Mechanisms of Resistance
Bacteria can resist antibiotics naturally without prior exposure; this is called what?
What is intrinsic resistance?
Uptake of naked DNA from the environment.
What is transformation?
The lowest concentration of drug preventing visible growth.
What is the minimum inhibitory concentration?
This color signifies >90% susceptibility on Altru’s antibiogram.
What is green?
When bacteria develop resistance during exposure to a drug through gene expression changes, it is called this.
What is an adaptive resistance?
Transfer by bacteriophages.
What is transduction?
β-lactams rely on this PK/PD principle: keep drug levels above MIC.
What is time-dependent killing?
E. coli shows 97% susceptibility to this drug for uncomplicated UTIs.
MRSA is resistant to β-lactams due to a target-site alteration in this enzyme.
What is PBP2a?
Transfer through a pilus (major driver of MDR in Gram-negatives).
What is conjugation?
Testing method that measures the zone of inhibition around antibiotic disks.
What is Kirby-Bauer disk diffusion?
Due to low ampicillin susceptibility (30%), this Enterococcus species is problematic.
What is E. faecium?
These enzymes break the β-lactam ring, inactivating penicillins.
What are beta-lactamases?
DNA “jumping” elements that can move resistance genes between plasmids and chromosomes.
What are transposons?
An organism labeled “S” means this about antibiotic levels at the site of infection.
MRSA remains 100% susceptible to these 3 agents in Altru’s data.
What are vancomycin, linezolid, and daptomycin?
This mechanism spreads ESBL and carbapenemase resistance between species using mobile DNA.
What is conjugation via plasmids/transposons?
Mobile elements that cause acquired resistance.
What are plasmids, transposons, chromosomal gene cassettes, and integrons?
MIC data must be interpreted differently for this infection because drug entry is limited.
What is meningitis? (different breakpoints)
Severe HAP/VAP uses cefepime + vancomycin — cefepime is chosen because of high susceptibility for this Gram-negative pathogen.
What is Pseudomonas aeruginosa?