RESUMEN

The monophasic variant of Salmonella enterica serovar Typhimurium with the antigenic formula 1,4,[5],12:i:- is one of the most common pathogenic bacteria causing global food-borne outbreaks. However, the research on molecular characteristics and evolution of monophasic S. typhimurium in China is still lacking. In the current study, 59 monophasic S. typhimurium strains were isolated from food animals and food products in South China between 2011 and 2018. A total of 87.5 % of monophasic S. typhimurium isolates were grouped into one independent clade with other monophasic S. typhimurium strains in China distinct from other countries by phylogenomic analysis. These isolates possess variable genotypes, including multiple ARGs on plasmid IncHI2, diverse evolutions at the fljAB locus, and virulence factors. Our results suggest that the monophasic S. typhimurium isolates currently circulating in China might be an independent epidemic subtype.

Asunto(s)

Infecciones por Salmonella , Animales , Infecciones por Salmonella/microbiología , Salmonella typhimurium/genética , Serogrupo , Plásmidos , Genotipo , Antibacterianos

RESUMEN

Carbapenem-resistant Enterobacteriaceae infections are among the most serious threats to human and animal health worldwide. Of the 1013 strains of Escherichia coli isolated and identified in 14 regions of China from 2007 to 2018, seven strains were resistant to meropenem and all were positive for blaNDM. The seven New Delhi metallo-ß-lactamase (NDM)-positive strains belonged to five different sequence types, indicating that most of the NDM-positive strains were nonclonal. An IncHI2 plasmid carrying the blaNDM-1 element was identified in the C1147 strain from a goose source and reported for the first time, showing a specific structure. Conjugation experiments revealed that the IncHI2 plasmid was conjugatable, and the horizontal propagation of the plasmid led to the rapid propagation of NDM in the same and different strains. This study revealed that waterfowl, as a potential transmission factor for carbapenem-resistant blaNDM-1, poses a threat to human health.

Asunto(s)

Infecciones por Escherichia coli , Escherichia coli , Animales , Antibacterianos/farmacología , Antibacterianos/uso terapéutico , beta-Lactamasas/genética , China , Escherichia coli/genética , Infecciones por Escherichia coli/veterinaria , Gansos/microbiología , Pruebas de Sensibilidad Microbiana , Plásmidos/genética

RESUMEN

The emergence of colistin resistance raises growing concerns because of its use as a last-resort antimicrobial for the treatment of severe gram-negative bacterial infections in humans. Plasmid-borne mobile colistin resistance genes (mcr) are particularly worrisome due to their high propensity to spread. An mcr-9-positive Escherichia coli was isolated from a piglet in Italy, representing the first isolation of this gene from an E. coli of animal origin in the country. Whole genome sequencing (WGS) revealed that mcr-9 was borne by an IncHI2 plasmid carrying several other resistance genes. The strain was indeed phenotypically resistant to six different antimicrobial classes, including 3rd and 4th generation cephalosporins. Despite the presence of mcr-9, the isolate was susceptible to colistin, probably because of a genetic background unfavourable to mcr-9 expression. The lack of colistin resistance, coupled with the fact that the farm of origin had not used colistin in years, suggests that mcr-9 in such a multidrug-resistant strain can be maintained thanks to the co-selection of neighbouring resistance genes, following usage of different antimicrobials. Our findings highlight how a comprehensive approach, integrating phenotypical testing, targeted PCR, WGS-based techniques, and information on antimicrobial usage is crucial to shed light on antimicrobial resistance.

RESUMEN

The emergence and dissemination of the extended spectrum ß-lactamase (ESBL)-producing Enterobacteriaceae harbouring antimicrobial resistance (AMR) genes has diminished the potential options for treating multidrug-resistant (MDR) bacterial infections. Until now, numerous studies reported the spreading of critical plasmid-borne AMR genes from different sources worldwide. While the knowledge on the occurrence of the plasmid-borne AMR genes, especially mcr genes in the dead chick embryos, remains obscure. A retrospective study was conducted to detect the presence of the mcr genes in forty-five Salmonella enterica isolates recovered from 2139 dead chick embryo samples, from breeding chicken hatcheries in Henan, China. Using multiplex PCR, we found only four isolates out of the forty-five were mcr-9-positive. These four isolates were found to be MDR, ESBL- producing and showed resistance to 10 antimicrobial drugs. Additionally, mcr-9 harbouring plasmids were successfully transferred into Escherichia coli (E. coli) J53 by conjugation and the mcr-9 gene was confirmed by PCR. We also found that the transconjugants exhibited higher MICs for ampicillin, gentamycin and colistin than the recipient. Whole-genome sequence analysis showed that the four isolates belonged to Salmonella Thompson ST26 and harboured IncHI2 plasmid replicon. Furthermore, the mcr-9 harbouring plasmids were reconstructed using in silico tools and found to be carried other AMR genes (blaDHA-1 and qnrB4). The studied isolates carried the typical virulence factors from Salmonella pathogenicity islands 1 and 2 (SPI-1 and SPI-2), in addition to pef and csg operons which are important in host adhesion and biofilm formation. The mgtC gene, which is involved in phagocytosis, has also been identified. Together, the increase in the phenotypic resistance of the transconjugants and the plasmid in silico reconstruction analysis confirmed that the corresponding resistance genes might be located together on the same plasmid. To track the potential phylogenomic relations of our detected ESBL S. Thompson isolates, we constructed a phylogenomic tree with available ESBL S. Thompson genomes (n = 26) that were reported worldwide. The studied isolates were independently clustered together with four other Chinese isolates of food origin in one clade, providing strong evidence of a potential recent and wide dissemination of ESBL S. Thompson across the food chain in China. In conclusion, we report the detection of four highly virulent ESBL-producing S. Thompson ST26 isolates harbouring mcr-9 gene obtained from dead chick embryos in Henan, China.

Asunto(s)

Proteínas de Escherichia coli , Escherichia coli , Embrión de Pollo , Animales , Escherichia coli/genética , Antibacterianos/farmacología , Proteínas de Escherichia coli/genética , Estudios Retrospectivos , Colistina , Plásmidos/genética , Salmonella/genética , Enterobacteriaceae/genética , Genómica , beta-Lactamasas/genética , Pruebas de Sensibilidad Microbiana/veterinaria

RESUMEN

BACKGROUND: Co-harbouring of carbapenem and colistin resistance genes in multidrug-resistant Enterobacterales strains poses a serious public health problem. In this study, an MCR-1.1 and NDM-5 coproducing Escherichia coli strain named EC6563 was isolated and characterized. OBJECTIVES: This study aimed to characterize a clinical carbapenem-resistant E. coli isolate which co-harbours mcr-1.1 and blaNDM-5 on separate plasmids, and explored the phenotypic and genotypic characteristics of the mcr-1.1- and blaNDM-5-harbouring plasmids. METHODS: E. coli isolate EC6563 was subjected to antimicrobial susceptibility testing, conjugation assay, stability of the plasmid and growth rate determination. In addition, the whole genome sequence of this strain was obtained and the genetic characteristics of the mcr-1.1- and blaNDM-5-harbouring plasmids were analyzed. RESULTS: Carbapenem-resistant E. coli isolate EC6563 was resistant to all the tested antibiotics except tigecycline. Bioinformatic analysis confirmed that the IncHI2 plasmid carrying mcr-1.1 was highly similar to the previously reported mcr-1.1-harbouring plasmid pGDP37-4, and carried multiple drug resistance genes and the IncI1-I plasmid carrying blaNDM-5 had low similarity to the published blaNDM-5-carrying IncI1-I plasmid pEC-16-10-NDM-5. The pEC6563-NDM5 plasmid was capable of conjugation with an efficiency of 1.34 × 10-2 in a filter mating experiment. The transconjugant J53/pEC6563-NDM5 was able to be stably inherited after 12 days of passage. CONCLUSIONS: To the best of our knowledge, this is the first time that an IncHI2 plasmid carrying mcr-1.1 and an IncI1-I plasmid carrying blaNDM-5 is found to coexist in an E. coli isolate. Our research expands the known diversity of plasmids in NDM-5-producing Enterobacterales strains. Meanwhile, effective measures should be taken to prevent the spread of these plasmids.

Asunto(s)

Infecciones por Escherichia coli , Proteínas de Escherichia coli , Humanos , Antibacterianos/farmacología , beta-Lactamasas/genética , beta-Lactamasas/farmacología , Carbapenémicos/farmacología , China , Farmacorresistencia Bacteriana Múltiple/genética , Escherichia coli/genética , Proteínas de Escherichia coli/genética , Pruebas de Sensibilidad Microbiana , Plásmidos/genética

RESUMEN

Understanding the fitness costs associated with plasmid carriage is a key to better understanding the mechanisms of plasmid maintenance in bacteria. In the current work, we performed multiple serial passages (63 days, 627.8 generations) to identify the compensatory mechanisms that Salmonella enterica serovar Typhimurium ATCC 14028 utilized to maintain the multidrug-resistant (MDR) IncHI2 plasmid pJXP9 in the presence and absence of antibiotic selection. The plasmid pJXP9 was maintained for hundreds of generations even without drug exposure. Endpoint evolved (the endpoint of evolution) S. Typhimurium bearing evolved plasmids displayed decreased growth lag times and a competitive advantage over ancestral pJXP9 plasmid-carrying ATCC 14028 strains. Genomic and transcriptomic analyses revealed that the fitness costs of carrying pJXP9 were derived from both specific plasmid genes and particularly the MDR regions and conjugation transfer region I and conflicts resulting from chromosome-plasmid gene interactions. Correspondingly, plasmid deletions of these regions could compensate for the fitness cost that was due to the plasmid carriage. The deletion extent and range of large fragments on the evolved plasmids, as well as the trajectory of deletion mutation, were related to the antibiotic treatment conditions. Furthermore, it is also adaptive evolution that chromosomal gene mutations and altered mRNA expression correlated with changed physiological functions of the bacterium, such as decreased flagellar motility, increased oxidative stress, and fumaric acid synthesis but increased Cu resistance in a given niche. Our findings indicated that plasmid maintenance evolves via a plasmid-bacterium adaptative evolutionary process that is a trade-off between vertical and horizontal transmission costs along with associated alterations in host bacterial physiology. IMPORTANCE The current idea that compensatory evolution processes can account for the "plasmid paradox" phenomenon associated with the maintenance of large costly plasmids in host bacteria has attracted much attention. Although many compensatory mutations have been discovered through various plasmid-host bacterial evolution experiments, the basis of the compensatory mechanisms and the nature of the bacteria themselves to address the fitness costs remain unclear. In addition, the genetic backgrounds of plasmids and strains involved in previous research were limited and clinical drug resistance such as the poorly understood compensatory evolution among clinically dominant multidrug-resistant plasmids or clones was rarely considered. The IncHI2 plasmid is widely distributed in Salmonella Typhimurium and plays an important role in the emergence and rapid spread of its multidrug resistance. In this study, the predominant multidrug-resistant IncHI2 plasmid pJXP9 and the standard Salmonella Typhimurium ATCC 14028 bacteria were used for evolution experiments under laboratory conditions. Our findings indicated that plasmid maintenance through experimental evolution of plasmid-host bacteria is a trade-off between increasing plasmid vertical transmission and impairing its horizontal transmission and bacterial physiological phenotypes, in which compensatory mutations and altered chromosomal expression profiles collectively contribute to alleviating plasmid-borne fitness cost. These results provided potential insights into understanding the relationship of coexistence between plasmids encoding antibiotic resistance and their bacterial hosts and provided a clue to the adaptive forces that shaped the evolution of these plasmids within bacteria and to predicting the evolution trajectory of antibiotic resistance.

Asunto(s)

Salmonella enterica , Salmonella typhimurium , Salmonella typhimurium/genética , Serogrupo , Plásmidos/genética , Salmonella enterica/genética , Antibacterianos/farmacología

RESUMEN

Salmonella enterica is a zoonotic food-borne pathogen threatening public health around the world. As is the case with many other pathogens, the spread of mobilized colistin resistance (mcr) alleles is of grave concern. In this study, totally 689 clinical Salmonella isolates were collected from a local hospital in Hangzhou, Zhejiang Province, China between 2009 and 2018. Resistance genes were screen by PCR. Two mcr-9-positive Salmonella strains S15 and S639 were identified which belong to serotype Typhimurium and Thompson, respectively. We observed that both mcr-9 genes were located on conjugative IncHI2 plasmids which encoded numerous resistance genes, likely facilitating the dissemination of mcr-9 by co-resistance mechanisms. The mcr-9 cassettes encoded on the two plasmids were not identical: downstream of the mcr-9 genes, we found IS1 on one plasmid (pS15), while the other had a WbuC-IS26 (pS639). Despite the presence of mcr-9 cassettes, the strains were not rendered colistin resistant. Yet, it is of epidemiological importance to implement surveillance to be able to observe and possibly control the spread of mcr-9 due to its potential to mediate resistance to the last-resort antibiotic colistin.

RESUMEN

Newborn dairy calves are often colonized by multidrug-resistant (MDR) extended-spectrum ß-Lactamase producing Escherichia coli (ESBL-EC), which pose significant risks to global healthcare. As the first meal of calves, the role of dairy colostrum as a potential source of MDR-E. coli has not been well-studied. Here, we report on similar antibiotic resistance patterns of E. coli strains, isolated from colostrum fed to dairy calves and their faeces. Four ESBL-EC strains from colostrum and faeces of newborn dairy calves were isolated by double-disc synergy testing and multiplex PCR. Strikingly, isolates from colostrum or faeces were found to have similar MDR profiles, showing a high resistance to cephalosporins and other conventional antibiotics. In addition, coexistence of blaCTX-M-15 and blaTEM-171 was detected on a self-transferable plasmid with a typical IncHI2 backbone. To the best of our knowledge, this is the first case reporting on ESBL-EC strains carrying blaCTX-M-15 and blaTEM-171 genes, and isolated from faeces and the colostrum stock fed to the dairy calves.

RESUMEN

Carbapenem resistance has posed potential harmful risks to human and animals. The objectives of this study were to understand the prevalence of blaNDM-5 in pigs and investigate the molecular characteristics of NDM-5-producing Escherichia coli isolates in Guangdong province in China. Carbapenem-resistant E. coli isolates were isolated from pigs and obtained using MacConkey plates containing 0.5 mg/L meropenem. Conjugation assay and antimicrobial susceptibility testing were conducted for the isolates and their transconjugants. Whole-genome sequence (WGS) was used to analyze the plasmid genetic feature. A total of five blaNDM-5-carrying E. coli isolates were obtained in the present investigations. They belonged to five ST types. The blaNDM-5 genes were found to be in IncX3 and IncHI2 plasmid. The IncX3 plasmid was 46,161 bp in size and identical to other reports. IncHI2 plasmid was 246,593 bp in size and similar to other IncHI2-ST3 plasmids. It consisted of a typical IncHI2 plasmid backbone region and a multiresistance region (MRR). The blaNDM-5 was closely associated with the IS3000-ISAba125-blaNDM-5-bleMBL-trpF-tat-IS26 unit. We first reported the blaNDM-5-carrying IncHI2 in E. coli isolates recovered from pigs and revealed the molecular characterization. Continued surveillance for the dissemination of blaNDM-5 among food-producing animals is required.

RESUMEN

A collection of 177 genomes of Salmonella Typhimurium and its monophasic variant isolated in 2014-2019 from Italian poultry/livestock (n = 165) and foodstuff (n = 12), previously screened for antimicrobial susceptibility and assigned to ST34 and single-locus variants, were studied in-depth to check the presence of the novel mcr-9 gene and to investigate their genetic relatedness by whole genome sequencing (WGS). The study of accessory resistance genes revealed the presence of mcr-9.1 in 11 ST34 isolates, displaying elevated colistin minimum inhibitory concentration values up to 2 mg/L and also a multidrug-resistant (MDR) profile toward up to seven antimicrobial classes. Five of them were also extended-spectrum beta-lactamases producers (bla SHV - 12 type), mediated by the corresponding antimicrobial resistance (AMR) accessory genes. All mcr-9-positive isolates harbored IncHI2-ST1 plasmids. From the results of the Mash analysis performed on all 177 genomes, the 11 mcr-9-positive isolates fell together in the same subcluster and were all closely related. This subcluster included also two mcr-9-negative isolates, and other eight mcr-9-negative ST34 isolates were present within the same parental branch. All the 21 isolates within this branch presented an IncHI2/2A plasmid and a similar MDR gene pattern. In three representative mcr-9-positive isolates, mcr-9 was demonstrated to be located on different IncHI2/IncHI2A large-size (∼277-297 kb) plasmids, using a combined Illumina-Oxford Nanopore WGS approach. These plasmids were also compared by BLAST analysis with publicly available IncHI2 plasmid sequences harboring mcr-9. In our plasmids, mcr-9 was located in a ∼30-kb region lacking different genetic elements of the typical core structure of mcr-9 cassettes. In this region were also identified different genes involved in heavy metal metabolism. Our results underline how genomics and WGS-based surveillance are increasingly indispensable to achieve better insights into the genetic environment and features of plasmid-mediated AMR, as in the case of such IncHI2 plasmids harboring other MDR genes beside mcr-9, that can be transferred horizontally also to other major Salmonella serovars spreading along the food chain.

RESUMEN

We report a novel IncHI2 plasmid coharboring blaVIM-1, two copies of blaKPC-3, and mcr-9.1 resistance genes in a human Escherichia coli isolate of the new serogroup O188. The blaVIM-1 gene was included in a class 1 integron, mcr-9.1 in a cassette bracketed by IS903 and ΔIS1R, and blaKPC-3 in two copies within a new composite Tn4401-like transposon. The emergence of carbapenem and colistin resistance genes in a single plasmid is of great concern for upcoming clinical therapies.

Asunto(s)

Farmacorresistencia Bacteriana Múltiple/genética , Infecciones por Escherichia coli/microbiología , Escherichia coli/efectos de los fármacos , Escherichia coli/genética , Plásmidos/genética , beta-Lactamasas/genética , Antibacterianos/farmacología , Escherichia coli/enzimología , Proteínas de Escherichia coli/genética , Humanos , Pruebas de Sensibilidad Microbiana , beta-Lactamasas/clasificación

RESUMEN

The reintroduction of colistin, a last-resort antibiotic for multidrug-resistant pathogens, resulted in the global spread of plasmid-mediated mobile colistin resistance (mcr) genes. Our study investigated the occurrence of colistin resistance among Escherichia coli isolated from patients with urinary tract infections admitted to a teaching hospital in Egypt. Out of 67 isolates, three isolates were colistin-resistant, having a minimum inhibitory concentration of 4 µg/mL and possessing the mcr-1 gene. A double mechanism of colistin resistance was detected; production of mcr-1 along with amino acid substitution in PmrB (E123D and Y358N) and PmrA (G144S). Broth mating experiments inferred that mcr-1 was positioned on conjugative plasmids. Whole-genome sequencing of EC13049 indicated that the isolate belonged to O23:H4-ST641 lineage and to phylogroup D. The mcr-1-bearing plasmid corresponded to IncHI2 type with a notable similarity to other E. coli plasmids previously recovered from Egypt. The unbanned use of colistin in the Egyptian agriculture sector might have created a potential reservoir for the mcr-1 gene in food-producing animals that spread to humans. More proactive regulations must be implemented to prevent further dissemination of this resistance. This is the first characterization of mcr-1-carrying IncHI2:ST4 plasmid recovered from E. coli of a clinical source in Egypt.

RESUMEN

BACKGROUND: The increasing number of carbapenemase-producing Enterobacteriaceae (CPE) has become a global problem. Most carbapenemases detected in Japan are imipenemase, which is an imipenem-degrading enzyme with low ability; thus, CPE could have been overlooked. Therefore, this study aimed to detect and analyze CPE, without overlooking CPE showing the low minimum inhibitory concentration phenotype. METHODS: CPE screening was conducted on 531 ceftazidime-resistant Enterobacteriaceae isolated from Kitasato University Hospital during 2006-2015. We confirmed the presence of the carbapenemase genes (blaIMP, blaVIM, blaKPC, blaNDM, and blaOXA-48) by multiplex polymerase chain reaction. The detected CPE strains were analyzed by antimicrobial susceptibility testing, multilocus sequence typing, conjugal experiments, replicon typing, and plasmid profiling by restriction enzyme treatment. RESULTS: The CPE detection rate in Kitasato University Hospital within the past 10 years was 0.0003% (nine CPE strains). These nine CPE strains were identified to harbor 8 blaIMP-1 or 1 blaNDM-5. The CPE strains consisted of five species including Klebsiella pneumoniae and Citrobacter freundii. Six of eight blaIMP-1 were coded by IncHI2 plasmid, and the other two were coded by IncA/C plasmid. Plasmid profiling revealed that K. pneumoniae and C. freundii isolated from the same patient harbored the same plasmid. CONCLUSION: The CPE detection rate in this study was significantly lower than those previously reported in Japan. In one case, IncA/C plasmid transmission through different bacterial species within the body was speculated. Although the number of CPE detected was low, these results indicated that the resistance plasmid could spread to other bacterial species.

Asunto(s)

Antibacterianos/farmacología , Enterobacteriaceae Resistentes a los Carbapenémicos/aislamiento & purificación , Infecciones por Enterobacteriaceae/tratamiento farmacológico , Hospitales/tendencias , Resistencia betalactámica/genética , Antibacterianos/uso terapéutico , Proteínas Bacterianas/genética , Proteínas Bacterianas/aislamiento & purificación , Enterobacteriaceae Resistentes a los Carbapenémicos/efectos de los fármacos , Enterobacteriaceae Resistentes a los Carbapenémicos/genética , Ceftazidima/farmacología , Ceftazidima/uso terapéutico , Citrobacter freundii/efectos de los fármacos , Citrobacter freundii/genética , Citrobacter freundii/aislamiento & purificación , ADN Bacteriano/genética , ADN Bacteriano/aislamiento & purificación , Infecciones por Enterobacteriaceae/epidemiología , Infecciones por Enterobacteriaceae/microbiología , Transferencia de Gen Horizontal , Genes Bacterianos/genética , Hospitales/estadística & datos numéricos , Humanos , Imipenem/farmacología , Imipenem/uso terapéutico , Japón/epidemiología , Klebsiella pneumoniae/efectos de los fármacos , Klebsiella pneumoniae/genética , Klebsiella pneumoniae/aislamiento & purificación , Pruebas de Sensibilidad Microbiana , Tipificación de Secuencias Multilocus , Plásmidos/genética , Plásmidos/aislamiento & purificación , Reacción en Cadena de la Polimerasa , Prevalencia , beta-Lactamasas/genética , beta-Lactamasas/aislamiento & purificación

RESUMEN

aEPEC are associated with persistent diarrhea, and diarrheal outbreaks in both humans and animals worldwide. They are differentiated from typical EPEC by the lack of bundle-forming pili, and from EHEC by the lack of phage-mediated stx toxins. However, phylogenetic analyses often associate aEPEC with EHEC, promoting the hypothesis that aEPEC are the progenitors of EHEC, which is supported by aEPEC conversion to EHEC by stx-carrying phages. While aEPEC can cause disease outright, the potential to acquire stx, one of the most potent bacterial toxins known, merits close monitoring. Escherichia coli ST302 (O108:H9, O182:H9, O45:H9) are aEPEC that have been isolated from diarrheic human, pig and rabbit hosts, as well as in healthy pigs, however, no study to date has focused on E. coli ST302 strains. Through WGS and hybrid assembly we present the first closed chromosome, and two circularized plasmids of an ST302 strain - F2_18C, isolated from a healthy pig in Australia. A phylogenetic analysis placed E. coli ST302 strains in proximity to EHEC ST32 (O145:H28) strains. Public databases were interrogated for WGSs of E. coli ST302 strains and short-read gene screens were used to compare their virulence-associated gene (VAG) and antimicrobial resistance gene (ARG) cargo. E. coli ST302 strains carry diverse VAGs, including those that typically associated with extraintestinal pathogenic E. coli (ExPEC). Plasmid comparisons showed that pF2_18C_FIB shared homology with EHEC virulence plasmids such as pO103 while pF2_18C_HI2 is a large multidrug resistance IncHI2:ST3 plasmid. A comparison of 33 HI2:ST3 plasmids demonstrated that those of Australian origin have not acquired resistances to extended-spectrum beta-lactams, colistin, fosfomycin or rifampicin, unlike those originating from Asia. F2_18C was shown to carry two additional pathogenicity islands - ETT2, and the STEC-associated PAI CL 3, plasmid-associated heavy metal resistance genes, as well as several unoccupied stx-phage attachment sites. This study sheds light on the virulence and AMR potential of E. coli ST302 strains and informs AMR genomic surveillance.

RESUMEN

During a regular monitoring of antimicrobial resistance in a farrowing farm in Southern China, 117 Escherichia coli isolates were obtained from sows and piglets. Compared with the isolates from piglets, the isolates from sows exhibited higher resistance rates to the tested cephalosporins. Correspondingly, the total detection rate of the bla CMY-2/bla CTX-M genes in the sow isolates (34.2%) was also significantly higher than that of the piglet isolates (13.6%; p < 0.05). The bla CMY-2 gene had a relatively high prevalence (11.1%) in the E. coli isolates. MLST and PFGE analysis revealed the clonal spread of ST1121 E. coli in most (7/13) of the bla CMY-2-positive isolates. An indistinguishable IncHI2 plasmid harboring bla CMY-2 was also identified in each of the seven ST1121 E. coli isolates. Complete sequence analysis of this IncHI2 plasmid (pEC5207) revealed that pEC5207 may have originated through recombination of an IncHI2 plasmid with a bla CMY-2-carrying IncA/C plasmid like pCFSAN007427_01. In addition to bla CMY-2, pEC5207 also carried other resistance determinants for aminoglycosides (aacA7), sulfonamides (sul1), as well as heavy metals ions, such as Cu and Ag. The susceptibility testing showed that the pEC5207 can mediate both antibiotic and heavy metal resistance. This highlights the role of pEC5207 in co-selection of bla CMY-2-positive isolates under the selective pressure of heavy metals, cephalosporins, and other antimicrobials. In conclusion, clonal spread of an ST1121 type E. coli strain harboring an IncHI2 plasmid contributed to the dissemination of bla CMY-2 in a farrowing farm in Southern China. We also have determined the first complete sequence analysis of a bla CMY-2-carrying IncHI2 plasmid.

RESUMEN

Over a 6-year period (2007-2012), the emergence of Enterobacter cloacae isolates resistant to ß-lactams and with reduced susceptibility to carbapenems was observed in Hospital Universitario 12 de Octubre (Madrid, Spain). To determine the possible role of metallo-ß-lactamases (MBLs) in the resistance profile of these isolates, a molecular and clinical epidemiological study was performed, including determination of patients' clinical characteristics, genetic diversity of strains, resistance mechanisms to carbapenems, and the genetic environment of VIM-1. A total of 73 E. cloacae isolates showed resistance to extended-spectrum cephalosporins and reduced susceptibility to at least one carbapenem during 2007-2012. PCR amplification revealed the presence of bla(VIM-1) gene in 37 isolates, bla(VIM-2) in 1 isolate and bla(KPC) in 5 isolates. Molecular typing showed high clonal diversity of E. cloacae isolates carrying bla(VIM-1). The genetic environment of bla(VIM-1) was investigated and two integron structures were found: intI-bla(VIM-1)-aacA4-dfrB1-aadA1-catB2-qacEΔ1/sul1 (In624); and intI-bla(VIM-1)-aacA4-aadA1-qacEΔ1/sul1 (In488). Isolates belonging to three clones (A, F and G) harboured different types of integron (In624 or In488) despite belonging to the same clone. Conjugal experiments showed an association with a conjugative plasmid of ca. 300 kb belonging to IncHI2 group, which is common in Spanish hospitals, suggesting that the widespread dissemination of bla(VIM-1) may be due to horizontal transfer of mobile genetic determinants rather than the result of spreading of a few clones. These results have implications for infection control programmes in the hospital.

Asunto(s)

Enterobacter cloacae/clasificación , Enterobacter cloacae/enzimología , Infecciones por Enterobacteriaceae/epidemiología , Integrones , Tipificación Molecular , Plásmidos , Adulto , Anciano , Análisis por Conglomerados , Enterobacter cloacae/genética , Enterobacter cloacae/aislamiento & purificación , Infecciones por Enterobacteriaceae/microbiología , Femenino , Variación Genética , Genotipo , Humanos , Masculino , Persona de Mediana Edad , Epidemiología Molecular , Reacción en Cadena de la Polimerasa , Estudios Retrospectivos , España/epidemiología , beta-Lactamasas/metabolismo

RESUMEN

A total of 1623 clinical isolates of Salmonella belonging to 229 serotypes were received by the Senegalese Reference Center for Enterobacteria from January 1999 to December 2009. The most common serotypes were Enteritidis (19% of the isolates), Typhi (8%), Typhimurium (7%) and Kentucky (4%). A significant increase in the prevalence of resistance to amoxicillin (0.9% in 1999 to 11.1% in 2009) and nalidixic acid (0.9% in 1999 to 26.7% in 2009) was observed in non-typhoidal Salmonella serotypes. For critically important antibiotics, notably ciprofloxacin and extended-spectrum cephalosporins (ESCs), the rates of resistance were low: 0.3% and 0.5%, respectively. Seven ESC-resistant Salmonella strains and three additional ESC-resistant strains from Senegal (1990) and Mali (2007) were studied to identify the genetic basis of their antibiotic resistance. All ESC-resistant strains produced an extended-spectrum ß-lactamase (ESBL). These were CTX-M-15 (n = 6; 2000-2008), SHV-12 (n = 3; 2000-2001) and SHV-2 (n = 1; 1990). A large IncHI2 ST1 pK29-like plasmid was found in six strains (three producing SHV-12 and three CTX-M-15), whereas IncN and IncF plasmids were found in three strains and one strain, respectively. The association of plasmid-mediated quinolone resistance (PMQR) genes qnrB1 and aac(6')-Ib-cr was found in four ESBL-producing strains, leading to decreased susceptibility and even full resistance to ciprofloxacin (MIC range 0.75-2 mg/L) despite the absence of mutations in the quinolone resistance-determining region (QRDR) of gyrA, gyrB, parC and parE. This association of ESBL and multiple PMQR mechanisms within the same strains is therefore a serious concern as it hampers the use of both ESCs and fluoroquinolones for severe Salmonella infections.

Asunto(s)

Infecciones por Salmonella/epidemiología , Infecciones por Salmonella/microbiología , Salmonella enterica/enzimología , beta-Lactamasas/genética , Antibacterianos/farmacología , Farmacorresistencia Bacteriana , Humanos , Pruebas de Sensibilidad Microbiana , Plásmidos/análisis , Prevalencia , Salmonella enterica/clasificación , Salmonella enterica/aislamiento & purificación , Senegal/epidemiología , Serotipificación