Colistin-Resistant mcr-1 -Positive Escherichia coli on Public Beaches, an Infectious Threat Emerging in Recreational Waters

Abstract

The emergence and rapid spread of colistin-resistant Escherichia coli carrying the mcr-1 gene have generated an urgent need to strengthen surveillance. We performed a meticulous investigation of strains of this sort, which resulted in the identification of international clones of E. coli carrying IncX4-plasmid-mediated mcr-1 and bla CTX-M genes in recreational waters of public urban beaches in cities with high tourist turnover, highlighting a new environmental reservoir.KEYWORDS MCR-1, ESBL, CTX-M, IncX4, polymyxins, Brazil T he emergence and rapid spread of colistin-resistant Enterobacteriaceae carrying the mcr-1 gene have generated a profound sense of public alarm (1). Escherichia coli, one of the bacterial species that is most widely distributed and exchanged between the environment, animals, and humans, has been the main host of mcr-1 (2, 3). In South America, the occurrence of E. coli carrying mcr-1 and bla CTX-M genes in human (4-6) and wild animal (7) infections and food-producing animals (8) has created an urgent need to strengthen epidemiological surveillance. Using a whole-genome sequencing (WGS) approach, we performed a meticulous investigation of strains of this sort, which resulted in the identification of international clones of E. coli carrying mcr-1 and bla CTX-M-type genes in recreational waters of public urban beaches and highlighted a new source of transmission of this infectious threat.In September 2016, coastal water samples were collected from 11 different public beaches (in the southeastern Brazilian continental margin of São Paulo State) surrounding urban counties with a population of about 800,000 inhabitants, which can double during the summer. Following standard methods for the examination of water and wastewater (http://www.standardmethods.org), 500-ml surface water samples were collected, on the same day, in sterile bottles, transported to the laboratory in cooled containers (at about 4°C to 10°C), and processed within 6 h. From each water sample, 100 ml was concentrated by filtration through sterile membrane filters with a pore size of 0.45 m. The filters were placed on MacConkey agar plates and incubated for 24 h at 37°C. Next, the membrane filters were aseptically removed and placed separately in sterile tubes that had been filled previously with 10 ml of sterile Mueller-Hinton broth. After vortex mixing, an aliquot (100 l) of each culture was streaked on MacConkey agar plates supplemented with colistin (2 g/ml).Three colistin-resistant E. coli strains were recovered from different beaches located in the cities of São Vicente and Santos (Fig. 1); the latter is the major beachfront city of the region, with the largest shipping terminal in Latin America. The isolates were identified by matrix-assisted laser desorption ionization-time of flight mass spectrom-

Genetic and Functional Characterization of an MCR-3-Like Enzyme-Producing Escherichia coli Isolate Recovered from Swine in Brazil

“…There have been many reports of MCR producers in Brazil, with MCR-1 being the only variant systematically identified. These isolates were a single Salmonella enterica serotype Typhimurium isolate that was recovered from retail meat (18) and E. coli isolates recovered from chicken meat (19), from migratory penguins (20), on public beaches (21), or from patients with bloodstream infections (22,23). Also, KPC-2-producing E. coli isolates (24) and KPC-2-producing Klebsiella pneumoniae isolates belonging to ST392 and ST437 (25,26) were identified.…”

Detection of Colistin-Resistant MCR-1-Positive Escherichia coli by Use of Assays Based on Inhibition by EDTA and Zeta Potential

“…mcr-type genes encode phosphoethanolamine transferases that add PEtN to the phosphate group of the lipid A moiety (at the 4= position) anchored on LPS, reduce negative charges that are present in LPS, and consequently confer resistance to polymyxins (4,(9)(10)(11)(12). The mcr-1 gene has been identified as a plasmid-mediated resistance mechanism being widely disseminated among human, animal, food, and environmental E. coli isolates (6)(7)(8)(13)(14)(15)(16)(17)(18)(19).…”

“…PFGE and/or MLST data obtained from earlier studies revealed that most mcr-1-positive E. coli isolates were clonally unrelated(8,(13)(14)(15)(16)(17)33). The combined disk test method was performed in triplicate.…”

The global distribution and spread of the mobilized colistin resistance gene mcr-1

“…To date, mcr-1 has been observed on a wide variety of plasmid types, including IncI2, IncHI2, and IncX4 15 . Intensive screening efforts for mcr-1 have found it to be highly prevalent in a number of environmental settings, including the Haihe River in China 17 , recreational water at public urban beaches in Brazil 18 , and faecal samples from otherwise healthy individuals 19,20 . While both Brazil and China have now banned the use of colistin in agriculture, the evidence that mcr-1 can spread within hospital environments even in the absence of colistin use 19 as well as in the community 20 raises the possibility that the spread of mcr-1 will not be contained by these bans.…”