[EVOLUTION OF BETA-LACTAM ANTIBIOTIC RESISTANCE IN ENTEROBACTER SPP. IN CROATIA]

Area of Science:

• Microbiology
• Molecular Biology
• Antimicrobial Resistance

Background:

• Enterobacter spp. exhibit resistance to expanded-spectrum cephalosporins through various beta-lactamase mechanisms.
• Understanding these resistance mechanisms and their evolution is crucial for effective treatment strategies.

Purpose of the Study:

• To analyze resistance mechanisms to expanded-spectrum cephalosporins in Enterobacter spp.
• To investigate the evolution of these resistance mechanisms over a three-year period (2008-2010).

Main Methods:

• Antibiotic susceptibility testing using broth microdilution (CLSI standards).
• Detection of resistance genes via Polymerase Chain Reaction (PCR).
• Plasmid characterization using PCR-based replicon typing (PBRT).

Main Results:

• Derepressed AmpC beta-lactamases combined with CTX-M family ESBLs were the predominant resistance mechanism.
• Metallo-beta-lactamases (MBLs) emerged in the final year of the study.
• ESBL-encoding plasmids belonged to various incompatibility groups.

Conclusions:

• The study highlights the dynamic evolution of beta-lactam resistance in Enterobacter spp.
• Resistance mechanisms progressed from derepressed AmpC beta-lactamases and ESBLs towards carbapenemases.
• Diverse plasmid types contribute to the spread of ESBL resistance.