ppt chapter 08


Anti-Infective AgentsAnti-Infective Agents

Chapter 8


Development of Anti-Infective TherapyDevelopment of Anti-Infective Therapy

• 1920s

– Paul Ehrlich worked on developing a synthetic chemical effective only against infection-causing cells

– Scientists discovered penicillin in a mold sample

• 1935

– The sulfonamides were introduced


Drug Therapy Across the LifespanDrug Therapy Across the Lifespan


Mechanisms of ActionMechanisms of Action

• Interfere with biosynthesis of the bacterial cell wall

• Prevent the cells of the invading organism from using substances essential to their growth and development

• Interfere with steps involved in protein synthesis


Mechanisms of Action (cont.)Mechanisms of Action (cont.)

• Interfere with DNA synthesis

• Alter the permeability of the cell membrane to allow essential cellular components to leak out


Mechanism of Anti-Infective AgentsMechanism of Anti-Infective Agents


Anti-Infective ActivityAnti-Infective Activity

• Anti-infectives vary in their effectiveness against invading organisms.

• Some are selective – only effective for a few number of organisms

• Bactericidal – kill the cell

• Bacteriostatic – prevent reproduction of the cell


Narrow Spectrum vs. Broad SpectrumNarrow Spectrum vs. Broad Spectrum

• Narrow Spectrum of Activity

– Effective against only a few microorganisms with a very specific metabolic pathway or enzyme

• Broad Spectrum of Activity

– Useful in treating a wide variety of infections


Human Immune ResponseHuman Immune Response

• Goal of anti-infective therapy is reduction of the population of the invading organism.

• Drugs that would eliminate all traces of any invading pathogen might be toxic to the host as well.

• Immune response is a complex process involving chemical mediators, leukocytes, lymphocytes, antibodies, and locally released enzymes and chemicals.


Problems With Treating Infections in Immunosuppressed Patients

Problems With Treating Infections in Immunosuppressed Patients

• Anti-infective drugs cannot totally eliminate the pathogen without causing severe toxicity in the host.

• These patients do not have the immune response in place to deal with even a few invading organisms.


QuestionQuestion

Which of the following has been found to be as important as drug therapy when treating infections in the immunosuppressed?

A. Maintaining standard precautions

B. Proper nutrition

C. Good hand washing

D. Exercise


AnswerAnswer

B. Proper nutrition

Rationale: In helping these people (the immunosuppressed) cope with infections, prevention of infection and proper nutrition are often as important as drug therapy.


ResistanceResistance

• Anti-infectives act on specific enzyme system or biological process, many microorganisms that do not act on this system are not affected by this particular drug.

• This is considered natural or intrinsic resistance to that drug.


Acquired ResistanceAcquired Resistance

• Microorganisms that were once sensitive to the particular drug have begun to develop acquired resistance.

• This results in serious clinical problems.


Ways Anti-Infective Agents Resistance Develops

Ways Anti-Infective Agents Resistance Develops

• Producing an enzyme that deactivates the antimicrobial drug

• Changing cellular permeability to prevent the drug from entering the cell

• Altering transport systems to exclude the drug from active transport into the cell

• Altering binding sites on the membranes or ribosomes, which then no longer accept the drug

• Producing a chemical that acts as an antagonist to the drug


Preventing ResistancePreventing Resistance

• Limit the use of antimicrobial agents to the treatment of specific pathogens sensitive to the drug being used

• Make sure doses are high enough, and the duration of drug therapy long enough

• Be cautious about the indiscriminate use of anti-infectives


Identification of the PathogenIdentification of the Pathogen

• Identification of the infecting pathogen is done by culture

• A culture of a tissue sample from the infected area is done

– A swab of infected tissue is allowed to grow on an agar plate

– Staining techniques and microscopic examination identify the bacterium

• Stool can be examined for ova and parasites


Sensitivity of PathogenSensitivity of Pathogen

• Shows which drugs are capable of controlling the particular microorganism

• Is important with microorganisms that have known resistant strains

• Along with a culture, identifies the pathogen and appropriate drug for treatment


Factors Affecting PrescribingAnti-Infective Agents

Factors Affecting PrescribingAnti-Infective Agents

• Identification of the correct pathogen

• Selection of the right drug

– One that causes the least complications for that particular patient

– One that is most effective against the pathogen involved


Combination TherapyCombination Therapy

• Use of a smaller dosage of each drug

• Some drugs are synergistic

• In infections caused by more than one organism, each pathogen may react to a different anti-infective agent

• Sometimes, the combined effects of the different drugs delay the emergence of resistant strains


Prophylaxis of Anti-Infective AgentsProphylaxis of Anti-Infective Agents

• People traveling to an area where malaria is endemic

• Patients who are undergoing GI or genitourinary surgery

• Patients with known cardiac valve disease, valve replacements, and other conditions requiring invasive procedures


Adverse Reactions to Anti-Infective Therapy

Adverse Reactions to Anti-Infective Therapy

• Kidney Damage

• Gastrointestinal (GI) Tract Toxicity

• Neurotoxicity

• Hypersensitivity Reactions

• Superinfections


QuestionQuestion

You are caring for a patient who has just been diagnosed with a pseudomonas infection. You know that in deciding what medication to order for this patient the physician will take what into account?

A. The patient’s age

B. The patient’s gender

C. The drug that causes the least complication

D. The drug that has the longest half-life


AnswerAnswer

C. The drug that causes the least complication

Rationale: Identification of the correct pathogen

Selection of the right drug

• One that causes the least complications for that particular patient

• One that is most effective against the pathogen involved

ppt chapter 08

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