Serratia marcescens enzyme-2 (SME-2) carbapenemase (SME-2)

Serratia marcescens enzyme-2 (SME-2) is a chromosomally encoded Ambler Class A carbapenemase primarily found in the Gram-negative bacterium Serratia marcescens (Queenan & Bush, 2007). This enzyme is a significant factor in antibiotic resistance, as it efficiently hydrolyzes carbapenems, which are considered last-line treatments for multi-drug resistant infections (Naas et al., 1994). SME-2 operates through a serine-based mechanism, where a nucleophilic serine residue in the active site attacks and opens the beta-lactam ring, rendering the antibiotic inactive (Walther-Rasmussen & Hoiby, 2007). Unlike many other Class A carbapenemases like KPC, SME-2 is generally susceptible to inhibition by classical inhibitors such as clavulanic acid and tazobactam, as well as newer non-beta-lactam inhibitors like avibactam and vaborbactam (Majewski et al., 2016). The presence of this enzyme in clinical isolates poses a significant therapeutic challenge, necessitating the use of combination therapies to restore antibiotic efficacy (Bush & Bradford, 2016).

Other names

SME-2Serratia marcescens enzyme 2Class A carbapenemase SME-2blaSME-2SME-2 beta-lactamase

Hydrolysis of the beta-lactam ring of carbapenems and other beta-lactams via a catalytic serine residue (Walther-Rasmussen & Hoiby, 2007). Beta-lactamase inhibitors function by binding to the active site and preventing substrate access (Bush & Bradford, 2016).