chapter 20 : antimicrobial drugs ( specifically in the body )

Selective toxicity

selectively finding and destroying pathogens without damaging the host

Chemotherapy

the use of chemical to treat diseases

Antibiotic

a substance produced by a microbe that, in small amounts, inhibits another microbe ( umbrella term for both antimicrobials and drugs )

Antimicrobial drugs

synthetic substances that interfere with the frowth of microbes

antibiotics are naturally produced by

microboes

drugs are

synthetic

Streptomyces

the most studies generate for antibiotics

produced mostly antibiotics

Narrow spectrum of microbial activity

drugs that affect a narrow range of microbial types ( activity; the specific pathogen groups they can attack )

Broad-spectrum antibiotics

affect a broad range of gram-positive or gram-negative bacteria

isoniaized

efffective only against mycoacterium ( narroow)

tertracycline

effective against gram positive and gram-negative also mycobacteria, chlamydia, Rickettsia ( broad)

broad spectrum antibiotics are not the best to use because

they could lead to supper infections : overgrowth of normal microbiota ( an opportunistic pathogen part that was mart of your normal microbiota took the opportunity to grow bc antibiotic took out the competition )

Superinfection

overgrowth of normal microbiota that is resistant to antibiotics ( kills the competition )

bactericidal

kill microbes directly

Bacteriostatic

Prevent microbes from growing ( prevent dividing, not allowing the build of the cell wall )

Depending on the dose of a drug that can act

Bactericidal or Bacteriostatic

Inhibition of cell wall synthesis (MOA)

penicillin’s, cephalosporins, bacitracin, vancomycin

Inhibition of protien synthesis (MOA)

chloramphenicol, erythromycin, tetracyclines, streptomycin

inhibition of nucleic acid replication and transcription (MOA)

quinolones, rifampin

Injury to plasma memebrane (MOA)

polymyxin B

inhibition of essential metabolite synthesis

sulfanilamide,trimethopim ( compativie inhibition)

Penicillin ( inhibiting cell wall synthesis )

prevent the sysnthesis of crossbridges ( natural

low dose: prevents the making of cell wall

highdose: destorys the cell wall

semi-symphetic

natural antibiotics that were modified overcome antimicrobial resistance

ex. peneicilin is ntural SAB

beta-lactenin enzyme

what penicillin resisitent bacteria produce , attaches to the penicilin chemical and breaks it in half making it usless

specificly the beta lactam ring

enzymatic inactiviation

the abilitie of bacteria to break an antimicrobial into an enzyme

isoniazid (INH)

inhibits the mycolic acid synthesis in mycobacteria ( acid fast )

Ethambutol

Inhibits incorporation of mycolic acid into the cell wall

synergism

referring, to the use of two or more antimicrobials together which are more effective than using them independently

advantages:

can use lower doses of both rather than one high dose of one

less damage to the body

Inhibiting protein synthesis

targets bacterial 70s ribosomes in three ways

Chloramphenicol: Binds to 50s ( big subunit) portion and inhibits formation of peptide bond ( cant make DNA chain, can’t bind nucleotides )

Tetracyclines: interfere with the attachment of tRNA to mRNA the ribosome complex

Streptomycin: changes the shape of 30s portions, causing the code on mRNa to be read incorrectly ( incorrectly read, no protein )

Nitrofurantoin

converted to intermediates that attack bacteria ribosomal proteins

synthesized chemically

Treatment for urinary bladder infections

has to be processed —> it produces an intermediate byproduct to inhibit

injuring the plasma membrane

A polypeptide antibiotic changes membrane permeability

Antifungal drugs combine with membrane sterols

Has to be very specific

Injury to membranes ( synthesis )

lipopeptides

Daptomycin: attacks the bacterial cell membrane

Polymyxin B: topical; bactericidal; effective against gram-negatives

Polymyxin e ( colistin ) : effective agianst gram - negatives ( effects the transport )

nucleic acid synthesis inhibitors

Rifamycin ( rifampin) : inhibits mRNA synthesis, blocks bacterial RNA ( dosen’t effect us )

Antagonistic: increase liver metabolic activity (Don’t use with other microbial ( use by itself )

Quinolone and fluoroquinolones: Nalidixic acid, synthetic; inhibits DNA gyrase ( we don’t have this )

inhibiting the synthesis of essential metabolites ( bacterial pathogens )

Antimetabolites compete with normal substrates for an enzyme ( binds to active site) its made to compete

trimethoprim

Chloramphenicol ( IPS)

Binds to 50s ( big subunit) portion and inhibits formation of peptide bond ( cant make DNA chain, can’t bind nucleotides )

Tetracyclines (IPS)

interfere with the attachment of tRNA to mRNA the ribosome complex

Streptomycin ( IPS)

changes the shape of 30s portions, causing the code on mRNa to be read incorrectly ( incorrectly read, no protein )

trimethoprim

Inhibits the conversion of dihydromorin acid to tetrahydrofolic acid

combination of trimethoprim and sulfamethoxazole (TMP - SMZ) is an example of drug synergism

Antifungal Drugs

( selective toxic ) Usually, the first treatment of a broad spectrum if bacteria are specified

agents affecting cell membranes: ergosterol synthesis

agents affecting fungal cell walls

Polyenes & azoles - disrupt production of

imidazole’s ( AFD)

topical; treat cutaneous mycoses

Triazole ( AFD)

treat systemic fungal infections

Echinocandins

inhibit the synthesis of β-glucan ( main sugar for the cell wall )

Antiviral Drugs

two ways of preventing viral infections :

entry and fusion inhibitors

• block the receptors on the host cell that bind to the virus ( covering )

• Block fusion of the viruses and the cell

Preventing uncoating ( preventing DNA release)

• target RDRP

  • inhibit viral DNA integration into the host genome ( prophage )

Antiprotozoal Drugs

not well understood

Quinine and chloroquine treat malaria

Metronidazole, Tinidazole, Nitazoxanide - also interferes with anaerobic bacteria

treats trichomonas, giardiasis, and amebic dysentery

Persister cells ( RAD)

microbes with genetic characteristics allowing for their survival when exposed to an antibiotic ( what leads to microbial resistance)

superbugs

bacteria that are resistant to a large number of antibiotics Bacterial pathogens that are resistant to nearly all antibiotic cause healthcare-associated infections.

Acinetobacter baumanniii

pseudomonas aeruginosa

members of Enterobacteriaceae

enzymatic destruction or inactivation of the drug

Mech of resistance

Pre

Prevention of penetration to the target site within the microb

Mech of resistance ( P)

Alteration of the drug’s target site

mech of resistance ( a)

Rapid efflux( ejecting ) of the antibiotic

mech of resistance ( R)