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Stochastic epidemic models on networks are inherently high-dimensional and the resulting exact models are intractable numerically even for modest network sizes. Mean-field models provide an alternative but can only capture average quantities, thus offering little or no information about variability in the outcome of the exact process. In this article, we conjecture and numerically demonstrate that it is possible to construct partial differential equation (PDE)-limits of the exact stochastic susceptible-infected-susceptible epidemics on Regular, Erdős–Rényi, Barabási–Albert networks and lattices. To do this, we first approximate the exact stochastic process at population level by a Birth-and-Death process (BD) (with a state space of |$O(N)$| rather than |$O(2^N)$|⁠) whose coefficients are determined numerically from Gillespie simulations of the exact epidemic on explicit networks. We numerically demonstrate that the coefficients of the resulting BD process are density-dependent, a crucial condition for the existence of a PDE limit. Extensive numerical tests for Regular, Erdős–Rényi, Barabási–Albert networks and lattices show excellent agreement between the outcome of simulations and the numerical solution of the Fokker–Planck equations. Apart from a significant reduction in dimensionality, the PDE also provides the means to derive the epidemic outbreak threshold linking network and disease dynamics parameters, albeit in an implicit way. Perhaps more importantly, it enables the formulation and numerical evaluation of likelihoods for epidemic and network inference as illustrated in a fully worked out example. [ABSTRACT FROM AUTHOR]

Objective: To assess trends in the susceptibility to β -lactam agents and to fluoroquinolones of clinically relevant Enterobacteriaceae isolated over a 3-year period in 14 French hospital laboratories. Methods: During the second quarter of 1996, 1997 and 1998, 180 consecutive non-duplicate isolates of Enterobacteriaceae were collected in each center. Sixteen β -lactams and four quinolones were tested by the disk diffusion method. In addition, the double-disk synergy test was used to screen for the production of extended-spectrum β -lactamase (ESBL). Results: Totals of 2507, 2312 and 2506 clinical isolates were obtained in each period, respectively. The distribution of Enterobacteriaceae species according to clinical specimens and wards was similar in each study period. No significant variation in the susceptibility rates to β -lactams and fluoroquinolones was observed, except in Klebsiella pneumoniae and Enterobacter aerogenes. The prevalence of ESBL-producing isolates decreased from 18% to 9% in the former, while it increased from 32% to 54% in the latter. At the same time, the susceptibility to ofloxacin and pefloxacin increased for K. pneumoniae (P < 0.003) and cephalosporinase-producing species (P < 0.05), except Enterobacter spp. Conclusion: Over the 3-year study period β -lactams and fluoroquinolones remained highly active against Enterobacteriaceae clinical isolates, with the exception of E. aerogenes , probably as a result of the dissemination of multiresistant clones in French hospitals. [ABSTRACT FROM AUTHOR]

Objectives: In order to better establish a prevention strategy based on mupirocin, we evaluated nasal carriage of Staphylococcus aureus in haemodialysis patients over a 15 month period., Methods: Search for Staphylococcus aureus in the nasal cavities was made every 2 months in 92 chronic dialysis patients. These patients were divided into 3 groups according to the nature of the carriage: non-permanent, intermittent or permanent., Results: Among the 80 patients retained for analysis, there were 27.5% with intermittent carriage and 11.25% with permanent carriage. Factors which appeared to protect against carriage were rural residence and home self-dialysis., Conclusion: Repeated long-term search for nasal carriage of Staphylococcus aureus has provided reliable data for each patient and gave information on the effects of epidemiological conditions and health care structures.

The authors report fungal contamination of the water delivery system in one of their dialysis centers. They emphasize the insufficiency of the legal recommendations for water analysis, as well as the economical and logistical consequences of this type of contamination. Finally, they suggest disinfection procedures allowing eradication of fungi.

Since the more frequent use of highly permeable membranes and bicarbonate dialysate, hypersensitivity reactions are more often described during hemodialysis and raise the question of the entry of pyrogens from dialysate towards blood due to high permeability of membranes and to possible backfiltration. During dialysis sessions with such membranes, authors observed a severe collapse in a patient on bicarbonate fluid and a repeated Quincke's edema in another on acetate fluid. After exclusion of other causes of such hypersensitivity accidents, they discuss the role of bacterial contamination of dialysis fluid. They analyse the phenomenons of bidirectional high permeability and of backfiltration linked to these new membranes. They recall the different causes of dialysate contamination and give some means of avoiding these inconveniences which expose on one hand to acute severe reactions and on the other are prejudicial in the long term for the patients because of interleukin 1 production.

Using a recent technic according to the principes of counter-immuno-electrophoresis, the authors corroborate the fact biochemical tests for streptococci are deficient. The work is practised in 332 samples from hospital.