CUTOFF AT THE " ENTROPIC TIME " FOR SPARSE MARKOV CHAINS

International audienceWe study convergence to equilibrium for a large class of Markov chains in random environment. The chains are sparse in the sense that in every row of the transition matrix P the mass is essentially concentrated on few entries. Moreover, the random environment is such that rows of P are independent and such that the entries are exchangeable within each row. This includes various models of random walks on sparse random directed graphs. The models are generally non reversible and the equilibrium distribution is itself unknown. In this general setting we establish the cutoff phenomenon for the total variation distance to equilibrium, with mixing time given by the logarithm of the number of states times the inverse of the average row entropy of P. As an application, we consider the case where the rows of P are i.i.d. random vectors in the domain of attraction of a Poisson-Dirichlet law with index α ∈ (0, 1). Our main results are based on a detailed analysis of the weight of the trajectory followed by the walker. This approach offers an interpretation of cutoff as an instance of the concentration of measure phenomenon

Association of transcription factor 7-like 2 gene (TCF7L2) polymorphisms with stress-related hyperglycaemia (SRH) in intensive care and resulting outcomes: The READIAB study

International audienceObjective :The study aimed to evaluate the impact of the single nucleotide polymorphism (SNP) rs7903146 on the transcription factor 7-like 2 (TCF7L2) gene in stress-related hyperglycaemia (SRH), defined as blood glucose ≥ 11 mmol/L in at least two blood samples during the first 3 days in the intensive care unit (ICU), and on 28-day and 1-year mortality, and incidence of type 2 diabetes (T2D) at 6 months and 1 year in patients hospitalized in the ICU. Methods :This prospective observational (non-interventional) multicentre READIAB study, carried out during 2012–2016 in six French ICUs, involved adult patients admitted to ICUs for at least two organ failures; patients admitted for < 48 h were excluded. During the 3-day ICU observational period, genetic testing, blood glucose values and insulin treatment were recorded.Main results :The association of rs7903146 with SRH was assessed using logistic regression models. Cox proportional hazards regression models assessed the associations between rs7903146 and mortality and between SRH and mortality, both at 28 days and 1 year. A total of 991 of the 1000 enrolled patients were included in the READIAB–G4 cohort, but 242 (24.4%) had preexisting diabetes and were excluded from the analyses. SRH occurred within the first 3 days in the ICU for one-third of the non-diabetes patients. The association between the rs7903146 polymorphism and SRH did not reach significance (P = 0.078): OR(per one T copy): 1.24, 95% CI: 0.98–1.58. A significant association was found between rs7903146 and 28-day mortality after adjusting for severity scores (P = 0.026), but was no longer significant at 1 year (P = 0.61). At 28 days, mortality was increased in patients with SRH (HR: 2.09, 95% CI: 1.43–3.06; P < 0.001), and remained significant at 1 year after adjusting for severity scores (HR: 1.73, 95% CI: 1.32–2.28; P < 0.001). On admission, non-diabetes patients with SRH had a higher incidence of T2D at 6 months vs. those without SRH (16.0% vs. 7.6%, RR: 2.11, 95% CI: 1.07–4.20; P = 0.030). At 1 year, these figures were 13.4% vs. 9.2%, RR: 1.45, 95% CI: 0.71–2.96; P = 0.31). Moreover, the rs7903146 polymorphism was not significantly associated with T2D development at either 6 months (P = 0.72) or 1 year (P = 0.64).Conclusion :This study failed to demonstrate any significant association between rs7903146 and SRH. Nevertheless, the issue remains an important challenge, as SRH may be associated with increased rates of both mortality and T2D development

Anaplasma marginale and A. phagocytophilum in cattle in Tunisia

Abstract Background Tick-borne diseases caused by Anaplasma species put serious constraints on the health and production of domestic cattle in tropical and sub-tropical regions. After recovering from a primary infection, cattle typically become persistent carriers of pathogens and play a critical role in the epidemiology of the disease, acting as reservoirs of the Anaplasma spp. Methods In this study a duplex PCR assay was used for the simultaneous detection of Anaplasma marginale and Anaplasma phagocytophilum in cattle using two primer pairs targeting msp4 and msp2 genes, respectively. We used this method to analyze DNA preparations derived from 328 blood cattle samples that were collected from 80 farms distributed among Tunisia’s four bioclimatic zones. Results The prevalence of the A. marginale infection (24.7 %) was significantly higher and more widespread (in all bioclimatic areas) than that of A. phagocytophilum (0.6 %), which was found in a mixed infection with A. marginale. Conclusions The duplex PCR assay used proved to be a rapid, specific and inexpensive mean for the simultaneous detection of Anaplasma marginale and Anaplasma phagocytophilum in cattle blood. It allowed us to report the identification of A. phagocytophilum for the first time in cattle in Tunisia and confirm the presence of A. marginale in cattle from several geographical areas of the country. Further epidemiological studies undertaken using this assay will help improve the surveillance of the associated diseases in the regions where they are endemic