High plasmidome diversity of extended-spectrum beta-lactam-resistant Escherichia coli isolates collected during one year in one community hospital.

Plasmid-encoded antibiotic resistance encompasses many classes of currently used antibiotics. In globally distributed Escherichia coli lineages plasmids, which spread via horizontal gene transfer, are responsible for the dissemination of genes encoding extended-spectrum ß-lactamases (ESBL). In this study, we combined 2nd and 3rd generation sequencing techniques to reconstruct the plasmidome of overall 97 clinical ESBL-E. coli isolates. Our results highlight the enormous plasmid diversity in respect to size, replicon-type and genetic content. Furthermore, we emphasize the diverse plasmid distribution patterns among the clinical isolates and the high intra- and extracellular mobility potential of resistance conferring genes. While the majority of resistance conferring genes were located on large plasmids of known replicon type, small cryptic plasmids seem to be underestimated resistance gene vectors. Our results contribute to a better understanding of the dissemination of resistance-conferring genes through horizontal gene transfer as well as clonal spread.

Impact of a reduced water salinity on the composition of Vibrio spp. in recirculating aquaculture systems for Pacific white shrimp (Litopenaeus vannamei) and its possible risks for shrimp health and food safety.

Tropical shrimp, like Litopenaeus vannamei, in land-based recirculating aquaculture systems (RAS) are often kept at low water salinities to reduce costs for artificial sea salt and the amount of salty wastewater. Although these shrimp are tolerant against low salinities, innate immunity suppression and changes in the microbial composition in the water can occur. As especially Vibrio spp. are relevant for shrimp health, alterations in the species composition of the Vibrio community were analysed in water from six RAS, run at 15‰ or 30‰. Additionally, pathogenicity factors including pirA/B, VPI, toxR, toxS, vhh, vfh, tdh, trh, flagellin genes and T6SS1/2 of V. parahaemolyticus were analysed. The Vibrio composition differed significantly depending on water salinity. In RAS at 15‰, higher numbers of the potentially pathogenic species V. parahaemolyticus, V. owensii and V. campbellii were detected, and especially in V. parahaemolyticus, various pathogenicity factors were present. A reduced salinity may therefore pose a higher risk of disease outbreaks in shrimp RAS. Because some of the detected pathogenicity factors are relevant for human health, this might also affect food safety. In order to produce healthy shrimp as a safe food for human consumption, maintaining high water salinities seems to be recommendable.

Recommendations for identifying pathogenic Vibrio spp. as part of disease surveillance programmes in recirculating aquaculture systems for Pacific white shrimps (Litopenaeus vannamei).

Due to their pathogenic potential, identifying Vibrio species from recirculating aquaculture systems (RAS) for Pacific white shrimp (Litopenaeus vannamei) is of great importance to determine the risk for animal's as well as for the consumer's health. The present study compared identification results for a total of 93 Vibrio isolates, including type strains and isolates from shrimp aquaculture. Results from biochemical identifications, 16S rRNA sequencing, sequencing of the uridylate kinase encoding gene pyrH and analysis of the protein spectra assessed by MALDI-TOF MS were compared. The results achieved by these different methods were highly divergent for many of the analysed isolates and for several Vibrio spp difficulties in reliably identifying occurred. These difficulties mainly resulted from missing entries in digital databases, a low number of comparable isolates analysed so far, and high interspecific similarities of biochemical traits and nucleotide sequences between the closely related Vibrio species. Due to the presented data, it can be concluded that for identifying Vibrio spp. from samples in routine diagnostics, it is recommended to use MALDI-TOF MS analysis for a quick and reliable identification of pathogenic Vibrio sp. Nevertheless, editing the database, containing the main spectra of Vibrio is recommended to achieve reliable identification results.

Genomic epidemiology of clinical ESBL-producing Enterobacteriaceae in a German hospital suggests infections are primarily community- and regionally-acquired.

Clinical Enterobacteriaceae isolates that produce extended-spectrum ß-lactamases (ESBLs) have been increasingly reported at a global scale. However, comprehensive data on the molecular epidemiology of ESBL-producing strains are limited and few studies have been conducted in non-outbreak situations.We used whole-genome sequencing to describe the population structure of 294 ESBL-producing Escherichia coli and Klebsiella pneumoniae isolates that were recovered from a German community hospital throughout a 1 year sampling period in a non-outbreak situation.We found a high proportion of E. coli isolates (61.5 %) belonged to the globally disseminated extraintestinal pathogenic ST131, whereas a wider diversity of STs was observed among K. pneumoniae isolates. The E. coli ST131 population in this study was shaped by multiple introductions of strains as demonstrated by contextual genomic analysis including ST131 strains from other geographical sources. While no recent common ancestor of the isolates of the current study and other international isolates was found, our clinical isolates clustered with those previously recovered in the region. Furthermore, we found that the isolation of ESBL-producing clinical strains in hospitalized patients could only rarely be associated with likely patient-to-patient transmission, indicating primarily a community and regional acquisition of strains.Further genomic analyses of clinical, carriage and environmental isolates is needed to uncover hidden transmissions and thus discover the most common sources of ESBL-producing pathogen infections in our hospitals.