AmpC β-Lactamases in SPICE (Serratia, Pseudomonas, Indole-Positive Proteus, Citrobacter, Enterobacter) Organisms: A Rising Threat to Antimicrobial Therapy

The global rise of antimicrobial resistance (AMR) among Gram-negative bacteria is a major public health threat. AmpC β-lactamases, particularly in SPICE (Serratia, Pseudomonas, indole-positive Proteus, Citrobacter, Enterobacter) organisms, contribute significantly to multidrug resistance by hydrolyzing cephamycins and other β-lactam antibiotics. Unlike extended-spectrum β-lactamases (ESBLs), AmpC β-lactamases are generally not inhibited by classical β-lactamase inhibitors such as clavulanic acid, sulbactam, and tazobactam. However, newer non-β-lactam β-lactamase inhibitors, including avibactam and relebactam, demonstrate activity against many AmpC-producing organisms, thereby complicating treatment strategies. This review highlights the molecular mechanisms, epidemiological patterns, clinical implications, detection methods, and emerging therapeutic options for AmpC β-lactamases in SPICE organisms. The review underscores the urgent need for enhanced surveillance, rapid diagnostics, and antimicrobial stewardship to manage infections caused by these resistant pathogens.