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Carbapenem-resistant and hypervirulent K. pneumoniae (CR-HvKP) strains that have emerged recently have caused infections of extremely high mortality in various countries. In this study, we discovered a conjugative plasmid that encodes carbapenem resistance and hypervirulence in a clinical ST86 K2 CR-HvKP, namely 17ZR-91. The conjugative plasmid (p17ZR-91-Vir-KPC) was formed by fusion of a non-conjugative pLVPK-like plasmid and a conjugative blaKPC-2-bearing plasmid and is present dynamically with two other non-fusion plasmids. Conjugation of p17ZR-91-Vir-KPC to other K. pneumoniae enabled them to rapidly express the carbapenem resistance and hypervirulence phenotypes. More importantly, genome analysis provided direct evidence that p17ZR-91-Vir-KPC could be directly transmitted from K2 CR-HvKP strain, 17ZR-91, to ST11 clinical K. pneumoniae strains to convert them into ST11 CR-HvKP strains, which explains the evolutionary mechanisms of recently emerged ST11 CR-HvKP strains., Carbapenem-resistant and hypervirulent Klebsiella pneumoniae strains are emerging. Here Xie et al. show that these phenotypes are carried on a plasmid formed from the fusion of a virulence plasmid with a conjugative plasmid.

Objectives To investigate the prevalence and genetic contexts of the blaCTX-M-14 gene harboured by foodborne isolates of Vibrio spp. in China. Methods A total of 1856 Vibrio spp. isolates collected from raw meat and shrimp samples in Guangdong Province of China were screened for blaCTX-M-14 by PCR. The blaCTX-M-14-positive isolates were characterized by MIC, PFGE, MLST, conjugation, S1-PFGE and Southern blotting and WGS using Illumina and Nanopore platforms. Results A total of 35 (1.9%) Vibrio isolates were positive for blaCTX-M-14, including 33 Vibrio parahaemolyticus strains and two Vibrio alginolyticus strains. MLST showed that most of the blaCTX-M-14-bearing isolates could be assigned into two major STs, with ST163 being more prevalent (n = 23), followed by ST180 (n = 6). Whole-genome analysis of these 35 isolates revealed that the blaCTX-M-14 gene was associated with ISEcp1 in the upstream region, of which 32 blaCTX-M-14 genes were located in the same loci of chromosome I, 1 blaCTX-M-14 gene was located in a novel chromosomal integrative conjugative element (ICE) belonging to the SXT/R391 family and 2 blaCTX-M-14 genes were located in the same type of plasmid, which belonged to the IncP-1 group. Conjugation experiments showed that only the plasmid-borne blaCTX-M-14 gene could be transferred to the recipient strain Escherichia coli J53. Conclusions The emergence of the novel ICE and IncP-1 plasmids has contributed to the variable genetic contexts of blaCTX-M-14 among strains of Vibrio spp. and facilitated the horizontal transfer of such genes between Vibrio spp. and other zoonotic pathogens, resulting in a rapid increase in the prevalence of blaCTX-M-14-bearing bacterial pathogens worldwide.

Carbapenem-resistant hypervirulent Klebsiella pneumoniae (CR-HvKP) strains have been increasingly reported, and it is important to understand the evolutionary mechanisms of these highly pathogenic and resistant bacterial pathogens. In this study, we characterized a ST11 carbapenem-resistant K. pneumoniae strain which harbored an IncFIB/IncHI1B type virulence plasmid and an IncFII/IncR type blaKPC–2-bearing plasmid. The virulence plasmid was found to be conjugative and harbored a 35-kbp fragment including aerobactin encoding cluster from virulence plasmid pLVPK and multiple resistance genes, resulting in a mosaic multi-drug resistance and virulence plasmid. This virulence plasmid could be transferred via conjugation to Escherichia coli and K. pneumoniae strains alone as well as together with the blaKPC–2-bearing plasmid. Co-transmission of virulence and blaKPC–2-bearing plasmids would directly convert a classic K. pneumoniae strain into CR-HvKP strain, leading to a sharp increase in the prevalence of CR-HvKP in clinical settings, which poses a great threat to human health.

Acinetobacter sp. is among the ESKAPE organisms which represent the major nosocomial pathogens that exhibited a high resistance rate. A. pittii, frequently associated with antimicrobial resistance particularly to carbapenems, is one of the most common Acinetobacter species causing invasive infection. Pandrug resistant A. pittii has rarely been reported. Here, we report the case of a patient with acute exacerbations of chronic obstructive pulmonary disease three years after double lung transplantation and developed severe pneumonia associated with pandrug resistant A. pittii infection. Phenotypic and genomic characteristics of this pandrug resistant isolate (17-84) was identified, and the mechanisms underlying its resistance phenotypes were analyzed. Isolate 17-84 belonged to ST63, carried a non-typable and non-transferable plasmid encoding multiple acquired resistance genes including carbapenemase gene blaOXA-58. Point mutations and acquired resistance genes were identified which were associated with different drug resistance phenotypes. To our knowledge, this is the first detailed phenotypic and genomic characterization of PDR A. pittii causing severe infections in clinical settings. Findings from us and others indicate that A. pittii could serve as a reservoir for carbapenem determinants. The emergence of such a superbug could pose a serious threat to public health. Further surveillance of PDR A. pittii strains and implementation of stricter control measures are needed to prevent this emerging pathogen from further disseminating in hospital settings and the community.

A multidrug-resistant Vibrio alginolyticus isolate recovered from a shrimp sample with reduced carbapenem susceptibility produced a novel metallo-β-lactamase (MBL), VAM-1. That carbapenemase shared 67% to 70% amino acid identity with several VMB family subclass B1 MBLs, which were recently reported among some marine bacteria including Vibrio , Glaciecola , and Thalassomonas . The bla VAM-1 gene was located in a novel conjugative plasmid, namely, pC1579, and multiple copies of bla VAM-1 via an unusual mechanism of gene amplification were detected in pC1579.

Objectives To test whether antibiotics of different functional categories exhibit differential potential in promoting transmission of MDR-encoding plasmids among members of the gut microbiome. Methods Rats inoculated with blaNDM-1-bearing Klebsiella pneumoniae were subjected to treatment with different types of antibiotics. The structural changes in the gastrointestinal (GI) tract microbiome were determined by 16S rRNA sequencing and analysis. In addition, the efficiency of transmission of blaNDM-1-bearing plasmids to different subtypes of GI tract Escherichia coli was also confirmed in vitro. Results We showed that drugs that are commonly used to treat Gram-negative bacterial infections, such as ampicillin and amoxicillin, could enrich both carbapenem-resistant Enterobacteriaceae (CRE) and antibiotic-susceptible E. coli in the GI tract, thereby promoting transmission of the blaNDM-1-bearing plasmid in the gut microbiome. In contrast, meropenem was found to minimize the population of CRE in the gut microbiome, hence treatment with this drug exhibited drastically lower potential to promote transmission of the blaNDM-1-bearing plasmid to the recipient strains. We further showed that an increased population size of Proteobacteria due to a suppressive effect on Firmicutes is a key factor in enhancing the efficiency of transmission of the blaNDM-1-bearing plasmid and hence dissemination of carbapenem-resistant strains. Conclusions This study depicted for the first time the effect of different antibiotics on the structure of the rat GI tract microbiome, which in turn determined the pattern and rate of transmission of the blaNDM-1-bearing plasmid. Such findings can help establish new guidelines for prudent antibiotic usage to minimize the chance of dissemination of mobile resistance elements among members of the GI tract microbiome.

Klebsiella pneumoniae is increasingly being regarded as a reservoir of diverse antibiotic resistance genes and a pathogen that causes severe infections in both the hospital and the community. In this study, we performed molecular characterization of a carbapenem-resistant and highly virulent K. pneumoniae strain recovered from a hospital patient. The virulence-encoding genes rmpA2 and iucABCDiutA were found to be located in the chromosome and are flanked by IS26 elements. These chromosomally located virulence genes, if not incurring fitness costs, are expected to be much more stable than plasmid-located genes. Detailed analysis of the fragment in which these virulence genes are located showed that the fragment can readily form a circular intermediate that may promote integration of this virulence-encoding fragment into various plasmid backbones and other chromosomal regions. Findings in this work provide new insights into mechanisms of transmission of virulence-encoding genes in K. pneumoniae. IMPORTANCE This study reported for the first time and characterized in detail the genetic features of a mobile virulence-encoding fragment located in the chromosome of a clinical virulent K. pneumoniae strain and revealed the occurrence of a transposition event mediated by IS26. This genetic structure could mediate the transposition of the virulence-encoding fragment into various plasmid backbones and chromosomes through formation of a circular intermediate. Therefore, findings in this work provide important insights into the transmission mechanisms of mobile virulence profiles in K. pneumoniae strains and lay the foundation for devising effective intervention approaches aimed at preventing the dissemination of these virulence-encoding elements.

Objective The emergence of multidrug-resistant (MDR) and hypervirulent Klebsiella pneumoniae (hvKP) facilitates simultaneous dissemination of virulence and resistance in a single event, which poses serious threat to public health. Methods This study characterized the multidrug-resistant and moderately virulent ST11 K64 K. pneumoniae strain HB25-1 from a clinical case with microbiological and genomic approaches. Plasmids from strain HB25-1 were subjected to whole plasmid sequencing using both the Illumina NextSeq 500 sequencing platform and Nanopore MinION sequencer platforms. Klebsiella pneumoniae HB25-1 was subjected to a conjugation experiment and Galleria mellonella infection model to evaluate the transmission and virulence potential. Results We report the emergence of an ST11, serotype K64 K. pneumoniae isolate, which is resistant to third-generation cephalosporin and exhibited a moderate level of virulence. WGS revealed that this strain harboured a plasmid, pHB25-1, which carried multidrug resistance genes (blaDHA-1, qnrB4, dfrA12, aadA2, sul1, aac(3)-lld, blaTEM-1, mph(E)) and virulence-encoding genes (the regulator of mucoid phenotype A gene rmpA2 and the aerobactin gene cluster iutAiucABCD). Genomic analysis indicated that pHB25-1 was formed through co-integration of structural regions located in two different plasmids, enabling it to encode both resistance and virulent phenotypes. Conclusion Findings in this study provide evidence of active plasmid evolution in K. pneumoniae and suggest that surveillance of multidrug-resistant and hypervirulent K. pneumoniae is urgently needed.

We report the identification of a carbapenem-resistant, hypervirulent Klebsiella pneumoniae (hvKp) strain which produced the carbapenemase VIM-1. Genomic analysis showed that the strain belonged to sequence type ST23 and serotype K1, a major hvKp clone, and harbored three resistance-encoding plasmids. Among them, a bla VIM-1 -bearing plasmid was found to possess a mosaic structure presumably generated by multiple gene mobilization events.

This study aims to investigate and compare the complete nucleotide sequences of the multidrug resistance plasmids pVb0267 and pVb0499, which were recovered from foodborne Vibrio parahaemolyticus isolates, and analyze the genetic environment of blaCTX–M–55 to provide insight into the dissemination mechanisms of this resistance element. Analysis of the sequences of plasmids pVb0267 (166,467 bp) and pVb0499 (192,739 bp) revealed that the backbones of these two plasmids exhibited a high degree of similarity with pR148, a recognized type 1a IncC plasmid recovered from Aeromonas hydrophila (99% identity). The resistance genes, found in both plasmids, included qacH, aadB, arr2, blaOXA–10, aadA1, sul1, tet(A), and blaCTX–M–55, which were mostly arranged in a specific region designated ARI-A. Plasmid pVb0499 was found to possess a larger size of ARI-A than pVb0267, which lacked a mer determination region, a qnr A segment, an aacC3 gene and several mobility-encoding genes. Comparative analysis of resistance island (RI) of these plasmids and others revealed the potential evolution route of these RI sequences. In conclusion, plasmids harboring the blaCTX–M–55 gene has been recovered in Vibrio parahaemolyticus strains of food origin. It is alarming to find that IncC plasmids harboring resistance islands are disseminating in aquatic bacterial strains. The continuous evolution of resistance genes in conjugative plasmid in aquatic bacteria could be due to bacterial adaption to aquaculture environment, where antibiotics were increasingly used.

This report describes the first detection of a bla VEB-2 gene in a Vibrio parahaemolyticus strain isolated from a shrimp sample. The bla VEB-2 gene was carried on a novel Inc-type plasmid that was likely to have originated from aquatic organisms, as indicated by a comparison with other known genetic elements in the GenBank database. However, the plasmid contains resistance elements usually harbored by members of the family Enterobacteriaceae , suggesting that gene transfer events occurred and contributed to the formation of this multidrug resistance-encoding plasmid.

The rapid dissemination of non-conjugative virulence plasmids among non-K1/K2 types of Klebsiella pneumoniae poses an unprecedented threat to human health, yet the underlying mechanisms governing dissemination of such plasmids is unclear. In this study, a novel 68 581 bp IncFIA plasmid is discovered that can be fused to a hypervirulence-encoding plasmid to form a hybrid conjugative virulence plasmid in conjugation experiments; such fusion events involve homologous recombination between a 241 bp homologous region located in each of the two plasmids. The fusion hypervirulence-encoding plasmid can be conjugated to both classic and blaKPC-2 -bearing carbapenem-resistant K. pneumoniae strains through conjugation, enabling such strains to acquire the ability to express the hypervirulence phenotype. Dissemination of this fusion virulence plasmid will impose an enormous burden on current efforts to control and treat infections caused by multidrug resistant and hypervirulent K. pneumoniae.

Vibrio alginolyticus is a Gram-negative halophilic and mesophilic bacterium, particularly associated with severe epidemic vibriosis, which causes high mortality in marine animals, including fish, shellfish, and shrimp ([1][1]). The carbapenemase NDM-1 has been found mainly in Enterobacteriaceae

Objectives To investigate the genetic features of the blaVIM-1 gene first detected in a cephalosporin-resistant Vibrio alginolyticus isolate, Vb1978. Methods The MICs of V. alginolyticus strain Vb1978 were determined, and the β-lactamases produced were screened and analysed using conjugation, S1-PFGE and Southern blotting. The complete sequence of the blaVIM-1-encoding plasmid was also obtained using the Illumina and MinION sequencing platforms. Results V. alginolyticus strain Vb1978, isolated from a retail shrimp sample, was resistant to cephalosporins and exhibited reduced susceptibility to carbapenems. A novel blaVIM-1-carrying conjugative plasmid, designated pVb1978, was identified in this strain. Plasmid pVb1978 had 50 001 bp and comprised 59 predicted coding sequences (CDSs). The plasmid backbone of pVb1978 was homologous to those of IncP-type plasmids, while its replication region was structurally similar to non-IncP plasmids. The blaVIM-1 gene was found to be carried by the class 1 integron In70 and associated with a defective Tn402-like transposon. Conclusions A novel blaVIM-1-carrying conjugative plasmid, pVb1978, was reported for the first time in V. alginolyticus, which warrants further investigation in view of its potential pathogenicity towards humans and widespread occurrence in the environment.

Animal and human gastrointestinal tract is the key site from which resistant bacterial pathogens emerge. In this work, we tested whether antibiotics of different functional categories exhibited differential potential in promoting transmission of multidrug resistance-encoding plasmids among the gut microflora by measuring the population size of both donor and potential recipient strains before, during and after the treatment process. In this study, we showed that drugs that are commonly used to treat Gram negative bacterial infections such as ampicillin and amoxicillin could enrich both carbapenem resistant enterobacteriaceae (CRE) and antibiotic-susceptible E. coli in the gastrointestinal tract, thereby promoting transmission of the blaNDM-1-bearing plasmid in the gut microbiome. In contrast, meropenem was found to minimize the population of CRE in the gut microbiome, hence treatment with this drug exhibited drastically lower potential to promote transmission of the blaNDM-1-bearing plasmid to the recipient strains. We further showed that whether an antibiotic enriches or suppresses the population size of donor and recipient strains in the gastrointestinal tract is actually dependent on the relative inhibitory effects of the drug on the firmicutes or proteobacteria, and that an increased population size of proteobacteria due to a higher suppressive effect on firmicutes is a key factor in enhancing the efficiency of transmission of the blaNDM-1-bearing plasmid and hence dissemination of carbapenem resistant strains. In conclusion, this study identified and characterized the factors that affected the transmission of MDR plasmid in gut microbiome and its underlying mechanisms. Such findings can help establish new guidelines for prudent antibiotic usage to minimize the chance of dissemination of resistance mobile elements among the GI tract microflora. Funding Statement: The research was supported by the Collaborative Research Fund (C5026-16G) of the Hong Kong Research Grant Council and the Health and Medical Research Fund (HMRF) of the Food and Health Bureau, the Government of the Hong Kong SAR (14130402 to SC). Declaration of Interests: All authors declared no conflict of interests. Ethics Approval Statement: The experimental protocol was approved by the Research Animal Care and Use Committee of the Hong Kong Polytechnic University.