Exam 5 Flashcards
What is antibiotic selection?
The survival of an antibiotic resistant population of cells within a large population of antibiotic sensitive cells
AKA Survival of the Fittest
Where can ABX selection occur?
Practically anywhere that bacteria and abx is present
A common use for abx selection in microbiological research.
When identifying a particular cell that contains the DNA of interest (e.g. plasma) you can isolate the one you care about.
Why does every plasmid used for scientific research contain an abx resistance marker?
so you can identify the cells that got the plasma
Imagine you have a sample of bacteria that is a mixture of ampicillin resistant cells & ampicillin sensitive cells. How could you isolate the resistant ones?
Plate them of a medium with ampicillin. The ones that grow or produce colonies are resistant
What antibiotic class do cells containing BLA marker become resistant to?
ampicillin (any penicillins)
What antibiotic class do cells containing AAC marker become resistant to?
Kanamycin (aminoglycosides)
What antibiotic class do cells containing CAT marker become resistant to?
chloramphenicol acetyl transferase
a typical inducer of tet ON/OFF
doxycycline (dox)
tet ON with TET
turns gene expression ON
Makes repressor leave the operator
tet ON without TET
repressor binds to the operator no transcription
tet OFF with TET
turns gene expression OFF
Makes TA & repressor leave the operator
tet OFF without TET
TA binds to repressor, allows transcription
Typical way to administer TET or DOX to an animal
add to drinking water
contrast regulation of ABX in countries
U.S.= Dr. prescribed, prescription, pharmacy Other= over the counter
Over the counter
Pro: cheaper
Con: could experience antibiotic resistance
Prescription
Pro: Correct course, take correct drug
Con: expensive
Most prevalent use of ABX worldwide
agriculture
Effects do ABX have when added to animal food?
- Increased growth promotion (gp)
2. reduced risk of diseases
What is meant by gp
- faster time to increase weight for the market
- use less to get more
- more protein to fat in meat
How did advent of ABX help modern industrial production?
It allowed for less risk of spreading infection, allowing higher density of animals in cities
Name a class abx not used in animals
chloramphenicol (detect residue) or Oxazolidone
Why is monesin considered safe abx in cattle/dairy?
there is no document of ABX resistance to it. its also not a clinical ABX
Mechanism of action of monesin
ionfore: typically a sodium pump crosses the cell membrane, which causes bacteria to not grow
What is the accepted mechanism for ABX permit gp
it surpasses gut microbes, they take the energy from food. so if you eliminate them, it allows more energy into the animal which can reduce inflammation
What evidence led scientist to believe gp abx affected gut bacteria rather than physiology of animal?
- use of an ABX that doesn’t enter the blood stream still works for growth promotion, the ABX is just limited to the gut
- use germ free animals- give them ABX and there is no growth promotion( have to have microbiota to see growth effects)
ABX GP downside?
risk of increased abx resistance because abx selection is happening
Actual develop/modify in resistance zoonotic organisms harming human health is extremely difficult to document/quantify. Why gov. take action to limit abx in animal production?
- rather be safe than sorry. lower the chance of ABX resistance. be proactive even if no evidence
- even if had to document/ ABX selection has to be happening
Under U.S. VFD 2 conditions abx is given to animals
To treat disease
To prevent disease
Why is prevent disease controversial?
Hard to distinguish growth promotion
1st country to ban ABX for animals
Sweden 1986
Articulate an argument for banning abx use, not as good as it seems
-less prevention= animals get sick
you the have to use clinical ABX doses instead of subclinical
-Use in human abx resistant (empirical)
Changing consumer demands led to less abx use for food
Consumers are increasingly demanding & will pay extra for meat that was not treated with ABX
why is it difficult to determine if meat was never treated w abx?
You cant trace it
Identify 3 steps involved new compound to clinical abx
Phase 1-3
Toxicity test
Animal testing
FDA review
1 reason abx development not attractive to pharm. companies?
If the revenue is not going to be very profitable, more than or equal to the cost to make, then its only going to cost them
1 reason market size for abx is smaller than other drugs
Abx is a curative drug, its only taken for a short time
only accounts for 6.2% of the saturated drug market
Push incentive for ABX development
reduce cost of development
Pull incentive for ABX development
Clinical, bring to market
increase revenue
New abx discovered, market size would be small why?
Abx stewardship must be met
Market is saturated
Dr would reverse for situations where nothing else worked (last resort)
Insensitive for ABX development do what?
reduce developer cost to bring in revenue
cost back to balance so they can actually make money
2 common entities that support incentives
Government
Privation organizations
Microbiome
all the bacteria living in a specific niche
2 commensal bacteria help against pathogen
- crowd out, compete out
2. produce specific compounds that act against pathogenic species
Which GI niche do our bodies contain the most bacteria
GI tract
does everyone have the same resident bacteria in their gut
NO (but there are trends in families, towns, countries)
Factors associated with gut microbiome
different diet
genetics
How is composition of microbiome assessed?
16s rDNA sequencing
What type of sample is used to access gut biome
stool/fecal matter sample
whys is 16s rDNA good to access bacteria in a sample
The gene has some regions that are the same in all bacteria
but it also has variation from taxon to taxon (phyla, genus, and sometimes species) amplifying all DNA using universal seq (ones that dont vary)
in 16s rDNA how do we estimate abundance of bacterial species in an original sample?
abundance in the original sample is proportional to
seq to sample
assume proportion of sequence from original species is proportional to DNA species
more seq, greater proportion
half seq is from e coli, half the dNA is from e coli
2 weakness of 16s rDNA
- does not distinguish between live/dead bacteria cells
2. cant infer function
6 bacteria phyla
firmicutes: gram +, strong skin (cuticle) sporoformers
bacteriodites: gram - rods, bacteroid species
proteobacterias: gram - e coli
actinobacteria: gram + symphyses
vervucomicrobia: rare
fusobacteria: rare
2 that dominate healthy
firmicutes, bacteriodites
Name 5 factors that interact with the human gut microbiota either unidirectionally or bidirectiona
jet lag, diet, age, exercise, stress
Is the gut microbiota relatively insensitive to conditions, or does it respond quickly to changing condition
highly responsive not static, dynamic
Name two diseases that are associated with substantial changes to th
type II diabetes, IBD-inflammatory bowel disease
How could you test the effect of a particular host gene on the gut micro
use a mouse model. make a knock out of the gene and see if microbiota is changed
How could you test whether a particular microbiotal composition can affect a host phenotype?
transfer feces microbiota, transplant to a germ free mouse, access phenotype like glucose insensitivity
How is a fecal microbiotal transplant (FMT) achieved
take feces, homogenize it in a sterile buffer, mix it all up, filter to remove solid matter,
administer the purified bacteria to recipient, for a mouse stick a needle down throat to stomach, or rectal
Name two changes in host factors/behavior that impact that microbiota such that it can change a host phenotype when transplanted
- changes in diet (high fat to low fat)
2. changes in circadian rhythms
How do we initially get our gut microbiome
inoculated from the world around us, mothers and foods
When does our microbiome transition from the infant-type microbiome to the adult-type microbiome
ages 1-2 as we stop drinking breast milk and transition to adult diet
What is the “bacterial baptism” hypothesis, what practice has it led to, and why is it corrected?
idea is that we obtain our healthy microbiome from mothers in vaginal birth, vaginal fluids get wiped on babies body. Using sterile gauze on face. Important because initial inoculation scientist urged caution bc we don’t truly understand how important it is.
When is our gut microbiome most important for future health
first 2 years of life
Given the importance of the early microbiome, what is one practical way that parents can try to guard against harmful alterations to their child’s microbiome?
Be conservative about using antibiotics, not using them 24/7.
What strategies might future interventions employ to stabilize and restore the human gut microbiome in a person?
Specific diets.
*Probiotic use.
What are three benefits that the gut microbiota provides for a human host?
- breakdown of indigestible food structures like celluloses
- projections of compounds that promotes immune system development health
- glucose homeostasis in our blood
About how many antibiotic-resistant bacterial infections occur in the United States each year? How many deaths from such infections?
about 2 million 2.7-2.8 infections
about 1%- 30,000 deaths
About how many courses of antibiotics are prescribed in the United States each year (to the nearest 10 million)?
around 260-270 million
about 1%
What are the five main points (in brief) of the WHO’s Global Action Plan on Antimicrobial Resistance?
- increase awareness through training
- strengthening knowledge in evidence based research
- reduce infection incidents, through better hygiene
- optimize use of microbial medicines, find the right abx
- increase investmate in new medicines, vaccines, developments
How would a rapid antibiotic-susceptibility test improve antibiotic stewardship and also lower costs at the clinic?
rapid test, dr. could prescribe the right abx the first time.
you avoid using the wrong 1, 1 dr visit, one drug short course.. quicker save life
Name an antimicrobial compound that until recently was a popular ingredient in consumer products labeled “antimicrobial” but is now not generally regarded as safe by FDA.
triclosan (Irgasan)
Articulate an argument for not using triclosan-containing soaps and other consumer products.
It becomes an environmental contaminate. 75% of adults have detectable in urine
