Quiz 4 (Lecture 18) Flashcards
Who and when discovered penicillin?
Alexander Fleming and received the Nobel prize in 1945
When was penicillin resistance found?
same year (1945) Stanford found different strains of staphylococcus that do not respond to penicillin
What are antibiotics?
- a heterogeneous class of molecules that interfere with the growth of bacteria
- many antibiotics occur naturally and are isolated from bacteria & fungi
What are the three mode of actions in antibiotics?
- mimic a critical molecule
- bind irreversibly to an active site
- compete with a naturally occurring molecule for binding, passage or transport
What are the objectives of action in antibiotics?
- to slow growth or kill target organisms
- a therapeutic antibiotic needs to do this minimal toxicity to the host
– usually accomplished by directing the antibiotic at a phylogenetically unique feature of the bacterial target
How do bacteria acquire resistance genes?
- mutations
- horizontal gene transfer
Do the genes for drug resistance exist in the pathogen population prior to infection or do they originate through mutation after infection?
- if the former, the strong, prolonged, antibiotic treatment selects for antibiotic resistance
- if the latter, treatment reduces the size of the pathogen population and the probability that a resistance mutation will ocur
What did traditional therapies wrongly assume that antibiotic resistance arises through?
mutation
What is a fix to antibiotic resistance?
use antibiotics to slow the rate of infection and control it rather than eliminate
- by letting immune system finish the job, we could slow/avoid the evolution of resistance
What does evidence suggest about most infections?
that they already contain pathogens with resistance genes
What was an example of the evolution of antibiotic resistance in a single patient?
- JH acquired a staph infection after a heart valve operation
-treated with rifampin and vancomycin - heart valved was replaced after 3 months
- died 2 weeks later
What is the problem with using low levels of antibiotics?
- only slows the growth of bacteria
- bacteria w/ mutations that confer resistance to perform better; resistance genes will accumulate in the population
- resistant bacteria then infect humans (spread and infects other animals too)
What were the results from the chickens who were fed with a sub-therapeutic dose of antibiotic v not at all?
- after 2 weeks, 90% of experimental chicken excreted 100% resistant organisms in the feces
- by 4 months, resistance was transferred to control chickens which now began to excrete resistant microbes
- by 6 months, fecal samples of farmers also contained resistant bacteria
What was the result of farmers in Denmark reducing the amount of tylosin (antibiotic) in the feed of healthy pigs?
the prevalence of bacteria resistant to the drug dropped
In the 1990s the use of what dropped to less than 3% in the UK?
Sulfonamide (antibitoic)
