CH.20 ANTIMICROBIAL DRUGS Flashcards
selectively finding and destroying pathogens without damaging the host
Selective toxicity
the use of chemicals to treat a disease
Chemotherapy
a substance produced by a microbe that, in small amounts, inhibits another microbe
Antibiotic
synthetic substances that interfere with the growth of microbes
Antimicrobial drugs:
Paul Ehrlich
coined the term chemotherapy
Alexander Fleming
discovered penicillin,
drugs that affect a narrow range of microbial types
Narrow spectrum of microbial activity
affect a broad range of gram-positive or gram-negative bacteria
Broad-spectrum antibiotics
overgrowth of normal microbiota that is resistant to antibiotics
super infection
Antibacterial drugs target eukaryotic or prokaryotic?
Prokaryotic
Narrow-spectrum drugs affect only a select group of microbes; why?
Less likely to cause superinfections
Small, hydrophilic drugs can affect gram-negative cells.
Broad-spectrum drugs affect a more diverse range of microbes.
why?
Harm normal microbiota
More likely to result in superinfections
Major Action Modes of Antibacterial Drugs?
inhibition of cell wall synthesis (β-Lactam Penicillins prevent crosslinking of peptidoglycan)
inhibition of protein synthesis
inhibition nucleic acid and replication
injury to plasma membrane
inhibition of essential metabolite synthesis
The monobactam aztreonam affects only ?
gram-negative bacteria
Carbapenems
are broad-spectrum antibiotics that inhibit cell wall synthesis.
inhibit cell wall synthesis and are used against penicillin-resistant strains.
Cephalosporins
Polypeptides such as bacitracin inhibit ?
transport of cell wall subunits across membrane in gram-positive bacteria.
inhibits Nam/Nag subunit integration and may be used to kill penicillinase-producing staphylococci
Vancomycin
Isoniazid (INH) and ethambutol inhibit ?
cell wall synthesis in mycobacteria
Inhibiting protein synthesis
does what?
Target bacterial 70S ribosomes
Chloramphenicol (Binds to 50S portion ),
erythromycin,
streptomycin (changes shape of 30s portion),
tetracyclines (Interfere with attachment of
tRNA to mRNA–ribosome )
Injuring the plasma membrane?
and best used as a ?
Polypeptide and Ionophores damage plasma membrane allow uncontrolled movement of cations
Best used as a topical antibiotic
what do Agents affecting fungal membrane sterols do?
Interrupt the synthesis of ergosterol, making the membrane excessively permeable
Agents affecting fungal cell walls
Inhibit the synthesis of β-glucan
Agents inhibiting nucleic acids
cytosine analog interferes with RNA synthesis
What sterol in the cell membrane of fungi is the most common target for antifungal action
ergosterol
block host cell receptors
Entry inhibitors
competitive substrate inhibitors lacking 3’OH (Ex. Acyclovir)
Nucleoside/nucleotide reverse transcriptase inhibitors
non-competitive inhibitor of reverse transcriptase
Non-nucleoside reverse transcriptase inhibitors
: inhibit integration of viral DNA into host DNA
Viral integrase inhibitor
inhibit maturation of viral particles
Viral protease inhibitor
inhibit neuraminidase, an enzyme required for some viruses to bud from the host cell
Exit inhibitors
Produced by viral-infected cells to inhibit further spread of the infection
Interferons
Quinine and chloroquine
Treat malaria
anti-protozoan
Kills Plasmodium that causes malaria
Artemisinin
anti-protozoan
Also interferes with anaerobic bacteria
Treats Trichomonas, giardiasis, and amebic dysentery
Metronidazole
anti-protozoan
Inhibits cytochrome oxidase in mitochondria
Treats amebic encephalitis, and leishmaniasis
Miltefosine
anti-protozoan
Niclosamide
Prevents ATP production
Treats tapeworms
Alters membrane permeability
Treats tapeworms and flukes
Praziquantel
Interfere with nutrient absorption
Treat intestinal helminths
Mebendazole and albendazole
Paralysis of helminths
Treats roundworms and mites
Ivermectin
Determines the minimal inhibitory concentration (MIC)
Lowest antibiotic concentration preventing bacterial growth
E TEST
Determine the MIC and minimal bactericidal concentration (MBC) of an antimicrobial drug
BROTH DILUTION TESTS
Reports that record the susceptibility of organisms encountered clinically
Antibiograms
microbes with genetic characteristics allowing for their survival when exposed to an antibiotic
Persister cells
bacteria that are resistant to large numbers of antibiotics
Superbugs
Resistance genes are often spread horizontally among bacteria on ….?
plasmids or transposons via conjugation or transduction
What are some mechanisms that bacteria exhibit to resistance of antibiotic
rapid ejection of antibiotic
change surface receptors
alternate metabolic pathways
destroy the drug or inactiivate the drug through enzymatic activity
what are some common antibiotic misuses?
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
the effect of two drugs together is greater than the effect of either alone
Synergism
the effect of two drugs together is less than the effect of either alone
Antagonism
future of chemotherapeutic agents?
antimicrobial peptides produced by bacteria? produced by various organisms?
target virulence factors
sequester iron with feeds pathogens
Bacteriocines
Antimicrobial peptides
