Microbiology, 2021

574 14 • Antimicrobial Drugs
Drugs That Inhibit Bacterial Protein Synthesis
Molecular
Target
Mechanism of Action Drug Class Specific Drugs
Bacteriostatic
or
Bactericidal
Spectrum
of
Activity
30S
subunit
Causes mismatches
between codons and
anticodons, leading to
faulty proteins that
insert into and disrupt
cytoplasmic membrane
Aminoglycosides
Streptomycin,
gentamicin,
neomycin,
kanamycin
Bactericidal
Broad
spectrum
Blocks association of
tRNAs with ribosome
Tetracyclines
Tetracycline,
doxycycline,
tigecycline
Bacteriostatic
Broad
spectrum
Blocks peptide bond
formation between
amino acids
Macrolides
Lincosamides
Erythromycin,
azithromycin,
telithromycin
Lincomycin,
clindamycin
Bacteriostatic
Bacteriostatic
Broad
spectrum
Narrow
spectrum
50S
subunit
Not applicable Chloramphenicol Bacteriostatic
Broad
spectrum
Interferes with the
formation of the
initiation complex
between 50S and 30S
subunits and other
factors.
Oxazolidinones Linezolid Bacteriostatic
Broad
spectrum
Table 14.3
CHECK YOUR UNDERSTANDING
• Compare and contrast the different types of protein synthesis inhibitors.
Inhibitors of Membrane Function
A small group of antibacterials target the bacterial membrane as their mode of action (Table 14.4). The
polymyxins are natural polypeptide antibiotics that were first discovered in 1947 as products of Bacillus
polymyxa; only polymyxin B and polymyxin E (colistin) have been used clinically. They are lipophilic with
detergent-like properties and interact with the lipopolysaccharide component of the outer membrane of gramnegative
bacteria, ultimately disrupting both their outer and inner membranes and killing the bacterial cells.
Unfortunately, the membrane-targeting mechanism is not a selective toxicity, and these drugs also target and
damage the membrane of cells in the kidney and nervous system when administered systemically. Because of
these serious side effects and their poor absorption from the digestive tract, polymyxin B is used in over-thecounter
topical antibiotic ointments (e.g., Neosporin), and oral colistin was historically used only for bowel
decontamination to prevent infections originating from bowel microbes in immunocompromised patients or
for those undergoing certain abdominal surgeries. However, the emergence and spread of multidrug-resistant
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