Antimicrobial Therapy

1
Antimicrobial Therapy

• Julie Balk NP MS
• Nursing 220
• Spring 2005

2
Principles of Antimicrobial Therapy

• Selective Toxicity
• Classifications of Antimicrobial Drugs
• Resistance
• Selection of Antimicrobials
• Microbiology
• Host Factors
• Dosage and Duration of antimicrobials
• Misuses of Antibiotics
• Monitoring of Antibiotics

3
Selective Toxicity

• Ability of a drug to injure a target cell or
  organism without injuring other cells
• i.e. kill the bacteria without killing the host

4
Classifications of Antimicrobial Agents

• Disruption of Bacterial Cell Wall
• Bacteria are encased in a rigid cell wall
• Inhibition of an Enzyme unique to Bacteria
• Selective toxicity from inhibition of an enzyme
  that is essential for the bacterial growth but is
  not present in host cells
• Disruption of Bacterial Protein Synthesis
• Bacterial ribosomes of bacteria differ in
  structure from those of mammalian cells

5
Classification (cont)

• Spectrum of activity
• Broad Spectrum
• Narrow Spectrum
• Mechanism of Action
• Cell wall inhibition
• Increase cell membrane permeability
• Inhibition of bacterial protein synthesis
• Lethal or non lethal
• Inhibition of bacterial synthesis of nucleic acid
• Antimetabolites
• Inhibittion of viral enzymes

6
Resistance

• Four types of antimicrobial resistance
• Microbes elaborate drug-metabolizing enzymes
• Microbes may cease active uptake of certain drugs
• Microbial drug receptors may undergo change
  resulting in decreased antibiotic binding
• Microbes may synthesize compounds that antagonize
  drug actions

7
Acquired Resistance

• Spontaneous Mutation
• Gradual increase in resistance
• Conjugation
• Extrachromosomal DNA is transferred from one
  bacterium to another
• Primarily gram negative
• Results in multiple drug resistance

8
Resistance

• Antibiotic Utilization and Drug resistance
• Prevent Infection
• Dx and Rx infection effectively
• Use antimicrobial wisely
• Prevent transmision

9
12 Steps to Delay Resistance(CDC 2002)

• Vaccinate
• Get the catheters out
• Target the pathogen
• Access the experts
• Practice antimicrobial control
• Use local data
• Treat infection, not contamination
• Treat infection, not colonization
• Know when to say no to Vanco
• Stop treatment when infection is cured or
  unlikely
• Isolate the pathogen
• Break the chain of contagion

10
Selection of AntibioticsMicrobiology

• Empiric
• Best Guess
• Culture Directed Treatment
• Culture and Sensitivities
• Disk-Diffusion
• Broth Dilution

11
Selection of AntibioticsHost Factors

• Host Defenses
• Site of Infection
• Other Host Factors
• Age
• Pregnancy and Lactation
• Previous Allergic Reactions
• Genetic Factors

12
Antimicrobial Dosage and Duration of therapy

• Host Factors
• Site of infection
• Infecting Organism

13
Misuse of Antimicrobials

• Attempted Treatment of Untreatable Infections
• Treatment of Fever of Unknown Origin (FUO)
• Improper Dosage
• Treatment of Absence of Adequate Bacteriologic
  Information
• Omission of Surgical Drainage (ID)

14
Antimicrobial Monitoring

• Clinical Responses
• Fever, signs and symptoms of illness
• Laboratory results