Antimicrobials-

 Used to treat infectious diseases

 190 million doses of antibiotics are given in hospitals each day

 Modern antimicrobials: 1930s and 1940s

 Significantly reduced morbidity and mortality from infection

Basic Principles of Antimicrobial Therapy

 Antibiotic

o Strictly speaking, a chemical produced by one microbe that can harm other

microbes

 Antimicrobial agent

o Any agent that can kill or suppress microorganisms

Selective Toxicity-

 Toxic to microbes but harmless to host

 Differences in the cellular chemistry of mammals and microbes

 Disruption of bacterial protein synthesis and cell wall

 Inhibition of an enzyme unique to bacteria

Classification of Antimicrobial Drugs-

 Various classification systems

 The two used for this textbook:

o Classification by susceptible organism

o Classification by mechanism of action

Prophylactic Use of Antimicrobials-

 Agents are given to prevent infection rather than to treat an established infection:

o Surgery

o Bacterial endocarditis

o Neutropenia

o Other indications

Misuses of Antimicrobial Drugs

 Attempted treatment of viral infections

 Treatment of fever of unknown origin

 Improper dosage

 Treatment in the absence of adequate bacteriologic information

 Omission of surgical drainage

Monitoring of Antimicrobial Therapy

 Monitor clinical responses and laboratory results

 Frequency of monitoring should increase with severity of infection

 Clinical indicators of success

o Reduction of fever, resolution of signs/symptoms related to the affected organ

 Serum drug levels for toxicity

Classification of Antibiotics-

 Drugs work on:

 Cell wall synthesis

 Cell membrane permeability

 Protein synthesis (lethal)

 Nonlethal inhibitors of protein synthesis

 Synthesis of nucleic acids

 Antimetabolites

 Viral enzyme inhibitors

Classification of Antibiotics (Cont.)-

 Bacteriocidal

 Drugs are directly lethal to bacteria at clinically achievable concentrations

 Bacteriostatic

 Drugs can slow bacterial growth but do not cause cell death

Dosage Size and Duration-

 Antibiotic must be present:

o At the site of infection

o For a sufficient length of time

 Antibiotics must not be discontinued prematurely

 Teach patients to complete full prescription

Antibiotic Combinations-

 Antimicrobial effects of antibiotic combinations

o Additive, potentiative, antagonistic

 Indications

o Mixed infections, prevention of resistance, decreased toxicity, enhanced bacterial

action

 Disadvantages of combinations

Penicillins (Cont.)

 Action- Weaken the call wall of bacteria.

 Resistance- Is determined by inability to reach the target, inactivation by bacterial

enzymes and production of penicillin binding proteins that have a low affinity for it.

 Active against a variety of bacteria

 Direct toxicity: Low

 Principal adverse effect: Allergic reaction

 Structure includes a beta-lactam ring