BIO3 - Chapter 20

Antimicrobial drugs

chemotherapy

use of drugs to treat a disease

antimicrobial drugs

interfere with the growth of microbes within a host

antibiotic

substance produced by a microbe that inhbits another microbe (in small amounts)

selective toxicity

drug that kills harmful microbes without damaging the host

streptomyces

bacteria species that produce more than half of our antibiotics

narrow spectrum of microbial activity

drugs that affect a narrow range of microbial types; for mild issues

broad-spectrum antibiotics

affect a broad range of gram-positive or gram-negative bacteria; can contribute to antibiotic resistance

superinfection

overgrowth of normal microbiota that’s resistant to antibiotics; occurs after or on the tops of earlier infection

bactericidal

kills microbes directly

bacteriostatic

prevents microbes from growing without destruction

5 actions of microbial drugs

inhibiting cell wall synth, inhibiting protein synth, injuring plasma membrane, inhibiting nucleic acid synth, inhibiting synth of essential metabolites

selective toxicity

kills microbes w/o harming host cells

drugs that inhibit cell wall synthesis

penicillin: gram-pos. bacteria

drugs that inhibit protein synthesis

tetracyclines & streptomycin; both broad spectrum

drugs that injure plasma membrane

polymyxin b; tropicals shouldn’t be ingested since we also have plasma membranes

drugs that inhibit nuclic acid synth

quinolones & rifampin; interfere with dna replication & transcription

drugs that inhibit synth of essential metabolites (antimetabolites)

compete with normal substrates for an enzyme; sulfanilamide competes with para-aminobenzoi (PABA), stops folic acid synth

penicillin

contain B-lactam ring (differential), prevents cross-linking of peptidoglycan, cell wall construction

natural penicillins

extracted from penicillium fungi, narrow spectrum of activity, susceptible to penicillinases

semisynthetic penicillins

contain chem added side chains, resistant to penicillinases, broad spectrum

penicillinase-resistant penicillins

methicillin & oxacillin

extended-spectrum penicillins

effective against gram-neg & gram-pos

penicillins + B-lactamase inhibitors

contain clavulanic acid; noncompetitive inhibitor of penicillinase

sulfonamides (sulfa drug)

inhibit folic acid synth (needed for protein & nucleic acid synthesis, bind to enzyme for PABA prod

entry & fusion inhbitors

block receptors on host cell, block fusion of virus & cell

uncoating inhibitor

prevent viral uncoating

genome integration inhibitor

inhibit viral dna integration into host genome

nucleic acid synthesis inhibitor (antiviral)

nucleoside analog; inhibit RNA/DNA synth; non-nucleoside can also inhibit RNA synth

interferons

prod by viral-infected cells to inhibit the spread of infection; imiquimod (promotes interferon prod.)

RNA virus ex

HIV; antiretroviral used to treat it

6 ways antiviral drugs work

entry& fusion inhibitors, uncoating, genome integration, and nucleic acid synthesis inhibitors, interferons, antiretrovirals

mechanisms of resistance

block entry to antibiotic, enzymatic destruction/inactivation of drug, alteration of target site, efflux of antibiotic (moving it out)

ex of antibiotic misuse

using outdated/weaked antibiotic, using for inappropriate conditions, use in animal feed, failing to complete prescribed regimen, using someone else’s prescription

synergism

effect of 2 drugs together is greater than the effect of either alone

antagonism

effect of 2 drugs together is less than the effect of either alone

antimicrobial peptides

part of defense systems of most forms of life; disrupt microbial membrane, block attachment, broad-spectrum

magainin

frog skin gland

cecropin

moths

defensis

in birds, insects, plants

antisense agents

stop transcription from DNA to RNA or translation from RNA to protein

siRNA

complementary RNA that binds mRNA to inhibit translation

Florey & Ernst contributions

first clinical trials of penicillin

antiretrovirals

used for RNA viruses