Cibles, Modes d'Action et Choix des Antibiotiques PDF

# Memo pratique 12 ## Cibles, modes d'action et choix des antibiotiques * **Antibiotics**: chemical compounds, elaborated by a living organism or produced by synthesis, with high chemotherapeutic coefficient whose therapeutic activity is manifested at very low doses in a specific manner. They inhi...

# Memo pratique 12 ## Cibles, modes d'action et choix des antibiotiques * **Antibiotics**: chemical compounds, elaborated by a living organism or produced by synthesis, with high chemotherapeutic coefficient whose therapeutic activity is manifested at very low doses in a specific manner. They inhibit certain vital processes, in microorganisms or even certain multicellular beings. * **Antibiotic targets**: bacterial targets to antibiotics correspond to different organelles of the bacterial cell or to certain metabolic functions. **Table:** Cibles d'antibiotiques sur la cellule bactérienne | Cible | Familles d'antibiotiques ou molécules antibiotiques | |---|---| | **Paroi** | Cycloserine, bacitracine, glycopeptides, β-lactamines (penicillines, cephalosporins) | | **Membrane plasmique** | Colistine, daptomycine | | **Ribosomes** | | **Sous-unité 50S** | Phenicolés, macrolides & apparentés, linezolide | | **Sous-unité 30S** | Cyclines, aminoglycosides & apparentés, linezolide | | **Acides nucléiques** | | **Inhibiteurs ARN polymérase** | Ansamycines (rifamycines) | | **Inhibiteurs topoisomérases** | Quinolones | | **Inhibiteurs de l'acide folique** | Sulfamides et triméthoprime | ## Two types of antibiotiques: * **Bactericidal antibiotics**: kill bacteria * **Bacteriostatic antibiotics**: prevent bacterial multiplication ## Choosing an antibiotic * **Spectrum of activity**: corresponds to the range of bacteria the antibiotic is effective against. * **Responsible bacteria**: identified or suspected (based on probability). * **Antibiotic diffusion and ability to reach the site of infection**: depends on pharmacokinetics. * **Patient's health and age** * **Severity of infectious disease** ## Precautions related to antibiotic treatment * **Microbiological samples**: necessary before treatment to avoid false results. * **Patient questionnaire**: verify allergy history, or any contraindications to administration route. ## Prescription details * **Duration** * **Frequency** * **Dosage** * **Specific protocol** ## Monitoring antibiotic treatment Close monitoring of patients is necessary to detect side effects or treatment failures. ## Adaptation of antibiotic administration route * **Urgency of treatment**: priority to parenteral routes. * **Site of infection**: choose appropriate route for effective treatment. * **Patient's health**: Avoid routes with potential complications (e.g., swallowing difficulties). * **Drug interactions**: consider potential drug interactions. * **Galenic forms**: some antibiotics only exist as parenteral forms. ## Resistance to antibiotics ### Notion of resistance: * **Resistance**: occurs when the minimal inhibitory concentration (MIC) of an antibiotic is greater than the maximum achievable blood concentration with standard dosing. * **MIC**: lowest antibiotic concentration that inhibits 100% of bacterial growth (in vitro). * **Interpreting antibiogram results**: * **CMI ≤ c**: Sensitive (S) * **CMI > C**: Resistant (R) * **c < CMI < C**: Sensitive to high dosage ### Types of resistance: * **Natural resistance**: the antibiotic target is absent or inaccessible in the bacteria. * **Acquired resistance**: some proportion of initially sensitive bacteria become resistant to the antibiotic's action.