibiotics
TETRACYCLINES Gram positive,
gram negative,
rikketsciae,
chlamydiae,
mycoplasma
1) Chlortetracycline 250-
500mgs
qid
Oral
2) Tetracycline 250-
500mgs
qid
Oral
3) Doxycycline 200mgs
initially
then
100mgs
od
Oral
4) Minocycline 200mgs
initially
then
100mgs
od
Oral
Chloramphenicol Gram negative,
gram positive,
anaerobic
bacteria,

6. chlamydiae,
mycoplasma
AMINOGLYCOSIDES Gram negative
anaerobic
bacilli
1) Streptomycin 1-
2gms/day
IM
2) Gentamycin 3-5mg/kg
in three
divided
doses
IM/IV
3) Tobramycin 3-5mg/kg
in three
divided
doses
IM/IV
4) Amikacin 15mg/kg
in 2-3
divided
doses
IM/IV
5) Netilmycin 4-6mg/kg
in 2-3
divided
doses
IM/IV
MACROLIDES
Erythromycin Narrow
spectrum, gram
positive and
few gram
negative
organisms
1) Erythromycin
stearate
250-
500mgs
qid 7-14
days
Oral
2) Erythromycin
estolate
250-
500mgs
qid 7-14
days
Oral
3) Roxitromycin 150mgs Oral
4) Azitromycin 500mgs

7. then
250mgs
od next
three
days
Adverse effects
1. Fluoroquinolones:--
Tendinitis with assosciated risk of tendon rupture.they damage
growing cartilage resulting in anthrppathy . Hence contraindicated up to
18 years of age.
2. Pencillin:--
(i) Hypersensitivity reactions ranging from skin
rashes,urticaria,fever,bronchospsm,serum rickness and rarely exfoliature
dermatitis and anaphylaxis.
(ii) Jarish-herxheimex reaction -when pencillin is injected in a patient
with syphilis,there is sudden destruction of spirochetes and release of its
tylio products which triggers a reaction with fever,myalgia,shivering.
3. Cephalosporins :-- 20% patients allergic to pencillon show reactivity to
cephalosporins
4. Tetracyclines:--
hepatoloxity,renal toxity,phototoxity.
out dated tetracyclines cause fanconils
syndrome.(vomting,polyuria,protienuria,glycosuria)
effect on teeth and bones:--tetracyclines chelate calicium.the
calicium tetracycline orthophosphate complexes yet deposited in
developing teeth and bones .he deormites depend on time of
tetracycline administration.
Period structures affected
deformity
mild pregnancy to 5 months of dicicluous teeth
broconish discolouration,ill portnatal
formed,more caries

8. suseptible
2months to 5 years of age perment teeth
pigmentation,discolouration
pregnancy and childhood up to 8 skeleton 
depressed bone growth
Chloramphenicol:--
Gray baby syndrome:-- new born babies may develop vomting,
hypotension, hyperthermia and ashen gray cyanosis asthey cannot
metabolise and excret chloramphenicol.
Inoglyclorids:-- Ootoloxity,nephrotoxity
Erthromycin:--
Inhibits hepatic metabolism and rises plasma levels of
carbemazepine, terfanidine, valproate,aligoxin and results in their
toxicity.
Roxythromicin , clarithromicin and Azithomyccin do not have any drug
interactions.
Principles for choosing Antibiotics:---
In most clinical situations,it is easy to determine whether a patient
has an infection. Locally, the classical signs and symptoms of
pain,swelling,surface erythema,pus formation and
sustematically,fever,lymphadenopathy,malaise, a toxic appearance and
an elevated white blood cell count are formed.
Infections are ultimately cured by the host and not by antibiotics .
Antibiotic therapy reduces bacterial challenges and allows hort defences
to complete the treatment.
Initial empirical therapy may be instituted with a fair degree of reliability
if the following criteria are met .
(i) Site and features of infection have been well met
(ii) Circumstances leading to infection are well known.
(iii) Organism or organisms that most commonly cause such infections
are well known.
Definitive therapy is done after culture reports are received .
Early infections that present as cellulitis with out abcess formation
are most caused by aerobic bacteria. As the infection becomes

9. more severe ,the microbiology becomes more severe ,the
microbiology becomes a mixed flora of aerobic and anaerobic
bacteria are no longer able to survive in hypoxic acidic
environment.
Principles:---
1. State of host defences:--
Antibiotics help in situations which the host has been over
whelmed by bacteria or when especially virulent bacteria are
involved .When a patients defences are impaired ,antibiotics,
play a more important role in control of infections.
Eg:-- cancer,leukemias,malnutrition,poosly controlled diabetes.
Cycotoxic drugs and immune supressents like glucocorticoids,
azathioprine, cyclosprin affect host defences.
Aggressive antibiotic therapy must be considered in treating
established infections in patients in any of these categories .
Surgicaldrainage and incision may also deviate the use of an
antibiotic or may increase the effectiveness of an antibiotic as
vascular flow is restored.
Determination of Antibiotic sensitivity:--
Staphy lococcus infection must be treated with antibiotic
susceptibility information in hand.Pencillin G can be used only
if sensitivity studies support its effectiveness.Pencillinnase
resistant pencillins should be used. There is an increasing
incidenceof resistance to pencillinase resistant drugs ,which
currently is high enough to warrant antibiotic routine
susceptibility testing for staphylococcal infection.
PencillinExcellent for treatment of streptococcus infection.
Good to excellent for major odontogenic infectons
Erythromycineffective against streptococcus ,pepto
streptococcus, preuotella/
Clindamycingood for streptococcus.
CephalexinModerate active against streptococcus,good age
MetronidazoleNo action against Streptococcus.Excellent
activity against anaerobes

10. Use of narrow spectrum Antibiotic :--
Antibiotic with narrowest anti bacterial spectrum should be
used.
Eg:--If streptococcus is sensitive to pencillin, cephalosporin and
tetracycline . Pencillin should be used because it has narrowest
spectrum.
The other two act against a variety of gram negative organisms and their use
leads to development of resistent organisms.
Use of narrow spectrum antibiotics minimize the risk of super infections
because they allow large proportions of host flora to be maintained.
USE OF LEAST TOXIC ANTIBIOTICS:
Select least toxic drugs from among those that are effective. Eg: bacteria
causing odontogenic infections are sensitive to penicillin and chloramphenicol.
Though chloramphenicol is more effective than penicilin, it is not preferred
because of its potential to cause severe bone marrow depression.
PATIENT DRUG HISTORY:
Two aspects should be reviewed in drug history
 Previous allergic reactions
 Previous toxic reactions
Allergy rate to penicillin is approximately 5% so history of previous allergy
should be abtained. It is well documented that co-incident allergies to
cephalosporins and penicilins do exist. So if patient is allergic to penicillin,
cephalosporins should be used unless it is deemed necessary only after
preparations are made to treat severe reactions.
Penicillin allergy: skin testing should be done 24hrs before penicillin
administration. Potential reactions with other drugs, the patient is taking is
considered.

11. USE OF BACTERICIDAL RATHER THAN BACTERIOSTATIC DRUGS:
Advantages of bactericidal antibiotics:
 Less reliance on host resistance
 Killing of bacteria by antibiotic itself
 Faster results than bacteriostatic drugs
 Greater flexibility with dosage intervals
Bactericidal drugs exert their influence after they are incorporated into the
bacterial cells and the cell eventually dies.
Bacteriostatic drugs exert their action only when present in patients tissues so
the bacteria resume their growth after drug is eliminated. So rigorous time
schedule should be followed up.
In immunocompromised patients bactericidal drugs are preferred to
bacteriostatic drugs.
Cotrimoxazole, fluoroquinolones, penicillins, cephalosporins, aminoglycosides,
vancomycin, teicoplanin are bactericidal.
Sulfonamides, tetracyclines, chloramphenicol are bacteriostatic.
Erythromycin is bacteriostatic in low doses and bactericidal in higher doses.
USE OF ANTIBIOTICS WITH A PROVEN HISTORY OF SUCCESS:
The best evaluation of the efficacy of a drug in a particular situation is the
critical observation of its clinical effectiveness over a prolonged period.
Standard drug should not be disapproved for an unapproved drug without
good reason. The newer drug should be effective for bacteria against which no
other antibiotic is effective.
Eg. Methicillin for penicillinase.
Such drugs should be used only for those bacteria with proven sensitivity.
We can select a new antibiotic if it is less expensive, more potent, less toxic,
few side effects than older one but should be used with caution.

12. COST OF ANTIBIOTIC:
Reasonably affordable price should be considered.
PRINCIPLES OF ANTIBIOTIC ADMINISTRATION:
Antibiotic must be administered properly. This involves consideration of
dosage, route of administration and combination therapy.
PROPER DOSE:
Any drug should be administered in sufficient amounts to achieve deserved
therapeutic effect but should not cause injury to host. Minimum inhibitory
concentration of an antibiotic for a specific bacteria should be calculated. For
therapeutic purposes, the peak concentration of antibiotics at the site of
injection should be 3-4 times the minimum inhibitory concentration. Dose
above this level does not improve the therapeutic results but will cause
toxicity. Eg. Gentamicin is effective in concentrations up to 4-6 microgram/ml
but the incidence of nephrotoxicity increases dramatically at 10 microgram/dl
plasma level.
In cases of infections isolated from blood supply, increased antibiotic doses can
be given. The high plasma concentration can cause greater amount of
antibiotic to reach the sealed of bacteria by simple diffusion.
Sub therapeutic doses should not be given as they supress clinical
manifestation without actually killing microbes and hence may result in
recurrence of infection after discontinuation of drug.
PROPER TIME INTERVAL:
The usual dosage interval for the therapeutic use of antibiotic is four times the
t1/2. At five times t1/2 95% of drug is excreted.
Eg. T1/2 of cefazolin is 2hrs . so interval between doses should be 8hrs.
In patients with compromised renal function, prolonged interval should be
given because excessive plasma levels due to decreased clearance would cause
toxicity.

13. ROUTE OF ADMINISTRATION:
Some times only parenteral route of administration would provide adequate
serum level of antibiotic. If given orally, should be given 30mins before or 2 hrs
after meals for maximum absorption.
When long term parenteral administration is necessary IV is preferred over IM
as IM is poorly accepted by patient.
CONSISTENCY IN ROUTE OF ADMINISTRATION:
In case of serious infections parenteral route is preferred. After initial response
we usually switch to oral administration. But this may cause recurrence of
infection as blood levels of drug are lower when we switch to oral route on
second or third day of therapy. After 5 days oral levels are sufficient.
“Maintenance of peak blood levels of antibiotics for adequate period is
important to achieve maximum tissue penetration and effective bacterial
killing.” In case of mild infection oral administration is sufficient.
COMBINATION ANTIBIOTIC THERAPY:
Combination antibiotic therapy should be avoided for routine infections as it
may provide broad spectrum exposure leading to emergence of resistent
bacteria.
Indications of combination therapy:
 When it is necessary to increase the antibacterial spectrum in patients
with life threatening sepsis of unknown cause.
 When increased bactericidal effect against a specific organism is
desired.
 To prevent rapid emergence of resisrent bacteria. Eg: treatment of
tuberculosis by multiple drugs.
 In emperic treatment of certain odontogenic infections. Eg: severe
cellulitis type of infections rapidly progressing posteriorly around the
lateral and retropharyngeal spaces, bactericidal activity against
streptococcus and oral anaerobes is important. As prevotella is
resistent to penicillin, both parenteral penicillin and metronidazole

14. should be given to provide bactericidal activity against both
streptococcus and anaerobes.
 Patient monitoring : patient should be monitered for response to
treatment and development of alveolar reactions.
Response to treatment: no response to antibiotics occurs in 24-48 hrs.
Action begins after second after second day.
Objective signs and symptoms are decreased temperature, swelling
pain.
Eradication of infection is reached by third day with decrease of
symptoms. In case of uncomplicated odontogenic infections
improvement begins on second day of therapy and marked resolution
is seen by third day and an additional two days is needed to resolve
the infection. In case of severe infection, seven day course is needed.
If patients condition does not improve after initial therapy, antibiotic
should not be changed immediately as it takes some time and
following clarifications should be done.
1. Carefully evaluate the patient
2. Look for need for additional surgery to drain pus or
release pressure or remove foreign body.
3. Other possible sites of infection should be evaluated
4. Portals of entry such as IV catheter should be checked
5. Adequate hydration and nutritional support are
necessary.
If initial therapy failed the following clarifications should be made
1. Is the route of administration adequate to deliver effective dose of drug
2. Is patient taking antibiotic prescribed
3. Are physcians order followed
4. Is choice of antibiotic correct
If initial therapy failed culture should be done before changing the drug. A
second empirical choice should be avoided due to low success rate.

15. Development of adverse reactions:
Adverse reactions may be in the form of anaphylactic reaction or less severe
reaction associated with edema urticaria and itching or there may be delayed
reaction presenting only as a low grade temperature. Patient should be
cautioned about allergy. If allergic reaction occurs it should be treated and
patient should be informed about the drug used and type of reaction and
should be advised caution in future.
ANTIBIOTIC ASSOCIATED COLLITIS:
It is a toxic reaction. It was originally associated with clindamycin but noe
ampicillin, amoxicillin and cephalosporins are also found responsible.
Clinical features: watery diarrhoea, creamping abdominal pain, fever.
Treatment: Discontinue causative antibiotic. Restore fluid and electrolyte
balance. Administer clostridial antibiotics., vancomycin and metronidazole can
be used.
SUPER INFECTION AND RECURRENT INFECTION:
In normal state, normal flora acts as a defence mechanism, but when this
mechanism is altered or eliminated due to use of antibiotics superinfection
occurs. Eg: candida infection due to long term treatment with penicillins as in
actinomycosis and osteomyelitis.
In case of osteomyelitis and actinomycosis more carefull and longer follow up
is necessary as the nonvital bone provides a barrier to antibiotic effectiveness
and is a potential focus of re-infection. In such cases, re institution of
antibiotics should be done with additional surgical intervention if necessary.
THERAPEUTIC USES OF ANTIBIOTICS IN ORAL AND MAXILLOFACIAL SURGERY:
ABSCESS: Penicillin is the drug of choice. Adjunctive treatment like endodontic
treatment, extraction of tooth or surgical drainage should be done.
PERICORONITIS: Anaerobic bacteria including gram positive cocci and gram
negative rods are obtained on culture. Penicillin is the drug of choice.

16. ODONTOGENIC INFECTIONS AND DEEP FASCIAL SPACE INFECTIONS OF
DENTAL ORIGIN: Well localized and easily drained dentoalveolar abscess can
be treated by surgical drainage. Antibiotic therapy is needed in case of
 Poorly localized, extensive abscess associated with diffuse
cellulitis.
 Abscess in case of immunocompromised patients, patients with
poorly controlled diabetes and patients on renal dialysis.
Majority of infections consists of mixed aerobic and anaerobic flora. According
to MOENING(1989) “it would seem presumptuous to state that penicillin is
currently not effective against most odontogenic infections and premature to
consider substituting another antibiotic as the drug of chioce for mild to
moderate odontogenic infection especially when low cost and lack of toxicity is
considered.”
In case of more severe infections antibiotic sensitivity tests may be needed.
Metronidazole is effective supplement to penicillin as it acts against
anaerobes. Erythromycin is poorly absorbed and is less effective in case of
odontogenic infections. Azithromycin is better tolerated than erythromycin. In
case of very severe infections combination of amoxicillin and clavulanic acid is
preferred. First and second generation cephalosporins are used. Tetracyclines
are not recommended. Minocycline and doxycycline can be used for low grade
odontogenic infections. Patients requiring hospitalization for odontogenic
infections and for immunocompromised host, the treatment regimen is
CLINDAMYCIN alone (or)
CLINDAMYCIN+METRONIDAZOLE
(or)
GENTAMICIN
(or)
PARENTERAL AMPICILLIN+SULBACTUM

17. OSTEOMYELITIS: causative organisms are staphylococcus epidermis, hemolytic
streptococci, prevotella, porphyromonas. Most of these organisms are
penicillin resistent so metronidazole is effective.
ANTIBIOTIC REGIMEN FOR OSTEOMYELITIS OF JAWS:
Regimine 1: for hospitalized /medically compromised patient or when IV
therapy is indicated.
1) Aq penicillin 2 million units IV 4 hrly , metronidazole 500mg 6 hrly
When improved for 48-72hrs, switch to penicillin V 500mg per oral 4 hrly
plus metronidazole 500mg per oral 6 hrly for an additional 4-6 weeks.
Ampicillin/sulbactum 1.5 -3 gms IV 6hrly, when improved for 48-72 hrs
switch to amoxicillin/clavunate 875/125 mg per oral bid for an addditional
4-6 weeks.
Regimen 2: for out patient treatment
PenicillinV 2gm plus metronidazole 0.5 gm 8hrly per oral for 2-4 weeks
after last sequestrum removed and patient without symptoms.
Clindamycin 600-900mg 6hrly IV then clindamycin 300-450mg 6hrly per oral.
Cefoxitin 1.0 gm 8hrly IV or 2gm 4hrly IM or IV untill no symptoms, then switch
to cephalexin 500mg 6hrly per oral for 2-4 days.
For penicillin allergic patients, clindamycin and cefoxitin can be given.
Cephalosporins are not first choice in the management of osteomyelitis
because they are only moderately effective against oral anaerobes and their
broad spectrum coverage increase antibiotic complications.
Erythromycin and other macrolides like clarithromycin, azithromycin, are not
recommended for treatment of osteomyelitis because they are no longer
reliably effective against the oral streptococci and anaerobes.
CHRONIC SUPPURATIVE OSTEOMYELITIS:
Usually requires surgical procedures such as sequestrectomy and removal of
foreign bodies such as wires, bone plates etc. Treatment should begin with IV

18. therapy and continue even after discharge using home IV therapy usually with
ampicillin/salbactum sodium because it is stable for 24hrs after mixing with IV
fluids.
IV therapy for 2 weeks or untill the patient has shown improvement for 48-72
hrs. Oral therapy should be continued for 4-6 weeks after patient has no
symptoms or from the date of last debridement.
If ampicillin/sulbactum sodium is ineffective clindamycin therapy is indicated.
Antibiotic impregnated beads deliver higher concentration of antibiotic into
wound bed and in immediate proximity to infected bone as antibiotic is
leached out from beads, thus low systemic toxicity. These are useful for
chronically infected bone associated with fracture and in chronic sclerosing
osteomyelitis refractory to systemic antibiotics. eg.tobramycin or gentamicin in
acrylic resin bone cement beads. They are removed after 10-14 days.
SALIVARY GLAND INFECTIONS:
Empirical therapy:
Out patient- amoxicillin+clavulanic acid
In patient- ampicillin+sulbactum(parenteral)
In case of penicillin allergy clindamycin is used. Erythromycin is not indicated
due to high bacterial resistance. Azithromycin and clarithromycin can be used
in out patient community acquired acute bacterial parotitis. Antibiotic therapy
should be continued untill atleast 1 week after resolution of signs and
symptoms.
ANTIBIOTIC PROPHYLAXIS IN HEAD AND NECK SURGERY:
Antibiotic prophylaxis in oral and maxillofacial surgery aims the prevention of
infection of the surgical wound, either due to characteristics of surgery or the
general state of the patient. Prophylactic antibiotic therapy creates an area of
resistance to microorganisms by means of antibiotic serum concentrations that
may avoid the multiplication and spread of bacteria through the surgical injury.
ADVANTAGES:
 Decreased patient infection

19.  Decreased post operative morbidity
 Decreased cost of health care
 Decreased amount of antibiotics used.
DISADVANTAGES:
 They may alter host flora
 Sometimes when the risk of infection is low, antibiotics donot have
effect.
PRINCIPLES:
1.RISK OF INFECTION MUST BE SIGNIFICANT:
a) Bacterial innoculum should be sufficient size to cause infection.
b) Prolonged and extensive surgery.
c)Presence of foriegn body
d) Depressed host defences
2.CHOOSE CORRECT ANTIBIOTIC:
a) Antibiotic must be effective against causative organism.
b) Choose narrow spectrum antibiotic
c) It should be least toxic
d) Select bactericidal antibiotic
3.ANTIBIOTIC PLASMA LEVELS MUST BE HIGH:
a) Prophylactic doses should be higher than therapeutic doses
b) Antibiotic should diffuse into all fluids and tissue spaces where surgery
is going on.
c) Doses should be atleast two times the therapeutic dose.
Eg:penicillin-1gm
Cephalosporins-1gm

20. Clindamycin-300mg
Clarithromycin-500mg
4.ANTIBIOTIC MUST BE TIMED CORRECTLY:
For maximum benefit ,antibiotic should be given before surgery begins.
If the surgery is prolonged and intra operative dose is required,intervels
should be shorter(half the usual therapeutic dose interval).This will ensure
that the peak plasma levels are maintained and avoids periods of inadequate
antibiotic levels in tissue fluids.
Eg: penicillin should be given every 2 hrs.
Cephalexin should be given every 2 hrs
Clindamycin should be given every 3 hrs
5.USE SHORTEST ANTIBIOTIC EXPOSURE THAT IS EFECTIVE:
No additional antibiotic is neede after surgery. Final dose of antibiotic
should be given at the termination of surgery.
ANTIBIOTIC PROPHYLAXIS OF WOUND INFECTION:
1.PARENTERAL REGIMEN:
1. Penicillin:
 Preoperative 1 million units IV
 Intraoperative 1 million units IV q2hrs
 Post operative 1 million units IV in recovery room
2.Cephazolin(penicillin allergic patients)
 Preoperatively 1gm IV
 Intraoperatively 1gm Ivq 4h
 Postoperatively 1gm IV in recovery room.

21. 3.Clindamycin
 Preoperatively 600mg IV
 Intraoperatively 600mg IV 4h
 Post operatively 600mg IV in recovery room
2.ORAL REGIMEN:
1.Penicillin
 Preoperative 2mg po 30min before
 Intraoperative 1mg per oral 2hrly
 Post operative 1mg per oral 2hrly
2. erythromycin
 Preoperative 1gm 1hr before
 Intraoperative 500mg per oral 2hrs
 Post operative 500mg peroral 2hrs
PROPHYLAXIS FOR SUBACUTE BACTERIAL ENDOCARDITIS:
Parenteral-oral combined regimen:
1. Preoperatively 30-60 mins
 Aqueous penicilinG – 1million units IM
 Procaine penicillinG – 6,00,000 units IM
2. Post operatively 8 doses
 PenicillinV 500mg peroral 6hrly.
Children:
Preoperatively 30-60mins
 Aqueous penicillinG- 30,000 units/kg IM
 Procaine penicillinG- 6,00,000 units IM.
Post operatively 8doses
a) PenicillinV
I) Less than 27kg(60lb) 250mg peroral 6hrly

22. II) More than 27kg(60lb)500mg peroral 6hrly
Oral regimen:
ADULTS:
1. Preoperatively 30-60 mins
penicilinV –
 Procaine penicillinG – 6,00,000 units IM
3. Post operatively 8 doses
 PenicillinV 500mg peroral 6hrly.
Children:
Preoperatively 30-60mins
 Aqueous penicillinG- 30,000 units/kg IM
 Procaine penicillinG- 6,00,000 units IM.
Post operatively 8doses
b) PenicillinV
III) Less than 27kg(60lb) 250mg peroral 6hrly
IV) More than 27kg(60lb)500mg peroral 6hrly
FOR PATIENTS ALLERGIC TO PENICILLIN:
Adults:
Preoperatively ½-2hrs
Erythromycin 1.0gm peroral
Postoperatively 8doses
Erythromycin 500mg peroral 6hrly
Children:
Preoperatively ½-2hrs
Erythromycin 20mg/kg peroral

23. Postoperatively 8 doses
Erythromycin 10mg/kg peroral 6hrly
ANTIBIOTIC MISUSE:
The misuse and increased use of antibiotics are inducing the rapid growth of
antibiotic resistant bacteria(super bug), making it difficult for clinicians to treat
infections.
PREVENTION:
a) Narrow spectrum antibiotics should be prescribed.
b) Microbiology lab results should be the only factor determining the type
of antibiotic medication prescribed to patients.
c) Patients should be educated regarding misuse and increased use of
antibiotics.
d) Patients should follow prescribed directions.
e) Sale of over the counter antibiotics should be emphasized upon.
ANTIBIOTIC RESISTANCE:
The increase in antibiotic resistant bacteria is largely due to wide spread use of
antibiotics in medicine, animal care and agriculture.
MULTIPLE DRUG RESISTANT ORGANISMS:
Multiple drug resistant organisms are resistant to treatment with several,
often unrelated, antimicrobial agents. Some of the most important types of
multiple drug resistant organisms are
 MRSA- methicillin/oxacillin resistant staphylococcus aureus
 VRE- Vancomycin resistant enterococci
 ESBLs-extended spectrum beta lactamases(which are resistant to
cephalosporins and monobactams)
 PRSP-Penicillin resistant streptococcus pneumoniae
MECHANISM OF ANTIBIOTIC RESISTANCE IN BACTERIA:
1) Chloramphenicol- reduced uptake into cell
2) Tetracycline- active efflux from cell

24. 3) Beta lactums,erythromycin, lincomycin- eliminates or reduces binding
of antibiotic to cell target.
4) Beta lactums, aminoglycosides,chloramphenicol- enzymatic cleavage
or modification to inactive antibiotic molecule
5) Sulfonamides, trimethoprim- metabolic bypass of inhibited reaction
PREVENTION:
 Search for new antibiotics
 Stop the use of antibiotics as growth promoting substances in farm
animals
 Use the right antibiotic
 Stop unnecessary antibiotic prescription
 Finish antibiotic prescription
CONCLUSION:
The discovery of antibiotic was a leap in modern medicine. They have been
able to stop the growth or kill many different kinds of microorganisms.
However, bacteria have proven to be much more innovative and adaptive than
we imagined and have developed resistance to antibiotics at an ever increasing
pace. Bad practices and mismanagement have only exacerbated the situation.
However, with more research education of public and well thought out
regulations, the problems can be solved.