ABSTRACT
Salmonella enterica subspecies enterica is one of the most important foodborne pathogens and the causative agent of salmonellosis, which affects both humans and animals producing numerous infections every year. The study and understanding of its epidemiology are key to monitoring and controlling these bacteria. With the development of whole-genome sequencing (WGS) technologies, surveillance based on traditional serotyping and phenotypic tests of resistance is being replaced by genomic surveillance. To introduce WGS as a routine methodology for the surveillance of food-borne Salmonella in the region, we applied this technology to analyze a set of 141 S. enterica isolates obtained from various food sources between 2010 and 2017 in the Comunitat Valenciana (Spain). For this, we performed an evaluation of the most relevant Salmonella typing methods, serotyping and sequence typing, using both traditional and in silico approaches. We extended the use of WGS to detect antimicrobial resistance determinants and predicted minimum inhibitory concentrations (MICs). Finally, to understand possible contaminant sources in this region and their relationship to antimicrobial resistance (AMR), we performed cluster detection combining single-nucleotide polymorphism (SNP) pairwise distances and phylogenetic and epidemiological data. The results of in silico serotyping with WGS data were highly congruent with those of serological analyses (98.5% concordance). Multi-locus sequence typing (MLST) profiles obtained with WGS information were also highly congruent with the sequence type (ST) assignment based on Sanger sequencing (91.9% coincidence). In silico identification of antimicrobial resistance determinants and minimum inhibitory concentrations revealed a high number of resistance genes and possible resistant isolates. A combined phylogenetic and epidemiological analysis with complete genome sequences revealed relationships among isolates indicative of possible common sources for isolates with separate sampling in time and space that had not been detected from epidemiological information. As a result, we demonstrate the usefulness of WGS and in silico methods to obtain an improved characterization of S. enterica enterica isolates, allowing better surveillance of the pathogen in food products and in potential environmental and clinical samples of related interest.
ABSTRACT
Objetivos: Evaluar las propiedades antimicrobianas de una espuma de poliuretano que libera iones de plata sobre diversos microorganismos. Se estudia la difusión al medio de Ag+, así como la posible citotoxicidad sobre células humanas. Material y métodos Estudio de liberación de plata de V.A.C. GranuFoam Silver® mediante espectrometría de masas (Inductively Coupled Plasma Mass). Estudio experimental in vitro para evaluar la capacidad bactericida mediante curvas de letalidad sobre A. baumannii, P. aeruginosa, S. maltophilia, K. pneumoniae, E. coli, P. mirabilis, S. aureus resistente a meticilina, E. faecium, S. pyogenes y C. minutissimum. Estudio de citotoxicidad sobre fibroblastos humanos. Resultados La liberación de Ag+ muestra una curva exponencial con una fase estable de meseta a partir de las 3h, con niveles de 0,22-0,24mg/l. En 3h se logró una reducción superior al 99,9% en todos los gramnegativos excepto en E. coli que fue del 92,5%. La reducción fue superior al 99% a las 2h en S. pyogenes y C. minutissimum, a las 6h en S. aureus y a las 14h en E. faecium. En simulación in vivo estas reducciones se alcanzaron en 6h en los gramnegativos y en 24h en los grampositivos. Las concentraciones de Ag+ no fueron citotóxicas sobre fibroblastos humanos, sin observar diferencias entre las células expuestas a Ag+ y los controles (p = 0,7).Conclusión V.A.C. Granufoam Silver® liberó concentraciones bactericidas de Ag+ que no fueron perjudiciales para los fibroblastos humanos. Se presenta como una buena alternativa para el control y prevención local de las infecciones (AU)
Introduction: The antimicrobial properties of a silver ion (Ag+)-releasing polyurethane foam were evaluated using different microorganisms. The diffusion of Ag+ from the medium, aswell as any possible cytotoxicity on human cells, was also studied. Material and methods: Silver release from V.A.C. Granu Foam Silver1 was assessed by using inductively coupled plasma mass spectrometry (ICP-MS). An in vitro experimental study was designed to evaluate the bactericide capacity using lethal dose curves on A. baumannii,P. aeruginosa, S. maltophilia, K. pneumoniae, E. coli, P. mirabilis, methicillin resistant S. aureus,E. faecium, S. pyogenes and C. minutissimum. A cytotoxicity study was also performed on human fibroblasts. Results: The silver release showed an exponential curve with a stable meseta phase after 3 hours, with levels of 0.22-0.24 mg/l. A reduction of 99.9% of all the gram-negatives was achieved at 3 hours. The reduction was greater than 99% at 2 hours in S. pyogenes and C. minutissimum, at 6 h in S. aureus and at 14 h in E. faecium. In an in vivo simulation model, these reductions were achieved in 6 hours in the gram negatives and 24 h inthe gram positives. The silver concentrations were no cytotoxic to human fibroblasts, with no differences being observed between the cells exposed to Ag+ and the controls(p = .7)Conclusion: V.A.C. Granufoam Silver1 releases bactericide concentrations of Ag+ that did not damage human fibroblasts. It appears to be a good alternative for the control and prevention of local infections (AU)
