Studied by 3 people
Define Chemotherapeutic drugs
any chemical used to treat disease
Define prophylaxis
use of a drug to prevent imminent infection of a person at risk
Define antimicrobial chemotherapy
the use of chemotherapeutic drugs to control infection
Define antimicrobials
all-inclusive term for any antimicrobial drug
Define antibiotics
substances derived from living organisms that can inhibit or destroy other microbes
Define semisynthetic drugs
drugs made from a natural source, then chemically modified
Define synthetic drug
drugs entirely produced by chemical reactions
narrow vs. broad spectrum
Narrow: antimicrobials effective against a limited array of microbes.
Broad: wide variety
Broad spectrum antibiotics are the best!
T or F
Not always. A prolonged use of broad spectrum antibiotics can kill off your natural flora (get rid of the good bacteria)
Paul Ehrlich
tested arsenic-containing compounds against Treponema palladium
originated the concept of selective toxicity
Selective toxicity means
a drug should harm the pathogen and not the host
Toxic vs Therapeutic dose
toxic = harm to host
therapeutic = eliminated pathogens in the host
Characteristics of the Ideal Antimicrobial Drug
selectively toxic
microbicidal
soluble
remains potent for long enough
does not lead to resistance
complements or assists host’s defenses
remains active
readily delivered to site of infection
reasonably priced
doesn’t disrupt host’s health
E-test tests for…
what concentration is the best
MIC = minimum inhibitory concentration
Tube dilution tests
tests for drug susceptibility
more sensitive and quantitative than Disc-diffusion tests
List the Modes of Action for Antibacterial drugs
+ examples
Inhibition of cell wall synthesis
stop peptidoglycan from forming
ex. penicillin
Inhibition of protein synthesis
stops translation
ex. tetracyclines
Inhibition of nucleic acid replication and transcription
interfere with DNA synthesis by inhibiting topoisomerase. interferes with RNA synthesis
ex. rifampin
Injury to the Plasma membrane
destroy membrane structures and impair function
ex. polymyxin B
Inhibition of synthesis of essential metabolites
inhibit enzymes
ex. sulfanilamide
What inhibits the biosynthesis of peptidoglycan (cabin logs)?
ampicillin
What leads to antibiotic resistance
improper or excessive use
How Antibiotic resistance comes to be…
random mutation
some bacterial cells of the population has the mutation for resistance. this resistance is not used when the antibiotic is not present.
exposure
when the population is treated with antibiotics, the sensitive ones die off, the resistant ones thrive. the resistant gene becomes operative
resistance
the resistant bacteria now multiply and fill the environment
Define Superinfection
infection occurring after or on top of an earlier infection, especially following treatment with broad-spectrum antibiotics
What allows for resistant strains to overgrow susceptible ones?
unnecessarily large antibiotic doses
How can antibiotic resistance spread?
meat consumption (antibiotics are used in livestock feed)
bacterial cells passing resistance genes to other bacterial cells
What are some ways humans misuse antibiotics and encourage antibiotic resistance?
stop taking the antibiotics before your prescription is empty.
saving it for when you feel bad later
Mechanisms of antibiotic resistance
new enzymes are synthesized, inactivating the drug
permeability/uptake of drug is decreased
drug is immediately eliminated (pumped right back out)
decreased binding sites for drugs
an alternative pathway is used (detour)
What is antibiotic inactivation?
a mechanism of resistance
enzymes destroy antibiotics or prevent them from binding to target sites
Antifungal Agents cause
membrane damage. causes contents to leak out
inhibit sterol synthesis
Nystatin is used for…
antifungal used against Candida albicans infections in the intestines or vagina
topical (you physically apply it)
affects cell membrane function
Amphotericin B is used for…
antifungal used against serious systemic fungal infections
pill
affects cell membrane function
The goal of antiprotozoal agents is to…
eradicate the parasite
Aminoquinolines (Quinine) is a…
Antiprotozoal Agent
Antimalarial drug that accumulates in parasitized red blood cells.
Interferes with parasite’s ability to break down and digest hemoglobin
Nitroimidazoles is a…
Antiprotozoal Agent
interferes with DNA synthesis
treats
amoebiasis
giardiasis
trichomoniasis
What can be used against African trypanosomiasis?
a derivative of arsenic
Name some Antihelminthic agents
Praziqyantel, mebendazole, Ivermectins
Praziqyantel does what?
changes membrane permeability in cestodes and trematodes
causes contraction and paralysis in the parasite
Mebendazole does what?
inhibit nutrient uptake in worms
Ivermectins do what?
cause paralysis in roundworms
Actions of Antiviral Drugs
inhibition of virus entry (can’t enter new cells)
ex. Enfuvirtide
inhibition of nucleic acids (can’t replicate)
ex. Acyclovir
inhibition of assembly/release (can’t get out)
ex. Indinavir
How does the disk-diffusion method work to characterize antibiotic resistance?
If there is a zone of inhibition, the bacteria is susceptible and the antibiotic works. No zone of inhibition means the bacteria is resistant.
More than half our antibiotics are produced by _____
bacteria
Describe the problems of chemotherapy for viral, fungal, protozoan, and helminthic infections
Fungi, protozoa, and helminths are eukaryotes and have very similar cells to humans & it's hard to find things that are not toxic to us.
Viral infections are hard to treat because viruses control the human host cell to replicate the virus so it's hard to attack the virus without killing the healthy host cells
Define broad spectrum antibiotic
affect a broad range of gram-positive or gram-negative bacteria
Define spectrum of activity
The range of pathogens the drug is effective against
Why is it hard to target a pathogenic virus without hurting the host’s cells
the virus is in the cells
Describe two tests for microbial susceptibility to chemotherapeutic agents.
Disk-diffusion
measure zone of inhibition
Tube dilution tests
more sensitive & quantitative
finds MIC
What does MIC and MBC stand for? what is the difference between the two?
MIC = minimum inhibitory concentration (inhibits growth)
MBC = minimum bactericidal concentration (kills bacteria)
Modes of action of current antihelminthic drugs
Prevents ATP production
Alters membrane permeability
Interfere with nutrient absorption
Paralysis of helminths
Note 
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