Antibacterial resistance

What is innate resistance?

inherent structural or functional characteristics that are chromosomally encoded

What is acquired resistance?

mutation in resident gene via vertical or horizontal gene transfer

What are the main types of horizontal gene transfer?

transformation

transduction

conjugation

What is transformation?

naked DNA uptake from donor cell

What is transduction?

phage-mediated transfer

What is conjugation?

plasmid DNA donation during cell-to-cell contact

How are bacteria able to resist antibiotics?

preventing antibiotic from reaching its target

or modifying/bypassing antibiotic targe

how are bacteria able to keep antibiotics from entering the cell?

altering porins in cell wall

How do bacteria expel antibiotics out of the cell?

via efflux pumps that can export then out as fast as they enter

decreases antibiotic concentration in side the cell (too low to have effect)

How are bacteria able to degrade/modify antibiotic? What is an example?

enzymes

B-lactamases

What are B-lactamase inhibitors?

used w/ B-lactam to extend the activity spectrum

inhibits B-lactamase (blocks active site of inhibitor and allows antibiotic to function)

How can bacteria modify an antimicrobial target? What is an example?

some have acquired mutations/modified structures that are then no longer recognized by the antibiotic

vancomycin resistant enterococci end of NAM chain is changed to Ser or Lac instead of Ala

How can bacteria bypass the antibiotic target?

acquiring a new enzyme that allows a bypass in the metabolic pathway

What are some steps to prevent antibacterial resistance?

prescribe only for bacterial infections

educate clients on proper use

determine most appropriate antibiotic to use to effectively tx infection

Why is it important to give antibiotics as directed?

many infections are polymicrobial

when end antibiotic course early then allow moderately susceptible and resistant bacteria to regrow

How do you determine the best antibiotic to use per case?

antibiotic susceptibility testing!

What is the Kirby Bauer method?

surface of plate innoculated then tests susceptiblity to different antibiotics

diameters of zone of inhibition are read from standardized chart

What is broth dilution method?

serial dilutions of antibiotics inoculated w/ standard suspension of bacteria

gives quantitative determination

What is MIC?

minimum inhibitory concentration

lowest concentration of antibiotic that inhibits bacterial growth

What is MBC?

minimum bactericidal concentration

lowest concentraiton of antibiotic that kills 99.9% of bacteria

What is the E-test?

plate inoculated then plastic strips impregnated with gradual decreasing concentration of antibiotic placed onto plate

MIC is where elliptical zone of inhibition crosses the strip