Microbiology 11 - Chapter 11 Antimicrobial Drugs Mechanisms of Antimicrobial Action Goal of antimicrobial agent is to \u2022 Interfere with metabolism

Microbiology 11 - Chapter 11 Antimicrobial Drugs...

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Chapter 11 Antimicrobial Drugs Mechanisms of Antimicrobial Action Goal of antimicrobial agent is to Interfere with metabolism or structure of organism so that it cannot survive or reproduce Microbicidal Kills microbes Can kill normal flora—potential for superinfection Microbiostatic Reversibly inhibits growth Antimicrobial agents use different mechanisms of action to either kill or inhibit microbial growth . These mechanisms are varied and can target highly specific structures or metabolic functions necessary for the survival of the microorganism These are divided into five basic categories : 1 . Cell wall synthesis inhibition 2 . Protein synthesis inhibition 3 . Nucleic acid synthesis inhibition 4 . Cell membrane disruption 5 . Metabolic antagonism/disruption Inhibition of Cell Wall Synthesis Causes weakness of peptidoglycan layer Vulnerable to lysis - Penicillin - Cephalosporins Inhibition of Protein Synthesis Disruption of translation at ribosome
Ribosomes of eukaryotic cells not affected Due to this difference, human cells are usually not affected by the inhibitory action of these agents because they selectively act against bacteria I nhibition of Nucleic Acid Synthesis Disruption of DNA and RNA synthesis Complexity of metabolic process leads to disruption at many points - Disruption of the synthesis of nucleotide components - Inhibition of DNA replication - Interference with RNA transcription Competitive inhibition is process mimicking the normal substrate of an enzyme When these agents are supplied to the cell in high concentrations they will substitute for the true substrate of an important enzyme, thus preventing the enzyme from producing a needed product and causing the metabolism of the cell to slow or stop . Examples: sulfonamides and trimethoprim Disruption of Plasma Membrane Affects transport in/out of cell Weakens cell s physical integrity Can affect prokaryotic and eukaryotic cells Because all microorganisms (except for viruses) share the same basic plasma membrane structure, these agents are useful against both bacteria and fungi . Inhibition of Metabolic Pathways Antimicrobial agents disrupt the metabolic pathways involved in the synthesis of proteins and nucleic acids, but can affect numerous cellular metabolic processes that can lead to cell death . Disruption of numerous cellular metabolic processes Disruption of enzyme activity/production
Disruption of essential metabolic compounds Characteristics of Antimicrobial Agents Almost all antimicrobial agents share a set of common characteristics that are important to remember when selecting a drug for treatment Spectrum of action Selective toxicity Microbicidal vs. microbiostatic Delivery to infection site Solubility and potency Time it remains active Degree of resistance Characteristics of Antimicrobial Agents (Cont (.

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