Practices to prevent non-ventilator hospital-acquired pneumonia: a narrative review.

Nosocomial infection has significant consequences in health care, both at the individual level due to increased morbidity and mortality, and at the organizational level due to increased costs. Hospital-acquired pneumonia (HAP) is the most common nosocomial infection, and is associated with high excess mortality, frequent use of broad-spectrum antimicrobials and increased length of stay. This review explores the preventative strategies that have been examined in non-ventilator HAP (NV-HAP). The management of aspiration risk, interventions for oral hygiene, role of mobilization and physiotherapy, modification of environmental factors, and vaccination are discussed. Many of these interventions are low risk, acceptable to patients and have good cost-benefit ratios. However, the evidence base for prevention of NV-HAP is weak. This review identifies the lack of a unified research definition, under-recruitment to studies, and variation in intervention and outcome measures as limitations in the existing literature. Given that the core risk factors for acquisition of NV-HAP are increasing, there is an urgent need for research to address the prevention of NV-HAP. This review calls for a unified definition of NV-HAP, and identification of a core outcome set for studies in NV-HAP, and suggests future directions for research in NV-HAP. Improving care for people with NV-HAP will reduce morbidity, mortality and healthcare costs significantly.

Clinical challenge of diagnosing non-ventilator hospital-acquired pneumonia and identifying causative pathogens: a narrative review.

Non-ventilated hospital-acquired pneumonia (NV-HAP) is associated with a significant healthcare burden, arising from high incidence and associated morbidity and mortality. However, accurate identification of cases remains challenging. At present, there is no gold-standard test for the diagnosis of NV-HAP, requiring instead the blending of non-specific signs and investigations. Causative organisms are only identified in a minority of cases. This has significant implications for surveillance, patient outcomes and antimicrobial stewardship. Much of the existing research in HAP has been conducted among ventilated patients. The paucity of dedicated NV-HAP research means that conclusions regarding diagnostic methods, pathology and interventions must largely be extrapolated from work in other settings. Progress is also limited by the lack of a widely agreed definition for NV-HAP. The diagnosis of NV-HAP has large scope for improvement. Consensus regarding a case definition will allow meaningful research to improve understanding of its aetiology and the heterogeneity of outcomes experienced by patients. There is potential to optimize the role of imaging and to incorporate novel techniques to identify likely causative pathogens. This would facilitate both antimicrobial stewardship and surveillance of an important healthcare-associated infection. This narrative review considers the utility of existing methods to diagnose NV-HAP, with a focus on the significance and challenge of identifying pathogens. It discusses the limitations in current techniques, and explores the potential of emergent molecular techniques to improve microbiological diagnosis and outcomes for patients.

Lactate dehydrogenase in dermatology practice.

Lactate dehydrogenase (LDH) is used in dermatology practice, particularly as a prognostic marker for cutaneous lymphoma. LDH is an intracellular enzyme involved in anaerobic glycolysis, and is found at low concentrations in the blood. LDH is produced in every tissue, thus cell damage releases LDH into the circulation, so the causes of elevated LDH levels are multiple. The utility of LDH in dermatology practice is reviewed, alongside current diagnostic and staging guidelines.

Conformational fluctuations and protein reactivity. Determination of the rate-constant spectrum and consequences in elementary biochemical processes.

When a protein's active site happens to be strongly coupled with the protein structure, the rate constant of the reaction may eventually be modulated by the conformational fluctuations. Evidence for this effect has long been provided by extensive flash photolysis investigations of liganded hemoproteins and more recently of the non-heme respiratory protein hemerythrin in hydro-organic solvents. Within a given protein conformational substate, an elementary reaction step is characterized by one single free energy barrier and by a first-order rate constant, k, which changes with temperature according to an Arrhenius law. At physiological temperature and low viscosity, ultrafast conformational relaxation causes efficient averaging of the reaction rates and the protein displays exponential kinetics with an average rate constant (k). Under sufficiently general conditions, it can be shown that (k) also follows a simple Arrhenius law with 'effective' values of the pre-exponential factor Aeff and activation enthalpy Heff. It is found that Aeff strongly depends on the overall shape of the rate constant distribution and that Heff actually corresponds to the lower limit of the enthalpy of activation, i.e. the value associated with the highest possible reaction rate. The underlying distribution of rate constants can be reconstructed from a set of experiments in which the kinetics depart from an exponential, i.e. at low temperature and high viscosity. The most probable distribution of exponentials consistent with the observed kinetics of the geminate recombinations of oxygen with photodissociated hemerythrin has been determined by using a new approach, known as the maximum entropy method. The results are consistent with a single pre-exponential value and a distributed enthalpy spectrum. As expected, Heff does not coincide either with the most probable nor with the average value of the enthalpy. The most salient findings are that the probability for any protein molecule to have an enthalpy of activation equal to the effective value Heff vanishes and that Aeff differs by nearly three orders of magnitude from the true value A0. Biochemical reaction rates are actually average values, since protein reactions are measured under physiological conditions, where conformational relaxation is always fast. Our understanding of the significance of Aeff and Heff is therefore entirely dependent on the knowledge of the distribution function of the rate constants. In particular, enthalpy and entropy terms of similar reactions performed by different proteins cannot be compared as long as the distribution of the rate constants remains unknown.

Time-resolved fluorescence of the single tryptophan residue in rat alpha-fetoprotein and rat serum albumin: analysis by the maximum-entropy method.

The time-resolved fluorescence emissions of the lone tryptophan residues in rat alpha-fetoprotein (RFP) and rat serum albumin (RSA) were studied. The total fluorescence intensity decays in both proteins were multiexponential. Analysis of the data by nonlinear least squares as a sum of discrete exponentials showed that four exponentials were needed for a satisfactory fit for both proteins. Analysis by the maximum entropy method using 150 logarithmically equally spaced exponentials yielded four well-resolved excited-state lifetime classes with barycenters and relative amplitudes values (ci) that corresponded to those obtained from the nonlinear least-squares method. Changing the temperature affected the relative amplitudes of the lifetime classes but had little effect on the lifetime values themselves. This suggests that the four classes reflect local conformational substates that exchange slowly with respect to the time window of observation defined by the longest lifetime. The internal rotational dynamics of the tryptophan in each protein was monitored by fluorescence anisotropy decay measurements. The mobility of the tryptophan appeared to be larger and faster in RFP than in RSA. The nonlinear least-squares analysis suggests the existence of three rotational correlation times of 0.1, 3, and 55 ns for this protein. As a function of temperature, the long correlation time did not follow the Perrin's law expected for a rigid rotating body. This suggests that this correlation time may reflect not only the Brownian rotation of the whole protein but also the flexibilities of domains in the protein. For RSA a two-component model with correlation times of 0.4 and 31 ns was sufficient to describe the data.(ABSTRACT TRUNCATED AT 250 WORDS)

Analyzing the distribution of decay constants in pulse-fluorimetry using the maximum entropy method.

The maximum entropy method (MEM) is used to analyze time-resolved pulse-fluorescence spectrometry. The central problem in such analyses is the recovery of the distribution of exponentials describing the decay of the fluorescence (i.e., inverting the Laplace transform) which is, in turn, convolved by the shape of the excitation flash. MEM is shown to give high quality results from both computer-generated "noisy" data and experimental data from chemical and biological molecules.The use of the Shannon-Jaynes entropy function is justified and both the theoretical and practical advantages of MEM are presented. The MEM results are easy to interpret and can help to overcome some experimental limitations. In particular MEM could be a powerful tool to analyze the heterogeneity of fluorescent emission of biological macromolecules which can be correlated with their conformational dynamics in solution.

Plasma 25-hydroxyvitamin D and rickets in infants of extremely low birthweight.

Rickets is now a well-known entity in infants of very low birthweight. In a 1-year period (1981) 8 of 15 neonatal survivors whose birthweight was less than 1000 g (extremely low birthweight) developed rickets despite high supplementation with ergo-calciferol, 2000 units a day. At the time of radiological diagnosis their postnatal age was 8 (range 5-14) weeks, and they all had normal or high plasma concentrations of 25-hydroxyvitamin D (mean 80 nmol/l, range 40-160 nmol/l). Although 4 infants received alfacalcidol which healed the rickets, in 4 infants the rickets healed spontaneously without change in treatment. The results suggest that inadequate vitamin D supplementation is not the cause of rickets in such infants.

A study of the histological basis of textural analysis.

In an attempt to quantitate histological structure by textural analysis, the characters of a stained microscopical field were recorded as a frequency polygon of the relative areas defined by successive increments of optical density: this is known as the optical density/area (OD/A) profile. In a study of lymph-nodes in Hodgkin's disease and of carcinoma of the female breast, each stained tissue section was found to have an OD/A profile of characteristic shape: moreover, in each of the lesions studied it was shown that the shape of the profile could be replicated by summing the profiles of each constituent cell type and intercellular matrix in proportions determined by differential cell counts and direct measurement of the degree of cell packing in the tissue. In an investigation of the influence of specimen preparation on OD/A profile, it was shown that density of staining and section thickness were important variables. Using the density of staining of tissue lymphocytes as an internal standard, a simple method was developed of compensating for differences in the density of Mayer's haemalum staining greater than those met with in practice. Attempts to compensate for intentionally large differences in section thickness were much less successful, but this was considered to be relatively unimportant since, in practice, the variation in thickness of sections cut on a modern microtome by a competent microtomist had been shown to be slight and to have a negligible effect on the OD/A profile.

Cytological basis of histological typing of diffuse Hodgkin's disease. Demonstration of an implied misnomer in the terminology of the Rye classification.

Differential cell counts were made on nine lymph nodes whose structure was replaced by diffuse Hodgkin's disease; two of these nodes had the classical histological appearance of the lymphocytic predominance subtype, four of the mixed cellularity subtype, and three of the lymphocytic depletion subtype. Our attempts to achieve valid sampling methods are recorded. The counts, in general, confirm the postulated histological basis of the Rye classification of the subtypes of the diffuse disease. The major discrepancy is that, contrary to the histological descriptions, our direct counts have shown that lymphocytes, are, in general, more numerous in the lymphocytic depletion than in the mixed cellularity subtypes. The cell counts also show that normal mononuclear cells (mainly fibroblasts and macrophage-type cells) are much more numerous in the mixed cellularity subtype than in the other forms of diffuse Hodgkin's disease; this feature has not been emphasised in the Rye classification. On the basis of our differential counts, a hypothesis is proposed that could explain the natural history of the different subtypes of diffuse Hodgkin's disease as the resultant of three processes: (a) tumour aggressiveness, (b) specific cell-mediated immunological reactions, and (c) non-immunological stromal responses.

Self-observation in general practice--the bleep method.

Recent trends in general practice towards working in multi-disciplinary teams from purpose-built premises have emphasised the need to study the ways in which doctors and other staff spend their working time.This paper describes a well-established work-study technique (activity sampling), which has been adapted to enable doctors to assess how they use their time. The method needs no observer and is cheap to operate. Five general practitioners undertook to record their surgeries for two separate weeks using the bleep method of activity sampling. The results they obtained show that the technique is both practicable in normal working conditions and is capable of providing information highly relevant to the management of general practice.