PH15: Antimicrobial Resistance Flashcards
What agents are encompassed in “antimicrobial”?
Antibacterial, antiviral, antifungal, antiparastic
What are antimicrobials used for?
therapy, prophylaxis, and metaphylaxis
Define microbiological resistance.
When a bacterium can tolerate higher concentrations of an antimicrobial than phenotypically related bacteria of the original or “wild-type” strain, it is defined as being resistant
Define clinical resistance.
Clinically-resistant infections are defined as those infections having a low probability of clinically responding to treatment, even if maximum doses of a given antimicrobial are administered.
When is a bacterial isolate considered clinically resistance?
When Minimum Inhibitory Concentration (MIC) of the drug is associated with a high likelihood of therapeutic failure of treatment with that drug
Define inherent (intrinsic) resistance of bacteria.
Any resistance that the bacteria contains naturally.
For example, the target of the antimicrobial agent may be absent in that species, the cell wall may have poor permeability for certain types of molecules of the bacterial species may inherently produce enzymes that destroy the antimicrobial agent.
By what methods can bacteria acquire resistance?
Mutation or by uptake of exogenous genes
Define cross-resistance
Because antimicrobials can have similar structure or mode of action - a microbes ability to resist one implies that it can resist others that act in a similar or identical manner
Cross-resistance may also occur in relation to unrelated classes, if the target overlaps or if the mechanism of resistance is of low specificity.
What are the four groups of resistance mechanisms?
Enzymatic inactivation/degradation
Alternative pathways
Permeability changes
Target alteration
Define co-resistance
When two or more different resistance genes are physically linked (by genetic elements like integrons, transposons, or plasmids).
Consequently selection for one resistance will also select for the other resistance gene
What are the three different mechanisms of transferring resistance genes between bacteria?
Conjugation: where a mobile genetic element can be transferred from one bacterium to another bacterium
Transduction: where a bacteriophage takes up a resistance gene from one bacterium and transfers this to another bacterium
Transformation: where naked DNA released from one bacterium is taken up by another bacterium
What is the direct hazard of antimicrobial resistance in food?
The direct hazard is the presence on food of an antimicrobial resistance pathogenic bacterium which can colonise or infect a human being after ingestion of the food, or as a hazard that arises if a person acquires the infection through handling contaminated food.
What is the indirect hazard of antimicrobial resistance in food?
The indirect hazard arises when an antimicrobial resistant bacterium may transfer resistance genes to a bacterium pathogenic for humans, either directly, or via another commensal bacterium. In this case, the hazard is considered as being the resistance gene.
What are ESBLs?
Plasmid-encoded enzymes in Enterobacteriaceae that confer resistance to a variety of B-lactam antibiotics (penicillins, cephalosporins, and monobactams)
Safe against: carbapenems or cephamycins
Give two examples of ESBLs containing bacteria.
E. Coli Klebsiella pneumoniae
