Characterization of Genetic Elements Carrying mcr-1 Gene in Escherichia coli from the Community and Hospital Settings in Vietnam

Whole genome analysis of multidrug-resistant Escherichia coli isolate collected from drinking water in Armenia revealed the plasmid-borne mcr-1.1-mediated colistin resistance

The rate of polymyxin-resistant Enterobacteriaceae, as well as human and animal infections caused by them, is increasing worldwide, posing a high epidemiological threat since colistin represents a last-resort antibiotic to treat complicated infections. The study of environmental niches, in particular, aquatic ecosystems in terms of genome analysis of inhabiting antimicrobial-resistant (AMR) microorganisms as reservoirs of acquired resistance determinants (AMR genes), represents a specific concern from a One Health approach. Here, we present a phenotypic AMR analysis and molecular characterization of Escherichia coli isolate found in municipal drinking water after an accident in the water supply system of a residential building in Armenia in 2021. CrieF1144 E. coli isolate was resistant to ampicillin, ampicillin/sulbactam, cefuroxime, ciprofloxacin, levofloxacin, trimethoprim/sulfamethoxazole, colistin, and tigecycline, whereas whole genome sequencing (WGS) revealed blaTEM-1B, tet(A), and a combination of dfrA14 with sul1 resistance determinants, which corresponds well with phenotypic resistance above. Moreover, the multidrug-resistant isolate studied harbored mcr-1.1 gene on a conjugative 251 Kb IncHI2 plasmid, whose structure was determined using hybrid short- and long-reads assembly. CrieF1141_p1 plasmid carried all antimicrobial resistance genes revealed in the isolate and did not harbor any virulence determinants, so it could contribute to the spread of AMR genes in the bacterial population. Two copies of ISApl1 transposase-encoding element, which is likely to mediate mcr-1.1 gene mobilization, were revealed surrounding this gene in a plasmid.

IMPORTANCE

Evolutionary patterns of Escherichia coli show that they usually develop into highly pathogenic forms by acquiring fitness advantages such as antimicrobial resistance (AMR) and various virulence factors through horizontal gene transfer mediated by mobile elements. This has led to high prevalence of multidrug-resistant (MDR) strains, which highlights the relevancy of enhanced surveillance to monitor and prevent transmission of the MDR bacteria to human and animal populations. However, the limited number of reports regarding the whole genome sequencing (WGS) investigation of MDR E. coli strains isolated from drinking water and harboring mcr genes hampers the adoption of a comprehensive approach to address the relationship between environmental E. coli populations and human and veterinary infections. Our results highlight the relevance of analyzing the environment, especially water, as a part of the surveillance programs to understand the origins and dissemination of antimicrobial resistance within the One Health concept.

Molecular Epidemiology of mcr-1-Positive Polymyxin B-Resistant Escherichia coli Producing Extended-Spectrum β-Lactamase (ESBL) in a Tertiary Hospital in Shandong, China

Escherichia coli, a rod-shaped Gram-negative bacterium, is a significant causative agent of severe clinical bacterial infections. This study aimed to analyze the epidemiology of extended-spectrum β-lactamase (ESBL)-producing mcr-1 -positive E. coli in Shandong, China. We collected 668 non-duplicate ESBL-producing E. coli strains from clinical samples at Shandong Provincial Hospital between January and December 2018, and estimated their minimum inhibitory concentrations (MICs) using a VITEK® 2 compact system and broth microdilution. Next-generation sequencing and bioinformatic analyses identified the mcr-1 gene and other resistance genes in the polymyxin B-resistant strains. The conjugation experiment assessed the horizontal transfer capacity of the mcr-1 gene. Of the strains collected, 24 polymyxin B-resistant strains were isolated with a positivity rate of 3.59% and among the 668 strains, 19 clinical strains carried the mobile colistin resistance gene mcr-1, with a positivity rate of approximately 2.8%. All 19 clinical strains were resistant to ampicillin, cefazolin, ceftriaxone, ciprofloxacin, levofloxacin, and polymyxin B. Seventeen strains successfully transferred the mcr-1 gene into E. coli J53. All transconjugants were resistant to polymyxin B, and carried the drug resistance gene mcr-1. The 19 clinical strains had 14 sequence types (STs), with ST155 (n = 4) being the most common. The whole-genome sequencing results of pECO-POL-29_mcr1 revealed that no ISApl1 insertion sequences were found on either side of the mcr-1 gene. Our study uncovered the molecular epidemiology of mcr-1-carrying ESBL-producing E. coli in the region and suggested horizontal transmission mediated by plasmids as the main mode of mcr-1 transmission.

Investigation of Escherichia coli isolates from pigs and humans for colistin resistance in Lao PDR- a cross-sectional study

Background

In Laos, colistin is not currently registered for use in humans. This One Health study aimed to estimate the prevalence of meat-producing pigs carrying colistin-resistant Escherichia coli, and investigate if E. coli causing invasive human infections were colistin-resistant.

Methods

Between September 2022 and March 2023, rectal swabs were collected from 895 pigs from abattoirs in 9/17 Lao provinces. Pig rectal swabs and stored E. coli isolates from human blood cultures, submitted to Mahosot Hospital Microbiology laboratory between 2005 and 2022, were screened for colistin resistance on selective chromogenic agar with organism identification confirmed using MALDI-TOF MS. Suspected colistin-resistant isolates underwent colistin susceptibility testing by broth microdilution following European Committee on Antimicrobial Susceptibility Testing (EUCAST) guidelines. Isolates with MIC values of ≥2 μg/ml were tested for plasmid-mediated colistin resistance genes (mcr-1, mcr-2, and mcr-3) by multiplex SYBR Green PCR.

Results

A total of 15/620 (2.41%) invasive human E. coli isolates were phenotypically colistin-resistant by broth microdilution (MIC values 4 to 8 μg/ml). The earliest isolate was from 2015 in a patient from Phongsaly province in Northern Laos. A total of 582/895 (65.02%) pig rectal swab samples contained colistin-resistant E. coli. The detected colistin resistance genes were predominantly mcr-1 (57.8%, 346/598), followed by mcr-3 (20.23%,121/598), and 22.24% (133/598) were found to co-harbour mcr-1 and mcr-3. Among the 15 human isolates with colistin MIC values of ≥4 μg/ml, 12/15 were mcr-1.

Conclusions

We found that colistin resistant E. coli is causing invasive infection in humans in Laos despite the fact it is not available for human use. Use in animals seems to be widespread, confirmed by high carriage rates of colistin-resistant E. coli in pigs. It is probable that food-producing animals are the source of colistin-resistant E. coli bloodstream infection in Laos, although these have been infrequent to date. This is a serious public health concern in the region that needs to be addressed by appropriate enforceable legislation.

Genetic characterization of multidrug-resistant Escherichia coli harboring colistin-resistant gene isolated from food animals in food supply chain

Colistin is widely used for the prophylaxis and treatment of infectious disease in humans and livestock. However, the global food chain may actively promote the dissemination of colistin-resistant bacteria in the world. Mobile colistin-resistant (mcr) genes have spread globally, in both communities and hospitals. This study sought to genomically characterize mcr-mediated colistin resistance in 16 Escherichia coli strains isolated from retail meat samples using whole genome sequencing with short-read and long-read platforms. To assess colistin resistance and the transferability of mcr genes, antimicrobial susceptibility testing and conjugation experiments were conducted. Among the 16 isolates, 11 contained mcr-1, whereas three carried mcr-3 and two contained mcr-1 and mcr-3. All isolates had minimum inhibitory concentration (MIC) for colistin in the range 1-64 μg/mL. Notably, 15 out of the 16 isolates demonstrated successful transfer of mcr genes via conjugation, indicative of their presence on plasmids. In contrast, the KK3 strain did not exhibit such transferability. Replicon types of mcr-1-containing plasmids included IncI2 and IncX4, while IncFIB, IncFII, and IncP1 contained mcr-3. Another single strain carried mcr-1.1 on IncX4 and mcr-3.5 on IncP1. Notably, one isolate contained mcr-1.1 located on a chromosome and carrying mcr-3.1 on the IncFIB plasmid. The chromosomal location of the mcr gene may ensure a steady spread of resistance in the absence of selective pressure. Retail meat products may act as critical reservoirs of plasmid-mediated colistin resistance that has been transmitted to humans.

A Review of Resistance to Polymyxins and Evolving Mobile Colistin Resistance Gene (mcr) among Pathogens of Clinical Significance

The global rise in antibiotic resistance in bacteria poses a major challenge in treating infectious diseases. Polymyxins (e.g., polymyxin B and colistin) are last-resort antibiotics against resistant Gram-negative bacteria, but the effectiveness of polymyxins is decreasing due to widespread resistance among clinical isolates. The aim of this literature review was to decipher the evolving mechanisms of resistance to polymyxins among pathogens of clinical significance. We deciphered the molecular determinants of polymyxin resistance, including distinct intrinsic molecular pathways of resistance as well as evolutionary characteristics of mobile colistin resistance. Among clinical isolates, Acinetobacter stains represent a diversified evolution of resistance, with distinct molecular mechanisms of intrinsic resistance including naxD, lpxACD, and stkR gene deletion. On the other hand, Escherichia coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa are usually resistant via the PhoP-PhoQ and PmrA-PmrB pathways. Molecular evolutionary analysis of mcr genes was undertaken to show relative relatedness across the ten main lineages. Understanding the molecular determinants of resistance to polymyxins may help develop suitable and effective methods for detecting polymyxin resistance determinants and the development of novel antimicrobial molecules.

Comparative genome analysis of colistin-resistant Escherichia coli harboring mcr isolated from rural community residents in Ecuador and Vietnam

The spread of colistin-resistant bacteria among rural community residents of low- and middle-income countries is a major threat to community health. Although the mechanism of the spread of colistin-resistant bacteria in communities is unknown, geographic and regional characteristics may influence it. To elucidate the spread mechanism of colistin-resistant bacteria, we analyzed the genomes of colistin-resistant Escherichia coli isolated from Vietnam and Ecuador residents, which are geographically and socially different. Stool specimens of 139 and 98 healthy residents from Ecuador and Vietnam rural communities, respectively, were analyzed for colistin-resistant E. coli with mcr. Its prevalence in the residents of all the communities assessed was high and approximately equal in both countries: 71.8% in Ecuador and 69.4% in Vietnam. A phylogenetic tree analysis revealed that the sequence type of colistin-resistant E. coli was diverse and the major sequence types were different between the two countries. The location of mcr in the isolates showed that the proportion of chromosomal mcr was 35.1% and 8.5% in the Vietnam and Ecuador isolates, respectively. Most of these chromosomal mcr genes (75%-76%) had an intact mcr-transposon Tn6330. Contrastingly, the replicon types of the mcr-carrying-plasmids were diverse in both countries, but almost all belonged to IncI2 in Ecuador and IncX1/X4 in Vietnam. Approximately 26%-45% of these mcr-plasmids had other resistance genes, which also varied between countries. These results suggest that although the overall profile of the colistin-resistant E. coli isolates is diverse in these countries, the phylogenesis of the isolates and mcr-carrying plasmids has regional characteristics. Although the contributing factors are not clear, it is obvious that the overall profile of colistin-resistant bacteria dissemination varies between countries. Such different epidemic patterns are important for establishing country-specific countermeasures against colistin-resistant bacteria.

Distribution and Antibiotic Resistance Characteristics of Bacteria Isolated from Blood Culture in a Teaching Hospital in Vietnam During 2014-2021

Purpose

Studies on the epidemiology of bloodstream infection (BSI) and antimicrobial resistance (AMR) are limited in Vietnam. Thus, the present study aimed to elucidate the epidemiology of BSI and AMR of BSI-causing bacteria in Vietnam.

Methods

Data regarding blood cultures from 2014 to 2021 were collected and analyzed using the chi-square test, Cochran-Armitage test, and binomial logistic regression model.

Results

Overall, 2405 (14.15%) blood cultures were positive during the study period. In total, 55.76% of BSIs occurred in patients aged ≥60 years. The male-to-female ratio of patients with BSI was 1.87:1. Escherichia coli (26.11%), Staphylococcus aureus (15.79%), Klebsiella pneumoniae (10.44%), Acinetobacter baumannii (4.70%), and Pseudomonas aeruginosa (3.45%) were the leading bacterial species causing BSI. The AMR rate of these bacteria isolated in the intensive care unit (ICU) was significantly higher compared with that of those in other wards. E. coli was the least resistant to carbapenems (2.39%-4.14%), amikacin (3.85%), and colistin (11.54%) and most resistant to penicillins (>80.0%). S. aureus was the least resistant to glycopeptides (0%-3.38%), quinupristin-dalfopristin (0.59%), and linezolid (1.02%) and most resistant to clindamycin (71.57%). K. pneumoniae was the least resistant to ertapenem (8.86%), amikacin (9.39%), and colistin (15.38%) and most resistant to aztreonam (83.33%). A. baumannii was the least resistant to amikacin (16.67%) and colistin (16.67%) and highly resistant to other antibiotics (≥50.0%). P. aeruginosa was the least resistant to colistin (16.33%) and piperacillin (28.17%) and highly resistant to other antibiotics (≥50.0%). Notably, the multidrug resistance rate of E. coli (76.41%) was the highest among common pathogens, followed by A. baumannii (71.57%), P. aeruginosa (64.56%), S. aureus (56.99%), and K. pneumoniae (43.72%).

Conclusion

The AMR rate of BSI-causing bacteria, particularly strains isolated from ICU, was alarmingly high. There is a need for new antibiotics, therapeutic strategies, as well as prevention and control to combat BSI and AMR.

Occurrence and Genomic Characterization of mcr-1-Harboring Escherichia coli Isolates from Chicken and Pig Farms in Lima, Peru

Resistance to colistin generated by the mcr-1 gene in Enterobacteriaceae is of great concern due to its efficient worldwide spread. Despite the fact that the Lima region has a third of the Peruvian population and more than half of the national pig and poultry production, there are no reports of the occurrence of the mcr-1 gene in Escherichia coli isolated from livestock. In the present work, we studied the occurrence of E. coli carrying the mcr-1 gene in chicken and pig farms in Lima between 2019 and 2020 and described the genomic context of the mcr-1 gene. We collected fecal samples from 15 farms in 4 provinces of Lima including the capital Lima Metropolitana and recovered 341 E. coli isolates. We found that 21.3% (42/197) and 12.5% (18/144) of the chicken and pig strains were mcr-1-positive by PCR, respectively. The whole genome sequencing of 14 mcr-1-positive isolates revealed diverse sequence types (e.g., ST48 and ST602) and the presence of other 38 genes that confer resistance to 10 different classes of antibiotics, including beta-lactamase bla_CTX-M-55. The mcr-1 gene was located on diverse plasmids belonging to the IncI2 and IncHI1A:IncHI1B replicon types. A comparative analysis of the plasmids showed that they contained the mcr-1 gene within varied structures (mikB-mcr1-pap2, ISApl1-mcr1-pap2, and Tn6330). To the best of our knowledge, this is the first attempt to study the prevalence of the mcr-1 gene in livestock in Peru, revealing its high occurrence in pig and chicken farms. The genetic diversity of mcr-1-positive strains suggests a complex local epidemiology calling for a coordinated surveillance under the One-Health approach that includes animals, retail meat, farmers, hospitals and the environment to effectively detect and limit the spread of colistin-resistant bacteria.

Genomic epidemiological analysis of mcr-1-harboring Escherichia coli collected from livestock settings in Vietnam

Livestock has been implicated as a reservoir for antimicrobial resistance (AMR) genes that can spread to humans when antimicrobials are used in animals for food production to treat clinical diseases and prevent and control common disease events. In Vietnam, mcr-1-harboring Escherichia coli (MCRPEC) strains have been isolated from humans, animals (chickens, pigs, and dogs) feces, flies, foods, and the environment (rainwater, well water, and irrigation water) in communities and from clinical specimens in hospitals. The relationship between levels of AMR in livestock and its occurrence in humans is complex and is driven by many factors. We conducted whole genome sequencing of MCRPEC to analyze the molecular epidemiological characteristics, history, and relatedness of 50 isolates obtained in 2019 from different reservoirs in farms and markets in Ha Nam province, Vietnam. 34 sequence types (STs) with 3 new STs were identified in multilocus sequence typing analysis: ST12945 and ST12946 from chicken feces, and ST12947 from flies. The AMR phenotypes of 50 MCRPEC isolates were as follows: ampicillin (100%, 50/50), cefotaxime (10%, 5/50), gentamicin (60%, 30/50), amikacin (8%, 4/50), meropenem (6%, 3/50), ceftazidime (18%, 9/50), colistin (24%, 12/50) and ciprofloxacin (80%, 40/50). All 50 MCRPEC isolates were identified as MDR. 100% (50/50) isolates carried AMR genes, ranging from 5 to 22 genes. The most prevalent plasmid replicon types carrying mcr-1 were IncP-1 (17/37, 45.9%), IncX4 (7/37, 18.9%), and IncHI2/IncHI2A (6/37, 16.2%). These data suggest that the epidemiology of the mcr-1 gene is mostly determined by plasmid spreading instead of clonal dissemination of MCRPE strains. The co-occurrence of several STs such as ST10, ST48, ST155, ST206, ST2705 in various sample types, joined to the higher prevalence of a few types of Inc plasmids, confirms the dissemination of the mcr-1 carrying plasmids in E. coli clones established in livestock. 5 over 8 STs identified in flies (ST206, ST2705, ST155, ST10, and ST48) suggested the fly contribution in the transmission of AMR bacteria in environments. These popular STs also occur in human samples and 100% of the human samples were positive for the mcr-1 gene.