RESUMEN
BACKGROUND: Dialysis patients are frequently exposed to Staphylococcus aureus due to stays in dialysis centers, hospitals or rest homes. The hemodialysis vascular access is a potential entry site for S. aureus, in particular when using a central venous catheter (CVC) which increases the risk of sepsis compared to arteriovenous (AV) fistula. We prospectively followed a cohort of 86 hemodialysis patients from an outpatient dialysis center over 25 months analyzing S. aureus carrier status, S. aureus infection rates and mortality. METHODS: Demographic data and patients´ medical histories were collected and followed from all hemodialysis patients. Blood samples, nasal swabs and swabs from the hemodialysis vascular access site were taken every six months for a period of 25 months and tested for S. aureus. Strains were cultured and further characterized by spa PCR and microarray-based genotyping. Resulting data were compared with those from the general population. RESULTS: In cross-sectional analyses, an average of 40% of hemodialysis patients were S. aureus carriers compared to 27% in the general population. Longitudinally, a total of 65% were S. aureus carriers: 16% were persistent carriers, 43% were intermittently colonized. The most common S. aureus lineage in the dialysis patient cohort was the clonal complex (CC) 8 and the spa type t008, while in the general population, the clonal complex CC30 dominates. During the study period, we observed six S. aureus-associated blood stream infections with one S. aureus attributable death. S. aureus carriers with an AV fistula were more densely colonized in the nasal mucosa compared to patients with a CVC. Overall mortality was lower for hemodialysis patients with a positive S. aureus carrier status compared to non-carriers (hazard ratio of 0.19). CONCLUSIONS: Compared to the general population, hemodialysis patients were more frequently colonized with S. aureus and displayed both different S. aureus colonization densities as well as lineages, possibly explained by more frequent exposure to health care environments. The lower overall mortality in carriers compared to non-carriers is intriguing and will be investigated in detail in the future. TRIAL REGISTRATION: ISRCTN 14385893 , 2. October 2018, retrospectively registered.
Asunto(s)
Portador Sano/diagnóstico , Infecciones Relacionadas con Catéteres/diagnóstico , Staphylococcus aureus Resistente a Meticilina/aislamiento & purificación , Diálisis Renal/efectos adversos , Infecciones Estafilocócicas/diagnóstico , Adulto , Anciano , Anciano de 80 o más Años , Derivación Arteriovenosa Quirúrgica , Bacteriemia/diagnóstico , Bacteriemia/microbiología , Portador Sano/microbiología , Infecciones Relacionadas con Catéteres/microbiología , Infecciones Relacionadas con Catéteres/mortalidad , Causas de Muerte , Catéteres Venosos Centrales/microbiología , Infección Hospitalaria/microbiología , Estudios Transversales , Femenino , Estudios de Seguimiento , Alemania , Humanos , Masculino , Staphylococcus aureus Resistente a Meticilina/genética , Persona de Mediana Edad , Nariz/microbiología , Estudios Prospectivos , Diálisis Renal/mortalidad , Infecciones Estafilocócicas/microbiología , Infecciones Estafilocócicas/mortalidad , Factores de Tiempo , Adulto JovenRESUMEN
Members of the phylum Bacteroidetes are abundant in many marine ecosystems and are known to have a pivotal role in the mineralization of complex organic substrates such as polysaccharides and proteins. We studied the decomposition of the algal glycans laminarin and alginate by 'Gramella forsetii' KT0803, a bacteroidetal isolate from North Sea surface waters. A combined application of isotope labeling, subcellular protein fractionation and quantitative proteomics revealed two large polysaccharide utilization loci (PULs) that were specifically induced, one by alginate and the other by laminarin. These regulons comprised genes of surface-exposed proteins such as oligomer transporters, substrate-binding proteins, carbohydrate-active enzymes and hypothetical proteins. Besides, several glycan-specific TonB-dependent receptors and SusD-like substrate-binding proteins were expressed also in the absence of polysaccharide substrates, suggesting an anticipatory sensing function. Genes for the utilization of the beta-1,3-glucan laminarin were found to be co-regulated with genes for glucose and alpha-1,4-glucan utilization, which was not the case for the non-glucan alginate. Strong syntenies of the PULs of 'G. forsetii' with similar loci in other Bacteroidetes indicate that the specific response mechanisms of 'G. forsetii' to changes in polysaccharide availability likely apply to other Bacteroidetes. Our results can thus contribute to an improved understanding of the ecological niches of marine Bacteroidetes and their roles in the polysaccharide decomposition part of carbon cycling in marine ecosystems.