Antibiotics and Resistance Flashcards
When the body’s normal defences cannot prevent or overcome a disease, it can be treated by
chemotherapy with antimicrobial drugs
How do antimicrobial drugs act?
By killing or by interfering with the growth of the microorganisms
What is the important principle of selective toxicity?
Antimicrobials must act within the host without damaging the host
Who started modern chemotherapy and what was speculated about?
Paul Ehrlich - magic bullet
Alexander Fleming observed inhibition of the growth of
Staphylococcus aureus by penicillin produced by penicillium notatum
When did Alexander Fleming discover penicillin?
1928
What is antibiosis?
The mechanism of inhibition of one microorganism by another
What is an antibiotic?
A substance produced by microorganisms which inhibits another microorganism
Antibiotics are rather easy to discover but few antibiotics are of
medical and/or commercial value
Give an example of the commercial use of an antibiotic
As a supplement in animal feed rather than for treating diseases
Which species produces the majority of our antibiotics and where is it found?
Streptomyces in the soil
A few antibiotics are produced by endospore forming bacteria such as
Bacillus
Some antibiotics are produced by ______, mostly the genera penicillium and ceplasporium
Molds/fungi
Antibacterial drugs do not affect the eukaryotic cells of humans. why?
Cell types differ substantially
e.g. presence/absence of cell walls, struc of ribosomes
Selective toxicity has many targets
Why are antimicrobials targeting protozoans or helminths difficult to use?
The drug that targets these pathogens usually damages the host too
They are more similar to the human cell on a cellular level
Some drugs have a narrow spectrum of microbial activity. What does this mean?
They have a narrow range of different microbial types they effect
Penicillin G has a narrow spectrum of microbial activity, how?
Affects gram-positive bacteria, but very few gram negative bacteria
What are broad-spectrum antibiotics?
Antibiotics that affect a broad range of gram positive and gram negative bacteria
For an antibiotic to affect a gram negative bacterium, what are two key requirements
Drugs that pass through the porin channels must be relatively small and preferably hydrophilic
Drugs that are lipophilic (affinity for lipids)o r especially large do not enter the Gram -ve bacteria readily
What is an opportunistic pathogen?
An opportunistic infection is an infection caused by bacterial, viral, fungal, or protozoan pathogens that take advantage of a host with a weakened immune system or an altered microbiota (such as a disrupted gut flora). Many of these pathogens do not cause disease in a healthy host that has a normal immune system.
Bacteria may become opportunistic pathogens. How?
The antibiotic destroys competitors of normal microbiota
What is a superinfection?
The growth of a target pathogen.
Also the term applied to the growth of a target pathogen that has developed resistance to the antibiotic
What does bactericidal mean?
Kills microbes directly
What does bacteriostatic mean?
The prevention of microbes from growing
