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Identification of mcr-2 and mcr-3 Genes in Colistin-Resistant E. coli O157:H7 Isolated From Raw Meat Samples in
Fatima H Fneish1, Souraya A Domiati2, Khaled H Abd El Galil3
1Department of Pharmaceutical Sciences, Faculty of Pharmacy, Beirut Arab University, Beirut, Lebanon.
Abstract:
Colistin is a last-resort antibiotic used to treat multidrug-resistant Gram-negative bacterial infections. The global emergence of colistin resistance has been attributed to plasmid-mediated mobile colistin resistance (mcr) genes. In Lebanon, bacteria carrying the mcr-1 gene have increasingly been identified in food animal sources. This study is aimed at detecting colistin-resistant Shiga toxigenic Escherichia coli O157:H7 in raw meat samples from local markets in the suburbs of Beirut and evaluating their antimicrobial resistance profiles. A total of 50 meat samples, including 25 minced beef and 25 burger samples, were collected and analyzed. Antimicrobial resistance patterns were determined using the Kirby-Bauer method, while colistin resistance and the presence of mcr-2 and mcr-3 genes were assessed using broth microdilution and PCR amplification techniques. Among these samples, 23 (46%) tested positive for E. coli O157:H7. Resistance to ampicillin and amoxicillin/clavulanic acid was observed in 96% of the samples, while 61% were resistant to trimethoprim/sulfamethoxazole, and 43% to chloramphenicol. Notably, 87% of the samples displayed colistin resistance, with a minimum inhibitory concentration (MIC) of ≥ 4 μg/mL. The mcr-2 gene was present in four isolates (17.4%), and the mcr-3 gene was identified in 10 isolates (43.4%). This study is the first to document the presence of plasmid-mediated colistin resistance genes, mcr-2 and mcr-3, in E. coli O157:H7 strains in Lebanon. These findings highlight a serious public health concern for the Lebanese community. Therefore, the responsible use of antibiotics across all healthcare sectors, combined with strict hygiene measures in food handling, is essential to control the spread of colistin-resistant genes.
Insights
Colistin resistance genes mcr-2 and mcr-3 were found in Shiga toxigenic Escherichia coli O157:H7 from raw meat in Lebanon. This discovery highlights a significant public health risk requiring urgent antibiotic stewardship and food safety measures.
Area of Science:
- Microbiology
- Public Health
- Food Safety
Background:
- Colistin is a critical last-resort antibiotic for multidrug-resistant Gram-negative bacterial infections.
- The rise of plasmid-mediated mobile colistin resistance (mcr) genes poses a global threat.
- Increasing identification of mcr-1 in food animals in Lebanon necessitates further investigation.
Purpose of the Study:
- To detect colistin-resistant Shiga toxigenic Escherichia coli O157:H7 in raw meat samples.
- To analyze the antimicrobial resistance profiles of these isolates.
- To identify the presence of mcr-2 and mcr-3 genes in E. coli O157:H7 from Lebanese markets.
Main Methods:
- Collection and analysis of 50 raw meat samples (25 minced beef, 25 burger).
- Antimicrobial susceptibility testing using Kirby-Bauer method.
- Colistin resistance determination via broth microdilution (MIC) and PCR for mcr-2 and mcr-3 genes.
Main Results:
- 23% of samples were positive for E. coli O157:H7.
- High resistance rates observed for ampicillin (96%), amoxicillin/clavulanic acid (96%), trimethoprim/sulfamethoxazole (61%), and chloramphenicol (43%).
- 87% of isolates showed colistin resistance (MIC ≥ 4 μg/mL), with mcr-2 found in 17.4% and mcr-3 in 43.4%.
Conclusions:
- This study is the first to report mcr-2 and mcr-3 genes in E. coli O157:H7 in Lebanon.
- The findings indicate a significant public health concern regarding colistin resistance in the food chain.
- Responsible antibiotic use and stringent food handling hygiene are crucial to mitigate the spread of colistin resistance.
