Draft Genome Sequences of 12 Leuconostoc carnosum Strains Isolated from Cooked Ham Packaged in a Modified Atmosphere and from Fresh Sausages

Leuconostoc carnosum is a lactic acid bacterium that preferentially colonizes meat. In this work, we present the draft genome sequences of 12 Leuconostoc carnosum strains isolated from modified-atmosphere-packaged cooked ham and fresh sausages. Three strains harbor bacteriocin genes

Comparative genomics of Leuconostoc carnosum

Leuconostoc carnosum is a known colonizer of meat-related food matrices. It reaches remarkably high loads during the shelf life in packaged meat products and plays a role in spoilage, although preservative effects have been proposed for some strains. In this study, the draft genomes of 17 strains of L. carnosum (i.e., all the strains that have been sequenced so far) were compared to decipher their metabolic and functional potential and to determine their role in food transformations. Genome comparison and pathway reconstruction indicated that L. carnosum is a compact group of closely related heterofermentative bacteria sharing most of the metabolic features. Adaptation to a nitrogen-rich environment, such as meat, is evidenced by 23 peptidase genes identified in the core genome and by the autotrophy for nitrogen compounds including several amino acids, vitamins, and cofactors. Genes encoding the decarboxylases yielding biogenic amines were not present. All the strains harbored 1-4 of 32 different plasmids, bearing functions associated to proteins hydrolysis, transport of amino acids and oligopeptides, exopolysaccharides, and various resistances (e.g., to environmental stresses, bacteriophages, and heavy metals). Functions associated to bacteriocin synthesis, secretion, and immunity were also found in plasmids. While genes for lactococcin were found in most plasmids, only three harbored the genes for leucocin B, a class IIa antilisterial bacteriocin. Determinants of antibiotic resistances were absent in both plasmids and chromosomes.Published versio

Single-Cell Oral Delivery Platform for Enhanced Acid Resistance and Intestinal Adhesion

Oral delivery of cells, such as probiotics and vaccines, has proved to be inefficient since cells are generally damaged in an acidic stomach prior to arrival at the intestine to exert their health benefits. In addition, short retention in the intestine is another obstacle which affects inefficiency. To overcome these obstacles, a cell-in-shell structure was designed with pH-responsive and mucoadhesive properties. The pH-responsive shell consisting of three cationic layers of chitosan and three anionic layers of trans-cinnamic acid (t-CA) was made via layer-by-layer (LbL) assembly. t-CA layers are hydrophobic and impermeable to protons in acid, thus enhancing cell gastric resistance in the stomach, while chitosan layers endow strong interaction between the cell surface and the mucosal wall which facilitates cell mucoadhesion in the intestine. Two model cells, probiotic L. rhamnosus GG and dead Streptococcus iniae, which serve as inactivated whole-cell vaccine were chosen to test the design. Increased survival and retention during oral administration were observed for coated cells as compared with naked cells. Partial removal of the coating (20–60% removal) after acid treatment indicates that the coated vaccine can expose its surface immunogenic protein after passage through the stomach, thus facilitating vaccine immune stimulation in the intestine. As a smart oral delivery platform, this design can be extended to various macromolecules, thus providing a promising strategy to formulate oral macromolecules in the prevention and treatment of diseases at a cellular level

Whole-genome sequencing of nontyphoidal Salmonella enterica isolates obtained from various meat types in Ghana

Here, we report the draft genome sequences of 16 nontyphoidal Salmonella enterica isolates obtained from locally produced meats in Tamale, Ghana, which are commonly consumed by most natives as an important protein source. The draft genomes will help provide a molecular snapshot of Salmonella enterica isolates found in these retail meats in Tamale.Published versio

Conjugative IncX1 plasmid harboring colistin resistance gene mcr-5.1 in Escherichia coli isolated from chicken rice retailed in Singapore

Colistin is regarded as one of the last-resort antimicrobials for treatment of Gram-negative bacterial infections (1). Several cases of plasmid-borne colistin resistance genes mcr-1, mcr-3-like, and mcr-4.2 in clinical Enterobacteriaceae isolates, including Escherichia coli, have been reported in Singapore (2-4). However, the mcr-5 gene has not been reported in clinical isolates in Singapore. Previously, we reported the antimicrobial resistance (AMR) genotype and phenotype of E. coli SGEHI2010ENV103 isolates from ready-to-eat food in Singapore and documented the first isolate carrying mcr-5.1 in Singapore (5). In this study, we further analyzed this isolate. Here, we report the first complete nucleotide sequence of a transferable plasmid harboring mcr-5.1 in E. coli isolated from ready-to-eat chicken rice in Singapore. (Chicken rice is a common dish in Singapore which is composed of cooked chicken and seasoned rice, served with sauce and cucumber garnishes).Published versio

Phenotypic and genotypic characterization of antimicrobial resistant Escherichia coli isolated from ready-to-eat food in Singapore using disk diffusion, broth microdilution and whole genome sequencing methods

This study aimed to determine the antimicrobial resistance (AMR) profiles of Escherichia coli isolated from ready-to-eat (RTE) food sold in retail food premises in Singapore. In this study, a total of 99 E. coli isolates from poultry-based dishes (n = 77) and fish-based dishes (n = 22), obtained between 2009 and 2014, were included for disk diffusion testing. Of the 99 isolates, 24 (24.2%) were resistant to at least one antimicrobial agent. These isolates were then subjected to broth microdilution testing against 33 antimicrobial agents, including beta-lactams, aminoglycosides, tetracycline, fluoroquinolones and polymyxin E (also known as colistin) to determine the minimum inhibitory concentration (MIC) of isolates. Finally, whole genome sequence (WGS) was carried out on the strains in order to correlate resistant phenotypes to putative antimicrobial-related genes. Of the 24 isolates, 15 (62.5%) were found to be resistant to three or more classes of antimicrobials and thus were defined as multidrug resistant strains. Two isolates (8.3%) were confirmed as Extended-Spectrum Beta-Lactamase (ESBL)-producing E. coli by double-disk synergy test. Based on WGS data, online analysis tool ResFinder detected 7 classes of AMR genes and resistance-related chromosomal point mutations in 19 of the 24 E. coli isolates. Prediction of AMR using WGS data was evaluated for six antimicrobials including ampicillin, chloramphenicol, colistin, fluoroquinolones, tetracycline and trimethoprim. By analyzing the WGS contigs using BLASTn and KmerFinder, quinolone resistance genes, ESBL genes and transferable colistin resistance gene mcr-1 and mcr-5 were determined to be located on plasmids, which could pose a greater risk of AMR transfer among bacteria. Mutations were detected in four isolates within genes previously shown to confer resistance to quinolones (gyrA and parE) and tetracycline (rrsB). This study showed the presence of AMR E. coli isolates in RTE food, and raises a concern on the possible transmission of AMR bacteria from food to humans.Nanyang Technological UniversityNational Environmental Agency (NEA)This study was supported by the National Environment Agency (NEA) and Nanyang Technological University Research Initiative. Authors would like to thank Man Ling Chau and Ramona Alikiiteaga Gutiérrez for manuscript vetting, and thank Food Hygiene team members in the Environmental Health Institute of NEA for providing isolates and experimental guidance

Occurrence and antimicrobial resistance traits of Escherichia coli from wild birds and rodents in Singapore

Antimicrobial resistance (AMR) in Escherichia coli (E. coli) poses a public health concern worldwide. Wild birds and rodents, due to their mobility, are potential vehicles for transmission of AMR bacteria to humans. Ninety-six wild birds’ faecal samples and 135 rodents’ droppings samples were collected and analysed in 2017. Forty-six E. coli isolates from wild birds and rodents were subjected to AMR phenotypic and genotypic characterisation. The proportion of E. coli isolates resistant to at least one of the antimicrobials tested from wild birds (80.8%) was significantly higher than that of isolates from rodents (40.0%). The proportion of E. coli isolates resistant to each antimicrobial class for wild birds was 3.8% to 73.1% and that for rodents was 5.0% to 35.0%. Six out of 26 E. coli isolates from wild birds (23.1%) and two out of 20 (10.0%) isolates from rodents were multi-drug resistant (MDR) strains. These MDR E. coli isolates were detected with various antimicrobial resistance genes such as blaTEM-1B and qnrS1 and could be considered as part of the environmental resistome. Findings in this study suggested that wild birds and rodents could play a role in disseminating antimicrobial resistant E. coli, and this underscores the necessity of environment management and close monitoring on AMR bacteria in wild birds and rodents to prevent spreading of resistant organisms to other wildlife animals and humans.Nanyang Technological UniversityNational Environmental Agency (NEA)Published versionThe authors thank the Rodent Control Unit, of the Central Regional Office, National Environment Agency for the collection of rodent droppings. In addition, the authors thank collaborators from the National Parks Board Singapore, and the Wildlife Reserves Singapore who provided the wild birds samples (carcasses). Lastly, the authors thank Singapore Centre for Environmental Life Sciences Engineering, Nanyang Technological University for providing whole genome sequencing services

A Glycosylated Cationic Block Poly(β‐peptide) Reverses Intrinsic Antibiotic Resistance in All ESKAPE Gram‐Negative Bacteria

Carbapenem‐resistant Gram‐negative bacteria (GNB) are heading the list of pathogens for which antibiotics are the most critically needed. Many antibiotics are either unable to penetrate the outer‐membrane or are excluded by efflux mechanisms. Here, we report a cationic block β‐peptide (PAS8‐b‐PDM12) that reverses intrinsic antibiotic resistance in GNB by two distinct mechanisms of action. PAS8‐b‐PDM12 does not only compromise the integrity of the bacterial outer‐membrane, it also deactivates efflux pump systems by dissipating the transmembrane electrochemical potential. As a result, PAS8‐b‐PDM12 sensitizes carbapenem‐ and colistin‐resistant GNB to multiple antibiotics in vitro and in vivo. The β‐peptide allows the perfect alternation of cationic versus hydrophobic side chains, representing a significant improvement over previous antimicrobial α‐peptides sensitizing agents. Together, our results indicate that it is technically possible for a single adjuvant to reverse innate antibiotic resistance in all pathogenic GNB of the ESKAPE group, including those resistant to last resort antibiotics.Accepted versio