Utilidad diagnóstica de la audiometría de alta frecuencia en sujetos expuestos a ruido recreacional / Diagnostic utility of high frequency audiometry in subjects exposed to recreational noise

INTRODUCCIÓN: Recientes investigaciones mencionan que, debido a los altos niveles de ruidos, el 75% de los habitantes en las ciudades industrializadas padecen algún tipo de deficiencia auditiva. La audiometría de alta frecuencia es un examen complementario importante para detectar tempranamente la pérdida de audición. OBJETIVO: Determinar la utilidad diagnóstica de la audiometría de alta frecuencia en la detección temprana de la hipoacusia en sujetos expuestos a ruido recreacional. MATERIAL Y MÉTODO: Estudio analítico de corte transversal. Se evaluaron 87 estudiantes de fonoaudiología. Se aplicó una audiometría convencional y de alta frecuencia mediante audiómetro clínico. RESULTADOS: La audiometría de alta frecuencia presenta una sensibilidad del 100%, especificidad del 64,60%. El valor predictivo (+) es de 14,70%, mientras que el valor predictivo (-) es del 100%. La razón de verosimilitud (+) es de 2,28, y para la razón de verosimilitud (-) es de 0,0. CONCLUSIÓN: La audiometría de alta frecuencia puede ser utilizada para monitorizar la audición de los sujetos, comprobando que efectivamente los umbrales auditivos de alta frecuencia se encuentren dentro de rangos normales. Lo anterior, dado por sus valores de sensibilidad, valor predictivo negativo, razón de verosimilitud negativa y por el aumento entre la probabilidad preprueba y posprueba.

INTRODUCTION: Recent research mentions that, due to the high noise levels, 75% of the habitants in industrialized cities suffer from some type of hearing impairment. High frequency audiometry is an important complementary test to detect early hearing loss. AIM: To determine the diagnostic utility of high frequency audiometry in the early detection of hearing loss in subjects exposed to recreational noise. MATERIAL AND METHODS: Study analytical type and cross section. 87 speech therapy students were evaluated. A conventional and high frequency audiometry was applied, using a clinical audiometer. RESULTS: High frequency audiometry has a sensitivity of 100%, specificity of 64,60%. The predictive value (+) is 14,70%, while the predictive value (-) is 100%. The likelihood ratio (+) is 2,28, and for the likelihood ratio (-) it is 0,0. CONCLUSION: High frequency audiometry can be used to monitor the hearing of the subjects, checking that effectively the high frequency hearing thresholds are within normal ranges. The above, given by their values of sensitivity, negative predictive value, negative likelihood ratio and the increase between the pre-test probability and the posttest probability.

Estudio normativo: umbrales auditivos de alta frecuencia (9-20 kHz) en normoyentes entre 8 años y 23 años y 11 meses, pertenecientes a la ciudad de Chillán / Normative study: high frequency hearing tresholds (9-20kHz) in normal-hearing patients in between the ages of 8 and 23 years and 11 months old, from Chillan city

Introducción: Diversos estudios evidencian que la audiometría de alta frecuencia cumple un importante rol en la detección temprana de pérdida auditiva; sin embargo, en Chile aún no se dispone de una normativa para su aplicación clínica. Objetivo: Normalizar los umbrales audiométricos de alta frecuencia (9-20 kHz) en normoyentes entre 8 y 23 años y 11 meses pertenecientes a la ciudad de Chillán. Material y método: No experimental, tipo descriptivo y corte transversal. Se evaluaron a 259 sujetos normoyentes, estudiantes de enseñanza básica, media y universitaria. A la muestra se le aplicó una audiometría de alta frecuencia, empleando un audiómetro (Gradson Stadler) GSI61 con fonoauriculares (Sennheiser) HDA 200. Resultados: Los umbrales auditivos incrementaron su valor según la edad y frecuencia. No se encontraron diferencias significativas según sexo. Se observaron diferencias significativas interaural en 9, 10 y 14 kHz. Los valores de los umbrales se presentaron en percentiles, considerando como normalidad aquellos ubicados entre el P10 y P75. Conclusión: Esta norma podría ser utilizada como referencia de normalidad para pesquisar tempranamente a sujetos en riesgo de pérdida auditiva y tomar las acciones sanitarias más pertinentes a cada caso en particular, empleando equipamiento similar.

Introduction: There are several studies showing that high frequency audiometry serves the important purpose in hearing loss early detection; nonetheless, Chile does not have a standard regulation for clinical implementation of the previously mentioned exam. Aim: To standardize high frequency thresholds (9-20) in patients with normal hearing in between the ages of 8 and 23 years and 11 months old from Chillan city. Material and method: Non-experimental, descriptive and held in a transversal lapse of time. 259 normal-hearing subjects were evaluated, belonging to elementary, middle, high school and higher -university- levels of education. All subjects underwent a high-frequency audiometry for which was used a (Gradson Stadler) GSI61 audiometer, with (Sennheiser) HDA 200 headphones. Results: It was observed that high-frequency thresholds tended to increase their figures according to age and frequency requirements. No meaningful differences -regarding male or female subjects- were found, although there were note worthy differences in 9, 10 and 14 kHz frequencies. The numbers of the thresholds were presented as percentiles, considering 'normal' those located in between P10 and P75. Conclusion: This regulation can be used as a point of reference for normality in order to early detect subjects having a hearing loss risk, and to also take health-related action suitable for each particular case, by using similar equipment to the one described in this study.

[Mucociliary clearance system in lung defense]. / Dinámica y patología del barrido mucociliar como mecanismo defensivo del pulmón y alternativas farmacológicas de tratamiento.

The first line of defense to maintain the sterility of the intrapulmonary airways is the mucociliary clearance system. This rapidly responding, non-specific, immune defensive system is challenged by approximately 12,000 liters of air filtered by the lungs each day, containing millions of particles like spores, environmental and eventually toxic pollutants. The main components of this system are the floating mucus "blanket", the underlying mucus propelling cilia with periciliary fluid, and the airway epithelium with secretory and ciliated type of cells. The fine and coordinated regulation of these three components is critical for an effective performance. Deregulation resulting from continuous insults, inherited ion channel disease, infections or abnormal immune response may lead to mucus alterations, goblet cell hyperplasia and metaplasia, airway obstruction, air trapping and chronic lung disease. Options for treatment are limited. Understanding this system may reveal new targets for treatment of lung disease.

Dinámica y patología del barrido mucociliar como mecanismo defensivo del pulmón y alternativas farmacológicas de tratamiento / Mucociliary clearance system in lung defense

The first line of defense to maintain the sterility of the intrapulmonary airways is the mucociliary clearance system. This rapidly responding, non-specific, immune defensive system is challenged by approximately 12,000 liters of air filtered by the lungs each day, containing millions of particles like spores, environmental and eventually toxic pollutants. The main components of this system are the floating mucus "blanket", the underlying mucus propelling cilia with periciliary fluid, and the airway epithelium with secretory and ciliated type of cells. The fine and coordinated regulation of these three components is critical for an effective performance. Deregulation resulting from continuous insults, inherited ion channel disease, infections or abnormal immune response may lead to mucus alterations, goblet cell hyperplasia and metaplasia, airway obstruction, air trapping and chronic lung disease. Options for treatment are limited. Understanding this system may reveal new targets for treatment of lung disease.

Changes in digestive enzyme activities during larval development of leopard grouper (Mycteroperca rosacea).

The leopard grouper is an endemic species of the Mexican Pacific with an important commercial fishery and good aquaculture potential. In order to assess the digestive capacity of this species during the larval period and aid in the formulation of adequate weaning diets, this study aimed to characterize the ontogeny of digestive enzymes during development of the digestive system. Digestive enzymes trypsin, chymotrypsin, acid protease, leucine-alanine peptidase, alkaline phosphatase, aminopeptidase N, lipase, amylase and maltase were quantified in larvae fed live prey and weaned onto a formulated microdiet at 31 days after hatching (DAH) and compared with fasting larvae. Enzyme activity for trypsin, lipase and amylase were detected before the opening of the mouth and the onset of exogenous feeding, indicating a precocious development of the digestive system that has been described in many fish species. The intracellular enzyme activity of leucine-alanine peptidase was high during the first days of development, with a tendency to decrease as larvae developed, reaching undetectable levels at the end of the experimental period. In contrast, activities of enzymes located in the intestinal brush border (i.e., aminopeptidase and alkaline phosphatase) were low at the start of exogenous feeding but progressively increased with larval development, indicating the gradual maturation of the digestive system. Based on our results, we conclude that leopard grouper larvae possess a functional digestive system at hatching and before the onset of exogenous feeding. The significant increase in the activity of trypsin, lipase, amylase and acid protease between 30 and 40 DAH suggests that larvae of this species can be successfully weaned onto microdiets during this period.

Antibacterial and antitumorigenic properties of microcin E492, a pore-forming bacteriocin.

Microcins are a family of low-molecular weight bacteriocins produced and secreted by Gram-negative bacteria. This review is focused on microcin E492, a pore-forming bacteriocin produced by Klebsiella pneumoniae RYC492 that exerts its antibacterial action on related strains. The steps necessary for the production of active microcin E492 involve post-translational modification with a catechol-type siderophore at the C-terminal and proteolytic processing during export to the extracellular space. This bacteriocin has a modular structure, with a toxic domain at the N-terminal and an uptake domain at the C-terminal of the mature protein. The mechanism by which the C-terminal of microcin E492 is recognized by catecholate siderophore receptors is called the "Trojan horse" strategy, because the C-terminal structure mimics essential bacterial elements, which are recognized by the respective receptors and translocated across the outer membrane to exert antibacterial action. The C-terminal uptake module can be exchanged and used with other toxic domains. Microcin E492 also has a cytotoxic effect on malignant human cell lines. The cytotoxic mechanism is through apoptosis, a desired mechanism for cancer therapy. The ability of microcin E492 to form amyloid-like fibrils constitutes a property that can be exploited in the formulation of this bacteriocin as an antitumoral agent, because these fibrils can behave as stable depots to ensure the sustained release of a biologically active molecule. Alternatively, live bacteria can be used as a continuous source of microcin E492 production in specific tumors.

Síndrome hemolítico urémico en Chile: presentación clínica, evolución y factores pronósticos / Hemolytic-uremic syndrome in Chile: clinical features, evolution and prognostic factors

Background: Hemolytic-uremic syndrome (HUS) is characterized by acute renal failure, microangiopathic hemolytic anemia and thrombocytopenia. Aim: To describe the characteñstics ofpatients with the diagnosis ofHUS in Chile, and to identify the most reliable early predictors oímorbidity and moñality. Material and methods: The clinical records ofpatients with HUS aged less than 15 years, attended between January 1990 and December 2003 in 15 hospitals, were reviewed. Demographic, clinical, biochemical, hematological parameters, morbidity and mortality were analyzed. Results: A cohort of 587 patients aged 2 to 8 years, 48 percent males, was analyzed. Ninety two percent had diarrhea. At the moment of diagnosis, anuria was observed in 39 percent of the patients, hypertension in 45 percent and seizures in 17 percent. Forty two percent required renal replacement therapy (RRT) and perítoneal dialysis was used in the majoríty of cases (78 percent). The most frequently isolated etiological agentwas Escherichia coli. Mortality rate was 2.9 percent in the acute phase of the disease and there was a positive correlation between mortality and anuria, seizures, white blood cell count (WCC) >20.000/mm³ and requirements of renal replacement therapy (p <0.05). Twelve percent of patients evolved to chronic renal failure and the risk factors during the acute phase were the need for renal replacement therapy, anuria, WCC >20.000/mm³, seizures and hypertension. Conclusions: The present study emphasizes important clinical and epidemiological aspeets ofHUSin a Chilean pediatricpopulation.

[Hemolytic-uremic syndrome in Chile: clinical features, evolution and prognostic factors]. / Síndrome hemolítico urémico en Chile: presentación clínica, evolución y factores pronósticos.

BACKGROUND: Hemolytic-uremic syndrome (HUS) is characterized by acute renal failure, microangiopathic hemolytic anemia and thrombocytopenia. AIM: To describe the characteristics of patients with the diagnosis of HUS in Chile, and to identify the most reliable early predictors of morbidity and mortality. MATERIAL AND METHODS: The clinical records of patients with HUS aged less than 15 years, attended between January 1990 and December 2003 in 15 hospitals, were reviewed. Demographic, clinical, biochemical, hematological parameters, morbidity and mortality were analyzed. RESULTS: A cohort of 587 patients aged 2 to 8 years, 48% males, was analyzed. Ninety two percent had diarrhea. At the moment of diagnosis, anuria was observed in 39% of the patients, hypertension in 45% and seizures in 17%. Forty two percent required renal replacement therapy (RRT) and peritoneal dialysis was used in the majority of cases (78%). The most frequently isolated etiological agent was Escherichia coli. Mortality rate was 2.9% in the acute phase of the disease and there was a positive correlation between mortality and anuria, seizures, white blood cell count (WCC)>20.000/mm3 and requirements of renal replacement therapy (p<0.05). Twelve percent of patients evolved to chronic renal failure and the risk factors during the acute phase were the need for renal replacement therapy, anuria, WCC>20.000/mm3, seizures and hypertension. CONCLUSIONS: The present study emphasizes important clinical and epidemiological aspects of HUS in a Chilean pediatric population.

[Renal scars after one year of follow up in children with a first episode of acute pyelonephritis]. / Cicatriz renal detectada mediante cintigrama renal DMSA en niños con primera pielonefritis aguda: estudio de factores de riesgo.

BACKGROUND: Acute pyelonephritis in children can leave a kidney scar that eventually can lead to hypertension or renal failure. 99mTc-dimercaptosuccinic acid renal scintigraphy (RC DMSA) is a widely accepted technique to assess children with acute pyelonephritis. AIM: To evaluate the presence of residual kidney scars detected through RC DMSA, in children with a first episode of acute pyelonephritis. PATIENTS AND METHODS: Clinical records of children with a first episode of acute pyelonephritis that were assessed within seven days of the episode with RC DMSA were reviewed. Children were considered eligible if they did not have a new episode of acute pyelonephritis and a second RC DMSA, one year after the first episode, was performed. The presence or absence of a renal scar after one year was associated to demographic, scintigraphy and laboratory variables. RESULTS: Fifty nine children, aged 1 month to 10 years, 35 females, were studied. Thirty nine percent had a renal scar in the scintigraphy perfomed after one year of follow up. The presence of a scar was correlated with a C reactive protein over 130 mg/dl and an altered relative renal function (below 44%), during the acute phase. CONCLUSIONS: A high C reactive protein and alterations of relative renal function during the acute phase of acute pyelonephritis in children, may be risk factors for the development of renal scars in the long term follow up.

Cicatriz renal detectada mediante cintigrama renal DMSA en niños con primera pielonefritis aguda: estudio de factores de riesgo / Renal scars after one year of follow up in children with a first episode of acute pyelonephritis

Background: Acute pyelonephritis in children can leave a kidney scar that eventually can lead to hypertension or renal failure. 99mTc-dimercaptosuccinic acid renal scintigraphy (RC DMSA) is a widely accepted technique to assess children with acute pyelonephritis. Aim: To evaluate the presence of residual kidney scars detected through RC DMSA, in children with a first episode of acute pyelonephritis. Patients and methods: Clinical records of children with a first episode of acute pyelonephritis that were assessed within seven days of the episode with RC DMSA were reviewed. Children were considered eligible if they did not have a new episode of acute pyelonephritis and a second RC DMSA, one year after the first episode, was performed. The presence or absence of a renal scar after one year was associated to demographic, scintigraphy and laboratory variables. Results: Fifty nine children, aged 1 month to 10 years, 35 females, were studied. Thirty nine percent had a renal scar in the scintigraphy perfomed after one year of follow up. The presence of a scar was correlated with a C reactive protein over 130 mg/dl and an altered relative renal function (below 44%), during the acute phase. Conclusions: A high C reactive protein and alterations of relative renal function during the acute phase of acute pyelonephritis in children, may be risk factors for the development of renal scars in the long term follow up.

Síndrome hemolítico urémico en Santiago de Chile: evolución de la función renal y factores pronósticos / Hemolytic uremic syndrome (HUS), prognostic factors and follow up of renal function, in Santiago, Chile

Introducción: El Síndrome Hemolítico Urémico (SHU) se caracteriza por falla renal aguda, anemia hemolítica microangiopática y trombocitopenia; es la causa más frecuente de insuficiencia renal aguda en la infancia. Objetivo: a) Describir las características actuales del cuadro inicial de SHU en nuestro medio y comparar con lo descrito anteriormente; b) Describir la evolución a 1 año plazo y evaluar posibles factores pronósticos de función renal. Sujetos y Métodos: Se estudiaron variables demográficas, presentación clínica, exámenes bioquímicos y hematológicos, en 374 pacientes con SHU diagnosticados entre Enero 1990 a Diciempe 2002 en 9 hospitales de la Región Metropolitana; se evaluó además función renal al año de seguimiento en una muestra de 213 pacientes y se identificaron factores pronósticos de insuficiencia renal crónica y mortalidad utilizando el análisis de regresión logística. Resultados: Se analizaron 374 pacientes, 50,5 por ciento mujeres, 65,5 por ciento de la Región Metropolitana, edad promedio 1,5 ± 1,4 años (0,2 a 8); 91 por ciento presentó diarrea, 31 por ciento ocurrió en verano, al ingreso 57 por ciento presentó anuria, 43,3 por ciento hipertensión arterial y convulsiones 23 por ciento. Al alta 28 por ciento persistía hipertenso. Las terapias de sustitución renal utilizadas fueron: diálisis peritoneal (50 por ciento), hemodiafiltración (6 por ciento) y hemodiálisis (3 por ciento); recibió plasmaféresis 1 por ciento. Se aisló agente etiológico en 17 por ciento, siendo en 69 por ciento E. coli enterohemorrágica. La mortalidad fue de 2,7 por ciento, siendo la causa principal la falla orgánica múltiple. En el seguimiento al año: 80 por ciento mantuvo función renal normal, 14 por ciento presento deterioro de la función renal, 6 por ciento proteinuria y 4 por ciento hipertensión. Se encontró significativo como factor pronóstico de daño renal: hipertensión arterial (p < 0,0001), necesidad de peritoneodiálisis y hemodiálisis (p: 0,001, p: 0,0015 respectivamente), anuria (p: 0,005) y convulsiones (p: 0,01). Se correlacionó con mortalidad en la etapa aguda: convulsiones, requerimiento de hemodiafiltración y plasmaféresis, (p < 0,0001, p: 0,0001 y p < 0,0001 respectivamente).

Cintigrama renal DMSA en niños con primera pielonefritis aguda: correlación con exámenes de laboratorio, ecografía y la presencia de reflujo vésico ureteral / Tc 99M DMSA scintigraphy in children with a first episode of pyelonephritis

Background: Tc99m DMSA (dimercaptosuccinic acid) scintigraphy has a high sensitivity for the detection of cortical kidney damage. Aim: To evaluate the Tc99m DMSA renal scintigraphy in children with a first episode of acute pyelonephritis and its association with laboratory parameters, kidney ultrasound and vesicoureteral reflux. Patients and methods: We studied 143 children (age range 8 days, 12 years, 66 percent female) hospitalized with the clinical diagnosis of acute pyelonephritis (first episode) with a positive urine culture and a renal scintigraphy performed within seven days of diagnosis. DMSA was considered the gold standard for the detection of cortical lesions. Its results were related to the presence of fever, C-reactive protein (CRP), erythrocyte sedimentation rate (VHS), white blood count (WBC), ultrasound examination and vesicoureteral reflux. Results: Seventy nine percent of the population had an abnormal DMSA scan. There were no differences between sex, age and laboratory parameters in children with normal or abnormal DMSA scans, except for CRP (p <0.005). Ultrasound was coincident with the scan in 32 percent of patients. Eighteen percent had vesicoureteral reflux. Conclusions: There is a high proportion of abnormal DMSA scans in children with a first episode of acute pyelonephritis (Rev Méd Chile 2004; 132: 58-64).

Trasplante renal en pediatría, una década de experiencia multicéntrica: a decade of experience / Pediatric renal transplant

El trasplante renal en pediatria representa la modalidad óptimade manejo de la insuficiencia renal crónica, ya que permite recuperar en diversos grados las severas complicaciones propias de la uremia, especialmente el retraso del crecimiento. Objetivo: Evaluar los resultados del trasplante renal pediátrico en 3 centros hospitalarios del país,en un período de 10 años(1989-1999). Pacientes y Método: Evaluación retrospectiva de los trasplantes renales enbase a un protocolo común, efectuados en los hospitales Exequiel González ,Cortés, Luis Calvo Mackenna y San Juan de Dios, entre julio de 1989 y juliode 1999. Se analizaron 3 grupos de variables: un primer grupo de tipo descriptivo para variables demográficas; un segundo grupo para analizar el crecimiento desde el período de recién nacido hasta el último año de seguimiento, y un tercer grupo que analizó aspectos con relación al trasplante, en especial la inmunosupresión, las complicaciones y la función del injerto por períodos anuales. Las variables continuas fueron expresadas como promedio±desviación estándar, el crecimiento como puntaje Z, la función renal se graficó como el inverso de creatinina en plasma,y al igual que la evaluación del rechazo agudo enrelación al tipode donante vivo o cadáver, se analizó con la prueba de chi2 de Pearson. El análisis de la función renal en relación a los tiempos de isquemia tibia y fría se evaluó por el test t de Student, y la sobrevida a 1,3 y 5 años para el injerto y pacientes se estudió por la curva de Kaplan Meier. Seconsideró significativo un p <5S%. Resultados: Se realizaron 98 trasplantes en 92 pacientes, edad 10,9 + 3,2 años, rango 2 a 17; las 3 patologías más importantes causantes de la insuficiencia renal que llevó al trasplante fueron la nefropatía del reflujo, las displasias o bipoplasias renales,y la glomerulonefritis crónica. El crecimiento mostró una caída de un Z-0,6 al nacer a-2,14 al inicio de la diálisis(p <0,005), y a-2,57 al momento del trasplante (p < 0,05). A los 3 años postrasplante el Z fue de -2,38 , y a los 5 años-2,93. La sobrevida actuarial de los pacientes a1, 3 y 5 años fue de 97,8/95,2 y 92,6 respectivamente para los trasplantes donante vivo, y de 92,6/92,6 y 92,6 en los mismos plazos para los trasplantes donante cadáver. La sobrevida del injerto fue de 89,78 y 71%al 1,3 y 5 años para donante vivo, y de 84,76 y 70% respectivamente para donante cadáver. Entre lascausas de pérdida del injerto destacan el abandono del tratamiento en 8 casos,la trombosis de los vasos renales en 6, el rechazo crónico en 4 y el rechazo agudo en 3 trasplantes. Las causas de fallecimiento en los 4 pacientes de la serie fueron una septicemia en 2 casos, una bronconeumonía por CMV en 1, y la ruptura de arteria renal en 1 caso. Conclusiones: Este reporte confirma que el trasplante renal pediátrico puede ser realizado en nuestro medio con aceptable morbilidad, baja mortalidad y con una sobrevida del injerto semejante a reportes internacionales.

Paedriatric renal transplantis the treatment of choice in chronic renal failure(CRF), in that it permits the recuperation to differing degrees the severe consequences of uraemia, especially in terms of growth retardation. Objective: To evaluate the results of renal transplantation in 3 hospital centers during a 10 year period(1989-99). Patients and Methods: A retrospective study using a standard protocol carried out in the hospitals Exequiel Gonzá1ez Cortés,Luis Calvo Mackenna and San Juan de Dios between july 1989 and july 1999. 3 types of variables were analyzed; 1)demograpbic description, 2)growth between birth and the last year of follow-up, and 3) transplant related factors, especially innnunosuppression, transplantcomplications and graft function during annual periods.Continuous variables were expressed as mean + SD, growth as Z score, renal function as l/plasma creatinine, and togelher with the analysis of acute rejection in relation to live or cadaveric donor, were analyzed using Pearsons Chi-squared. Renal function with regards to warm or cold ischaemia was evaluated using Students t-test ,while Kaplan-Meier curves were used in the analysis of survival at 1,3, and 5 years both for patients and grafts. In all the tests a pvalue< 0,05 was considered significant. Results: 98 transplants were carried out on92patients, aged 10.9 + 3.2 years, range 2-17,the 3 most important causes of CRF were reflux nephropathy, renal dis-or hypoplasia and chronic glomerulonephritis. Growth showed a fall from a Z of-0.6 at birth, to-2.14 at the beginning of dialysis (p <0.05) to-2.57 at the moment of transplant (p < 0,05). At 3 and 5 yrs post transplant the Z values were-2.38 and-2.93 respectively. Actuarial patient survival rates at 1,3 and 5 yrs were 97.8, 95.2 and 92.6 for live donors and 92.6,92.6,and 92.6 for cadaveric donors respectively. Graft survival for livedonors was 89,78 and 71% and cadaveric donors 84, 76 and 70% during the same time intervals. Reasons for graft failure were abandoning treatment 8 cases, renal vessel thrombosis 6, chronic rejection 4 and acute rejection 3 cases,4 patients died, 2 from septicaemia, 1 from bronchopneumonia and 1dueto renal artery rupture. Conclusions: This report confirms that paedriatric renal transplant can be performed in Chile with an acceptable morbidity, a low mortality and with graft survivals similar to intemational centers.

Structure, organization and characterization of the gene cluster involved in the production of microcin E492, a channel-forming bacteriocin.

Microcin E492 is a low-molecular-weight, channel-forming bacteriocin produced and excreted by Klebsiella pneumoniae RYC492. A 13 kb chromosomal DNA fragment from K. pneumoniae RYC492 was sequenced, and it was demonstrated by random Tn5 mutagenesis that most of this segment, which has at least 10 cistrons, is needed for the production of active microcin and its immunity protein. Genes mceG and mceH correspond to an ABC exporter and its accessory protein, respectively, and they are closely related to the colicin V ABC export system. The microcin E492 system also requires the product of gene mceF as an additional factor for export. Despite the fact that this bacteriocin lacks post-translational modifications, genes mceC, mceI and mceJ are needed for the production of active microcin. Genes mceC and mceI are homologous to a glycosyl transferase and acyltransferase, respectively, whereas mceJ has no known homologue. Mutants in these three genes secrete an inactive form of microcin, able to form ion channels in a phospholipidic bilayer, indicating that the mutation of these microcin genes does not alter the process of membrane insertion. On the other hand, microcin isolated from mutants in genes mceC and mceJ has a lethal effect when incubated with spheroplasts of sensitive cells, indicating that the microcin defects in these mutants are likely to alter receptor recognition at the outer membrane. A model for synthesis and export is proposed as well as a novel maturation pathway that would involve conformational changes to explain the production of active microcin E492.

Defining the burden of pneumonia in children preventable by vaccination against Haemophilus influenzae type b.

OBJECTIVES: To determine the burden of pneumonia requiring hospitalization in infants and young children preventable by vaccination against Haemophilus influenzae type b (Hib). DESIGN: Vaccination centers in Santiago, Chile, were randomly selected to administer PRP-T, an Hib conjugate vaccine, combined with diphtheria-tetanus toxoids-pertussis (DTP) vaccine or DTP alone. SUBJECTS: Infants who received > or =2 doses of DTP or DTP and Hib conjugate vaccine combined. MAIN OUTCOME MEASURES: Pneumonia episodes leading to hospitalization accompanied by indicators of likely bacterial infection including radiologic evidence of alveolar consolidation or pleural effusion, an elevated erythrocyte sedimentation rate (> or =40 mm/h) or bronchial breath sounds on auscultation. RESULTS: In participants age 4 to 23 months, PRP-T reduced the incidence of pneumonia associated with alveolar consolidation or pleural effusion by 22% (95% confidence interval, -7 to 43) from 5.0 to 3.9 episodes per 1000 children per year. When the pneumonia case definition included any of the following, alveolar consolidation, pleural effusion, erythrocyte sedimentation rate > or =40 mm/h or bronchial breath sounds, PRP-T provided 26% protection (95% confidence interval, 7 to 44) and prevented 2.5 episodes per 1000 children per year. CONCLUSIONS: Hib vaccine provides substantial protection against nonbacteremic pneumonia, particularly those cases with alveolar consolidation, pleural effusion or other signs of likely bacterial infection. Hib vaccination prevented approximately 5 times as many nonbacteremic pneumonia cases in infants as meningitis cases, thus indicating that the largest part of the effect of Hib vaccination might be undetectable by routine culture methods.

Effect of small bowel bacterial overgrowth on the immunogenicity of single-dose live oral cholera vaccine CVD 103-HgR.

Several live oral vaccines (polio, bovine rotavirus, CVD 103-HgR cholera) are less immunogenic in developing than in industrialized countries. It was hypothesized that proximal small bowel bacterial overgrowth (common in children in less developed countries but rare in industrialized settings) diminishes the vibriocidal antibody response to CVD 103-HgR. In total, 202 fasting Santiago schoolchildren aged 5-9 years had lactulose breath H2 tests to detect proximal small bowel bacteria 1 day before ingesting CVD 103-HgR. Florid small bowel overgrowth was observed in 10 (5.6%) of 178 analyzable children. In children with florid overgrowth, vibriocidal seroconversion differed little from other children (60% vs. 67%), but the geometric mean titer was lower (160 vs. 368; P=.25). By logistic regression, increased peak breath H2 at small bowel time points was associated with diminished seroconversion (P=.04), as was the interaction of H2 value and weight (children >25 kg had lower seroconversion rates among subjects with heaviest overgrowth).