Microbiome, Biofilm, AMR Flashcards
What is the microbiome?
The collection of genomes from all microorganisms in any given environment
What is microbiota?
Collection of microorganisms within a specific environment
Why is the microbiome important?
It is associated with the proper functioning of the immune system, heart, and many other aspects of health.
What is dysbiosis?
A disruption to the microbiome resulting in an imbalance in the microbiota
* Gain or loss of community members or
* Changes in relative abundance of microbes
What is the term for an imbalance in the microbiota?
Dysbiosis
What can impact the microbiome?
- Antimicrobials
- Diet
- Stress
- Age
- Maternal microbiota
etc.
Describe necrotic enteritis.
In poultry, eimeria infection, feeding indigestible non-starch polysaccharides, or immunosuppression can lead to reduced abundance of certain bacteria (such as lactic acid producing ones). This change can promote the proliferation of Clostridium perfringens or overgrowth of enterobacteriaceae in the intestine.
Note: Clostridium is a normal component of the gut microbiome but causes problems when there are factors that can disrupt the microbiome.
Which normal bacteria can cause problems if the microbiome is disrupted?
Gut: Clostridium
Skin: Staphylococcus
Respiratory: Pasteurella, mycoplasma, bordetella
Urogenital: Escherichia
Describe post-weaning diarrhea.
Stress at weaning disrupts the microbiota (reduces Lactobacillus spp.) which promotes the proliferation of enterotoxigenic E. coli.
What are biofilms and why are they important?
Biofilms are a way that micoorganisms grow in structured communities. It is the population that is attached to a surface and all the substance that envelops it.
They are important because they have an extracellular matrix that protects the bacteria from a harmful environment.
- Dehydration
- UV light
- Immune system
- Disinfectants
- Antimicrobials
How are biofilms formed?
- Reversible adhesion (bacteria attach to a surface)
- Irreversible adhesion
- Biofilm proliferation
- Biofilm maturation (other spp. enter the biofilm)
- Deadhesion
Why do some bacteria form biofilms and
others do not?
Biofilms are associated with virulence genes so only those with the genes will form biofilms.
Describe a biofilm problem in veterinary
medicine
- Biofilms can form in the milking equipment, sprinklers, and bulk tanks in dairy barns. This can lead to mastitis transmission among dairy cows or cause corrosion of equipment.
- In food production areas, can contaminate food products which reduces shelf life.
- Plaque is a biofilm that constantly forms on teeth.
How do antimicrobials act?
- Inhibition of cell wall synthesis
- Damage to cell membrane
- Inhibition of protein synthesis
- Inhibition of nucleic acid synthesis or function
How do bacteria become resistant?
Bacteria can either acquire resistance mechanisms (AMR genes) through mobile genetic elements passed by horizontal gene transfer OR can develop resistance through mutations.
How do resistance mechanisms work?
- Development of alternative pathways (e.g., sulfonamides)
- Drug inactivation (e.g., beta-lactams = drug is broken down by beta-lactamases)
- Decreased permeability (less drug in cell = does not reach necessary concentration)
- Efflux pumps (less drug in cell = does not reach necessary concentration)
5- Target modification (e.g., mecA and beta-lactams)
What are the most pressing AMR-related issues in human medicine?
- Increasing AMR in ‘ESKAPE’ pathogens and a few others (healthcare-associated) = infections are hard to kill when caused by these pathogens.
- Clostridioides difficile infections following antimicrobial therapy = takes advantage of dysbiosis.
- Increasing AMR in community acquired bacteria
What are the most pressing AMR-related issues in vet medicine?
- Dogs and cats -> Methicillin-resistant Staphylococcus (aureus [MRSA],
pseudintermedius) - Beef cattle -> BRD-associated bacteria resistance to macrolides
- Horses -> MRSA skin infections
- Fish and shrimp -> Antimicrobial-resistant Edwardsiella spp. infections
- Chickens, pigs -> zoonotic concern (Salmonella, campylobacter)
Can antimicrobial use in animals affect human health?
Yes but most AMR problems in humans are due to antimicrobial use in humans.
What are some of the best practices related to antimicrobial use in vet med?
- Prescribe the most appropriate treatment (right drug, right reason, right patient, right time, right duration, right records)
- When antimicrobial need has been identified, your first choice should be an approved veterinary drug, on-label or extra-label
- Opt for drug categories less important for human medicine if possible
What is AMR?
Ability of microbes to overcome the effect of antibiotics that it was previously susceptible to.
What is the difference between antibiotics and antimicrobials?
Antibiotics are produced naturally that specifically target bacteria.
Antimicrobials are a more broad category that target a larger range of microorganisms.
How do beta lactams work? Why do they have low toxicity?
They target bacterial cell wall (which we don’t have) = low tox.
They disrupt the cell wall by….
How do antimicrobials promote AMR?
Use of antimicrobials reduces the population of susceptible bacteria = resistant bacteria proliferate and population becomes composed of mainly resistant.
