Chapter 12

Prophylaxis

use of a drug to prevent imminent infection of a person at risk

Antimicrobial chemotherapy

the use of drugs to control infection

Antimicrobials

any microbial drug

Antibiotics

can inhibit or destroy microorganisms, generally used for targeting bacteria

Semisynthetic drugs

chemically modified in the lab after being isolated from natural sources

Synthetic drugs

made entirely by chemical reactions in a lab

Narrow spectrum (limited spectrum)

antimicrobials effective against a limited array of microbes, like mainly for gram-positive

Broad spectrum (extended spectrum)

effective against a wide variety of microbe types

Salvarsan

first effective antibiotic and was chemically made in the lab

Actinobacteria

rich source of chemicals that hurts bacteria

Streptomyces

in soil and associated with places, some make metabolic products that are useful in medicine

penicillin

first released in the 40s, first drug to stop infections of different kinds in their tracks

Selecting the right antimicrobial

Test the in vitro activity by exposing a pure culture to different drugs

Kirby-bauer technique

agar diffusion test where the surface of a plate of special medium is spread with the est bacteria and small discs with an antimicrobial are put on the bacteria lawn

Tube dilution test

Antimicrobial is diluted in tubes of broth, then inoculated in a small pure culture, incubated and examined for growth

Minimum inhibitory concentration

smallest concentration of drug that visibly inhibits growth, useful in determining the smallest dose needed

Therapeutic index

the ratio of the dose of the drug that is toxic to humans to its effective dose

The smaller the ratio is in the therapeutic index

the greater the potential for toxic drug reactions (is worse for humans)

Therapeutic window

the concentrations of the drug in the blood, the range of blood level of the drug where it produces the desired effect without being toxic

Selectively toxic

kill microbes, but not host tissues

Antimicrobial categories

inhibition of cell wall synthesis, RNA and DNA structure and function, protein synthesis (ribosomes), cell membrane structure or function, and folic acid synthesis

Major side effects of drugs

direct damage to tissues, allergic reactions, disruption in balance of normal microbes

Tetracyclines

not advised for under 8 yrs old because they bind to enamel of teeth, and pregnant women can have liver damage

Superinfection

when antimicrobe destroys beneficial resident species, microbes that were a smaller number overgrow and cause disease

B-lactum

end in -cillin, named for having a chemical ring (the B lactum), penicillin is part of the group

Cephalosporins

have a B-lactum structure that can be altered. have -cef -ceph or -kef. Most effective against gram-positive bacteria

aminoglycosides

made of 1+ amino sugars and a 6 carbon ring, come from streptomyces and micromonospora. Inhibit protein synthesis

Tetracyclines

derived from streptomyces, bind to ribosomes and block protein synthesis

Macrolides

large chemical ring (lactone), has sugars attached. Low toxicity, block protein synthesis by attaching to a ribosome

pleuromutilins

block action of peptidyl transferase, only for skin infections

synercid

from streptogramin, effective against staphylococcus and enterococcus. Binds to sites on the 50S ribosome, inhibiting translation

Sulfa drugs

do not come from bacteria or fungi, man-made

Quinolone

have a wide variety of gram positive and negative bacterial species. Readily absorbed from the intestine

Biofilm resistance caused by

different phenotypes expressed by biofilm bacteria

Drugs that target the cell wall

penicillin, cephalosporins, carbapenems, bacitracin

Drugs that target protein synthesis

aminoglycosides, tetracyclines and glycylcyclines, macrolides, streptogramins, oxazolidinones, pleuromutilins

Drugs that affect folic acid synthesis

sulfa drugs

Drugs that target cell membranes

polymyxins

Drugs toxic to fungal cells are also capable of harming

human tissues

Quinine

extracted from bark of cinchona tree, treated malaria, now replaced by synthesizes quinolones have less toxicity to humans

Artemisinin

comes from wormwood plant, helps with malaria

Metronidazole

treats mild and severe intentional infections

Albendazole

broad spectrum. Inhibits function of microtubules of worms, eggs and larvae

Major modes of action in antiviral drugs

bar penetration into host cell, block replication and transcription, prevent maturity

Fuzeon

anti-HIV, keep virus from attaching to its cell receptor, preventing fusion of HIV

Retrovirus

carries genetic info in the form of RNA instead of DNA. when infected, RNA genome is used as a template by enzyme reverse transcriptase to make a DNA copy of virus genes

Resistance factors

transferred through conjugation transformation or transduction

Clostridiodies difficile

fecal transplants in these infections include the transfer of feces with healthy bacteria into patients via colonoscopy