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Staphylococcus pseudintermedius is a commensal and an opportunistic pathogen in dogs, and is also an opportunistic pathogen in humans. Here we report about a case of bacteraemia with a fatal outcome in a 77-year-old co-morbid male likely caused by a S. pseudintermedius and the investigation into the possible transmission from the two dogs in the patient's household. The two dogs carried the same S. pseudintermedius strain, but this dog strain was unrelated to the strain from the patient. In contrast to the patient strain, the dog strain showed reduced susceptibility to several antibiotics and both dogs had received antibiotic treatment prior to sampling. So, it is conceivable that these treatments can have eliminated the patient's strain between the transmission event and the dog sampling. It is also worth noting that the patient strain was positive for the expA gene, which encodes an exfoliative toxin closely related to the S. aureus exfoliative toxin B. This toxin has been linked to canine pyoderma, but its effect on humans remains unknown. Transmission of S. pseudintermedius was confirmed in the household between the dogs. However, we could not verify that the dogs were the source for the S. pseudintermedius in the patient.

Objectives: The global increase in carbapenem-resistant Enterobacteriaceae (CRE) is a growing health concern. Infections caused by CRE are associated with increased mortality and length of hospital stay, emphasising the health and economic burden posed by these pathogens. Although CRE can inhabit the human gut asymptomatically, colonisation with CRE is associated with an increased risk of CRE infection and mortality. In this study, we investigated the occurrence and characteristics of CRE in faecal samples from healthy persons in 12 villages in Shandong Province, China. Methods: Screening for CRE in faecal samples was performed by selective cultivation. Minimum inhibitory concentrations (MICs) of meropenem were determined by the agar dilution method. Multilocus sequence typing (MLST) and carbapenemase gene carriage of the isolates were determined by whole-genome sequencing. Genetic relatedness of Escherichia coli isolates was determined by core genome MLST. Results: CRE carriage increased from 2.4% in 2015 to 13.4% in 2017. Most CRE isolates (93.0%) were E. coli and all carried NDM-type carbapenemases. Sequence types (STs) among the E. coli isolates were diverse. The single most common ST was the highly epidemic strain ST167, which was only observed in 2017. Conclusion: We report a rapid increase in occurrence of CRE (from 2.4% to 13.4%) among faecal samples collected from healthy rural residents of Shandong Province from 2015 to 2017. Colonisation with CRE is known to increase the risk of CRE infection, and the worrying deterioration of the epidemiological situation in the region reported here indicates a need for further monitoring and possible interventions. (C) 2021 The Authors. Published by Elsevier Ltd on behalf of International Society for Antimicrobial Chemotherapy., Funding Agencies|National Natural Science Foundation of China [41771499, 81361138021]; Swedish Research Council [D0879801]; Swedish Research Council Formas [2016-00640]; Region Ostergotland [LIO-793191, LIO-899871]; Shandong Key Research and Development Plan Project [2017GSF218062]; Medical and Health Technology Development Program of Shandong Province [2017WS447]; ALF Grants

In the spring of 2010, it was discovered that a large proportion of broilers in Sweden were colonized withEscherichia coliproducing extended-spectrum beta-lactamases (ESBL) or plasmid mediated AmpC (pAmpC). It was hypothesized that the high prevalence was due to transfer from an upper level in the production pyramid and sampling upwards in the production pyramid was initiated. From 2010 to 2019, all shipments (n = 122) of broiler breeders were screened on arrival to Sweden for the occurrence of ESBL- or pAmpC-producingE. coliusing selective methods. Samples of paper linings from shipments of breeders were cultured on MacConkey agar supplemented with cefotaxime (1 mg/L) after pre-enrichment in either MacConkey broth with cefotaxime (1 mg/L), or from late June 2015 in buffered peptone water without antibiotics. ESBL- or pAmpC-producingE. coliwas isolated from 43 (35%) of these. Over the years, the proportion of positive imports have decreased and during 2018 and 2019 all imports were negative. In conclusion, the occurrence of ESBL- or pAmpC-producingE. coliin broiler breeders on arrival to Sweden has decreased. Such bacteria have not been detected in any shipments since 2017., Funding Agencies|Swedish Board of Agriculture [6.2.18-14284/2018]; National Veterinary Institute (SVA), Uppsala, Sweden

Sweden has a long tradition of monitoring occurrence of antibiotic resistant bacteria in both animals and humans, but there currently is no organised and harmonized monitoring on carriage of Enterobacteriaceae producing extended-spectrum beta-lactamase (ESBL), plasmid-mediated AmpC beta-lactamase (pAmpC), or methicillin-resistant coagulase positive staphylococci e.g. methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-resistant Staphylococcus pseudintermedius (MRSP) in dogs. The aim of the current study was therefore to determine the prevalence of ESBL/pAmpC producing Enterobacteriaceae and methicillin-resistant coagulase positive staphylococci in healthy dogs in Sweden, and to phenotypically and genotypically characterize any identified isolates. It was shown that 0.9% (95% confident interval 0.3-2.7%) of the dogs (n = 325) carried multi-resistant ESBL-producing Escherichia coli, but that no methicillin-resistant coagulase positive staphylococci could be detected. In conclusion, the occurrence of multi-drug resistant bacteria remains rare among healthy dogs in Sweden. In addition, the ESBL-producing E. coli identified showed genetic characteristics related to those reported from humans., Funding Agencies|Linkoping University; AniCura Research fund; National Veterinary Institute (SVA), Uppsala, Sweden

In the spring of 2010, it was discovered that a large proportion of broilers in Sweden were colonized withEscherichia coliproducing extended-spectrum beta-lactamases (ESBL) or plasmid mediated AmpC (pAmpC). It was hypothesized that the high prevalence was due to transfer from an upper level in the production pyramid and sampling upwards in the production pyramid was initiated. From 2010 to 2019, all shipments (n = 122) of broiler breeders were screened on arrival to Sweden for the occurrence of ESBL- or pAmpC-producingE. coliusing selective methods. Samples of paper linings from shipments of breeders were cultured on MacConkey agar supplemented with cefotaxime (1 mg/L) after pre-enrichment in either MacConkey broth with cefotaxime (1 mg/L), or from late June 2015 in buffered peptone water without antibiotics. ESBL- or pAmpC-producingE. coliwas isolated from 43 (35%) of these. Over the years, the proportion of positive imports have decreased and during 2018 and 2019 all imports were negative. In conclusion, the occurrence of ESBL- or pAmpC-producingE. coliin broiler breeders on arrival to Sweden has decreased. Such bacteria have not been detected in any shipments since 2017., Funding Agencies|Swedish Board of Agriculture [6.2.18-14284/2018]; National Veterinary Institute (SVA), Uppsala, Sweden

Objectives: The aim of this study was to investigate the occurrence of the newly described transferable colistin resistance gene mcr-9 in extended-spectrum beta-lactamase (ESBL)-producing clinical Enterobacteriaceae isolates from horses in Sweden. Methods: A total of 56 whole-genome sequenced ESBL-producing Enterobacteriaceae isolates from horses were subjected to in silico detection of antimicrobial resistance genes and identification of plasmid replicons types. The colistin minimum inhibitory concentration (MIC) for mcr-positive isolates was determined by broth microdilution. Relatedness between Enterobacteriaceae carrying mcr genes was determined by multilocus sequence typing (MLST) and core genome MLST. Results: Thirty ESBL-producing Enterobacteriaceae isolates from horses were positive for the colistin resistance gene mcr-9. These isolates included Enterobacter cloacae, Escherichia coli, Klebsiella oxytoca and Citrobacter freundii and belonged to diverse MLST sequence types within each species. Two of the mcr-9-containing isolates originated from the same horse. All mcr-9-positive isolates had colistin MICs below or equal to the EUCAST epidemiological cut-off value of 2 mg/L and were negative for the two potential regulatory genes qseB-like and qseC-like for mcr-9. Except for one isolate carrying only bla(TEM-1B), all of the isolates carried bla(SHV-12) and bla(TEM-1B), and were all considered multidrug-resistant as they harboured genes encoding resistance to aminoglycosides, chloramphenicol, fosfomycin, macrolides, quinolones, sulfonamides, trimethoprim and tetracyclines. Plasmid replicon types IncHI2 and IncHI2A were detected in all mcr-9-positive isolates. Conclusion: The occurrence of mcr-9 was common among clinical ESBL-producing Enterobacteriaceae isolates from horses in Sweden and was linked to the ESBL-encoding gene bla(SHV-12) and plasmid replicon types IncHI2 and IncHI2A. (C) 2019 The Author(s). Published by Elsevier Ltd on behalf of International Soc, Funding Agencies|Swedish Board of Agriculture [6.2.18-15925/2017]

Sweden has a long tradition of monitoring occurrence of antibiotic resistant bacteria in both animals and humans, but there currently is no organised and harmonized monitoring on carriage of Enterobacteriaceae producing extended-spectrum beta-lactamase (ESBL), plasmid-mediated AmpC beta-lactamase (pAmpC), or methicillin-resistant coagulase positive staphylococci e.g. methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-resistant Staphylococcus pseudintermedius (MRSP) in dogs. The aim of the current study was therefore to determine the prevalence of ESBL/pAmpC producing Enterobacteriaceae and methicillin-resistant coagulase positive staphylococci in healthy dogs in Sweden, and to phenotypically and genotypically characterize any identified isolates. It was shown that 0.9% (95% confident interval 0.3-2.7%) of the dogs (n = 325) carried multi-resistant ESBL-producing Escherichia coli, but that no methicillin-resistant coagulase positive staphylococci could be detected. In conclusion, the occurrence of multi-drug resistant bacteria remains rare among healthy dogs in Sweden. In addition, the ESBL-producing E. coli identified showed genetic characteristics related to those reported from humans., Funding Agencies|Linkoping University; AniCura Research fund; National Veterinary Institute (SVA), Uppsala, Sweden

Objectives: The aim of this study was to investigate the occurrence of the newly described transferable colistin resistance gene mcr-9 in extended-spectrum beta-lactamase (ESBL)-producing clinical Enterobacteriaceae isolates from horses in Sweden. Methods: A total of 56 whole-genome sequenced ESBL-producing Enterobacteriaceae isolates from horses were subjected to in silico detection of antimicrobial resistance genes and identification of plasmid replicons types. The colistin minimum inhibitory concentration (MIC) for mcr-positive isolates was determined by broth microdilution. Relatedness between Enterobacteriaceae carrying mcr genes was determined by multilocus sequence typing (MLST) and core genome MLST. Results: Thirty ESBL-producing Enterobacteriaceae isolates from horses were positive for the colistin resistance gene mcr-9. These isolates included Enterobacter cloacae, Escherichia coli, Klebsiella oxytoca and Citrobacter freundii and belonged to diverse MLST sequence types within each species. Two of the mcr-9-containing isolates originated from the same horse. All mcr-9-positive isolates had colistin MICs below or equal to the EUCAST epidemiological cut-off value of 2 mg/L and were negative for the two potential regulatory genes qseB-like and qseC-like for mcr-9. Except for one isolate carrying only bla(TEM-1B), all of the isolates carried bla(SHV-12) and bla(TEM-1B), and were all considered multidrug-resistant as they harboured genes encoding resistance to aminoglycosides, chloramphenicol, fosfomycin, macrolides, quinolones, sulfonamides, trimethoprim and tetracyclines. Plasmid replicon types IncHI2 and IncHI2A were detected in all mcr-9-positive isolates. Conclusion: The occurrence of mcr-9 was common among clinical ESBL-producing Enterobacteriaceae isolates from horses in Sweden and was linked to the ESBL-encoding gene bla(SHV-12) and plasmid replicon types IncHI2 and IncHI2A. (C) 2019 The Author(s). Published by Elsevier Ltd on behalf of International Soc, Funding Agencies|Swedish Board of Agriculture [6.2.18-15925/2017]

Objectives: The aim of this study was to investigate the occurrence of the newly described transferable colistin resistance gene mcr-9 in extended-spectrum beta-lactamase (ESBL)-producing clinical Enterobacteriaceae isolates from horses in Sweden. Methods: A total of 56 whole-genome sequenced ESBL-producing Enterobacteriaceae isolates from horses were subjected to in silico detection of antimicrobial resistance genes and identification of plasmid replicons types. The colistin minimum inhibitory concentration (MIC) for mcr-positive isolates was determined by broth microdilution. Relatedness between Enterobacteriaceae carrying mcr genes was determined by multilocus sequence typing (MLST) and core genome MLST. Results: Thirty ESBL-producing Enterobacteriaceae isolates from horses were positive for the colistin resistance gene mcr-9. These isolates included Enterobacter cloacae, Escherichia coli, Klebsiella oxytoca and Citrobacter freundii and belonged to diverse MLST sequence types within each species. Two of the mcr-9-containing isolates originated from the same horse. All mcr-9-positive isolates had colistin MICs below or equal to the EUCAST epidemiological cut-off value of 2 mg/L and were negative for the two potential regulatory genes qseB-like and qseC-like for mcr-9. Except for one isolate carrying only bla(TEM-1B), all of the isolates carried bla(SHV-12) and bla(TEM-1B), and were all considered multidrug-resistant as they harboured genes encoding resistance to aminoglycosides, chloramphenicol, fosfomycin, macrolides, quinolones, sulfonamides, trimethoprim and tetracyclines. Plasmid replicon types IncHI2 and IncHI2A were detected in all mcr-9-positive isolates. Conclusion: The occurrence of mcr-9 was common among clinical ESBL-producing Enterobacteriaceae isolates from horses in Sweden and was linked to the ESBL-encoding gene bla(SHV-12) and plasmid replicon types IncHI2 and IncHI2A. (C) 2019 The Author(s). Published by Elsevier Ltd on behalf of International Soc, Funding Agencies|Swedish Board of Agriculture [6.2.18-15925/2017]

In the spring of 2010, it was discovered that a large proportion of broilers in Sweden were colonized withEscherichia coliproducing extended-spectrum beta-lactamases (ESBL) or plasmid mediated AmpC (pAmpC). It was hypothesized that the high prevalence was due to transfer from an upper level in the production pyramid and sampling upwards in the production pyramid was initiated. From 2010 to 2019, all shipments (n = 122) of broiler breeders were screened on arrival to Sweden for the occurrence of ESBL- or pAmpC-producingE. coliusing selective methods. Samples of paper linings from shipments of breeders were cultured on MacConkey agar supplemented with cefotaxime (1 mg/L) after pre-enrichment in either MacConkey broth with cefotaxime (1 mg/L), or from late June 2015 in buffered peptone water without antibiotics. ESBL- or pAmpC-producingE. coliwas isolated from 43 (35%) of these. Over the years, the proportion of positive imports have decreased and during 2018 and 2019 all imports were negative. In conclusion, the occurrence of ESBL- or pAmpC-producingE. coliin broiler breeders on arrival to Sweden has decreased. Such bacteria have not been detected in any shipments since 2017., Funding Agencies|Swedish Board of Agriculture [6.2.18-14284/2018]; National Veterinary Institute (SVA), Uppsala, Sweden

Sweden has a long tradition of monitoring occurrence of antibiotic resistant bacteria in both animals and humans, but there currently is no organised and harmonized monitoring on carriage of Enterobacteriaceae producing extended-spectrum beta-lactamase (ESBL), plasmid-mediated AmpC beta-lactamase (pAmpC), or methicillin-resistant coagulase positive staphylococci e.g. methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-resistant Staphylococcus pseudintermedius (MRSP) in dogs. The aim of the current study was therefore to determine the prevalence of ESBL/pAmpC producing Enterobacteriaceae and methicillin-resistant coagulase positive staphylococci in healthy dogs in Sweden, and to phenotypically and genotypically characterize any identified isolates. It was shown that 0.9% (95% confident interval 0.3-2.7%) of the dogs (n = 325) carried multi-resistant ESBL-producing Escherichia coli, but that no methicillin-resistant coagulase positive staphylococci could be detected. In conclusion, the occurrence of multi-drug resistant bacteria remains rare among healthy dogs in Sweden. In addition, the ESBL-producing E. coli identified showed genetic characteristics related to those reported from humans., Funding Agencies|Linkoping University; AniCura Research fund; National Veterinary Institute (SVA), Uppsala, Sweden

Objectives: The aim of this study was to investigate the occurrence of the newly described transferable colistin resistance gene mcr-9 in extended-spectrum beta-lactamase (ESBL)-producing clinical Enterobacteriaceae isolates from horses in Sweden. Methods: A total of 56 whole-genome sequenced ESBL-producing Enterobacteriaceae isolates from horses were subjected to in silico detection of antimicrobial resistance genes and identification of plasmid replicons types. The colistin minimum inhibitory concentration (MIC) for mcr-positive isolates was determined by broth microdilution. Relatedness between Enterobacteriaceae carrying mcr genes was determined by multilocus sequence typing (MLST) and core genome MLST. Results: Thirty ESBL-producing Enterobacteriaceae isolates from horses were positive for the colistin resistance gene mcr-9. These isolates included Enterobacter cloacae, Escherichia coli, Klebsiella oxytoca and Citrobacter freundii and belonged to diverse MLST sequence types within each species. Two of the mcr-9-containing isolates originated from the same horse. All mcr-9-positive isolates had colistin MICs below or equal to the EUCAST epidemiological cut-off value of 2 mg/L and were negative for the two potential regulatory genes qseB-like and qseC-like for mcr-9. Except for one isolate carrying only bla(TEM-1B), all of the isolates carried bla(SHV-12) and bla(TEM-1B), and were all considered multidrug-resistant as they harboured genes encoding resistance to aminoglycosides, chloramphenicol, fosfomycin, macrolides, quinolones, sulfonamides, trimethoprim and tetracyclines. Plasmid replicon types IncHI2 and IncHI2A were detected in all mcr-9-positive isolates. Conclusion: The occurrence of mcr-9 was common among clinical ESBL-producing Enterobacteriaceae isolates from horses in Sweden and was linked to the ESBL-encoding gene bla(SHV-12) and plasmid replicon types IncHI2 and IncHI2A. (C) 2019 The Author(s). Published by Elsevier Ltd on behalf of International Soc, Funding Agencies|Swedish Board of Agriculture [6.2.18-15925/2017]

In the spring of 2010, it was discovered that a large proportion of broilers in Sweden were colonized withEscherichia coliproducing extended-spectrum beta-lactamases (ESBL) or plasmid mediated AmpC (pAmpC). It was hypothesized that the high prevalence was due to transfer from an upper level in the production pyramid and sampling upwards in the production pyramid was initiated. From 2010 to 2019, all shipments (n = 122) of broiler breeders were screened on arrival to Sweden for the occurrence of ESBL- or pAmpC-producingE. coliusing selective methods. Samples of paper linings from shipments of breeders were cultured on MacConkey agar supplemented with cefotaxime (1 mg/L) after pre-enrichment in either MacConkey broth with cefotaxime (1 mg/L), or from late June 2015 in buffered peptone water without antibiotics. ESBL- or pAmpC-producingE. coliwas isolated from 43 (35%) of these. Over the years, the proportion of positive imports have decreased and during 2018 and 2019 all imports were negative. In conclusion, the occurrence of ESBL- or pAmpC-producingE. coliin broiler breeders on arrival to Sweden has decreased. Such bacteria have not been detected in any shipments since 2017., Funding Agencies|Swedish Board of Agriculture [6.2.18-14284/2018]; National Veterinary Institute (SVA), Uppsala, Sweden

Sweden has a long tradition of monitoring occurrence of antibiotic resistant bacteria in both animals and humans, but there currently is no organised and harmonized monitoring on carriage of Enterobacteriaceae producing extended-spectrum beta-lactamase (ESBL), plasmid-mediated AmpC beta-lactamase (pAmpC), or methicillin-resistant coagulase positive staphylococci e.g. methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-resistant Staphylococcus pseudintermedius (MRSP) in dogs. The aim of the current study was therefore to determine the prevalence of ESBL/pAmpC producing Enterobacteriaceae and methicillin-resistant coagulase positive staphylococci in healthy dogs in Sweden, and to phenotypically and genotypically characterize any identified isolates. It was shown that 0.9% (95% confident interval 0.3-2.7%) of the dogs (n = 325) carried multi-resistant ESBL-producing Escherichia coli, but that no methicillin-resistant coagulase positive staphylococci could be detected. In conclusion, the occurrence of multi-drug resistant bacteria remains rare among healthy dogs in Sweden. In addition, the ESBL-producing E. coli identified showed genetic characteristics related to those reported from humans., Funding Agencies|Linkoping University; AniCura Research fund; National Veterinary Institute (SVA), Uppsala, Sweden

Objectives: The aim of this study was to investigate the occurrence of the newly described transferable colistin resistance gene mcr-9 in extended-spectrum beta-lactamase (ESBL)-producing clinical Enterobacteriaceae isolates from horses in Sweden. Methods: A total of 56 whole-genome sequenced ESBL-producing Enterobacteriaceae isolates from horses were subjected to in silico detection of antimicrobial resistance genes and identification of plasmid replicons types. The colistin minimum inhibitory concentration (MIC) for mcr-positive isolates was determined by broth microdilution. Relatedness between Enterobacteriaceae carrying mcr genes was determined by multilocus sequence typing (MLST) and core genome MLST. Results: Thirty ESBL-producing Enterobacteriaceae isolates from horses were positive for the colistin resistance gene mcr-9. These isolates included Enterobacter cloacae, Escherichia coli, Klebsiella oxytoca and Citrobacter freundii and belonged to diverse MLST sequence types within each species. Two of the mcr-9-containing isolates originated from the same horse. All mcr-9-positive isolates had colistin MICs below or equal to the EUCAST epidemiological cut-off value of 2 mg/L and were negative for the two potential regulatory genes qseB-like and qseC-like for mcr-9. Except for one isolate carrying only bla(TEM-1B), all of the isolates carried bla(SHV-12) and bla(TEM-1B), and were all considered multidrug-resistant as they harboured genes encoding resistance to aminoglycosides, chloramphenicol, fosfomycin, macrolides, quinolones, sulfonamides, trimethoprim and tetracyclines. Plasmid replicon types IncHI2 and IncHI2A were detected in all mcr-9-positive isolates. Conclusion: The occurrence of mcr-9 was common among clinical ESBL-producing Enterobacteriaceae isolates from horses in Sweden and was linked to the ESBL-encoding gene bla(SHV-12) and plasmid replicon types IncHI2 and IncHI2A. (C) 2019 The Author(s). Published by Elsevier Ltd on behalf of International Soc, Funding Agencies|Swedish Board of Agriculture [6.2.18-15925/2017]

In the spring of 2010, it was discovered that a large proportion of broilers in Sweden were colonized withEscherichia coliproducing extended-spectrum beta-lactamases (ESBL) or plasmid mediated AmpC (pAmpC). It was hypothesized that the high prevalence was due to transfer from an upper level in the production pyramid and sampling upwards in the production pyramid was initiated. From 2010 to 2019, all shipments (n = 122) of broiler breeders were screened on arrival to Sweden for the occurrence of ESBL- or pAmpC-producingE. coliusing selective methods. Samples of paper linings from shipments of breeders were cultured on MacConkey agar supplemented with cefotaxime (1 mg/L) after pre-enrichment in either MacConkey broth with cefotaxime (1 mg/L), or from late June 2015 in buffered peptone water without antibiotics. ESBL- or pAmpC-producingE. coliwas isolated from 43 (35%) of these. Over the years, the proportion of positive imports have decreased and during 2018 and 2019 all imports were negative. In conclusion, the occurrence of ESBL- or pAmpC-producingE. coliin broiler breeders on arrival to Sweden has decreased. Such bacteria have not been detected in any shipments since 2017., Funding Agencies|Swedish Board of Agriculture [6.2.18-14284/2018]; National Veterinary Institute (SVA), Uppsala, Sweden

Sweden has a long tradition of monitoring occurrence of antibiotic resistant bacteria in both animals and humans, but there currently is no organised and harmonized monitoring on carriage of Enterobacteriaceae producing extended-spectrum beta-lactamase (ESBL), plasmid-mediated AmpC beta-lactamase (pAmpC), or methicillin-resistant coagulase positive staphylococci e.g. methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-resistant Staphylococcus pseudintermedius (MRSP) in dogs. The aim of the current study was therefore to determine the prevalence of ESBL/pAmpC producing Enterobacteriaceae and methicillin-resistant coagulase positive staphylococci in healthy dogs in Sweden, and to phenotypically and genotypically characterize any identified isolates. It was shown that 0.9% (95% confident interval 0.3-2.7%) of the dogs (n = 325) carried multi-resistant ESBL-producing Escherichia coli, but that no methicillin-resistant coagulase positive staphylococci could be detected. In conclusion, the occurrence of multi-drug resistant bacteria remains rare among healthy dogs in Sweden. In addition, the ESBL-producing E. coli identified showed genetic characteristics related to those reported from humans., Funding Agencies|Linkoping University; AniCura Research fund; National Veterinary Institute (SVA), Uppsala, Sweden

Objectives: The aim of this study was to investigate the occurrence of the newly described transferable colistin resistance gene mcr-9 in extended-spectrum beta-lactamase (ESBL)-producing clinical Enterobacteriaceae isolates from horses in Sweden. Methods: A total of 56 whole-genome sequenced ESBL-producing Enterobacteriaceae isolates from horses were subjected to in silico detection of antimicrobial resistance genes and identification of plasmid replicons types. The colistin minimum inhibitory concentration (MIC) for mcr-positive isolates was determined by broth microdilution. Relatedness between Enterobacteriaceae carrying mcr genes was determined by multilocus sequence typing (MLST) and core genome MLST. Results: Thirty ESBL-producing Enterobacteriaceae isolates from horses were positive for the colistin resistance gene mcr-9. These isolates included Enterobacter cloacae, Escherichia coli, Klebsiella oxytoca and Citrobacter freundii and belonged to diverse MLST sequence types within each species. Two of the mcr-9-containing isolates originated from the same horse. All mcr-9-positive isolates had colistin MICs below or equal to the EUCAST epidemiological cut-off value of 2 mg/L and were negative for the two potential regulatory genes qseB-like and qseC-like for mcr-9. Except for one isolate carrying only bla(TEM-1B), all of the isolates carried bla(SHV-12) and bla(TEM-1B), and were all considered multidrug-resistant as they harboured genes encoding resistance to aminoglycosides, chloramphenicol, fosfomycin, macrolides, quinolones, sulfonamides, trimethoprim and tetracyclines. Plasmid replicon types IncHI2 and IncHI2A were detected in all mcr-9-positive isolates. Conclusion: The occurrence of mcr-9 was common among clinical ESBL-producing Enterobacteriaceae isolates from horses in Sweden and was linked to the ESBL-encoding gene bla(SHV-12) and plasmid replicon types IncHI2 and IncHI2A. (C) 2019 The Author(s). Published by Elsevier Ltd on behalf of International Soc, Funding Agencies|Swedish Board of Agriculture [6.2.18-15925/2017]