First Known Report of mcr-Harboring Enterobacteriaceae in the Dominican Republic

Area of Science:

• Microbiology
• Antimicrobial Resistance
• Food Safety

Background:

• Colistin is a critical last-resort antibiotic for treating multidrug-resistant Gram-negative bacterial infections.
• Travelers returning from the Dominican Republic have been linked to pathogenic bacteria harboring the mobile colistin resistance gene, mcr-1.
• The presence of mcr genes in food animals poses a potential public health risk.

Purpose of the Study:

• To investigate the prevalence of mobile colistin resistance (mcr) genes in Enterobacteriaceae from food animal sources in the Dominican Republic.
• To identify the specific mcr genes and associated bacterial species.
• To assess the co-occurrence of other antibiotic resistance determinants.

Main Methods:

• Bacterial isolates were obtained from 311 food animal samples.
• Real-time PCR was used to screen for mcr genes.
• Whole-genome sequencing (WGS) was performed on presumptive mcr-positive and negative isolates.
• Isolates were identified as Escherichia coli and characterized for plasmid replicons.

Main Results:

• Of 311 samples, 70.7% tested positive for mcr genes by real-time PCR.
• 3.2% of 1354 bacterial isolates carried mcr genes.
• Whole-genome sequencing confirmed 39 isolates carried mcr genes, predominantly Escherichia coli with IncX4 plasmid replicons.
• Nearly all mcr-positive isolates also harbored resistance genes for other medically important antibiotics.

Conclusions:

• Mobile colistin resistance genes are present in food animal populations in the Dominican Republic.
• The findings indicate a potential pathway for the transmission of antibiotic resistance from food animals to humans.
• Co-resistance to other antibiotics in mcr-carrying bacteria is a significant concern for public health.