Critical reflexivity in financial markets: a Hawkes process analysis

We model the arrival of mid-price changes in the E-Mini S&P futures contract as a self-exciting Hawkes process. Using several estimation methods, we find that the Hawkes kernel is power-law with a decay exponent close to -1.15 at short times, less than approximately 10^3 seconds, and crosses over to a second power-law regime with a larger decay exponent of approximately -1.45 for longer times scales in the range [10^3, 10^6] seconds. More importantly, we find that the Hawkes kernel integrates to unity independently of the analysed period, from 1998 to 2011. This suggests that markets are and have always been close to criticality, challenging a recent study which indicates that reflexivity (endogeneity) has increased in recent years as a result of increased automation of trading. However, we note that the scale over which market events are correlated has decreased steadily over time with the emergence of higher frequency trading.Comment: 9 pages, 6 figures. Some clarification and correction made to section II, minor alterations elsewher

Colistin resistance in Parisian inpatient faecal Escherichia coli as the result of two distinct evolutionary pathways

Background: Beyond plasmid-encoded resistance (mcr genes) prevalence in strain collections, large epidemiological studies to estimate the human burden of colistin-resistant Escherichia coli gut carriage are lacking.Objectives: To evaluate the prevalence of colistin-resistant E. coli carriage in inpatients and decipher the molecular support of resistance and the genetic background of the strains.Methods: During a 3 month period in 2017, we prospectively screened patients in six Parisian hospitals for rectal carriage of colistin-resistant E. coli using a selective medium, a biochemical confirmatory test and MIC determination. WGS of the resistant strains and their corresponding plasmids was performed.Results: Among the 1217 screened patients, 153 colistin-resistant E. coli strains were isolated from 152 patients (12.5%). The mcr-1 gene was identified in only seven isolates (4.6%) on different plasmid scaffolds. The genetic background of these MCR-1 producers argued for an animal origin. Conversely, the remaining 146 colistin-resistant E. coli exhibited a phylogenetic distribution corresponding to human gut commensal/clinical population structure (B2 and D phylogroup predominance); 72.6% of those isolates harboured convergent mutations in the PmrA and PmrB proteins, constituting a two-component system shown to be associated with colistin resistance.Conclusions: We showed that the occurrence at a high rate of colistin resistance in human faecal E. coli is the result of two distinct evolutionary pathways, i.e. the occurrence of chromosomal mutations in an endogenous E. coli population and the rare acquisition of exogenous mcr-1-bearing strains probably of animal origin. The involved selective pressures need to be identified in order to develop preventative strategies

Decrease of hospital- and community-acquired bloodstream infections due to Streptococcus pneumoniae and Streptococcus pyogenes during the first year of the COVID-19 pandemic: A time-series analysis in Paris region

Members of the Collégiale de Bactériologue – Virologie – Hygiène (CBVH)Guillaume Arlet, Laurence Armand Lefevre, Alexandra Aubry, Laurent Belec, Béatrice Bercot, Stéphane Bonacorsi, Vincent Calvez, Emmanuelle Cambau, Etienne Carbonnelle, Stéphane Chevaliez, Jean-Winoc Decousser, Constance Delaugerre, Diane Descamps, Florence Doucet-Populaire, Jean-Louis Gaillard, Antoine Garbarg-Chenon, Elyanne Gault, Jean-Louis Herrmann, Vincent Jarlier, Jérôme Le Goff, Jean-Christophe Lucet, Jean-Luc Mainardi, Anne-Geneviève Marcellin, Laurence Morand-Joubert, Xavier Nassif, Jean-Michel Pawlotsky, Jérôme Robert, Anne-Marie Roque Afonso, Martin Rottman, Christine Rouzioux, Flore Rozenberg, François Simon, Nicolas Veziris, David Skurnik, Jean-Ralph Zahar, Guilene Barnaud, Typhaine Billard Pomares, Gaëlle Cuzon, Dominique Decré, Alexandra Doloy, Jean-Luc Donay, Laurence Drieux-Rouzet, Isabelle Durand, Agnès Ferroni, Vincent Fihman, Nicolas Fortineau, Camille Gomart, Nathalie Grall, Christelle Guillet Caruba, Françoise Jaureguy, Valérie Lalande, Luce Landraud, Véronique Leflon, Patricia Mariani, Liliana Mihaila, Didier Moissenet, Latifa Noussair, Isabelle Podglajen, Isabelle Poilane, Hélène Poupet, Emilie Rondinaud, Valérie Sivadon Tardy, David Trystram, Charlotte Verdet, Emmanuelle Vigier, Sophie Vimont BillarantInternational audienceThe impact of the COVID-19 pandemic on bloodstream infections (BSIs) due to Streptococcus pneumoniae and Streptococcus pyogenes was assessed in 25 university hospitals of Paris. Monthly BSIs incidence rates that appeared stable in 2018 and 2019, decreased for the 2 pathogens during the 2 COVID-19 lockdown periods of 2020. Containment policies, including social distancing, masking and hand hygiene strengthening in both community and hospital settings are likely to reduce BSIs due to these pathogens

French national epidemiology of bacterial superinfections in ventilator-associated pneumonia in patients infected with COVID-19: the COVAP study

International audienceAbstract Background Description and comparison of bacterial characteristics of ventilator-associated pneumonia (VAP) between critically ill intensive care unit (ICU) patients with COVID-19-positive, COVID + ; and non-COVID-19, COVID-. Methods Retrospective, observational, multicenter study that focused on French patients during the first wave of the pandemic (March–April 2020). Results 935 patients with identification of at least one bacteriologically proven VAP were included (including 802 COVID +). Among Gram-positive bacteria, S. aureus accounted for more than two-thirds of the bacteria involved, followed by Streptococcaceae and enterococci without difference between clinical groups regarding antibiotic resistance. Among Gram-negative bacteria, Klebsiella spp. was the most frequently observed bacterial genus in both groups, with K. oxytoca overrepresented in the COVID- group (14.3% vs . 5.3%; p < 0.05). Cotrimoxazole-resistant bacteria were over-observed in the COVID + group (18.5% vs . 6.1%; p <0.05), and after stratification for K. pneumoniae (39.6% vs . 0%; p <0.05). In contrast, overrepresentation of aminoglycoside-resistant strains was observed in the COVID- group (20% vs . 13.9%; p < 0.01). Pseudomonas sp. was more frequently isolated from COVID + VAPs (23.9% vs . 16.7%; p <0.01) but in COVID- showed more carbapenem resistance (11.1% vs . 0.8%; p <0.05) and greater resistance to at least two aminoglycosides (11.8% vs . 1.4%; p < 0.05) and to quinolones (53.6% vs . 7.0%; p <0.05). These patients were more frequently infected with multidrug-resistant bacteria than COVID + (40.1% vs . 13.8%; p < 0.01). Conclusions The present study demonstrated that the bacterial epidemiology and antibiotic resistance of VAP in COVID + is different from that of COVID- patients. These features call for further study to tailor antibiotic therapies in VAP patients

Human Immunodeficiency Virus Type 1 Group O Infection in France: Clinical Features and Immunovirological Response to Antiretrovirals

International audienc