Antibiotic Selection.Part 1

What Drug for What Bug

Dr.T.V.Rao M DProfessor, Department of Microbiology

Jubilee Mission Medical College, and Research Institute,Thrissur, Kerala. India

E mail ;tvraodoctor2000@yahoo.co.in

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 earliest

Severe Don’t loose time

( Best guess is life saving )

Skills In Antibiotic Therapy. Seniors - Colleagues – Juniors Follow

Most General Practitioners

Dangerous trend Promotional

Best way learn your own skills.

Etiological Diagnosis Do we need to know about causative agent

always ? No Development of skills apply to the situation. But the following conditions warrant a good

knowledge on causative agent.

CNS, Hepatobiliary,Renal Systemic infections, Bacteremias Cardiac infections.

What is best guess. Past experience of Antibiotic therapy, Basic principles of antibiotic therapy, Many times best guess is life saving. Many surveys prove -- Physicians in

Developing Nations

Depending on 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 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 a ideal Sample.

Drug susceptibility Testing. Always needed ? No

e.g. Group A hemolytic streptococci.

Clostridial infection,

Drug susceptibility Testing. Most Important in

Enterobacteriaceae

Majority of times 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

patters, eg Pneumococcus,EnterococciBe familiar with Changing pattern 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,

Failed responses( Cont ) Super infection 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,Diabetus.

Failed Response (Cont ) Treating non infectious disorders with

Antibiotics eg Autoimmune disorders.

Slow Responses

Osteomyletis,Endocarditis,

Slow responding microbes,

Staphylococcus, Fungal

Mycobacterial infections.

Fast Responders Viridians Streptococci.

Estimation of Antibiotic Levels. Important on prolonged usage. e.g. Amino glycosides,Flucytosine, In all cases of altered clearance. (Renal

Diseases.)

Duration of Antibiotic Therapy. No specified guidelines in Major Infections. Author variation is wide Controversial. Most Important. Effective clinical response. Eg Clinical laboratory parameters in UTI Location of infection

Endocarditis,Osteomyletis.

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 I,V line infections. It is proved that I.V offers no advantage than 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 last 2 years usage.

New Facts on Antibiotic Resistance. Drug resistance

Not related to

1.Volume of use.

2.Years of Use.

3.Class of Antibiotics

eg Cephalosporin's.

But agent specific.

Ceftazidime.

New Uses of Older Antibiotics. > 1980 Beta lactum / Quinolones.

Dominates the Antibiotic prescriptions.

Less Commonly Used, Doxycycline, Minocycline, Clindamycin, TMP-SMX Nitrofurantoin.

Tetracycline and related.Doxycycline,Minocycline,

Can be used as first line 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 osteomyletis. 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 use of Newer Antibiotics

Do not choose in Hurry, Should posses unique attributes, At least 2 years of experience before a

routine choice, Many newer formulations have less side

effects and improved tolerability.

Conclusion

Antibiotics are life saving pearls,Let use them precisely, wisely

to a appropriate situation Dr.T.V.Rao.M D.