Final answer:
CRE have acquired genes coding for ß-lactamases, causing resistance to carbapenems and posing a severe healthcare challenge.
Step-by-step explanation:
Carbapenem-Resistant Enterobacteriaceae (CRE) have acquired one of three genes that code for ß-lactamases, which provide resistance to carbapenem antibiotics.
These enzymes are capable of inactivating a broad spectrum of ß-lactam antibiotics, including carbapenems.
CRE infections are a significant healthcare concern due to their resistance not only to carbapenems but also to multiple classes of antibacterials, and they pose a risk of spreading in healthcare settings such as hospitals.