One of the currently most relevant resistance mechanisms in Enterobacteriaceae is the production of enzymes that lead to modern expanded-spectrum cephalosporin and even carbapenem resistance, mainly extended-spectrum ␤-lactamases (ESBLs) and carbapenemases. A worrisome aspect is the spread of ESBL and carbapenemase producers into the environment. The aim of the present study was to assess the occurrence of ESBL-and carbapenemase-producing Enterobacteriaceae and to further characterize ESBL-and carbapenemase-producing Enterobacteriaceae in rivers and lakes in Switzerland. ESBL-producing Enterobacteriaceae were detected in 21 (36.2%) of the 58 bodies of water sampled. One river sample tested positive for a carbapenemase-producing Klebsiella pneumoniae subsp. pneumoniae strain. Seventy-four individual strains expressing an ESBL phenotype were isolated. Species identification revealed 60 Escherichia coli strains, seven Klebsiella pneumoniae subsp. pneumoniae strains, five Raoultella planticola strains, one Enterobacter cloacae strain, and one Enterobacter amnigenus strain. Three strains were identified as SHV-12 ESBL producers, and 71 strains carried genes encoding CTX-M ESBLs. Of the 71 strains with CTX-M ESBL genes, 8 isolates expressed CTX-M-1, three produced CTX-M-3, 46 produced CTX-M-15, three produced CTX-M-55, one produced CTX-M-79, six produced CTX-M-14, and four produced CTX-M-27. Three of the four CTX-M-27 producers belonged to the multiresistant pandemic sequence type E. coli B2:ST131 that is strongly associated with potentially severe infections in humans and animals.

SummaryWe report isolation and characterization of the novel T4-like Salmonella bacteriophage vB_SenM-S16. S16 features a T-even morphology and a highly modified 160 kbp dsDNA genome with 36.9 mol % G+C, containing 269 putative coding sequences and three tRNA genes. S16 is a virulent phage, and exhibits a maximally broad host range within the genus Salmonella, but does not infect other bacteria. Synthesis of functional S16 full-length long tail fibre (LTF) in Escherichia coli was possible by coexpression of gp37 and gp38. Surface plasmon resonance analysis revealed nanomolar equilibrium affinity of the LTF to its receptor on Salmonella cells. We show that OmpC serves as primary binding ligand, and that S16 adsorption can be transferred to E. coli by substitution of ompC with the Salmonella homologue. S16 also infects 'rough' Salmonella strains which are defective in lipopolysaccharide synthesis and/or its carbohydrate substitution, indicating that this interaction does not require an intact LPS structure. Altogether, its virulent nature, broad host range and apparent lack of host DNA transduction render S16 highly suitable for biocontrol of Salmonella in foods and animal production. The S16 LTF represents a highly specific affinity reagent useful for cell decoration and labelling, as well as bacterial immobilization and separation.

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Objectives: The aim of this study was to characterize a collection of 520 Salmonella enterica serovar Infantis strains isolated from food (poultry meat), human infections and environmental sources from the years 2010, 2013 and 2015 in Switzerland.Methods: We performed antimicrobial susceptibility testing and pulsed-field gel electrophoresis (PFGE) analysis on all 520 S. Infantis isolates, and whole genome sequencing (WGS) on 32 selected isolates.Results: The majority (74.8%) of the isolates was multidrug resistant (MDR). PFGE analysis revealed that 270 (51.9%) isolates shared an identity of 90%. All isolates subjected to WGS belonged to sequence type (ST) 32 or a double-locus variant thereof (one isolate). Seven (21.9%) of the sequenced isolates were phylogenetically related to the broiler-associated clone B that emerged in Hungary and subsequently spread within and outside of Europe. In addition, three isolates harboring blaCTX-M-65 on a predicted large (∼320 kb) plasmid grouped in a distinct cluster.Conclusion: This study documents the presence of the Hungarian clone B and related clones in food and human isolates between 2010 and 2015, and the emergence of a blaCTX-M-65 harboring MDR S. serovar Infantis lineage.

Fruiting body lectins have been proposed to act as effector proteins in the defense of fungi against parasites and predators. The Marasmius oreades agglutinin (MOA) is a Gal␣1,3Gal/ GalNAc-specific lectin from the fairy ring mushroom that consists of an N-terminal ricin B-type lectin domain and a C-terminal dimerization domain. The latter domain shows structural similarity to catalytically active proteins, suggesting that, in addition to its carbohydrate-binding activity, MOA has an enzymatic function. Here, we demonstrate toxicity of MOA toward the model nematode Caenorhabditis elegans. This toxicity depends on binding of MOA to glycosphingolipids of the worm via its lectin domain. We show further that MOA has cysteine protease activity and demonstrate a critical role of this catalytic function in MOA-mediated nematotoxicity. The proteolytic activity of MOA was dependent on high Ca 2؉ concentrations and favored by slightly alkaline pH, suggesting that these conditions trigger activation of the toxin at the target location. Our results suggest that MOA is a fungal toxin with intriguing similarities to bacterial binary toxins and has a protective function against fungivorous soil nematodes.

BackgroundThe emergence and worldwide spread of carbapenemase-producing Enterobacteriaceae is of great concern to public health services. The aim of this study was to investigate the occurrence of carbapenemase-producing Enterobacteriaceae in fresh vegetables and spices imported from Asia to Switzerland.FindingsTwenty-two different fresh vegetable samples were purchased in March 2015 from different retail shops specializing in Asian food. The vegetables included basil leaves, bergamont leaves, coriander, curry leaves, eggplant and okra (marrow). Samples had been imported from Thailand, the Socialist Republic of Vietnam and India. After an initial enrichment-step, carbapenemase-producing Enterobacteriaceae were isolated from two carbapenem-containing selective media (SUPERCARBA II and Brilliance CRE Agar). Isolates were screened by PCR for the presence of blaKPC, blaNDM, blaOXA-48-like and blaVIM. An OXA-181-producing Klebsiella variicola was isolated in a coriander sample with origin Thailand/Vietnam. The blaOXA-181 gene was encoded in a 14′027 bp region flanked by two IS26-like elements on a 51-kb IncX3-type plasmid.ConclusionsThe results of this study suggest that the international production and trade of fresh vegetables constitute a possible route for the spread of carbapenemase-producing Enterobacteriaceae. The presence of carbapenemase-producing organisms in the food supply is alarming and an important food safety issue.

Objectives: The purpose of this study was to characterize sets of extended-spectrum β-lactamases (ESBL)-producing Enterobacteriaceae collected longitudinally from different flocks of broiler breeders, meconium of 1-day-old broilers from theses breeder flocks, as well as from these broiler flocks before slaughter.Methods: Five sets of ESBL-producing Escherichia coli were studied by multi-locus sequence typing (MLST), phylogenetic grouping, PCR-based replicon typing and resistance profiling. The blaCTX-M-1-harboring plasmids of one set (pHV295.1, pHV114.1, and pHV292.1) were fully sequenced and subjected to comparative analysis.Results: Eleven different MLST sequence types (ST) were identified with ST1056 the predominant one, isolated in all five sets either on the broiler breeder or meconium level. Plasmid sequencing revealed that blaCTX-M-1 was carried by highly similar IncI1/ST3 plasmids that were 105 076 bp, 110 997 bp, and 117 269 bp in size, respectively.Conclusions: The fact that genetically similar IncI1/ST3 plasmids were found in ESBL-producing E. coli of different MLST types isolated at the different levels in the broiler production pyramid provides strong evidence for a vertical transmission of these plasmids from a common source (nucleus poultry flocks).

Background Mcr-1-harboring Enterobacteriaceae are reported worldwide since their first discovery in 2015. However, a limited number of studies are available that compared full-length plasmid sequences of human and animal origins.MethodsIn this study, mcr-1-bearing plasmids from seven Escherichia coli isolates recovered from patients (n = 3), poultry meat (n = 2) and turkey meat (n = 2) in Switzerland were further analyzed and compared. Isolates were characterized by multilocus sequence typing (MLST). The mcr-1-bearing plasmids were transferred by transformation into reference strain E. coli DH5α and MCR-1-producing transformants were selected on LB-agar supplemented with 2 mg/L colistin. Purified plasmids were then sequenced and compared.ResultsMLST revealed six distinct STs, illustrating the high clonal diversity among mcr-1-positive E. coli isolates of different origins. Two different mcr-1-positive plasmids were identified from a single E. coli ST48 human isolate. All other isolates possessed a single mcr-1 harboring plasmid. Transferable IncI2 (size ca. 60–61 kb) and IncX4 (size ca. 33–35 kb) type plasmids each bearing mcr-1 were found associated with human and food isolates. None of the mcr-1-positive IncI2 and IncX4 plasmids possessed any additional resistance determinants. Surprisingly, all but one of the sequenced mcr-1-positive plasmids lacked the ISApl1 element, which is a key element mediating acquisition of mcr-1 into various plasmid backbones.ConclusionsThere is strong evidence that the food chain may be an important transmission route for mcr-1-bearing plasmids. Our data suggest that some “epidemic” plasmids rather than specific E. coli clones might be responsible for the spread of the mcr-1 gene along the food chain.