Diagnosis of bacteremia in febrile neutropenic episodes in children with cancer: microbiologic and molecular approach.

BACKGROUND: Bacterial isolation using conventional microbiologic techniques rarely surpasses 25% in children with clinical and laboratory findings indicative of an invasive bacterial infection. The aim of this study was to determine the role of real-time polymerase chain reaction (RT-PCR) from whole blood samples compared with automated blood cultures (BC) in detection of relevant microorganisms causing bacteremia in episodes of high-risk febrile neutropenia (HRFN) in children with cancer. METHODS: Children presenting with HRFN at 6 hospitals in Santiago, Chile, were invited to participate. Blood samples were obtained at admission for BC, and at admission and 24 hours for RT-PCR targeting DNA of Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa causing bacteremia in children with HRFN. RESULTS: A total of 177 HRFN episodes were evaluated from May 2009 to August 2010, of which 29 (16.3%) had positive BC, 9 (5%) positive for 1 of the 3 selected bacterial species: 5 for E. coli, 3 for S. aureus, and 1 for P. aeruginosa. RT-PCR detected 39 bacteria in 36 episodes (20%): 14 E. coli, 20 S. aureus, and 5 P. aeruginosa. The sensitivity, specificity, and positive and negative predictive values of RT-PCR compared with BC were 56%, 80%, 13%, and 97%. The final clinical diagnosis was compatible with an invasive bacterial infection in 30/36 (83%) RT-PCR-positive episodes. CONCLUSIONS: In our series, RT-PCR significantly improved detection of the most relevant bacteria associated with HRFN episodes. Large number of patients and close clinical monitoring, in addition to improved RT-PCR techniques will be required to fully recommend RT-PCR-based diagnosis for the routine workup of children with cancer, fever, and neutropenia.

Relaciones entre el metabolismo oxidativo y la obesidad Parte 2: obesidad: inercia evolutiva de los organismos y la vida moderna de los seres humanos / Oxidative metabolism and obesity Part 2: Obesity: evolutive inertia of the organisms and the modern human life

En todos los seres humanos, el crecimiento y el desarrollo, desde la condición de oocito fecundado, están predeterminados por el programa genético, incluso la acumulación de reservas energéticas en el tejido adiposo, a fin de poder sobrevivir a largos períodos invernales y de hambruna. Por lo tanto, la natural tendencia a la obesidad tiene un valor selectivo para el individuo, así como para la especie, lo que es válido desde épocas prehistóricas hasta la actualidad. Sin embargo, en los tiempos modernos, la excesiva oferta de toda clase de alimentos, y la vida sedentaria, ha alterado dramáticamente el balance entre la oferta de kilocalorías de los diversos alimentos y los requerimientos metabólicos de cada organismo, tanto en reposo como en actividad muscular. La ausencia de un control ponderal periódico, durante la vida de cada individuo, y la estrecha vigilancia de los hábitos anormales en cuanto a la alimentación y la actividad física, dan origen a un círculo vicioso, que se origina en la primera infancia y termina con una obesidad patológica, que muchas veces es refractaria a todo tratamiento racional. Finalmente, se analiza el concepto de “epidemia”, en relación con el problema de la obesidad en nuestros días.

In all human beings, both growth and development, beginning from the condition of a fertilized egg-cell, are predetermined by the genetic program, inclusively the accumulation of energy reserves within the adipose tissue, with the aim to be able to survive during long winter periods or of prolonged famines. In consequence, the natural tendency to get obesity has a selective value, both for each individual or for a given species, which is valid since prehistoric times up to the present. Nevertheless, in modern times, the excessive supply of all kinds of foods and the sedentary life stile, have dramatically changed the proper balance between the supply of kilocalories of different foods and the metabolic requirements of each organism, both during rest and muscular activity. The absence of a periodic weight control during the whole life of each human being and the close vigilance of abnormal behaviors, particularly with regard to nutrition and exercise, will originate a vicious circle which appear in the first childhood and ends with a pathological obesity, which often is refractory to any kind of therapy. Finally, the recent concept of obesity as an “epidemic” is discussed.

Relaciones entre el metabolismo oxidativo y la obesidad Parte 1: Alometría: el álgebra de la vida / Oxidative metabolism and obesity Part 1: Allometry: algebra of the life

El análisis cuantitativo de la relación entre la intensidad metabólica y eltamaño del cuerpo de los mamíferos terrestres se fundamenta en someterlos datos empíricos a una transformación logarítmica, con el propósito de obtener una relación lineal entre estas variables. El análisis de regresión permite obtener los parámetros de la ecuación alométrica de Huxley, los que pueden ser comparados con aquellos obtenidos de la teoría de similitud biológica, que se basa en el análisis dimensional de la Física. La clásica ley de la superficie de Rubner relaciona superficies y volúmenes de diversos cuerpos geométricos y no puede ser aplicada directamente a la investigación clínica. Es costumbre expresar la intensidad metabólica exclusivamente en condiciones basales en la Fisiología Comparada como en la práctica clínica, en tanto que en todos los organismos el metabolismo puede variar en un rango de 1 a 10 cuando se compara la condición reposo con la de ejercicio máximo.

The quantitative analysis of the relationship between metabolic rate and body size in terrestrial mammals is based in the log-log transformation of the experimental data in order to obtain a linear correlation. The regression analysis allows obtaining the two characteristic parameters of Huxley’s allometric equation, which can be compared with those obtained from dimensional analysis and biological, similarity theories. Rubner’s classic surface law deals only with surfaces and volumes of geometric bodies, which are not applicable in clinical research. It is customary in Comparative Physiology and clinical practice to deal exclusively with the basal metabolic rate, whereas in all organisms oxidative metabolism comprises a range which is 1:10 when resting conditions and maximal oxygen consumption during exercise are compared.

Two alternative models concerning the perialveolar microcirculation in mammalian lungs.

Despite the fact that the concept of sheet-flow in the pulmonary microcirculation of mammals was introduced more than three decades ago, the capillary circulatory model still prevails in the physiological literature. Since cardiac output is identical in the systemic and in pulmonary circulations, it is noteworthy that in the former, the resulting arterial pressure is five times higher than that of the latter, which means that the corresponding microcirculations must be radically different. The present study addresses this problem from both morphological and physiological perspectives.

[Homeostatic range of the oxidative metabolism: 60 years of integrative fisiometry]. / Rango homeostático del metabolismo oxidativo: 60 años de fisiometría integrativa.

The energetic metabolism and its relationship with body weight generated a vivid controversy, since the Rubner's surface law was introduced into biology. Recently, the multifactor theory (Darveau et al) has caused again a revival of this polemic topic. Moreover, the investigations concerning metabolism and body weight include all terrestrial mammals, from the shrew (3 grams) to the elephant (three tons). The corresponding allometric exponent for standard metabolic rate, both theoretical and empirical, fluctuates around an average value of 0.75, in contrast with the surface law, which postulated a value of 0.67. The "metabolic range" (rest vs maximal exercise) does vary from 1 to 10, due to the prevalent influence of the skeletal muscle activity. Recent investigations have emphasized the fact that the allometric exponent is not unique (0.75), but it should be subjected to statistical variability, both in standard and in maximal exercise.

Two alternative models concerning the perialveolar microcirculation in mammalian lungs

Despite the fact that the concept of sheet-flow in the pulmonary microcirculation of mammals was introduced more than three decades ago, the capillary circulatory model still prevails in the physiological literature. Since cardiac output is identical in the systemic and in pulmonary circulations, it is noteworthy that in the former, the resulting arterial pressure is five times higher than that of the latter, which means that the corresponding microcirculations must be radically different. The present study addresses this problem from both morphological and physiological perspectives.