RESUMEN
The aim of this study was to explore the characteristics of blaCTX-M-27 carriage and mobilization in Salmonella and Escherichia coli isolates from food-producing animals in China. A total of 2280 E. coli and 229 Salmonella isolates collected from food animals from June 2003 to September 2014 were screened for the presence of blaCTX-M-27 gene. The blaCTX-M-27-positive isolates were typed and plasmid DNA sequenced to determine the genetic context of blaCTX-M-27 and plasmid types present. Bacterial fitness was evaluated by growth curve and plasmid stability in vitro. CTX-M-27-positive E. coli (18, 0.79 %) and Salmonella (34, 14.85 %) were detected. PFGE profiles of CTX-M-27-positive strains revealed a wide variety of genotypes and S. Indiana was the most prevalent serotype. Replicon typing, S1-PFGE and hybridization of CTX-M-27-carrying plasmids confirmed that blaCTX-M-27 gene was located on IncFII (12/18), IncN (4/18), and non-typeable (2/18) plasmids in E. coli and on P1-like bacteriophage (21/34), IncP (4/34), IncFIB (4/34), IncN (2/34), IncHI2 (2/34), and IncA/C (1/34) plasmids in Salmonella. Comparison and analysis of gene context of blaCTX-M-27 in P1-like bacteriophage and plasmids revealed they shared the same structure and contained an identical genetic context with the Tn1721-like structure ΔISEcp1B-blaCTX-M-27-IS903D-iroN-Δmap-Tn1721. In addition, plasmid stability tests indicated that the blaCTX-M-27 P1-like bacteriophage were more stable than plasmids in the absence of cefotaxime selective pressure. These results demonstrate that Tn1721-like transposons harboring CTX-M-27 could be mobilized between different plasmids in E. coli and P1-like bacteriophage disseminated among Salmonella.
Asunto(s)
Proteínas de Escherichia coli/genética , Escherichia coli/genética , Salmonella/virología , beta-Lactamasas/genética , Animales , Animales Domésticos/microbiología , Antibacterianos/farmacología , China , Farmacorresistencia Bacteriana Múltiple , Escherichia coli/química , Escherichia coli/efectos de los fármacos , Microbiología de Alimentos , Pruebas de Sensibilidad Microbiana , Plásmidos/genética , Salmonella/química , Salmonella/efectos de los fármacos , Salmonella/genéticaRESUMEN
Carbapenem-resistant Enterobacteriaceae are some of the most important pathogens responsible for nosocomial infections, which can be challenging to treat. The blaNDM carbapenemase genes, which are expressed by New Delhi metallo-ß-lactamase (NDM)-producing Escherichia coli isolates, have been found in humans, environmental samples, and multiple other sources worldwide. Importantly, these genes have also been found in farm animals, which are considered an NDM reservoir and an important source of human infections. However, the dynamic evolution of blaNDM genetic contexts and blaNDM-harboring plasmids has not been directly observed, making it difficult to assess the extent of horizontal dissemination of the blaNDM gene. In this study, we detected NDM-1 (n = 1), NDM-5 (n = 24), and NDM-9 (n = 8) variants expressed by E. coli strains isolated from poultry in China from 2016 to 2017. By analyzing the immediate genetic environment of the blaNDM genes, we found that IS26 was associated with multiple types of blaNDM multidrug resistance regions, and we identified various IS26-derived circular intermediates. Importantly, in E. coli strain GD33, we propose that IncHI2 and IncI1 plasmids can fuse when IS26 is present. Our analysis of the IS26 elements flanking blaNDM allowed us to propose an important role for IS26 elements in the evolution of multidrug-resistant regions (MRRs) and in the dissemination of blaNDM. To the best of our knowledge, this is the first description of the dynamic evolution of blaNDM genetic contexts and blaNDM-harboring plasmids. These findings could help proactively limit the transmission of these NDM-producing isolates from food animals to humans. IMPORTANCE Carbapenem resistance in members of the order Enterobacterales is a growing public health problem that is associated with high mortality in developing and industrialized countries. Moreover, in the field of veterinary medicine, the occurrence of New Delhi metallo-ß-lactamase-producing Escherichia coli isolates in animals, especially food-producing animals, has become a growing concern in recent years. The wide dissemination of blaNDM is closely related to mobile genetic elements (MGEs) and plasmids. Although previous analyses have explored the association of many different MGEs with mobilization of blaNDM, little is known about the evolution of various genetic contexts of blaNDM in E. coli. Here, we report the important role of IS26 in forming multiple types of blaNDM multidrug resistance cassettes and the dynamic recombination of plasmids bearing blaNDM. These results suggest that significant attention should be paid to monitoring the transmission and further evolution of blaNDM-harboring plasmids among E. coli strains of food animal origin.
RESUMEN
The aim of this study was to investigate the characteristics of a fosA3 carrying IncC-IncN plasmid from a multidrug-resistant Salmonella isolate HNK130. HNK130 was isolated from a chicken and identified as ST17 Salmonella enterica serovar Indiana and exhibited resistance to 13 antibiotics including the cephalosporins and fosfomycin. S1 nuclease pulsed-field gel electrophoresis and Southern blot assays revealed that HNK130 harbored only one â¼180-kb plasmid carrying fosA3 and bla CTX-M-14, which was not transferable via conjugation. We further examined 107 Escherichia coli electro-transformants and identified 3 different plasmid variants, pT-HNK130-1 (69), pT-HNK130-2 (15), and pT-HNK130-3 (23), in which pT-HNK130-1 seemed to be the same as the plasmid harbored in HNK130. We completely sequenced an example of each of these variants, and all three variants were IncC-IncN multi-incompatible plasmid and showed a mosaic structure. The fosA3 gene was present in all three and bounded by IS26 elements in the same orientation (IS26-322bp-fosA3-1758bp-IS26) that could form a minicircle containing fosA3. The bla CTX-M-14 gene was located within an IS15DI-ΔIS15DI-iroN-IS903B-bla CTX-M-14 -ΔISEcp1-IS26 structure separated from the fosA3 gene in pT-HNK130-1, but was adjacent to fosA3 in pT-HNK130-3 in an inverted orientation. Linear comparison of the three variants showed that pT-HNK130-2 and pT-HNK130-3 resulted from the sequence deletion and inversion of pT-HNK130-1. Stability tests demonstrated that pT-HNK130-1 and pT-HNK130-3 could be stably maintained in the transformants without antibiotic selection but pT-HNK130-2 was unstable. This is the first description of an IncC-IncN hybrid plasmid from an ST17 S. Indiana strain and indicates that this plasmid may further facilitate dissemination of fosfomycin and cephalosporin resistance in Salmonella.
RESUMEN
The emergence and increase in prevalence of resistance to cephalosporins amongst isolates of Salmonella from food animals imposes a public health threat. The aim of the present study was to investigate the prevalence and characteristics of CTX-M-producing Salmonella isolates from raw meat and food animals. 27 of 152 (17.76%) Salmonella isolates were ESBL-positive including 21/70 (30%) from food animals and 6/82 (7.32%) from raw meat. CTX-M-55 was the most prevalent ESBL type observed (12/27, 44.44%). 7 of 12 CTX-M-55-positive Salmonella isolates were Salmonella Indiana, 2 were Salmonella Typhimurium, 2 were Salmonella Chester, and the remaining isolate was not typeable. Eight CTX-M-55-positive Salmonella isolates were highly resistant to fluoroquinolones (MICCIP = 64 ug/mL) and co-harbored aac(6')-Ib-cr and oqxAB. Most of the CTX-M-55 positive isolates (11/12) carried bla CTX-M-55 genes on the chromosome, with the remaining isolate carrying this gene on a transferable 280 kb IncHI2 plasmid. A chromosomal bla CTX-M-55 gene from one isolate transferred onto a 250 kb IncHI2 plasmid which was subsequently conjugated into recipient strain J53. PFGE and MLST profiles showed a wide range of strain types were carrying bla CTX-M-55. Our study demonstrates the emergence and prevalence of foodborne Salmonella harboring a chromosomally located bla CTX-M-55 in China. The co-existence of PMQR genes with bla CTX-M-55 in Salmonella isolates suggests co-selection and dissemination of resistance to both fluoroquinolones and cephalosporins in Salmonella via the food chain in China represents a public health concern.