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Detection and quantification of the plasmid-mediated mcr-1 gene conferring colistin resistance in wastewater
Itziar Lekunberri1, José Luis Balcázar1, Carles M Borrego2
1Catalan Institute for Water Research (ICRA), Scientific and Technological Park of the University of Girona, Girona, Spain.
Abstract:
There is a global concern about the increasing resistance of bacterial pathogens to colistin, an antibiotic of last resort for the treatment of multidrug-resistant Gram-negative bacterial infections (e.g. carbapenemase-producing Enterobacteriaceae). In this study, an increasing prevalence of colistin resistance in raw and treated wastewater was demonstrated using a new developed SYBR Green-based real-time PCR assay for specific detection and quantification of the plasmid-mediated mcr-1 gene. Raw and treated wastewater samples were collected from a wastewater treatment plant in Girona (Spain) at two different time periods (November 2011-January 2012 and December 2016-February 2017). In both periods, the absolute abundance of the mcr-1 gene was significantly higher (P <0.05) in raw sewage samples, suggesting that conventional wastewater treatment reduces colistin-resistant bacteria. Moreover, the analysis revealed an increase from 1-2 orders of magnitude in the absolute abundance of mcr-1 between the studied periods (winter 2011 versus winter 2016, P <0.05), suggesting that colistin resistance has increased over time. This study gives evidence of the growing spread of mcr-1 and provides a real-time PCR assay for its rapid detection and quantification.
Insights
Colistin resistance is rising globally. A new real-time PCR assay detected increasing levels of the mcr-1 gene in wastewater, indicating a growing public health threat from resistant bacteria.
Area of Science:
- Environmental microbiology
- Molecular biology
- Public health
Background:
- Colistin is a critical last-resort antibiotic for multidrug-resistant Gram-negative infections.
- Increasing bacterial resistance to colistin poses a significant global health concern.
- The plasmid-mediated mcr-1 gene is a primary driver of colistin resistance.
Purpose of the Study:
- To develop and validate a SYBR Green-based real-time PCR assay for detecting the mcr-1 gene.
- To investigate the prevalence and trends of colistin resistance in wastewater.
- To assess the effectiveness of wastewater treatment in reducing colistin-resistant bacteria.
Main Methods:
- Development of a specific SYBR Green-based real-time PCR assay.
- Collection and analysis of raw and treated wastewater samples from Girona, Spain.
- Quantification of the absolute abundance of the mcr-1 gene in samples from two distinct time periods (2011-2012 and 2016-2017).
Main Results:
- The mcr-1 gene was detected in both raw and treated wastewater samples.
- Absolute abundance of the mcr-1 gene was significantly higher in raw sewage compared to treated samples.
- A significant increase (1-2 orders of magnitude) in mcr-1 gene abundance was observed between 2011-2012 and 2016-2017.
Conclusions:
- Conventional wastewater treatment effectively reduces the load of colistin-resistant bacteria.
- The prevalence of the mcr-1 gene in wastewater has significantly increased over time.
- The developed real-time PCR assay is a valuable tool for rapid detection and quantification of colistin resistance.
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