Antibiotic Resistent Organisms Flashcards
(38 cards)
What 4 factors contribute to the development of antibiotic resistance?
- Misuse and overuse of antibx
- Hospital environment
- Food
- No new antibx on the horison
Explain why misuse and overuse of antibx causes AROs?
- Incorrect prescribing (UTI)
- Too low of a dose
- Treatment too short
- Patient error (non-adherence/sharing)
- Agricultural use in livestock
- Over-availablility
- Manufacturing plants leaching
Explain why the hospital environemnt can cause AROs?
- Large amount of immunicompromised people
- Close pt proximinity
- Invasive procedures
- Teaching hospitals have the sickes and highest acuity patients
Explain how food causes AROs?
- More meals are consumed outside the home (easier spread)
- Contamination of food source with pathogens (ie: melons and recall)
Explain how lack of new antibx contributes to AROs?
- No new pathways to tackling bacteria as there is no particular financial gain
What is drug resistence?
An adaptive response in which microorganisms beging to toelrate an amount of antibx that would normally inhibit or kill it
What is the ability to resist antibx due to?
Genetic versatility and adaptablity of the microbial population
What are the two types of ARO resistence?
- Inherent (natural) resistnace
- Aquired resistence
Explain inherent resistance
Bacteria may be naturally resistant due to structural advantage
Can also be called “insensitivity” since it occurs in organisms that have never before been suspectible to that dtug
Ex: Gram - bacteria are immune to vano
Ex: Microplasm have no cell wall so no antbiotic that targets cell wall will work
Knowledge of the intrinsic resistance of a pathogen is of great importance to clinicians?
Avoid prescribing inappropaite or ineffective therapies
What is aquired resistence?
When bacteria become resistent to antibx due to vertical gene transfer or horizontal gene transfer
Describe vertical gene transfer
- Spontanous mutation happens that results in resistence
- Resistence advantage is then tranferred directly to its offspring
- Bacteria have fast growth rate so this change gets passed on quick
** Is an example of natural selection*
Define horizontal gene transfer?
DNA is transfered between indivddual bacteria of the same species (staph aureus to staph aureus) or even different species (enterococcus facieals to staph aureus)
What 3 methods can horizontal gene transfer occur?
- Conjugation
- Transformation
- Transduction
Explain conjugation in horizontal gene transfer
This process is mediated by a plasmid, a part of DNA that replicates independently
It occurs when there is a direct contact between 2 bacterias and facilitated by a hollow bridge called sex pillus that forms to allow plasmids to transfer between bacterias
Genes for ARO or virulence (toxicity, enzymes, adhesion molecules) can be transferred
Describe conjugation in gram negative bacteria
Gram negative bacteria have a specialized plasmid called a fertility factor or F factor, once cell, the donor bacterium (F+), gives up DNA; and another bacterium, the recipient cell (F-), receives the DNA.
What is a resistance factor? (R factor)
A plasmid containing multiple genes for drug resistance
Explain the process of transformation in horizontal gene transfer
When a bacteria is lysed and breaks apart, DNA gets released into the surrounding environemnt. Other bacteria can scavenge this free floating DNA and incorporate it in. This can have advantageous genes.
Genes transfered from one bacteria to another are called naked DNA
Cells capable of accepting new DNA are called competent, once the donated DNA is inserted into the reciepient (competent) cell it is now transformed
Explain the process of transduction in horizontal gene transfer
Bacterial DNA is transfered from one bacteria to another INSIDE a virus that infects bacteria (bacteriophage).
Phage enters bacteria and produces more pahge, during this process bacterial DNA can be plugged into the phage.
Phage then goes and invades another bacteria
Phage goes and invades another bacteria and now the NEW bacteria gets genes from the first bacteria
What are the three specific methods of antibiotic resistence?
- Destruction or inactivation of an enzyme
- Expulsion of the antimicrobial agent from the cell using efflux pumps
- Alteration of drug binding sites
Explain destruction or inactivation of enzymes
- Bacteria possess genes that can make enzymes to deactivate the antibiotic
- When the beta-lactam ring of is destroyed by the enzyme beta lactamase the antibx no longer works
Pencilinases destroy the beta-lactum ring in pennicilin
Cephalosporinases destroy the beta-lactam ring in cephalosporin
Explain efflux pumps in AROs
- Both gram - and + can become resistent to antibx through efflux
- Efflux pump is a cahnnel that activesly transfport substances out of the cell (gram - transport toxins out)
- Antimicrobial enters the bacteria through a porin channel and then gets pumped out by the efflux pump preventing the accumulation inside the cell
- Some pumps can only pump out one type of antibx while others can be Multi Drug Resistant Pumps (MDRP)
Explain alteration of drug binding sites in AROs
Drugs bind mostly on a specific target such as a portien, RNA, DNA or membrane structure. By changing the nature of these targets, you can prevent the drugs from binding and having an effect
Explain aminoglycosides
Aminoglycosides work by binding to 30s ribosomes so if the ribosome binding
site is changed this antimicrobial can’t bind thus has no effect
