Gram Positive
Staph Aureus
Plain Penicillins – beta-lactamase (enzyme)
Methicillin (MRSA) – binding target modification
Enterococcus
Penicillins – binding target modification
Vancomycin (VRE) – binding target modification
Gram Negative
Extended-Spectrum Beta-lactamases (ESBLs) – hydrolyzes a broader range of ABX than expected (eg, 3rd gen cephalosporins)
Enterobacterales mostly
Carbapenem-Resistant Enterobacterales (CREs) - resistance to broadest ABX
Tons of other classes of enzymes
Often combine with other resistance mechanisms (efflux; target modification) to produce bug from hell