Molecular Cut-off Values for Aliarcobacter butzleri Susceptibility Testing

Area of Science:

• Clinical Microbiology
• Genomics
• Infectious Diseases

Background:

• Aliarcobacter butzleri is an emerging gastrointestinal pathogen with increasing prevalence worldwide.
• Current antimicrobial susceptibility testing (AST) for A. butzleri relies on criteria for other bacteria, leading to potential misinterpretations.
• There is a lack of established interpretative criteria for AST, hindering effective clinical management.

Purpose of the Study:

• To propose specific epidemiological cut-off values for key antimicrobial agents against A. butzleri.
• To identify genetic markers associated with antimicrobial resistance in A. butzleri.
• To improve the accuracy of AST for this emerging pathogen.

Main Methods:

• Whole-genome sequencing (WGS) of 30 resistant A. butzleri isolates.
• Analysis of genetic mutations and genes associated with resistance.
• Adjustment of disk diffusion (DD) and minimum inhibitory concentration (MIC) cut-off values.

Main Results:

• Identification of a β-lactamase conferring ampicillin resistance and a T85I GyrA mutation linked to ciprofloxacin resistance.
• Adjustment of DD and MIC cut-off values for ampicillin and ciprofloxacin based on identified resistance mechanisms.
• Inability to estimate cut-off values for erythromycin and tetracycline due to the absence of known resistance mechanisms.

Conclusions:

• The study provides adjusted AST cut-off values for ampicillin and ciprofloxacin, crucial for accurate A. butzleri susceptibility testing.
• Genomic analysis is a robust method for identifying resistance mechanisms and refining AST parameters.
• Establishing consensus-based AST criteria for A. butzleri is essential for global public health.