Ch.20 Antimicrobial Drugs Flashcards
narrow spectrum antibiotics
is effective against specific families of bacteria.
broad-spectrum antibiotics
refers to antibiotics that act against a wide range of disease-causing bacteria.
superinfection:
overgrowth of normal microbiota that is resistant to antibiotic
bactericidal:
kill microbes directly
Major Action Modes of Antibacterial Drugs
- inhibition of cell wall synthesis:
penicillins
cephalosporins
bacitracin
vancomycin
bacteriostatic:
prevent microbes from growing
Major Action Modes of Antibacterial Drugs
- inhibition of protein synthesis
chloramphenicol
erythromycin
tetracyclines
streptomycin
Major Action Modes of Antibacterial Drugs
- inhibition of nucleic acid replication and transcription
quinolones
rifampin
Major Action Modes of Antibacterial Drugs
- injury to the plasma membrane:
polymyxin B
Major Action Modes of Antibacterial Drugs
- inhibition of essential metabolite synthesis:
sulfanilamide
trimethoprim
The action of microbial drugs:
inhibiting cell wall synthesis of peptidoglycan
Penicillins prevent the synthesis
of peptidoglycan
The action of microbial drugs:
injuring the plasma membrane
Polypeptide antibiotics change
membrane permeability.
Ionophore antibiotics: allow for uncontrolled movement of cations
The action of microbial drugs:
Inhibiting protein synthesis
Target bacterial 70S ribosomes
‒ Chloramphenicol, erythromycin,
streptomycin, tetracycline
Streptomycin
changes shape of the 30 S portion, causing code on mRNA to be read incorrectly
tetracyclines
interfere with the attachment of tRNA to mRNA-ribosome complex
The Action of Antimicrobial Drugs
inhibiting nucleic acid synthesis
interfere with DNA replication and transcription
Rifamycin, quinolones (nalidixic acid) & fluoroquinolones
The Action of Antimicrobial Drugs
inhibiting the synthesis of essential metabolites
anti-metabolites compete with the normal substrate for the enzyme
Modes of Antiviral Drugs
- Entry and fusion inhibitors
- Uncoating, genome integration, and nucleic acid synthesis inhibitors
- Assembly and exit inhibitors
- Interferons
Entry & fusion inhibitor
Block the receptors on the host cell that bind to the virus
‒ Block fusion of the virus and cell
Uncoating, genome integration, and nucleic acid synthesis
inhibitors
Prevent viral uncoating
‒ Inhibit viral DNA integration
into the host genome
‒ Nucleoside analogs inhibit RNA/ DNA synthesis
assembly and exit inhibitors
‒ Protease inhibitors: block the cleavage of inhibitor cleavage of protein precursors
‒ Exit inhibitors: inhibit neuraminidase, an enzyme required for some viruses to bud from the host cell
interferons
Produced by viral-infected cells to inhibit further spread of the
infection
Imiquimod:
promotes interferon production
antiretroviral drug is used to treat
HIV infections
persister cells:
microbes with genetic characteristics allowing for their survival when exposed to an antibiotic
superbugs:
bacteria that are resistant to a large number of antibiotics
Mechanisms of Resistance
Enzymatic destruction or inactivation of the drug
- Prevention of penetration to the target site within the microbe
- Alteration of the
drug’s target site - Rapid efflux (ejection)
of the antibiotic - Variations of
mechanisms of
resistance
Resistance genes are often spread
horizontally among bacteria
on plasmids or transposons via conjugation or transduction
Antibiotic Misuse
Using outdated or weakened antibiotics
Using antibiotics for the common cold and other
inappropriate conditions
Using antibiotics in animal feed
Failing to complete the prescribed regimen
Using someone else’s leftover prescription
synergism
the effect of two drugs together is greater than the effect of either alone
antagonism
the effect of two drugs together is less than the effect of either alone
