Cotransfer of resistance to cephalosporins, colistin, and fosfomycin mediated by an IncHI2/pSH16G4928-like plasmid in ESBL-producing monophasic Salmonella Typhimurium strains of pig origin.

AIMS: To assess the co-transmission risk of phenotypic and genetic resistance to cephalosporins, colistin, and fosfomycin in Salmonella strains collected along the whole pork production chain. METHODS AND RESULTS: From a total of 107 Salmonella isolates from samples collected in pig slaughterhouses and markets, 15 ESBL-producing Salmonella strains resistant to cefotaxime were identified by broth microdilution method and clavulanic acid inhibition test, including 14 monophasic Salmonella Typhimurium strains and one Salmonella Derby strain. Whole genome sequence analysis showed that nine monophasic S. Typhimurium strains coresistant to colistin and fosfomycin carried the resistance genes blaCTX-M-14, mcr-1, and fosA3. Conjugational transfer tests demonstrated that the phenotypic and genetic resistance to cephalosporins, colistin, and fosfomycin could cotransfer back and forth between Salmonella and Escherichia coli via an IncHI2/pSH16G4928-like plasmid. CONCLUSIONS: This study reports the cotransmission of phenotypic and genetic resistance to cephalosporins, colistin, and fosfomycin via an IncHI2/pSH16G4928-like plasmid in Salmonella strains of animal origin, giving an alarm for the prevention of the development and spread of bacterial multidrug resistance.

Adjustable diffusion enhancement of water molecules in a nanoscale water bridge.

The emergence of nanofluidics in the last few decades has led to the development of various applications such as water desalination, ultrafiltration, osmotic energy conversion, etc. In particular, understanding water molecule transport in nanotubes is of importance for designing novel ultrafiltration and filtering devices. In this paper, we use an electric field to form a nanoscale water bridge as an artificial water channel to connect two separate disjoint nanotubes by molecular dynamics simulations. The extended length of the water bridge under different electric field strengths could adjust the diffusion process of the water molecules crossing the two disjoint nanotubes and the diffusion coefficients could be remarkably enhanced up to 4 times larger than the value in bulk water. By analyzing the structure of the water bridge, it is found that the diffusion enhancement originates from the strengthened interactions and the increase of hydrogen bonds between the water molecules due to the restrained reorientation from the external electric field. Our result provides a promising insight for realizing an efficient mass transport between various disjoint nanochannels.

Prevalence and Characterization of Salmonella in Three Typical Commercial Pig Abattoirs in Wuhan, China.

This study was designed to investigate the prevalence and characteristics of Salmonella in three Chinese pig abattoirs (A, B, and C) in Wuhan city in 2016. Four types of pig samples were collected and cultured for Salmonella. Salmonella was detected from 329 samples among the 1440 tested (22.9%). There was no significant difference in the overall prevalence between the first visit and the second visit and among the three abattoirs. Rectal swabs (RS) exhibited a significantly higher prevalence than carcass swabs and pork. A total of 177 isolates were characterized by multilocus sequence typing, serotyping, and antimicrobial susceptibility testing. Among 17 sequence types (STs) and 13 serotypes detected, ST40, ST469, and ST34, corresponding to serovars Derby, Rissen, and Typhimurium, respectively, were predominant. The isolates from different abattoirs exhibited diverse ST distribution. The minimum inhibitory concentrations were determined using the microdilution broth method. Resistance to at least one of the antimicrobials was observed for 96.6% of the strains (171/177), and multidrug resistant (MDR) isolates accounted for 75.7% of the strains (134/177). The highest resistance proportion was for tetracycline (92.7%), and the lowest was for cefotaxime (14.1%). The isolates from abattoir A exhibited a significantly lower MDR proportion than those from other abattoirs (p < 0.05). The isolates recovered from RS and pork samples exhibited significantly higher MDR proportions than those recovered from carcass swab samples. Notably, among three predominant STs of isolates, the ST34 isolates showed the highest MDR proportion. In view of the high Salmonella prevalence and antimicrobial resistance, great attention must be paid to the monitoring and controlling of Salmonella in a full pork production chain.

Co-infection with porcine bocavirus and porcine circovirus 2 affects inflammatory cytokine production and tight junctions of IPEC-J2 cells.

Porcine bocavirus (PBoV) has a high prevalence in both healthy and diseased swine around the world. It was recently reported that PBoV and porcine circovirus type 2 (PCV2)-which contribute to porcine diarrheal disease-have a high rate of co-infection. To clarify the pathogenesis of PBoV, we examined the co-infection rate and effects of these two pathogens in IPEC-J2 porcine intestinal enterocytes. Both single and co-infection had cytopathic effects in IPEC-J2 cells. The apoptosis and proliferation rates of cells infected with both viruses did not differ significantly from those of cells infected with either one alone. PBoV and PCV2 induced the upregulation of inflammatory cytokines and the downregulation of the tight junction proteins occludin and claudin 1 in the early stage of infection, leading to destruction of epithelial barrier integrity and enhanced cytotoxicity. These findings provide insight into the pathogenic mechanisms of PBoV and PCV2 and a basis for developing effective strategies to prevent the spread of gastrointestinal diseases in pigs and other livestock.