The Importance of Cell Biology & AMR (antimicrobial resistance) Flashcards
Outline the importance of microbiology in veterinary science
It has a daily impact:
-Prevention (vaccinations, probiotics, owner education)
-Treatment (diarrhoea, skin infections, bite wounds)
-Sterilisation of instruments
-Biosecurity
-Epidemiology
-Antimicrobial Stewardship
Understanding disease processes
Antimicrobial Resistance
Describe the concept of antimicrobial stewardship
The actions veterinarians take individually and as a profession to preserve the effectiveness and availability of anti -microbial drugs through conscientious oversight and responsible medical decision-making, whilst safeguarding animal, public & environmental health
Outline what is meant by antimicrobial resistance
Multi-resistance mechanisms often carried on mobile genetic elements – rapid spread within and between bacterial species
It is naturally occurring and widespread within the environment
List drug targets for antibiotics
Cell wall synthesis
Cell membrane
Nucleic Acid synthesis
Protein Synthesis
How is the cell wall targeted by antibiotics?
Contains components unique to bacteria
Penicillin (β-lactam)
-Inhibits enzymes involved in forming the cross links between the peptidoglycans
Other Antibiotics:
-Ampicillin (β-lactam)
-Vancomycin (glycopeptide)
β-lactams inhibit transpeptidation by binding to penicillin-binding proteins (PBPs) on maturing peptidoglycan strands leading to decrease in peptidoglycan and promoting autolysin activity
Bactericidal
How is the cell membrane targeted by antibiotics?
Disrupted functional integrity of cell membrane leads to escape of macromolecules & ions from bacterial cell (lysis)
Antibiotics
-Polymyxin
-Colistin
Both target outer mebrane of gram negative bacteria
Bactericidal
What are the disadvantages to cell membrane targeted antibiotics?
Due to large similarities between animal and bacteria cell membranes, the drugs have an increased toxicity for animal cells.
Drugs are often used as a last resort in human medicine
How is protein synthesis targeted by antibiotics?
Difference in ribosome structure between eukaryotes (80 S ribosomes) & prokaryotes (70 S ribosomes)
-Tetracycline
Blocks tRNA molecules attachment site on 30 S sub unit
-Erythromycin
-Chloramphenicol
Both block 50 S sub unit preventing growth of polypeptide chain
-Aminoglycosides
Bind to 30 S sub unit inhibiting proof reading and initiation
Bacteriostatic
How is nucleic acid synthesis targeted by antibiotics?
Organisation and replication of bacterial DNA & RNA is different to eukaryotes
-Quinolones (Nalidixic acid)
-Novobiocin
Both act on DNA Gyrase (enzyme which separates DNA strands during bacterial
replication). They do this by binding to topoisomerase II or topoisomerase IV
-Rifampin
Interferes with DNA-dependent RNA polymerase activity so preventing RNA
synthesis
Bacteriostatic
Describe how bacteria of different groups can have different antibiotic resistances
Enzymes that degrade or inactivate antibiotic
B-lactamases - enzymes which degrade or inactivate antibiotic
Example of Antibiotic affected: penicillin/ ampicillin
Alteration of target site
Altered ribosome structure - alter target site (common with antibiotics whihc work
on ribosome structure)
Example of Antibiotic affected: erythromycin
Elimination of antibiotic from bacterial cell
Efflux Pump - rid the antibiotic out of the cell through this pump (expensive for
bacteria)
Conc of antibiotic in environment doesn’t change so bacteria will continually have to
pump
Example of Antibiotic affected: tetracycline
Bacterial cell impermeable for antibiotic
Gram negative cell wall - inherently resistant
Example of Antibiotic affected: penicillin
Rationally define the microbial disease process (Infection)
Invasion and / or colonisation by subsequent multiplication of pathogens in bodily part or tissue
Which can produce subsequent tissue injury
And progression to overt disease through a variety of cellular or toxic mechanisms
Rationally define the microbial disease process (Causation of disease)
Infection
Produce toxins
Often with infection but can be ingestion of preformed toxin
Host response
Allergic reaction
Outline Koch’s Postulates (1984) to define a pathogen
- The organism must be found in all animals suffering from the disease, but not in healthy animals.
- The organism must be isolated from a diseased animal and grown in pure culture.
- The cultured organism should cause disease when introduced into a healthy animal.
- The organism must be re-isolated from the experimentally infected animal.
Koch abandoned the second part of the first postulate altogether when asymptomatic carriers of cholera were discovered (Koch, 1893).
What is the terminology used when describing pathogen prevalence?
Sporadic
Diseases popping up here and there
Enzootic
Regularly affecting animals in a particular district or at a particular season.
Endemic
Term that relates to humans - regularly found among particular group people
or in a certain area. However, endemic is often used as a veterinary term.
What does latency mean?
Pathogen goes inert within the aniaml. Can be reactivated