BIOL 250 - Chapter 10 Vocab

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Chemotherapeutic agents

chemicals used to treat diseases

Antimicrobial agents/antimicrobials

chemotherapeutic drugs that treat infections

Antibiotics

antimicrobial agents that are produced naturally by an organism

Semisynthetic antimicrobials

chemically altered antibiotics; more effective, longer lasting and easier to administer than antibiotics

Synthetic drugs

antimicrobials completely synthesized in a laboratory

Selective toxicity

an effective antimicrobial agent must be more toxic to a pathogen than to the pathogen’s host

Beta-lactams

antimicrobials whose functional portions are called beta-lactam rings; prevents the cross-linkage of NAM subunits

Bacitracin

antimicrobial that also prevents cell wall formation; blocks transport of NAG and NAM across the cytoplasmic membrane to the wall

Isoniazid (INH) and ethambutol

disrupt the formation of mycolic acid in the cell walls of mycobacteria

Echinocandins

a class of antifungal drugs that inhibit the enzyme that synthesizes glucan–which assists in the formation of fungal cell walls

Aminoglycosides

change the shape of the 30S subunit of a prokaryotic ribosome, making it impossible for the ribosome to read the codons of mRNA correctly

Tetracyclines

block the tRNA docking site (A site), preventing the incorporation of additional amino acids into a growing polypeptide

Chloramphenicols

block the enzymatic site of the 50S subunit, preventing translation

Lincosamides, streptogramins and macrolides

bind to a different portion of the 50S subunit, preventing movement of the ribosome from one codon to the next, freezing translation

Antisense nucleic acids

RNA or single-stranded DNA molecules designed to be complementary to a pathogen’s mRNA molecules; block ribosomal subunits from attaching to pathogenic mRNA with no effect on human mRNA

Oxazolidinones

stop protein synthesis by blocking the initiation of translation

Mupirocin

a topical drug that selectively binds to isoleucyl-tRNA synthetase, making translation stop once an isoleucine codon is reached

Polyenes

an antifungal and antiprotozoal group of drugs that disrupt the cytoplasmic membrane by forming a channel through the membrane, damaging its integrity

Azoles and allylamines

antifungal and antiprotozoal drugs that act by inhibiting the synthesis of ergosterol, an important lipid in a fungal cell’s cytoplasmic membrane

Sulfonamides/sulfa drugs

antimetabolic drugs that are analogs of PABA, a molecule important in the synthesis of nucleotides in DNA and RNA synthesis; works as a competitor of PABA in the binding of an enzyme converting PABA to dihydrofolic acid

Quinolones

inhibit DNA gyrase, the enzyme in bacteria necessary for coiling and uncoiling of replicating bacterial DNA; have little effect on viruses and eukaryotes but may act on mitochondrial DNA in some eukaryotes

Nucleotide analogs/nucleoside analogs

molecules with structural similarities to nucleotide building blocks of nucleic acids; distort shapes of nucleic acid molecules and prevent further replication, transcription, or translation; used most often against viruses

Spectrum of action

the number of different kinds of pathogens a drug acts against

Narrow-spectrum

drugs that work only against a few kinds of pathogens

Broad-spectrum

drugs that are effective against many kinds of pathogens

Diffusion susceptibility test (Kirby-Bauer test)

involve uniformly inoculating a petri plate with a standardized amount of pathogen in question. Then small disks of paper containing standard concentrations of the drugs to be tested are firmly arranged on the surface of the plate. After incubation, the plate is observed for whether the drug(s) effectively inhibited the bacterial growth

Zone of inhibition

a clear area where bacteria do not grow (a large zone of inhibition \= more effective drug (in general))

Minimum inhibitory concentration (MIC) test

determines the lowest concentration of an antimicrobial agent that prevents visible growth of a microorganism

Broth dilution test

where a standardized amount of bacteria is added to serial dilutions of antimicrobials in tubes or wells containing broth. After incubation, turbidity is measured

Minimum bactericidal concentration (MBC) test

determines the amount of drug required to kill a microbe (different from MIC–which tests for inhibition, not killing)

Therapeutic index (TI)

the margin of safety of a drug–a ratio of the dose of a drug that is toxic to 50% of a patient population to the dose of the drug that is therapeutic in 50% of patients

R plasmids/R factors

resistance genes in bacteria that can be obtained through acquiring these genes via horizontal gene transfer

Multiple-drug-resistant pathogens (superbugs)

pathogens resistant to three or more types of antimicrobial agents

Cross resistance

a phenomenon where resistance to one antimicrobial may confer resistance to similar drugs; occurs when drugs are similar in structure

Synergism

where one drug may enhance the effect of a second drug