USING ANTIMICROBIAL

AGENTS TO CONTROL

MICROBIAL GROWTH IN

VIVO

CHAPTER 9

Chemotherapy- refers to the use of chemicals (drug/s)

to treat any disease or condition.- Paul Ehrlich, a German chemist, is the

father of chemotherapy.

Chemotheraputic agent is any drug used to treat any condition or disease.

• Antimicrobial agent is any chemical or drug used to treat an infectious disease, either by inhibiting or killing pathogens in a vivo.

• Antibacterial agents- drugs used to treat bacterial diseases

• Antifungal agents- drugs used to treat fungal diseases

• Antiprotozoal agents- drugs used to treat protozoal diseases

• Antiviral diseases- drugs used to treat viral diseases.

Antibiotic

• It is a substance produced by a microorganism that is effective in killing or inhibiting the growth of other microorganisms.

• Not all antimicrobial agents are antibiotics although antibiotics are all antimicrobial agents!

• The first antibiotic produced was penicillin by Sir Alexander Fleming in 1928.

Semisynthetic Antibiotics• These are chemically modified

antibiotics to kill a wider variety of pathogens or reduce side effects.

Examples:

1. Ampicillin

2. Carbenicillin

Ideal Qualities of an antimicrobial Agent

• Kill or inhibit the growth of pathogens• Cause no damage to the host• Cause no allergic reaction in the host• Be stable when stored in solid or liquid form• Remain in specific tissues in the body long

enough to be effective• Kill the pathogens before they mutate and

become resistant to it

5 Most Common Mechanisms of Action of Antimicrobial Agents:

1.Inhibition of cell wall synthesis

2.Damage to cell membranes

3.Inhibition to nucleic acid synthesis (either DNA or RNA synthesis)

4.Inhibition of protein synthesis

5.Inhibition of enzyme activity

Competitive Inhibitors• They inhibit growth of microorganisms

by competing with the enzyme required to produce essential metabolite.

Example: Sulfonamide drugs which inhibit the production of folic acid. Hence, they are bacteriostatic and not bactericidal agents.

• Bacteriostatic agents- inhibits the growth of the bacteria

• Bactericidal agents- kills bacteria

• Narrow-spectrum antibiotics are antimicrobial agents which destroy only Gram-negative bacteria

• Broad-spectrum antibiotics destroy both Gram-positive and Gram-negative bacteria.

• Multidrug therapy is needed when a single antimicrobial agent is not enough to destroy all the pathogens that develop during the course of a disease; thus, two or more drugs may be simultaneously used to have a successful outcome.

• Synergism is the term used when the two drugs being used don’t work against each other

• Antagonism, on the other hand, happens when the two drugs work against each other.

Antifungal Agents & Antiprotozoal Agents

•Antifungal agents and antiprotozoal agents tend to be more toxic to the patients!

Antiviral Agents

• The first antiviral agent effective against HIV is zidovudine also known as AZT. It was introduced in 1987.

DRUG RESISTANCE:“Superbugs”

• Superbugs are microorganisms (mainly bacteria) that have become resistant to one or more antimicrobial agents.

• Infections due to superbugs are more difficult to treat.