ANTIBIOTIC SELECTION

BASIC PRINCIPLES

Proper use-Favorable Results

Indiscriminate use- Drug Resistance Emerging Problem May produce Adverse Reactions

DECISION MAKING

Decide first that one is treating a Bacterial
Infection.
Mild -Wait
Moderate -Consider starting the earliest
Severe -Don’t lose time
( Best guess is life-saving)

SKILLS IN ANTIBIOTIC THERAPY

Seniors – Colleagues – Juniors Follow
Most General Practitioners
Dangerous trend Promotional
The best way to learn your own skills.

ETIOLOGICAL DIAGNOSIS

Do we need to know about causative agents
always? No
Development of skills applies to the situation.
But the following conditions warrant a good
knowledge of the causative agent.
CNS, Hepatobiliary, Renal Systemic infections,
Bacteremias Cardiac infections.

WHAT IS THE BEST GUESS

Past experience with Antibiotic therapy,
Basic principles of antibiotic therapy,
Many times best guess is life-saving.
Many surveys prove — Physicians in
Developing Nations
Depending on the Best guess.

ROLE OF MICROBIOLOGICAL DIAGNOSIS

Start collecting desired samples before
starting antibiotic therapy.
Consider the Technical soundness of the
Laboratories.
Many times Normal flora are reported as
pathogens and misguide the Junior
Physicians.

JUDGMENT ON CLINICAL RESPONSE

In routine circumstances, if the best guess
works ignore Microbiological reports
In Poor response consider the evaluation of
Microbiology reports.

ADHERENCE TO MICROBIOLOGY REPORTS

Isolates from Blood, CSF, Body Fluids,
A significant finding.
Implement the Microbiology Reports

DEALING WITH UNEXPECTED RESULTS

When the isolates from
Respiratory tract, GUT system Surface lesions.
Think before changing Antibiotics Many occasions Specimens are not properly collected.
Major failures are attributed to collecting and sending an ideal Sample.

DRUG SUSCEPTIBILITY TESTING

Always needed? No
e.g. Group A hemolytic streptococci.
Clostridial infection,

Most Important in Enterobacteriaceae Majority of the time stick to antibiotic
sensitivity patterns.

CURRENT TRENDS

Get familiar with your own ward reports.
All the knowledge from Journals May not suit local situations
Get familiar with Daily isolates and the Antibiotic patterns,
eg Pneumococcus,Enterococci
Be familiar with Changing patterns of resistance
e.g. Penicillin’s, Aminoglycosides, Vancomycin.

FAILED RESPONSES

One May not be treating a Bacterial
Infection.
 Selection of Inappropriate Drug, Dosage,
 Improper Administration.
 Missing a Pocket of Localized pus,
 Poorly diffusing drugs
 Don’t reach target, e.g. Cefoperazone in
meningitis,

Superinfection replacing primary infection,
 Suppression of Normal Flora.
 Fast-emerging drug-resistant strains,
 Two or More pathogens present
But treating one only.
Growing problems with
Immune deficiencies, Diabetes.

Treating noninfectious disorders with
Antibiotics eg Autoimmune disorders.
Slow Responses
Osteomyelitis, Endocarditis,
Slow-responding microbes,
Staphylococcus, Fungal
Mycobacterial infections.
Fast Responders Viridians Streptococci.

ESTIMATION OF ANTIBIOTIC LEVELS

Important on prolonged usage.
 e.g. Aminoglycosides, Flucytosine,
 In all cases of altered clearance. (Renal
Diseases.)

DURATION OF ANTIBIOTIC THERAPY

No specified guidelines for Major Infections.
 Author variation is widely Controversial.
 Most Important.
 Effective clinical response.
 Eg Clinical laboratory parameters in UTI
 Location of infection
Endocarditis, Osteomyelitis.

ORAL OR PARENTAL ROUTE

Note
 Oral Antibiotic therapy is equal to
parental therapy.
 Oral Drugs now have excellent
Bioavailability.

ADVANTAGES OF ORAL THERAPY

Less expensive.
 Early discharge from Hospital.
 Reduction in Health care costs.
 Avoid Chemical phlebitis.
 Eliminate IV line infections.
 It is proved that I.V offers no advantage over oral
therapy, except in critically ill.
 A sense of security in patients.

MOST PROMINENT ORAL ANTIBIOTICS

 Doxycycline,
 Clindamycin.
 Metronidazole.
 Levofloxacin.
 Chloramphenicol.
 TMX-SMX.
 Acyclovir.
 Fluconazole.
 Linezolid.

NEW USES OF OLD ANTIBIOTICS

Still useful on many occasions.
eg Doxycycline in Malaria.
Chloramphenicol – VRE.

ROLE OF NEWER ANTIBIOTICS

Do not come to prompt conclusions.
Consider-
1. Cost.
2 .Resistance potential.
3. Years of use.
4. Side effects.
5. Compare with current popular drugs.
6. Consider the profile of the last 2 year’s
usage.

NEW FACTS ON ANTIBIOTIC RESISTANCE

Drug resistance
Not related to
1. Volume of use.
2. Years of Use.
3. Class of Antibiotics
eg Cephalosporins.
But agent specific.
Ceftazidime.

NEW USES OF OLDER ANTIBIOTICS

1980 Beta-lactam / Quinolones Dominate the Antibiotic prescriptions.

LESS COMMONLY USED

 Doxycycline,
 Minocycline,
 Clindamycin,
 TMP-SMX
 Nitrofurantoin.

TETRACYCLINE AND RELATED. DOXYCYCLINE, MINOCYCLINE

Can be used as the first line of Drugs in
Atypical pneumonia,
Chronic Bronchitis,
Leptospirosis,
Non-gonococcal urethritis,
C.trachomatis,
Syphilis, Leptospirosis ( Penicillin Allergy )

TRIMETHOPRIM-SULFAMETHOXAZOLE

 Broad spectrum – Inexpensive.
Still useful in,
H.influenzae,
Moraxella,
E.coli.
Proteus mirabilis,
K.pneumoniae,
Shigella,
E.coli ( E.T )
Toxoplasmosis
MRSA ( some )

CLINDAMYCIN

 Serious Anaerobic infections.
 Polymicrobial osteomyelitis.
 Infections associated with Diabetic foot.
 Don’t Cross into CSF.

METRONIDAZOLE

 Anaerobic bacterial infections,
 Protozoal infections.
 Anaerobic brain abscess.
 H.pylori.
 Clostridium difficile

CHLORAMPHENICOL

 Pneumococcal infections
 Meningococcal infections
 H.influenzae
 Anaerobic activity
 VRE Enterococcus

RATIONALISM ON THE USE OF NEWER ANTIBIOTICS

 Do not choose in Hurry,
 Should possess unique attributes,
 At least 2 years of experience before a
routine choice,
 Many newer formulations have fewer side
effects and improved tolerability.

CONCLUSION

ANTIBIOTICS ARE LIFE-SAVING PEARLS, LET USE THEM PRECISELY, WISELY
TO A APPROPRIATE SITUATION.

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