Mobile Colistin Resistance (mcr) Genes in Cats and Dogs and Their Zoonotic Transmission Risks

Colistin Resistance Mediated by Mcr-3-Related Phosphoethanolamine Transferase Genes in Aeromonas Species Isolated from Aquatic Environments in Avaga and Pakro Communities in the Eastern Region of Ghana

Purpose

Colistin is classified by the World Health Organization (WHO) as a critically important and last-resort antibiotic for the treatment of infections caused by carbapenem-resistant bacteria. However, colistin resistance mediated by chromosomal mutations or plasmid-linked mobilized colistin resistance (mcr) genes has emerged.

Methods

Thirteen mcr-positive Aeromonas species isolated from water samples collected in Eastern Ghana were analyzed using whole-genome sequencing (WGS). Antimicrobial susceptibility was tested using the broth microdilution method. Resistome analysis was performed in silico using a web-based platform.

Results

The minimum inhibitory concentration (MIC) of colistin for all except three isolates was >4 µg/mL. Nine new sequence types were identified and whole-genome analysis revealed that the isolates harbored genes (mcr-3-related genes) that code for Lipid A phosphoethanolamine transferases on their chromosomes. BLAST analysis indicated that the amino acid sequences of the mcr-3-related genes detected varied from those previously reported and shared 79.04-99.86% nucleotide sequence identity with publicly available mcr-3 variants and mcr-3-related phosphoethanolamine transferases. Analysis of the genetic context of mcr-3-related genes revealed that the genetic environment surrounding mcr-3-related genes was diverse among the different species of Aeromonas but conserved among isolates of the same species. Mcr-3-related-gene-IS-mcr-3-related-gene segment was identified in three Aeromonas caviae strains.

Conclusion

The presence of mcr-3-related genes close to insertion elements is important for continuous monitoring to better understand how to control the mobilization and dissemination of antibiotic resistance genes.

Raw meat-based diet for pets: a neglected source of human exposure to Salmonella and pathogenic Escherichia coli clones carrying mcr, Portugal, September 2019 to January 2020

BackgroundThe pet industry is expanding worldwide, particularly raw meat-based diets (RMBDs). There are concerns regarding the safety of RMBDs, especially their potential to spread clinically relevant antibiotic-resistant bacteria or zoonotic pathogens.AimWe aimed to investigate whether dog food, including RMBD, commercially available in Portugal can be a source of Salmonella and/or other Enterobacteriaceae strains resistant to last-line antibiotics such as colistin.MethodsFifty-five samples from 25 brands (21 international ones) of various dog food types from 12 suppliers were screened by standard cultural methods between September 2019 and January 2020. Isolates were characterised by phenotypic and genotypic methods, including whole genome sequencing and comparative genomics.ResultsOnly RMBD batches were contaminated, with 10 of 14 containing polyclonal multidrug-resistant (MDR) Escherichia coli and one MDR Salmonella. One turkey-based sample contained MDR Salmonella serotype 1,4,[5],12:i:- ST34/cgST142761 with similarity to human clinical isolates occurring worldwide. This Salmonella exhibited typical antibiotic resistance (bla TEM + strA-strB + sul2 + tet(B)) and metal tolerance profiles (pco + sil + ars) associated with the European epidemic clone. Two samples (turkey/veal) carried globally dispersed MDR E. coli (ST3997-complexST10/cgST95899 and ST297/cgST138377) with colistin resistance (minimum inhibitory concentration: 4 mg/L) and mcr-1 gene on IncX4 plasmids, which were identical to other IncX4 circulating worldwide.ConclusionSome RMBDs from European brands available in Portugal can be a vehicle for clinically relevant MDR Salmonella and pathogenic E. coli clones carrying genes encoding resistance to the last-line antibiotic colistin. Proactive actions within the One Health context, spanning regulatory, pet-food industry and consumer levels, are needed to mitigate these public health risks.

Repeated Occurrence of Mobile Colistin Resistance Gene-Carrying Plasmids in Pathogenic Escherichia coli from German Pig Farms

The global spread of plasmid-mediated mobile colistin resistance (mcr) genes threatens the vital role of colistin as a drug of last resort. We investigated whether the recurrent occurrence of specific E. coli pathotypes and plasmids in individual pig farms resulted from the continued presence or repeated reintroduction of distinct E. coli strains. E. coli isolates (n = 154) obtained from three pig farms with at least four consecutive years of mcr detection positive for virulence-associated genes (VAGs) predicting an intestinal pathogenic pathotype via polymerase chain reaction were analyzed. Detailed investigation of VAGs, antimicrobial resistance genes and plasmid Inc types was conducted using whole genome sequencing for 87 selected isolates. Sixty-one E. coli isolates harbored mcr-1, and one isolate carried mcr-4. On Farm 1, mcr-positive isolates were either edema disease E. coli (EDEC; 77.3%) or enterotoxigenic E. coli (ETEC; 22.7%). On Farm 2, all mcr-positive strains were ETEC, while mcr-positive isolates from Farm 3 showed a wider range of pathotypes. The mcr-1.1 gene was located on IncHI2 (Farm 1), IncX4 (Farm 2) or IncX4 and IncI2 plasmids (Farm 3). These findings suggest that various pathogenic E. coli strains play an important role in maintaining plasmid-encoded colistin resistance genes in the pig environment over time.

Microbial-influenced pesticide removal co-occurs with antibiotic resistance gene variation in soil-earthworm-maize system

Within human-influenced landscapes, pesticides cooccur with a variety of antibiotic stressors. However, the relationship between pesticides removal process and antibiotic resistance gene variation are not well understood. This study explored pesticide (topramezone, TPZ) and antibiotic (polymyxin E, PME) co-contamination using liquid chromatography-tandem mass spectrometry (LC-MS/MS), bacterial-16 S rRNA sequencing and high-throughput quantitative polymerase chain reaction (HT-qPCR) in a soil-earthworm-maize system. After incubating soil for 28 days with TPZ and PME (10 mg kg-1 dry weight), earthworm weight-gain, mortality rates, and maize plant weight-gain only differed slightly, but height-gain significantly decreased. PME significantly increased TPZ-removal in the soil. Accumulation of TPZ in earthworm's tissues may pose potential risks in the food chain. Combined pollution altered the microbial community structure and increased the abundance of functional microorganisms involved in aromatic compound degradation. Furthermore, maize rhizosphere can raise resistance genes, however earthworms can reduce resistance genes. Co-contamination increased absolute abundance of mobile genetic elements (MGEs) in bulk-soil samples, antibiotic resistance genes (ARGs) in skin samples and number of ARGs in bulk-soil samples, while decreased absolute abundance of transposase gene in bulk-soil samples and number of ARGs in rhizosphere-soil samples. Potential hosts harbouring ARGs may be associated with the antagonistic effect during resistance and detoxification of TPZ and PMB co-occurrence. These findings provide insights into the mechanism underlining pesticide removal regarding occurrence of ARGs in maize agroecosystem.

Prospects for dog rabies elimination in Nigeria by 2030

The attainment of the global target of zero dog-mediated human rabies by 2030 depends on functional rabies programmes. Nigeria, a rabies-endemic country, and the most populous country in Africa has a very poor rabies control strategy with a score of 1.5 out of 5 based on the Stepwise Approach towards Rabies Elimination (SARE). In this article, we report a scoping review that we conducted to highlight the strengths, weaknesses, opportunities and threats as well as situational analysis of rabies control in Nigeria and suggest a timeline for key activities that are needed to ensure zero by 30. Our findings reveal that rabies is grossly under-reported as only 998 human and 273 dog-suspected rabies cases were reported across Nigeria between 2017 and 2022. Our literature review also demonstrates a paucity of information on rabies in both human and animal health sectors. A total of 49 studies on dog rabies in Nigeria, with a predominance of reports from the North Central geopolitical region (48%, n = 23) were therefore included in this study. Currently, only 16.2% (n = 6/37) of Nigerian states have available data related to the estimated dog populations, the dog ownership rates, the vaccination status of dogs or the incidence of dog bites. Based on a dog-to-human ratio of 1:16.3, we estimated that the dog population in Nigeria was 12,969,368 (95% CI: 12,320,900-13,617,836). Thus, to attain herd immunity and dog rabies control in Nigeria, at least 9.1 million dogs must be vaccinated annually. Our review reveals that, despite the strengths and available opportunities to achieve rabies control in Nigeria by 2030, the weaknesses and challenges will make the attainment of zero by 30 very difficult or impossible. Nigeria's best-case scenario by the year 2030 is SARE stage 3-4 (control-elimination) out of 5. Otherwise, the rabies control programme might not surpass SARE stages 2-3. To attain zero by 30, Nigeria must re-strategize its current rabies control programme by funding and implementing the national strategic plan for rabies control, creating a rabies desk office in the 37 states (FCT inclusive), rigorously conducting mass vaccination campaigns, providing post-exposure prophylaxis, prioritizing mass enlightenment with a focus on responsible pet ownership and conduct baseline national rabies surveillance in the animal and human health sectors.

Genotypic Characterization of Uropathogenic Escherichia coli from Companion Animals: Predominance of ST372 in Dogs and Human-Related ST73 in Cats

Extraintestinal pathogenic Escherichia coli (ExPEC) account for over 80% and 60% of bacterial urinary tract infections (UTIs) in humans and animals, respectively. As shared uropathogenic E. coli (UPEC) strains have been previously reported among humans and pets, our study aimed to characterize E. coli lineages among UTI isolates from dogs and cats and to assess their overlaps with human UPEC lineages. We analysed 315 non-duplicate E. coli isolates from the UT of dogs (198) and cats (117) collected in central Germany in 2019 and 2020 utilizing whole genome sequencing and in silico methods. Phylogroup B2 (77.8%), dog-associated sequence type (ST) 372 (18.1%), and human-associated ST73 (16.6%), were predominant. Other STs included ST12 (8.6%), ST141 (5.1%), ST127 (4.8%), and ST131 (3.5%). Among these, 58.4% were assigned to the ExPEC group and 51.1% to the UPEC group based on their virulence associated gene (VAG) profile (ExPEC, presence of ≥VAGs: papAH and/or papC, sfa/focG, afaD/draBC, kpsMTII, and iutA; UPEC, additionally cnf1 or hlyD). Extended-spectrum cephalosporin (ESC) resistance mediated by extended-spectrum β-lactamases (ESBL) and AmpC-β-lactamase was identified in 1.9% of the isolates, along with one carbapenemase-producing isolate and one isolate carrying a mcr gene. Low occurrence of ESC-resistant or multidrug-resistant (MDR) isolates (2.9%) in the two most frequently detected STs implies that E. coli isolated from UTIs of companion animals are to a lesser extent associated with resistance, but possess virulence-associated genes enabling efficient UT colonization and carriage. Detection of human-related pandemic lineages suggests interspecies transmission and underscores the importance of monitoring companion animals.

Genomic profiling of extended-spectrum β-lactamase-producing Escherichia coli from Pets in the United Arab Emirates: Unveiling colistin resistance mediated by mcr-1.1 and its probable transmission from chicken meat - A One Health perspective

BACKGROUND

The United Arab Emirates (UAE) has witnessed rapid urbanization and a surge in pet ownership, sparking concerns about the possible transfer of antimicrobial resistance (AMR) from pets to humans and the environment. This study delves into the whole-genome sequencing analysis of ESBL-producing E. coli strains from healthy cats and dogs in the UAE, which exhibit multidrug resistance (MDR). Additionally, it provides a genomic exploration of the mobile colistin resistance gene mcr-1.1, marking the first instance of its detection in Middle Eastern pets.

METHODS

We investigate 17 ESBL-producing E. coli strains from healthy UAE pets using WGS and bioinformatics analysis to identify genes encoding virulence factors, assign diverse typing schemes to the isolates, and scrutinize the presence of AMR genes. Furthermore, we characterized plasmid contigs housing the mcr-1.1 gene and conducted phylogenomic analysis to evaluate their relatedness to previously identified UAE isolates.

RESULTS

Our study unveiled a variety of virulence factor-encoding genes within the isolates, with fimH emerging as the most prevalent. Regarding β-lactamase resistance genes, the blaCTX group 1 gene family predominated, with CTX-M-15 found in 52.9% (9/17) of the isolates, followed by CTX-M-55 in 29.4% (5/17). These isolates were categorized into multiple sequence types (STs), with the epidemic ST131 being the most frequent. The presence of the mcr-1.1 gene, linked to colistin resistance, was confirmed in two isolates. These isolates belonged to ST1011 and displayed distinct profiles of β-lactamase resistance genes. Phylogenomic analysis revealed close connections between the isolates and those from chicken meat in the UAE.

CONCLUSION

Our study underscores the presence of MDR ESBL-producing E. coli in UAE pets. The identification of mcr-1.1-carrying isolates warrants the urgency of comprehensive AMR surveillance and highlights the role of companion animals in AMR epidemiology. These findings underscore the significance of adopting a One Health approach to mitigate AMR transmission risks effectively.

Antibiotic Resistance Genes Carried by Commensal Escherichia coli from Shelter Cats in Italy

Antimicrobial resistance is a widespread global health problem. The presence of resistant bacteria and antibiotic resistance genes has been demonstrated not only in humans but also in animals, including pets. Stray cats share the urban environment with people and pets. This may facilitate transmission of resistant bacteria and resistance genes between stray animals, people and domestic animals. Several studies have investigated the role of stray cats as a fecal carrier of ESBL-producing bacteria. However, there are many genes and resistance mechanisms that can be detected in commensal E. coli, which, because of its genetic plasticity, is considered an indicator for monitoring antibiotic resistance. In this study, rectal swabs were collected from stray cats from colonies and shelters in the city of Monza (Monza Brianza, Italy) to isolate commensal E. coli. Phenotypic tests, such as the minimum inhibitory concentration (MIC) and the double disc test (DDST), and molecular analyses to detect antimicrobial resistance genes (ARGs) were used to study the resistance of these isolates. The results obtained confirm that stray cats can carry ESBL-producing E. coli (6.7%) and genes conferring resistance to other important antibiotic classes such as tetracyclines and sulfonamides.

Detection of extended-spectrum β-lactamase-producing Escherichia coli genes isolated from cat rectal swabs at Surabaya Veterinary Hospital, Indonesia

Background and Aim

Escherichia coli causes a bacterial illness that frequently affects cats. Diseases caused by E. coli are treated using antibiotics. Because of their proximity to humans, cats possess an extremely high risk of contracting antibiotic resistance genes when their owners touch cat feces containing E. coli that harbor resistance genes. This study was conducted to identify multidrug-resistant E. coli and extended-spectrum β-lactamase (ESBL)-producing genes from cat rectal swabs collected at Surabaya City Veterinary Hospital to determine antibiotic sensitivity.

Materials and Methods

Samples of cat rectal swabs were cultured in Brilliant Green Bile Lactose Broth medium and then streaked on eosin methylene blue agar medium for bacterial isolation, whereas Gram-staining and IMViC tests were conducted to confirm the identification results. The Kirby-Bauer diffusion test was used to determine antibiotic sensitivity, and the double-disk synergy test was used to determine ESBL-producing bacteria. Molecular detection of the genes TEM and CTX-M was performed using a polymerase chain reaction.

Results

Based on morphological culture, Gram-staining, and biochemical testing, the results of sample inspection showed that of the 100 cat rectal swab samples isolated, 71 (71%) were positive for E. coli. Furthermore, 23 E. coli isolates (32.39%) demonstrated the highest resistance to ampicillin. Four isolates were confirmed to be multidurg-resistant and ESBL-producing strains. Molecular examination revealed that three E. coli isolates harbored TEM and CTX-M.

Conclusion

In conclusion, pet owners must be educated on the use of antibiotics to improve their knowledge about the risks of antibiotic resistance.

Antimicrobial resistance and genotyping of Pseudomonas aeruginosa isolated from the ear canals of dogs in Japan

The strong bond between dogs and their owners creates a close association that could result in the transfer of antibiotic-resistant bacteria from canines to humans, potentially leading to the spread of antimicrobial resistance genes. Pseudomonas aeruginosa, a common causative agent of persistent ear infections in dogs, is often resistant to multiple antibiotics. Assessing the antimicrobial resistance profile and genotype of P. aeruginosa is crucial for the appropriate use of veterinary pharmaceuticals. However, in recent years, few studies have been conducted on this bacterium in Japan. We determined the antimicrobial resistance profile and genotype of P. aeruginosa isolated from the ear canal of dogs in Japan in 2020. Analysis of antimicrobial resistance using disk diffusion tests indicated a high frequency of resistance to most antimicrobial agents. Particularly, 29 isolates from the ear canals of the 29 affected dogs (100%) were resistant to cefovecin, cefpodoxime, and florfenicol; however, they were susceptible to cefepime and piperacillin/tazobactam. Only 3.4, 10.3, and 10.3% of the isolates were resistant to ceftazidime, tobramycin, and gentamicin, respectively. Furthermore, upon analyzing the population structure using multilocus sequence typing, a considerably large clonal complex was not observed in the tested isolates. Three isolates, namely ST3881, ST1646, and ST532, were clonally related to the clinically isolated sequence types in Japan (such as ST1831, ST1413, ST1812, and ST1849), which is indicative of dog-to-human transmission. Considering the variation in antibiotic resistance compared to that reported by previous studies and the potential risk of dog-to-human transmission, we believe that the survey for antimicrobial resistance profile and population structure should be continued regularly. However, the prevalence of multidrug-resistant P. aeruginosa in dogs in Japan is not a crisis.

Mobile Colistin Resistance (mcr) Gene-Containing Organisms in Poultry Sector in Low- and Middle-Income Countries: Epidemiology, Characteristics, and One Health Control Strategies

Mobile colistin resistance (mcr) genes (mcr-1 to mcr-10) are plasmid-encoded genes that threaten the clinical utility of colistin (COL), one of the highest-priority critically important antibiotics (HP-CIAs) used to treat infections caused by multidrug-resistant and extensively drug-resistant bacteria in humans and animals. For more than six decades, COL has been used largely unregulated in the poultry sector in low- and middle-income countries (LMICs), and this has led to the development/spread of mcr gene-containing bacteria (MGCB). The prevalence rates of mcr-positive organisms from the poultry sector in LMICs between January 1970 and May 2023 range between 0.51% and 58.8%. Through horizontal gene transfer, conjugative plasmids possessing insertion sequences (ISs) (especially ISApl1), transposons (predominantly Tn6330), and integrons have enhanced the spread of mcr-1, mcr-2, mcr-3, mcr-4, mcr-5, mcr-7, mcr-8, mcr-9, and mcr-10 in the poultry sector in LMICs. These genes are harboured by Escherichia, Klebsiella, Proteus, Salmonella, Cronobacter, Citrobacter, Enterobacter, Shigella, Providencia, Aeromonas, Raoultella, Pseudomonas, and Acinetobacter species, belonging to diverse clones. The mcr-1, mcr-3, and mcr-10 genes have also been integrated into the chromosomes of these bacteria and are mobilizable by ISs and integrative conjugative elements. These bacteria often coexpress mcr with virulence genes and other genes conferring resistance to HP-CIAs, such as extended-spectrum cephalosporins, carbapenems, fosfomycin, fluoroquinolone, and tigecycline. The transmission routes and dynamics of MGCB from the poultry sector in LMICs within the One Health triad include contact with poultry birds, feed/drinking water, manure, poultry farmers and their farm workwear, farming equipment, the consumption and sale of contaminated poultry meat/egg and associated products, etc. The use of pre/probiotics and other non-antimicrobial alternatives in the raising of birds, the judicious use of non-critically important antibiotics for therapy, the banning of nontherapeutic COL use, improved vaccination, biosecurity, hand hygiene and sanitization, the development of rapid diagnostic test kits, and the intensified surveillance of mcr genes, among others, could effectively control the spread of MGCB from the poultry sector in LMICs.

Current Research on Infectious Diseases of Domestic Animals from a One Health Perspective

One Health is a well-known strategy for promoting and developing interdisciplinary collaboration across all aspects of health in human, animal, and environmental domains [...].

Screening of colistin-resistant bacteria in livestock animals from France

Colistin is frequently used as a growth factor or treatment against infectious bacterial diseases in animals. The Veterinary Division of the European Medicines Agency (EMA) restricted colistin use as a second-line treatment to reduce colistin resistance. In 2020, 282 faecal samples were collected from chickens, cattle, sheep, goats, and pigs in the south of France. In order to track the emergence of mobilized colistin resistant (mcr) genes in pigs, 111 samples were re-collected in 2021 and included pig faeces, food, and water from the same location. All samples were cultured in a selective Lucie Bardet Jean-Marc Rolain (LBJMR) medium and colonies were identified using MALDI-TOF mass spectrometry and then antibiotic susceptibility tests were performed. PCR and Sanger sequencing were performed to screen for the presence of mcr genes. The selective culture revealed the presence of 397 bacteria corresponding to 35 different bacterial species including Gram-negative and Gram-positive. Pigs had the highest prevalence of colistin-resistant bacteria with an abundance of intrinsically colistin-resistant bacteria and from these samples one strain harbouring both mcr-1 and mcr-3 has been isolated. The second collection allowed us to identify 304 bacteria and revealed the spread of mcr-1 and mcr-3 in pigs. In the other samples, naturally, colistin-resistant bacteria were more frequent, nevertheless the mcr-1 variant was the most abundant gene found in chicken, sheep, and goat samples and one cattle sample was positive for the mcr-3 gene. Animals are potential reservoir of colistin-resistant bacteria which varies from one animal to another. Interventions and alternative options are required to reduce the emergence of colistin resistance and to avoid zoonotic transmissions.

Colistin Resistance Mechanisms in Human and Veterinary Klebsiella pneumoniae Isolates

Colistin (polymyxin E) is increasingly used as a last-resort antibiotic for the treatment of severe infections with multidrug-resistant Gram-negative bacteria. In contrast to human medicine, colistin is also used in veterinary medicine for metaphylaxis. Our objective was to decipher common colistin resistance mechanisms in Klebsiella pneumoniae isolates from animals. In total, 276 veterinary K. pneumoniae isolates, derived from companion animals or livestock, and 12 isolates from human patients were included for comparison. Six out of 276 veterinary isolates were colistin resistant (2.2%). Human isolates belonging to high-risk clonal lineages (e.g., ST15, ST101, ST258), displayed multidrug-resistant phenotypes and harboured many resistance genes compared to the veterinary isolates. However, the common colistin resistance mechanism in both human and animal K. pneumoniae isolates were diverse alterations of MgrB, a critical regulator of lipid A modification. Additionally, deleterious variations of lipopolysaccharide (LPS)-associated proteins (e.g., PmrB P95L, PmrE P89L, LpxB A152T) were identified. Phylogenetic analysis and mutation patterns in genes encoding LPS-associated proteins indicated that colistin resistance mechanisms developed independently in human and animal isolates. Since only very few antibiotics remain to treat infections with MDR bacteria, it is important to further analyse resistance mechanisms and the dissemination within different isolates and sources.

mcr-1 colistin resistance gene sharing between Escherichia coli from cohabiting dogs and humans, Lisbon, Portugal, 2018 to 2020

BackgroundThe emergence of colistin resistance is a One Health antimicrobial resistance challenge worldwide. The close contact between companion animals and humans creates opportunities for transmission and dissemination of colistin-resistant bacteria.AimTo detect potential animal reservoirs of colistin-resistant Escherichia coli and investigate the possible sharing of these bacteria between dogs, cats and their cohabiting humans in the community in Lisbon, Portugal.MethodsA prospective longitudinal study was performed from 2018 to 2020. Faecal samples from dogs and cats either healthy or diagnosed with a skin and soft tissue or urinary tract infection, and their cohabiting humans were screened for the presence of colistin-resistant E. coli. All isolates were tested by broth microdilution against colistin and 12 other antimicrobials. Colistin-resistant isolates were screened for 30 resistance genes, including plasmid-mediated colistin resistance genes (mcr-1 to mcr-9), and typed by multilocus sequence typing. Genetic relatedness between animal and human isolates was analysed by whole genome sequencing.ResultsColistin-resistant E. coli strains harbouring the mcr-1 gene were recovered from faecal samples of companion animals (8/102; 7.8%) and humans (4/125; 3.2%). No difference between control and infection group was detected. Indistinguishable multidrug-resistant E. coli ST744 strains harbouring the mcr-1 gene were found in humans and their dogs in two households.ConclusionsThe identification of identical E. coli strains containing the plasmid-mediated mcr-1 gene in companion animals and humans in daily close contact is of concern. These results demonstrate the importance of the animal-human unit as possible disseminators of clinically important resistance genes in the community setting.

Colistin Resistance Mechanism in Enterobacter hormaechei subsp. steigerwaltii Isolated from Wild Boar (Sus scrofa) in France

Wild animals may act as efficient antimicrobial-resistance reservoirs and epidemiological links between humans, livestock, and natural environments. By using phenotypic and genotypic characterization, the present study highlighted the occurrence of an antimicrobial-resistant (i.e., amoxicillin, amoxicillin–clavulanic acid, cephalothin, and colistin) Enterobacter hormaechei subsp. steigerwaltii strain in wild boar (Sus scrofa) from France. The molecular analysis conducted showed non-synonymous mutations in the pmrA/pmrB and phoQ/phoP operons and the phoP/Q regulator mgrB gene, leading to colistin resistance. The present data highlight the need for continuous monitoring of multidrug-resistant bacteria in wild animals to limit the spread of these threatening pathogens.

Epidemiology and Traits of Mobile Colistin Resistance (mcr) Gene-Bearing Organisms from Horses

Mobile colistin resistance (mcr) genes (mcr-1 to mcr-10) threaten the efficacy of colistin (COL), a polymyxin antibiotic that is used as a last-line agent for the treatment of deadly infections caused by multidrug-resistant and extensively drug-resistant bacteria in humans and animals. COL has been used for more than 60 years for the prophylactic control and treatment of infections in livestock husbandry but not in horses. Polymyxin B is used for the prophylactic control and empirical treatment of infections in horses without conducting sensitivity tests. The lack of sensitivity testing exerts selection pressure for the acquisition of the mcr gene. By horizontal transfer, mcr-1, mcr-5, and mcr-9 have disseminated among horse populations globally and are harbored by Escherichia coli, Klebsiella, Enterobacter, Citrobacter, and Salmonella species. Conjugative plasmids, insertion sequences, and transposons are the backbone of mcr genes in the isolates, which co-express genes conferring multi- to extensive-drug resistance, including genes encoding extended-spectrum β-lactamase, ampicillinase C, fosfomycin, and fluoroquinolone resistance, and virulence genes. The transmission of mcr genes to/among bacterial strains of equine origin is non-clonal. Contact with horses, horse manure, feed/drinking water, farmers, farmers’ clothing/farm equipment, the consumption of contaminated horse meat and its associated products, and the trading of horses, horse meat, and their associated products are routes for the transmission of mcr-gene-bearing bacteria in, to, and from the equine industry.