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Introduction
The effectiveness of antibiotics to combat bacterial infections has diminished rapidly in the past decade due to incessant emergence of bacterial strains that exhibit novel and transmissible resistance mechanisms, such as carbapenem-resistant Enterobacteriaceae (CRE) strains that commonly cause untreatable and hard-to-treat infections among hospitalised patients. CRE are now considered an urgent public health threat according to reports by the European Centre for Disease Prevention and Control (ECDC) and the United States (US) Centers for Disease Control and Prevention (CDC) [1,2].
Colistin is currently considered a last-resort antibiotic that can be used to treat clinical CRE infections. Bacterial resistance to colistin was previously thought to be rare, and mainly attributed to chromosomal mutations leading to modification of lipid A or loss of lipopolysaccharide [3,4]. Recently, a new plasmid-encoded colistin resistance mechanism, mediated by the MCR-1 protein, a phosphoethanolamine transferase that modifies the phosphoethanolamine moiety of lipid A, has been reported [5].
Since its discovery in November 2015, the mcr-1genehas been associated with a wide range of mobile elements in different bacterial species, suggesting that this resistance element is highly transmissible, thereby posing a huge challenge to the use of colistin as a reserved drug for treatment of CRE infections [6].
Currently there is a lack of studies comprehensively screening for mcr-1 positive bacteria in the environment, and the most frequent sources investigated for such bacteria consist of human clinical samples and veterinary specimens. Hence, information on the prevalence of mcr-1 gene in various ecological niches is not available to assess of the degree of mcr-1 contamination, which can potentially impact the clinical use of colistin. This is due to a lack of methods for specific isolation of mcr-1-positive bacteria, since many species of bacteria are intrinsically resistant to colistin, interfering with the isolation of mcr-1-positive organisms.
In this study, we have developed a novel method that facilitates specific detection of mcr-1-positive bacteria. Using this method, we checked various environmental sources in China for the presence of mcr-1 positive bacteria. These included animal and human faecal samples, as well as sewage water, seawater and fresh water samples. Foods locally produced or imported from overseas were also tested.
- snip -
The mcr-1 gene may undergo evolutionary changes in the animal GI tract upon prolonged usage of colistin as growth promoter. The gene is then transmitted to human through the food chain or direct human contact with animals, as well as through contamination of the fresh and seawater system, which in turn cause contamination of vegetables and seafood. The persistence of mcr-1 in the human GI tract microflora can cause further contamination of the water systems through disposal of waste water containing human faeces. Fresh water systems outside these transmission routes remain clear of mcr-1 contamination.
LINK TO FULL REPORT
The effectiveness of antibiotics to combat bacterial infections has diminished rapidly in the past decade due to incessant emergence of bacterial strains that exhibit novel and transmissible resistance mechanisms, such as carbapenem-resistant Enterobacteriaceae (CRE) strains that commonly cause untreatable and hard-to-treat infections among hospitalised patients. CRE are now considered an urgent public health threat according to reports by the European Centre for Disease Prevention and Control (ECDC) and the United States (US) Centers for Disease Control and Prevention (CDC) [1,2].
Colistin is currently considered a last-resort antibiotic that can be used to treat clinical CRE infections. Bacterial resistance to colistin was previously thought to be rare, and mainly attributed to chromosomal mutations leading to modification of lipid A or loss of lipopolysaccharide [3,4]. Recently, a new plasmid-encoded colistin resistance mechanism, mediated by the MCR-1 protein, a phosphoethanolamine transferase that modifies the phosphoethanolamine moiety of lipid A, has been reported [5].
Since its discovery in November 2015, the mcr-1genehas been associated with a wide range of mobile elements in different bacterial species, suggesting that this resistance element is highly transmissible, thereby posing a huge challenge to the use of colistin as a reserved drug for treatment of CRE infections [6].
Currently there is a lack of studies comprehensively screening for mcr-1 positive bacteria in the environment, and the most frequent sources investigated for such bacteria consist of human clinical samples and veterinary specimens. Hence, information on the prevalence of mcr-1 gene in various ecological niches is not available to assess of the degree of mcr-1 contamination, which can potentially impact the clinical use of colistin. This is due to a lack of methods for specific isolation of mcr-1-positive bacteria, since many species of bacteria are intrinsically resistant to colistin, interfering with the isolation of mcr-1-positive organisms.
In this study, we have developed a novel method that facilitates specific detection of mcr-1-positive bacteria. Using this method, we checked various environmental sources in China for the presence of mcr-1 positive bacteria. These included animal and human faecal samples, as well as sewage water, seawater and fresh water samples. Foods locally produced or imported from overseas were also tested.
- snip -
The mcr-1 gene may undergo evolutionary changes in the animal GI tract upon prolonged usage of colistin as growth promoter. The gene is then transmitted to human through the food chain or direct human contact with animals, as well as through contamination of the fresh and seawater system, which in turn cause contamination of vegetables and seafood. The persistence of mcr-1 in the human GI tract microflora can cause further contamination of the water systems through disposal of waste water containing human faeces. Fresh water systems outside these transmission routes remain clear of mcr-1 contamination.
LINK TO FULL REPORT