Salmonella enterica remains an important foodborne pathogen in all regions of the world, with Typhimurium as one of the most frequent serotypes causing foodborne disease. However, the past two decades have seen a rapid worldwide emergence of a new Salmonella serotype, namely monophasic variant of S. Typhimurium, whose antigenic formula is 1,4,[5],12:i:-. It has become one of the 2–5 most common Salmonella serotypes responsible for animal and human infections in different regions. The global epidemic of monophasic S. 1,4,[5],12:i:- has mainly been characterized by an increase in multidrug-resistant S. 1,4,[5],12:i:- isolated in Europe since 1997. The unexpected link to swine has escalated monophasic S. Typhimurium infections to the status of a global public health emergency. The large-scale application of whole genome sequencing (WGS) in the last 10 years has revealed the phylogenetic associations of the bacterium and its antimicrobial resistance (AMR) genes. Local and global transmission reconstructed by WGS have shown that different clones have emerged following multiple independent events worldwide, and have elucidated the role of this zoonotic pathogen in the spread of AMR. This article discusses our current knowledge of the global ecology, epidemiology, transmission, bacterial adaptation, and evolution of this emerging Salmonella serotype.

In this study, we characterized five co-expressing ESBL and MCR-1 Escherichia coli recovered from food, food-producing animals and companion animals in China. Antimicrobial susceptibility tests, conjugation experiments, and plasmid typing were performed. Whole genome sequencing (WGS) was also undertaken for all five isolates using either PacBio RS II or Illumina HiSeq 2500 platforms. The cefotaxime and colistin resistance encoded by blaCTX-M and mcr-1 genes respectively was transferable by conjugation either together or separately for all five strains. Interestingly, the ESBL and mcr-1 genes could be co-selected by cefotaxime, while the colistin only selected the mcr-1-carrying plasmids during the conjugation experiments. Five E. coli sequence types were detected: ST88, ST93, ST602, ST162, and ST457. Although diverse plasmid profiles were identified, IncI2, IncFIB and IncFII plasmid types were predominant. These five clonally unrelated isolates harbored the mcr-1 gene located on similar plasmid backbones, which showed high nucleotide similarity to plasmid pHNSHP45. The mcr-1 gene can be disseminated via multiple mobile elements (with or without ISApl1) and be co-transmitted with blaCTX-M genes through IncI2 plasmids. Characterization of these co-existence ESBL and mcr-1 isolates extends our understanding on the dissemination of these resistance markers among bacteria of diverse origins.

As the spread of antimicrobial resistance genes becomes an increasing global threat, improved understanding of genetic structure and transferability of the resistant plasmids becomes more critical. The newly description of several plasmid-mediatedtet(X) variant genes, tet(X3), tet(X4) and tet(X5), poses a considerable risk for public health. This study aimed to investigate the recombination event that occurred during the conjugation process of a tet(X4)-bearing plasmid. A Tet(X4)-producing Escherichia coli isolate, 2019XSD11, was subjected to susceptibility testing, S1-PFGE and whole genome sequencing. The genetic features of plasmids and the recombination event were analyzed by sequence comparison and annotation. We performed electrotransformation assay to further test the transferability of the tet(X4)-bearing plasmid. A novel type of fusiontet(X4)-bearing plasmid was discovered from the transconjugant, plasmid p2019XSD11-TC2-284 (∼280-kbp). The sequence of this plasmid consisted of a hybrid episome of two plasmids p2019XSD11-190 (∼190-kbp) harboring tet(X4) and p2019XSD11-92 (∼92-kbp) harboring blaCTX-M-55 originated from 2019XSD11. The two plasmids were concatenated by IS26 elements. Analyses of the genetic constitution of the plasmids essential for transmission showed the plasmid p2019XSD11-190 lacked an intact type IV secretion system. Beyond this, the origin of transfer region and relaxase genes in plasmid p2019XSD11-190 had no sequence similarity with those in plasmid p2019XSD11-92. The fusion of the two plasmids probably formed through IS26 homologous recombination. Such recombination events presumably play an important role in the dissemination of the tet(X4). Molecular surveillance of tet(X) variant genes and genetic structures warrants further investigation to evaluate the underlying public health risk.

Foodborne diseases are important causes of illness and death. The first estimates of their burden were published by WHO in 2015. We updated WHO estimates of the global, regional, subregional, and national foodborne disease burden caused by 42 infectious and chemical hazards in 2021, including time trends for 2000-21. We provide a high-level summary of foodborne disease burden, expressed as incidence, deaths, and disability-adjusted life-years (DALYs). Data for burden estimation were provided from a WHO-commissioned series of systematic reviews on the incidence, aetiology, sequelae, and case fatality or mortality of the hazards. Data were analysed using hierarchical meta-regression modelling with geographical clustering and a global linear time trend, disease-specific computational models, and uncertainty propagation through Monte Carlo simulations to calculate 95% uncertainty intervals. Attribution to foodborne transmission was principally based on a structured expert judgement process. Economic impact was measured as lost productivity. For 2021, foodborne transmission of the 42 hazards caused 866 million (95% uncertainty interval 680-1090) illnesses, 1·52 million (0·783-2·51) deaths, and 57·1 million (39·4-81·1) DALYs. Inorganic arsenic, lead, and non-typhoidal Salmonella enterica (diarrhoeal and invasive disease) resulted in the most DALYs. The greatest burden of foodborne disease was in the African and South-East Asia regions. The incidence in children younger than 5 years was 2·7 times higher than in people aged 5 years or older, resulting in 4·3 times the rate of DALYs. The total burden from all hazards decreased over time. In 2021, these 42 hazards resulted in productivity losses of US$310 billion in nominal terms, and US$647 billion after adjusting for purchasing power parity. Foodborne diseases causes a burden similar to that from tuberculosis, HIV and AIDS, or malaria. The high burden of both communicable and non-communicable foodborne diseases requires countries to prioritise developing strategies to improve the safety of the food supply. WHO.

The spread of polymyxin-resistant Enterobacteriaceae poses a significant threat to public health and challenges the therapeutic options for treating infections on a global level. In this study, mcr-1 -bearing ST10 E. coli was isolated from pigs, pork, and humans simultaneously, which demonstrated that ST10 E. coli was an important vehicle for the spread of mcr-1 among animals, foods, and humans.