Antimicrobial Drugs

Antibiotic

A low molecular weight substance produced by a microorganism that inhibits or kills other microorganisms at low concentrations.

Antimicrobial drug

A natural or synthetic substance that inhibits or kills other microorganisms without causing damage to the host.

Semisynthetic drug

Natural antibiotics altered in the lab to produce variants with more desirable activities.

Synthetic drug

Completely man-made substances designed to have antimicrobial properties.

Bactericidal

Drugs that kill bacteria.

Bacteriostatic

Drugs that inhibit the growth of microbes but do not kill them, relying on the host's immune system to eliminate the bacteria.

Broad spectrum drug

Drugs that inhibit or kill most bacteria, potentially causing unnecessary damage to the microbiome.

Narrow spectrum drug

Drugs that inhibit or kill a specific group of bacteria.

Who discovered arsphenamine (Salvarasan)?

Paul Erlich discovered it, and it was used to treat syphilis.

Who discovered sulfa drugs?

Gerhard Domagk discovered sulfa drugs, which are synthetic antimicrobial agents.

Who discovered penicillin?

Alexander Fleming discovered penicillin, but its widespread use was delayed due to extraction difficulties.

Who discovered streptomycin?

Selman Waksman discovered streptomycin from soil bacteria (Streptomyces).

Targets of antibacterial drugs include:

1. Protein synthesis - selective due to different ribosomal structures. 2. Cell wall synthesis - targets actively dividing bacteria. 3. Nucleic acid synthesis - interferes with bacterial DNA/RNA processes. 4. Cell membrane disruptors - impacts bacterial integrity.

Why are bacteria sensitive to sulfa drugs while humans are not?

Humans do not follow the same metabolic pathways for synthesizing folic acid as bacteria do.

What do β-lactam drugs have in common?

They contain a ring structure of 3 carbon atoms and 1 nitrogen atom, and they target actively-dividing bacteria by inhibiting cell wall synthesis.

Considerations when prescribing an antibiotic include:

Routes to the infection site, blood-brain barrier penetration, half-life, patient immunocompetence, and drug resistance.

What is intrinsic drug resistance?

A structural feature of the microbe that prevents drug action, like penicillin resistance in mycoplasma or Gram-negative bacteria.

What is chronic resistance in bacteria?

Resistance due to persisters or altered physiological states, where cells may continue to survive and grow even after drug treatment has stopped.

What is acquired resistance?

Genetic changes within bacteria that lead to resistance against antimicrobial drugs.

Why are bacteria in biofilms more resistant?

Biofilm bacteria have persister cells, protective EPS matrices, and can contain enzymes that deactivate drugs.