Chapter 12: Principles of Antimicrobial Therapy
______spectrum drugs are effective against more than one group of bacteria (example: tetracyclines)
Broad
_______ spectrum drug only target a specific group (examples: polymyxin and penicillins. What are advantages of this type of treatment?
Narrow; less side effects
______ ______ has allowed the genes for antibiotics production to be preserved in evolution.
Selective advantage
__________ ________ are antimicrobial drugs should kill or inhibit microbial cells without simultaneously damaging host tissues
Selective toxicity
Antibiotics are common metabolic products of _____ & _______.
bacteria and fung
Penicillins, block the synthesis of the cell wall only in bacteria making it a(n) ___________ source of selective toxcity.
excellant
The closer these two figures are of a therapeutic index to each other (the smaller the ratio), the ______ the potential for toxic drug reactions.
greater (ex. 1:1 is risker than 10)
What kind of drugs most toxic to human cells?
-Drugs that act upon a structure common to both the infective agent and the host cell -As the characteristics of the infectious agent become more similar to that of the host, selective toxicity becomes more difficult
What are side effects of Tetracyclines?
-Gastrointestinal disruption -Deposition in hard tissues
What are some metabolic targets of chemotherapeutic agents?
-Inhibition of cell wall synthesis -Inhibition of nucleic acid (DNA and RNA) structure and function -Inhibition of protein synthesis -Interference with cell membrane structure or function -Inhibition of folic acid synthesis
Why must a patient's medical history need to be considered when treating patients with antimicrobial therapy?
-Preexisting medical conditions that will influence the activity of the drug or the response of the patient -History of allergy to a certain class of drugs -Underlying liver or kidney disease -Infants, elderly and pregnant women require special precautions
What are some possible reasons why a treatment would fail?
-The inability of the drug to diffuse into that body compartment (the brain, joints, skin) -Resistant microbes in the infection that didn't make it into the sample collected for testing -An infection caused by more than one pathogen (mixed), some of which are resistant to the drug
What are the benefits of the Tube dilution test?
-Useful in determining the smallest effective dosage of a drug -Provides a comparative index against other antimicrobials
What are 3 factors must be known before starting antimicrobial therapy?
1. The identity of the microorganism causing the infection 2. The degree of the microorganism's susceptibility (sensitivity) to various drugs 3. The overall medical condition of the patient
What is the goal of antimicrobial chemotherapy?
Administer a drug to an infected person that destroys infected agent without harming the host's cell.
The _____ _____ _____ the smallest concentration (highest dilution) of drug that visibly inhibits growth
Minimum inhibitory concentration:
_____ _____ is the ratio of the dose of the drug that is toxic to humans to its minimum effective (therapeutic) dose
Therapeutic Index (TI)
Tetracyclines are a natural parent compound and synthetic derivatives and have ______ spectum effects.
broad
Carbapenems targets the ______ ______.
cell wall
PCN targets the _____ ______.
cell wall
New drugs are created by chemically altering the structure of naturally occurring antibiotics to create _______ drugs.
semisynthetic
