[Prevalence of microbiologically-confirmed influenza in patients with influenza-like illness in primary care and clinical and epidemiological characteristics]. / Prevalencia de gripe confirmada microbiológicamente en pacientes con síntomas gripales en atención primaria y características clínico-epidemiológicas.

OBJECTIVE: We evaluated the prevalence of microbiologically-confirmed influenza infection among patients with influenza-like symptoms and compared the clinical and epidemiological characteristics of patients with and without influenza infection. METHODS: Retrospective study of a cohort of patients with influenza-like symptoms from 2016 to 2018 who participated in a clinical trial in thirteen urban primary centres in Catalonia. Different epidemiological data were collected. Patients rated the different symptoms and signs on a Likert scale (absent, little problem, moderate problem and severe problem) and self-reported the measure of health status with the EuroQol visual analogue scale. A nasopharyngeal swab was taken for microbiological isolation of influenza and other microorganisms. RESULTS: A total of 427 patients were included. Microbiologically confirmed influenza was found in 240 patients (56.2%). The percentage of patients with moderate-to-severe cough, muscle aches, tiredness and dizziness was greater among patients with microbiologically confirmed influenza. The self-reported health status was significantly lower among patients with true flu infection (mean of 36.3 ± 18.2 vs 41.7 ± 17.8 in patients without influenza; p<0.001). CONCLUSIONS: Clinical findings are not particularly useful for confirming or excluding the diagnosis of influenza when intensity is not considered. However, the presence of moderate-to-severe cough, myalgias, tiredness and dizziness along with a poor health status is more common in patients with confirmed flu infection.

On the edge energy of lipid membranes and the thermodynamic stability of pores.

To perform its barrier function, the lipid bilayer membrane requires a robust resistance against pore formation. Using a self-consistent field (SCF) theory and a molecularly detailed model for membranes composed of charged or zwitterionic lipids, it is possible to predict structural, mechanical, and thermodynamical parameters for relevant lipid bilayer membranes. We argue that the edge energy in membranes is a function of the spontaneous lipid monolayer curvature, the mean bending modulus, and the membrane thickness. An analytical Helfrich-like model suggests that most bilayers should have a positive edge energy. This means that there is a natural resistance against pore formation. Edge energies evaluated explicitly in a two-gradient SCF model are consistent with this. Remarkably, the edge energy can become negative for phosphatidylglycerol (e.g., dioleoylphosphoglycerol) bilayers at a sufficiently low ionic strength. Such bilayers become unstable against the formation of pores or the formation of lipid disks. In the weakly curved limit, we study the curvature dependence of the edge energy and evaluate the preferred edge curvature and the edge bending modulus. The latter is always positive, and the former increases with increasing ionic strength. These results point to a small window of ionic strengths for which stable pores can form as too low ionic strengths give rise to lipid disks. Higher order curvature terms are necessary to accurately predict relevant pore sizes in bilayers. The electric double layer overlap across a small pore widens the window of ionic strengths for which pores are stable.

Linking lipid architecture to bilayer structure and mechanics using self-consistent field modelling.

To understand how lipid architecture determines the lipid bilayer structure and its mechanics, we implement a molecularly detailed model that uses the self-consistent field theory. This numerical model accurately predicts parameters such as Helfrichs mean and Gaussian bending modulus kc and k̄ and the preferred monolayer curvature J(0)(m), and also delivers structural membrane properties like the core thickness, and head group position and orientation. We studied how these mechanical parameters vary with system variations, such as lipid tail length, membrane composition, and those parameters that control the lipid tail and head group solvent quality. For the membrane composition, negatively charged phosphatidylglycerol (PG) or zwitterionic, phosphatidylcholine (PC), and -ethanolamine (PE) lipids were used. In line with experimental findings, we find that the values of kc and the area compression modulus kA are always positive. They respond similarly to parameters that affect the core thickness, but differently to parameters that affect the head group properties. We found that the trends for k̄ and J(0)(m) can be rationalised by the concept of Israelachivili's surfactant packing parameter, and that both k̄ and J(0)(m) change sign with relevant parameter changes. Although typically k̄ < 0, membranes can form stable cubic phases when the Gaussian bending modulus becomes positive, which occurs with membranes composed of PC lipids with long tails. Similarly, negative monolayer curvatures appear when a small head group such as PE is combined with long lipid tails, which hints towards the stability of inverse hexagonal phases at the cost of the bilayer topology. To prevent the destabilisation of bilayers, PG lipids can be mixed into these PC or PE lipid membranes. Progressive loading of bilayers with PG lipids lead to highly charged membranes, resulting in J(0)(m) >> 0, especially at low ionic strengths. We anticipate that these changes lead to unstable membranes as these become vulnerable to pore formation or disintegration into lipid disks.