Members of the Enterobacteriaceae family demonstrate intrinsic patterns of resistance to certain antimicrobial agents. Resistance to additional antibiotics is achieved through multiple, acquired resistance mechanisms, including:
- Extended-spectrum beta-lactamases (ESBLs) - A diverse, complex, and rapidly evolving group of plasmid-mediated enzymes that hydrolyze penicillins, cephalosporins, and aztreonam.
- AmpC beta-lactamases - Cephalosporinases that are chromosomally- or plasmid-mediated enzymes (inducible in some organisms) that mediate resistance to cephalothin, cefazolin, cefoxitin, most penicillins, and beta-lactamase inhibitor/beta-lactam combinations.
This course will focus on the very serious resistance mechanism emerging in the Enterobacteriaceae
family, referred to as carbapenemase resistance. Carbapenemases are diverse enzymes that vary in their ability to hydrolyze carbapenems and other beta-lactams. Among Enterobacteriaceae
, there are two mechanisms that can result in carbapenem resistance:
- Carbapenemase production
- Cephalosporinase or ESBL combined with porin loss (which limits entry of carbapenem into the cell and can render an organism nonsusceptible)