Chapter 10: Antimicrobial Treatment
Principles of Antimicrobial Therapy
• The introduction of modern drugs to control infections was a medical
revolution in the 1940s.
• Antimicrobial drugs have reduced the incidence of certain infections, but
they have not eradicated infectious disease and probably never will.
• Today, doctors are worried that we are dangerously close to a post-antibiotic
era where the drugs we have are no longer effective.
• Antibiotics are common metabolic products of bacteria and fungi
– Produced to inhibit growth of competing microbes in the same habitat.
Starting Treatment
• Before actual antimicrobial therapy can begin, three factors must be known:
– What Organism?
o The nature of the microorganism causing the infection
The degree of the microorganism’s susceptibility to various drugs
The overall medical condition of the patient
Pre-existing Conditions that must be factored into treatment
plan:
• Allergies to certain drug classes
• Underlying kidney or liver disease
• Infant, elderly, or pregnant.
• Age affects absorption
• Doses for infants very critical
• Infection site (joints,brain
• Drug Interactions (what drugs patient is taking)
• Route of administration: usually liquid, by mouth. (if
person can-not swallow, IV risks infection of needle cite)
• Cost of drug
, Mechanisms of Drug Action
• Drugs must exhibit some degree of selective toxicity.
• Toxicity: important concern
– Desire drug with high selectivity and low toxicity.
– Therapeutic Index: a ratio to determine with antimicrobials what is
going to be the best job.
TI of 1.1 riskier than TI of 10
Toxic dose to human/therapeutic dose that kills organism
Toxic dose: 11 mg human / toxic dose 10 mg organism = 1.1
risky
Toxic dose: 10 mg human / toxic dose 1 mg organism= 10
Drug Failures
– Inability to diffuse into body compartment
– Resistant microbes not noted in sample tested but present in vivo
– Mixed Infection
– Patient (Drug) Compliance: finishing the course of antibiotic
• Characteristics of Ideal Antimicrobial Drug
table 10.1 pg.276
• Antimicrobial drug categories pg. 283
– Inhibition of cell wall synthesis
– Inhibition of nucleic acid structure and function
– Inhibition of protein synthesis
– Interference with cell membrane structure and function
– Inhibition of folic acid synthesis
Principles of Antimicrobial Therapy
• The introduction of modern drugs to control infections was a medical
revolution in the 1940s.
• Antimicrobial drugs have reduced the incidence of certain infections, but
they have not eradicated infectious disease and probably never will.
• Today, doctors are worried that we are dangerously close to a post-antibiotic
era where the drugs we have are no longer effective.
• Antibiotics are common metabolic products of bacteria and fungi
– Produced to inhibit growth of competing microbes in the same habitat.
Starting Treatment
• Before actual antimicrobial therapy can begin, three factors must be known:
– What Organism?
o The nature of the microorganism causing the infection
The degree of the microorganism’s susceptibility to various drugs
The overall medical condition of the patient
Pre-existing Conditions that must be factored into treatment
plan:
• Allergies to certain drug classes
• Underlying kidney or liver disease
• Infant, elderly, or pregnant.
• Age affects absorption
• Doses for infants very critical
• Infection site (joints,brain
• Drug Interactions (what drugs patient is taking)
• Route of administration: usually liquid, by mouth. (if
person can-not swallow, IV risks infection of needle cite)
• Cost of drug
, Mechanisms of Drug Action
• Drugs must exhibit some degree of selective toxicity.
• Toxicity: important concern
– Desire drug with high selectivity and low toxicity.
– Therapeutic Index: a ratio to determine with antimicrobials what is
going to be the best job.
TI of 1.1 riskier than TI of 10
Toxic dose to human/therapeutic dose that kills organism
Toxic dose: 11 mg human / toxic dose 10 mg organism = 1.1
risky
Toxic dose: 10 mg human / toxic dose 1 mg organism= 10
Drug Failures
– Inability to diffuse into body compartment
– Resistant microbes not noted in sample tested but present in vivo
– Mixed Infection
– Patient (Drug) Compliance: finishing the course of antibiotic
• Characteristics of Ideal Antimicrobial Drug
table 10.1 pg.276
• Antimicrobial drug categories pg. 283
– Inhibition of cell wall synthesis
– Inhibition of nucleic acid structure and function
– Inhibition of protein synthesis
– Interference with cell membrane structure and function
– Inhibition of folic acid synthesis
