[Enterobacteriaceae and beta-lactams : wild susceptibility patterns]

Area of Science:

• Microbiology
• Antimicrobial Resistance
• Biochemistry

Context:

• Enterobacteria resistance to beta-lactams has evolved since the 1980s.
• Initial resistance patterns included low-level penicillinase, cephalosporinase, and combined mechanisms.
• Current understanding acknowledges seven patterns, but a revised proposal of five is presented.

Purpose:

• To analyze and propose updated susceptibility patterns for enterobacteria against beta-lactam antibiotics.
• To characterize the emergence and implications of a fifth resistance pattern associated with chromosomal extended-spectrum beta-lactamases (ESBLs).
• To provide guidance for medical biologists in interpreting antimicrobial susceptibility testing results.

Summary:

• Historically, four susceptibility patterns for enterobacteria against older beta-lactams were identified.
• A fifth pattern, observed since 2005, involves chromosomal ESBLs capable of hydrolyzing advanced cephalosporins.
• Analysis of MICs, inhibition zones, beta-lactamase types, and amino acid sequences informed the proposed five patterns.
• The study highlights variability in resistance even within the same pattern due to diverse beta-lactamase production.

Impact:

• The emergence of ESBL-producing strains necessitates a re-evaluation of susceptibility patterns.
• Understanding these patterns is crucial for accurate antibiotic selection and treatment of infections.
• Distinguishing between chromosomal ESBLs and transferable resistance mechanisms is vital for epidemiological assessment.
• The findings underscore the importance of continuous monitoring of antimicrobial resistance trends.