🛡️ Comprehensive Antibacterial Drugs
Study Guide
This guide covers the classification, mechanisms, and clinical considerations of antibacterial
agents, organized by their physiological targets.
I. Introduction to Antimicrobials
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● Ideal Antimicrobial: Should interfere with the vital functions of pathogens without
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affecting host cells.
● Selective Targeting: Ideally targets unique pathogen groups to minimize adverse
effects on the host.
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○ Unique Targeting: Targets genetic or biochemical pathways unique to the
pathogen (e.g., bacterial cell wall synthesis).
○ Selective Targeting: Targets a protein isoform unique to the pathogen (e.g.,
dihydrofolate reductase or protein synthesis inhibitors).
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○ Common Targeting: Targets metabolic requirements specific to the pathogen.
● Classification by Activity:
○ Bactericidal: Kills the organism. Examples: beta-lactams, Vancomycin,
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Fluoroquinolones, Aminoglycosides, Daptomycin, Metronidazole.
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○ Bacteriostatic: Inhibits growth; requires host defenses to clear infection.
Examples: Macrolides, Clindamycin, Sulfonamides, Linezolid, Chloramphenicol,
Tetracyclines.
○ Combinations: Bacteriostatic + Bactericidal = Antagonistic. Two of the same
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type = Synergistic.
, II. Inhibitors of Cell Wall Synthesis
These drugs generally impair bacterial cell wall synthesis and are bactericidal.
1. beta-Lactams
Characterized by a beta-lactam ring, they bind covalently to the active site of
transpeptidase (Penicillin-Binding Protein).
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● Penicillins:
○ Standard: Benzylpenicillin (Penicillin G - IV) and Phenoxymethylpenicillin (Penicillin
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V - Oral).
○ beta-Lactamase-Resistant: Methicillin, Cloxacillin, Flucloxacillin (used for
staphylococci).
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○ Broad-Spectrum: Ampicillin, Amoxicillin (covers Gram-negative bacilli; Amoxicillin
is better absorbed).
○ Extended-Spectrum: Ticarcillin, Piperacillin (active against Pseudomonas
aeruginosa).
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○ beta-Lactamase Inhibitors: Clavulanate, Sulbactam, Tazobactam. Used in
combinations (e.g., Amoxicillin + Clavulanate) to treat resistant organisms.
● Cephalosporins: Divided into 5 generations. As generations progress, they show
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increased activity against aerobic Gram-negative bacilli and generally decreased
antistaphylococcal activity.
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● Carbapenems: (e.g., Imipenem, Meropenem). Broad-spectrum bactericidal agents.
● Monobactams: (e.g., Aztreonam). Active against Gram-negative organisms like
Pseudomonas, but no action against Gram-positives or anaerobes.
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2. Glycopeptides (Vancomycin & Teicoplanin)
Inhibit murein polymerization by binding to the D-Ala–D-Ala terminus of murein monomers.
● Clinical Use: Reserved for MRSA, C. difficile (oral use for pseudomembranous colitis),
and serious staphylococcal infections.
● Adverse Effects: Nephrotoxicity, ototoxicity, and "Red-man syndrome" (flushing due
to histamine release).
Study Guide
This guide covers the classification, mechanisms, and clinical considerations of antibacterial
agents, organized by their physiological targets.
I. Introduction to Antimicrobials
y
● Ideal Antimicrobial: Should interfere with the vital functions of pathogens without
Ja
affecting host cells.
● Selective Targeting: Ideally targets unique pathogen groups to minimize adverse
effects on the host.
ith
○ Unique Targeting: Targets genetic or biochemical pathways unique to the
pathogen (e.g., bacterial cell wall synthesis).
○ Selective Targeting: Targets a protein isoform unique to the pathogen (e.g.,
dihydrofolate reductase or protein synthesis inhibitors).
w
○ Common Targeting: Targets metabolic requirements specific to the pathogen.
● Classification by Activity:
○ Bactericidal: Kills the organism. Examples: beta-lactams, Vancomycin,
y
Fluoroquinolones, Aminoglycosides, Daptomycin, Metronidazole.
ud
○ Bacteriostatic: Inhibits growth; requires host defenses to clear infection.
Examples: Macrolides, Clindamycin, Sulfonamides, Linezolid, Chloramphenicol,
Tetracyclines.
○ Combinations: Bacteriostatic + Bactericidal = Antagonistic. Two of the same
st
type = Synergistic.
, II. Inhibitors of Cell Wall Synthesis
These drugs generally impair bacterial cell wall synthesis and are bactericidal.
1. beta-Lactams
Characterized by a beta-lactam ring, they bind covalently to the active site of
transpeptidase (Penicillin-Binding Protein).
y
● Penicillins:
○ Standard: Benzylpenicillin (Penicillin G - IV) and Phenoxymethylpenicillin (Penicillin
Ja
V - Oral).
○ beta-Lactamase-Resistant: Methicillin, Cloxacillin, Flucloxacillin (used for
staphylococci).
ith
○ Broad-Spectrum: Ampicillin, Amoxicillin (covers Gram-negative bacilli; Amoxicillin
is better absorbed).
○ Extended-Spectrum: Ticarcillin, Piperacillin (active against Pseudomonas
aeruginosa).
w
○ beta-Lactamase Inhibitors: Clavulanate, Sulbactam, Tazobactam. Used in
combinations (e.g., Amoxicillin + Clavulanate) to treat resistant organisms.
● Cephalosporins: Divided into 5 generations. As generations progress, they show
y
increased activity against aerobic Gram-negative bacilli and generally decreased
antistaphylococcal activity.
ud
● Carbapenems: (e.g., Imipenem, Meropenem). Broad-spectrum bactericidal agents.
● Monobactams: (e.g., Aztreonam). Active against Gram-negative organisms like
Pseudomonas, but no action against Gram-positives or anaerobes.
st
2. Glycopeptides (Vancomycin & Teicoplanin)
Inhibit murein polymerization by binding to the D-Ala–D-Ala terminus of murein monomers.
● Clinical Use: Reserved for MRSA, C. difficile (oral use for pseudomembranous colitis),
and serious staphylococcal infections.
● Adverse Effects: Nephrotoxicity, ototoxicity, and "Red-man syndrome" (flushing due
to histamine release).
