Introduction aux antibiotiques Flashcards
What is an antibiotic?
Antimicrobien qui arrête la croissance ou qui une bactérie
What are the names of “les autres antimicrobiens”?
- Antiviraux —> viruses
- Antifungiques —> champignons
- Antiparasitaires —> parasites
What is antibiotherapy?
L’art d’utiliser les antibiotiques adéquatement en clinique
What are the steps of antibiotherapy?
What are the two important microbiological findings that guide clinicians when selecting an appropriate ATB?
- Identification de l’agent pathogène (lorsque c’est possible)
- Analyse de sensibilité aux antibiotiques
What are the two steps used to identify a pathogen?
spécimen clinique —> laboratoire de microbiologie
-
Examen direct (on the specimen)
- Gram test —> preliminary result just to narrow down… no ID of species at this point
-
Confirmation
- Culture and molecular biology (PCR/mass spectrometry… but not used as much, still quite new)
What is an examen direct?
Done directly on the specimen to detect presence bacteria
Preliminary result —> Gram +/-
What are the most common gram + and - bacteria?
Gram + —> usually cocci
- ex: Staphylococcus, Streptococcus, Enterococcus
Gram - —> usually bacilli
- ex: Enterobacteria, non fermenting bacilli, anaerobes
What is identification de la culture? (step 2)
Confirm pathogen
Takes 48 hours
Atmosphères d’incubation: aérobie vs. anaérobie
Bactéries plus fastidieuses: Intracellulaires ou atypiques
- Legionella, Chlamydia, Chlamydophila
What are the 4 big groups of bacteria targeted by ATP according to microbiological analyses?
- Gram +: peau et tissus mous
- Gram -: infections urinaires
- Intracellulaires/atypiques: ITSS
- Anaérobies: infections intra-abdominales —> these bacteria are usually already found in the GI tract
What are the 5 principal characteristics of ATB?
- Mode d’action
- Spectre d’activité
- Voie d’administration
- Pharmacologie
- Mécanisme d’action
What are the two kinds of modes d’action?
- Bacteriostatic: inhibit growth of bacteria w/o killing them… reversible effect
- Bactericidal: kill bacteria, irreversible, typically used for more severe infections (bacteremia, endocarditis, meningitis, etc.)
What are the two spectres d’activités?
- Spectre étroit: specific treatment for an identified pathogen (ex: subcutaneous SARM infection —> IV vancomycin)
- Spectre étendu: empiric treatment depending on the “syndrome infectieux”, polymicrobial infection (ex: PAC sans germe identifié —> Ceftriaxone)
What are the three most common voies d’administration?
- Orale —> per os, PO
- Intraveineuse (IV)
- Intramusculaire (IM)
What are the different mécanismes d’action used by ATBs?
Agissent à différents niveaux du métabolisme bactérien
Interfere with vital functions of bacteria
What are the 6 most important vital functions of bacteria that ATB interfere with?
Inhibiting synthesis of:
- Paroi bactérienne
- Membrane bactérienne
- Acides nucléiques
- ARN polymérase
- Acide folique
- Protéines
What are the two classes of antibiotics that inhibit the synthesis of the paroi bactérienne?
- B-lactamines/lactams
- Glycopeptides
What is the common thing in the structure of B-lactamines?
What is the mécanisme d’action B-lactamines?
Inhibit the synthesis of peptidoglycans (rigid part of cell wall) found in Gram+ and - bacteria
What are the 4 main groups of B-lactamines?
Penicillins
Cephalosporins
Carbapenems
Monobactams
What are the 5 main kinds of penicillins?
- Natural
- Anti-staph
- Aminopenicillins
- Broad spectrum (carboxypenicillins, ureidopenicillin)
- Penicillin associated with a B-lactamase inhibitor
Natural penicillin:
Anti-staph penicillin:
Aminopenicillins:
Broad spectrum (carboxypenicillins, ureidopenicillin) penicillins
Penicillin associated with a B-lactamase inhibitor:
Spectre d’action des céphalos?
First generation céphalos:
Second generation céphalos:
Third generation céphalos:
Fourth and fifth generation céphalos:
Carbapenems:
Atomic bomb of antibiotics… kills everything in its path BUT used too much therefore resistance has started to develop
Monobactams:
Only one type… Aztreonam
Pure anti-gram negative —> enterobacteria, Pseudomonas
- Used in resistance cases or allergies
What is the most common glycopeptide?
VANCOMYCIN!
What class of antibiotics inhibit the synthesis of the membrane bactérienne?
Lipopeptides: Daptomycine
What are the two classes of antibiotics inhibit the synthesis of nucleic acids?
- Quinolones
- Metronidazole
Quinolones:
Matronidazole:
What are the antibiotics that inhibit the synthesis of folic acids?
What are the antibiotics that inhibit the synthesis of proteins?
Aminosides:
Macrolides:
Clindamycin:
prolonged postantibiotic effect —> It may decrease toxin production and increase microbial opsonization and phagocytosis
What are the 3 main ATB resistance mechanisms used by bacteria?
- Production of an enzyme that modifies the ATB (ex: B-lactamase)
- Alteration of the permeability of the cell membrane (GRAM NEGATIVE BACTERIA… ex: pseudomonas and carbapenems)
- Alter the “cible” of the ATB (mostly GRAM POSITIVE BACTERIA)
What is carbapénémase?
What are the two ways to alter membrane permeability?
-
Loss of porins:
- Can’t get in anymore
-
Pompes à efflux:
- Gets in… pumped right out
How does altering the cible work?
