Facts you need to know about Antibiotics (part 2): Considerations and Mechanisms

After we discuss some general facts about antibiotics, we will advance to the next facts about them before we discuss about each class of antibiotics.

Read this post first if you have not learned about antibiotics.


Fact # 4

What are the physician consider when giving antibiotic to his/her patient?

There are several factors to be considered.


1. How the antibiotic will penetrate to the site of infection. This is may be more important in meningitis or encephalitis; due to blood-brain barrier system. Cephalosporin (first generation) and clindamycin are two examples of antibiotics which cannot cross that barrier; thus cannot be used as therapy of meningitis.2. Severity of the patient's illness. The severe disease may require broad-spectrum antibiotic.
3. Age and underlying diseases; especially elderly, hepatic dysfunction, and renal dysfunction. Beware that they may have prolonged metabolism and greater risk of toxicity from antibiotics.
4. White blood (leucocyte) count. Neutropenia or leucopenia is an indication for immediate broad-spectrum intravenous antibiotic.
5. Duration of hospitalization. This factor is necessary to be separated from hospitally-acquired (healthcare-associated) infections.


Fact # 5

Who is the patient? Reconsider children and pregnant women!

This factor is particularly important especially in children and pregnant women.

Children under the age of 8 years should not be administered with tetracyclines since this class of antibiotic (doxycycline, minocycline, and tetracycline itself) stain their teeth with brown discoloration. Children under 18 years should not be given with fluoroquinolones due to arthropati risk.

Relatively-safe antibiotics for pregnant women are penicillins, cephalosporins, and macrolides. Chloramphenicol should not be given in late pregnancy. Fluoroquinolones and tetracyclines should not be given too. Sulfa drugs should be prohibited due to risk of birth defects.


Fact # 6

How the antibiotic works?

There are several ways for antibiotics to work against bacteria. Basically, there are three main mechanisms: intervention against bacterial cell wall or cytoplasmic membrane, intervention of DNA/RNA synthesis, or intervention of protein translation/synthesis.

How antibiotic works depicted in this graphic (source: Wiley.com).

What's Next in part 3:
We will start to discuss each class of antibiotics, including their indications and the choice in practices.


References:
Southwick F. Anti-infective Therapy; in Southwick F (eds). Infectious Diseases: A Clinical Short Course, 2nd ed. McGraw-Hill: 2007; 1-8.