Detection of ESBL- and AmpC-producing E. coli isolates from urinary tract infections

Area of Science:

• Microbiology
• Molecular Biology
• Clinical Science

Background:

• Extended-spectrum β-lactamases (ESBLs) and AmpC enzymes are prevalent in Enterobacteriaceae, leading to serious infections like urinary tract infections.
• These resistance mechanisms are often plasmid-mediated, and there's a lack of standardized guidelines for their detection.
• Characterizing ESBL and AmpC producers in *Escherichia coli* is crucial for effective treatment strategies.

Purpose of the Study:

• To characterize ESBL and AmpC producing *Escherichia coli* isolates from urinary tract infections.
• To evaluate the effectiveness of phenotypic methods, including disk diffusion and combined disk diffusion with phenyl boronic acid, for detecting these enzymes.
• To confirm the presence of specific resistance genes using Polymerase Chain Reaction (PCR).

Main Methods:

• 90 *E. coli* isolates from urinary tract infections were screened for ESBL and AmpC production using disk diffusion tests.
• Combined disk diffusion with phenyl boronic acid was employed for confirmation and differentiation.
• PCR was used to detect genes encoding TEM, CIT, and FOX β-lactamases (blaTEM, blaCMY-2).

Main Results:

• 59 out of 90 isolates (65.6%) showed resistance to third-generation cephalosporins.
• Phenotypic screening identified 37 isolates (41.1%) as ESBL producers and 3 isolates (3.3%) as AmpC producers.
• PCR confirmed 29 isolates (32.2%) positive for blaTEM and 3 isolates (3.3%) for blaCMY-2.

Conclusions:

• ESBL- and AmpC-producing *E. coli* contribute significantly to cephalosporin resistance in urinary tract infections.
• Phenyl boronic acid demonstrates utility in differentiating ESBL enzymes from AmpC enzymes phenotypically.
• Accurate and reliable phenotypic tests are needed to distinguish between AmpC and ESBL producers for improved clinical management.