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El último caso de viruela, la peor plaga que ha enfrentado la humanidad, fue diagnosticado hace 45 años y con él la enfermedad fue erradicada del planeta. Una hazaña épica iniciada a finales del siglo XVIII por Edward Jenner, el hombre que inoculó a su propio hijo con el pus de las lesiones de una ordeñadora que sufría viruela bovina, una enfermedad benigna antigénicamente relacionada con la viruela y que le confería inmunidad. Pocos años más tarde, en 1803, partía de España la "Real expedición filantrópica de la vacuna", llevando la vacuna a América y Asia, transportándola de brazo en brazo. A pesar del éxito de la vacuna, Jenner y la sociedad victoriana sufrieron los primeros movimientos antivacunas que hoy, en el contexto de la pandemia delCOVID-19, son catapultados por los sitios de noticias falsas que socaban el conocimiento científico.

En el contexto de la gran diversidad de la microflora oral, con más de 600 especies, se resalta el valor pedagógico de las micrografías electrónicas de placa alba y las imágenes de cultivos bacterianos, realizados en modelos dentales hechos con medios de cultivo, que muestran colonias bacterianas en los sitios anatómicos de los dientes colonizados más abundantemente. Este tipo de imágenes facilita la comprensión de la magnitud del microbioma oral, a estudiantes de carreras biomédicas, especialmente odontología y al público en general, por lo que el uso de estas imágenes pueden ser utilizadas en docencia como en campañas de salud oral.

SUMMARY Flakes detached from rocks of a volcano rivulet at ‘National Park Rincon de la Vieja Volcano’, Guanacaste, Costa Rica, revealed a green layer 2–3 mm deep into the rock matrix. Analysis by scanning electron microscopy showed a complex assemblage of microorganisms, beginning with a thin layer of Cyanidium and followed by diatoms of the genus Pinnularia and curved and straight bacteria. To our knowledge, this is the first description of an endolithic microbial consortium dominated by diatoms, and also the first report of endolithobionts from volcanic rocks in a tropical area.

Objetivo. Determinar la ocurrencia de Clostridium tetani a partir de muestras de suelo colectadas en la ciudad de Puntarenas, Costa Rica, y evaluar su toxigenicidad usando una prueba de ELISA de captura. Material y métodos. Treinta muestras de suelo fueron colectadas y secadas a 35°C durante al menos dos semanas. De cada muestra se hizo una suspensión de1g en 5 mL de solución salina estéril. Se tomaron dos alícuotas de 1.5 mL, una se calentó (60°C/10 min) y ambas se inocularon en medio de carne picada e incubaron a 35°C por 7 días. A los 2 y 7 días se tomaron alícuotas de 0.1 mL que fueron inoculadas en la periferia de placas de agar sangre haciendo una línea de 3-4 cm y se incubaron a 35°C por 24 horas en anaerobiosis (GasPak) para permitir el desplazamiento tipo “swarming”. Luego se tomaron muestras del borde de la película de “swarming”, si estaba presente, y se inocularon en placas de agar sangre (4% agar) para aislar colonias discretas. Las cepas similares a C. tetani fueron analizadas bioquímicamente y por ELISA para identificar la tetanospasmina. Resultados. Diez (33%) cepas de las 30 muestras fueron identificadas como C. tetani toxigénicos. Otras especies de clostridios que exhibieron una película de “swarming” similar fueron C. putrificum y C. glicolicum. Además se aislaron cepas de C. sporogenes, C. fallax, C. haemolyticum y C. beijerinkii. Discusión. Estos resultados confirman la alta frecuencia de cepas toxigénicas de C. tetani en suelos costarricenses, como fue descrito previamente para suelos de la Universidad de Costa Rica, de los cuales se aisló un 43% de cepas de C. tetani, el 30% de las cuales fueron toxigénicas, una proporción similar a lo descrito en el presente trabajo. Desde el punto de vista de la salud pública esta alta frecuencia de C. tetani en suelos es un recordatorio para mantener al día los esquemas de vacunación y la aplicación del toxoide tetánico a los pacientes con traumatismos para prevenir casos clínicos de tétanos.

In the context of the great diversity of oral microflora, including over 600 species, we highlight the educational value of electron micrographs and images of dental plaque cultures in dental models made with culture media, showing the bacterial colonies in the anatomic sites of the teeth that were most abundantly colonized. Such images allow for an easy understanding of the magnitude of the oral microbiome for students of biomedical careers--especially dentistry--and for the general public. As such, these images can be used in teaching programs and oral health campaigns.

En los últimos cinco años el taller de grabado de la Escuela de Artes Plásticas de la Universidad de Costa Rica, se convirtió en un laboratorio de experimentación para probar cualquier idea en busca de erradicar el ácido nítrico y otras sustancias peligrosas, que tradicionalmente se han usado en la rutina diaria del grabado. Hemos introducido el uso de mordentes como el sulfato salino para grabar placas de hierro o aluminio, o el cloruro férrico para trabajar las placas de cobre. Además, hemos recuperado la electrólisis para grabar cualquiera de los metales mencionados. Actualmente, estos procesos son parte de nuestra rutina diaria, porque el ácido nítrico fue erradicado. Mientras tanto, se continúa la investigación de nuevas alternativas, más económicas y prácticas. Otra de nuestras preocupaciones es el uso de solventes de petróleo como rutina para limpiar cualquier cosa en el taller de grabado, y como respuesta a ese problema, sugerimos emplear aceites vegetales o limpiadores domésticos a base de limoneno. En conclusión, el último quinquenio ha sido exitoso en nuestro objetivo por erradicar cualquier sustancia o proceso peligroso del taller de grabado y continuamos haciendo esfuerzos para divulgar las ventajas de la metodología del grabado no tóxico. In the last five years, the printmaking workshop at the University of Costa Rica’s Fine Arts School has become a research laboratory, to probe any idea to eradicate the nitric acid and other harmful substances that has been used traditionally as normal in daily printmaking routine. We have introduced the use of saline etching solutions, such as saline-sulfate in etching iron, aluminum or zinc plates, and ferric chloride to erode copper plates. Furthermore, we have brought back electrolysis to etch any of the mentioned metals. Nowadays, these procedures are our every day work as the standard routine, because the nitric acid has been eradicated. Meanwhile, new alternatives, more economical and practical, are still been researched. Another cause of concern, it is the use of petroleum base solvents as a routine for cleaning everything in the printmaking workshop, and to answering that problem we suggest the use of vegetal oils or domestic cleaning products with limonene. In conclusions, the past five year period has been fruitful in our aim to eradicate any harmful substance or procedures from the printmaking workshop and, that we have been doing and continue to do efforts to divulgate the advantages of printmaking non-toxic methodologies.

The diagnosis of Strongyloides stercoralis infections is routinely made by microscopic observation of larvae in stool samples, a low sensitivity method, or by other, most effective methods, such as the Baermann or agar culture plate methods. We propose in this paper a practical modification of Baermann method. One hundred and six stool samples from alcoholic patients were analyzed using the direct smear test, agar culture plate method, the standard Baermann method, and its proposed modification. For this modification the funnel used in the original version of the method is substituted by a test tube with a rubber stopper, perforated to allow insertion of a pipette tip. The tube with a fecal suspension is inverted over another tube containing 6 ml of saline solution and incubated at 37 degrees C for at least 2 h. The saline solution from the second tube is centrifuged and the pellet is observed microscopically. Larva of S. stercoralis were detected in six samples (5.7%) by the two versions of the Baermann method. Five samples were positive using the agar culture plate method, and only in two samples the larva were observed using direct microscopic observation of fecal smears. Cysts of Endolimax nana and Entamoeba histolytica/dyspar were also detected in the modification of Baermann method. Data obtained by the modified Baermann method suggest that this methodology may helps concentrate larvae of S. stercoralis as efficiently as the original method.

Cell-free extracts from 20 strains of Clostridium tetani isolated from soil samples, were tested for tetanus toxin production using an enzyme immunoassay. All the extracts were classified as positive for the toxin presence, and eight of them showed absorbance values corresponding to tetanus toxin concentrations between 3.2 and 88 ng/ml; thus, they fell within the linear absorbance range (0.135-0.317). All dilutions of toxin used to obtain the calibration curve (0.0071 to 1.1 ng) were lethal for mice.

Aedes aegypti is the main insect vector of Dengue fever and dengue hemorrhagic fever/dengue shock syndrome and represents the only vulnerable element in the control of this disease. Therefore, the identification and quantification of this mosquito is an important task; however, the majority of taxonomic keys are based on the 4th larval instar. For that reason, this study describes the four larval instars of A. aegypti using scanning electron microscopy. Morphological changes during larval development were observed at the pecten, comb scales and the ventral brush of the abdominal segment X; however, the 3rd and 4th instars showed similar structures with only a slight variation. The structures described in this study will be helpful in the identification of the four instars of A. aegypti, a fundamental task for comprehending the natural history of dengue mainly in new territories affected. Rev. Biol. Trop. 54 (3): 847-852. Epub 2006 Sept. 29.Aedes aegypti es el principal insecto vector de la fiebre del dengue y del dengue hemorrágico/síndrome del choque por dengue y es el único elemento atacable para el control de esta virosis. La identificación y cuantificación de éste es una tarea importante; no obstante, la mayoría de las llaves taxonómicas se basan en el cuarto estadio larval. Por esta razón, en este trabajo se describen los cuatro estadios larvales de A. aegypti los cuales fueron examinados mediante microscopia electrónica de rastreo. Los cambios morfológicos ocurridos durante el desarrollo larval fueron observados en el pecten, las escamas del peine, el cepillo ventral del décimo segmento. El 3ero y 4to estadios larvales mostraron estructuras similares con sólo ligeras variaciones. Las estructuras descritas en este artículo permiten identificar cualquiera de los cuatro estadios larvales de A. aegypti, lo cual representa una tarea importante en la comprensión de la historia natural del dengue en los nuevos territorios afectados.

Penetración de Vibrio mimicus a través de la cáscara del huevo de tortuga lora (Lepidochelys olivacea). El objetivo de esta investigación consistió en determinar la capacidad de penetración del Vibrio mimicus a través de la cáscara del huevo. La investigación se realizó en el Centro Nacional de Ciencia y Tecnología de Alimentos en el año 2000. Se inoculó la superfi cie de la cáscara con la bacteria y se procedió a incubar las muestras por 72 horas a 25°C. Después de este período se observaron las muestras bajo el microscopio electrónico. Los resultados obtenidos demuestran que el Vibrio mimicus se reproduce en la superfi cie externa de la cáscara del huevo de tortuga lora, y no es capaz de penetrarla después de las 72 horas de incubación a 25°C. Por lo tanto, cualquier tratamiento que se aplique con el fi n de reducir la contaminación con el vibrio y mejorar la inocuidad de los huevos, debe aplicarse en su exterior.

The common Spanish name of the moth Rothschildia lebeau (Saturniidae) is cuatro ventanas (four 'windows'), because it exhibits a transparent oval path in each wing. The scales of the colored areas and the bristles from the "window" were analyzed. We developed a simple device to measure transmittance across the "windows" with an spectrophotometer. A square section of "window" was mounted onto a flat black card and placed onto a clamp that hung in the path of the light - beam of the spectrophotometer. Absorbance was measured at 350 and 550 nm, with the "window" positioned perpendicular to the light beam (incidence of 90 degrees); then the measurements were repeated with the "window" moved at an angle of 45 degrees. Each measurement was replicated 5 times. Wing color spots were analyzed with a light dissection microscope (stereoscope) and with scanning electron microscopy. The scales have a minimum of 4 morphological types, 3 of them showed the typical appearance of unspecialized scales described for other butterflies; whereas the fourth has features particular to this species. On the "window" the scales are transformed in hair-like bristles that do not interfere with light, conferring the transparency that characterizes the "windows". However, if the wing is illuminated at an almost grazing-incidence, they reflect the light as a mirror. Two hypothetical functional explanation for the windows are mimicry and interspecies communication.

Microwave irradiation (MWI) has been applied to the development of rapid methods to process biological samples for scanning electron microscopy (SEM). In this paper we propose two simple and quick techniques for processing bacteria (Proteus mirabilis and Vibrio mimicus) for SEM using MWI. In the simplest methodology, the bacteria were placed on a cover-glass, air-dried, and submitted to conductivity stain. The reagent used for the conductivity stain was the mordant of a light microscopy staining method (10 ml of 5% carbolic acid solution, 2 g of tannic acid, and 10 ml of saturated aluminum sulfate 12-H2O). In the second method the samples were double fixed (glutaraldehyde and then osmium), submitted to conductivity stain, dehydrated through a series of ethanol solutions of increasing concentration, treated with hexamethyldisilazine (HMDS), and dried at 35 degrees C for 5 minutes. In both methods the steps from fixation to treatment with HMDS were done under MWI for 2 minutes in an ice-water bath, in order to dissipate the heat generated by the MWI. Although both techniques preserve bacterial morphology adequately, the latter, technique showed the best preservation, including the appearance of flagella, and that process was completed in less than 2 hours at temperatures of MWI between 4 to 5 degrees C.

In Costa Rica there were three national surveys of intestinal parasitism (1966, 1982, and 1996) that showed dramatic reduction of the prevalence of Trichuris, Ascaris, and Necator/Ancylostoma (hookworms); however, these nematodes persist with high prevalence in low socio-economically groups, as the squatter settlements around the cities; however, it is possible that pour Amerindian communities with substandard housing condition also suffer the burden of intestinal parasites. For this reason, the present study was planted in a rural disperse Amerindian community from the South of Costa Rica. 45 fecal samples were collected from children under 15 years old, and were processed according a modification of the Baermann method, which also permits the observation of other parasites beyond Strongyloides. 38 (84%) of the analyzed samples were positive for at least one parasite. The prevalence for nematodes was Ascaris (36%), hookworms (22%) Enterobius (4%), and Trichuris (2%). For protozoa was Endolimax nana (33%), Entamoeba coli (27%), and Entamoeba histolytica/dispar (11%). These data are the reflect of the inadequate sanitation conditions of this community

Este articulo esta disponible en http://www.uady.mx/sitios/biomedic/revbiomed/pdf/rb041528.pdf Platelet satellitism is described as an infrequent finding characterized by formation of platelet rosettes around polymorphonuclear (PMN) leucocytes, which are seen in Wright-stained peripheral blood smears prepared from EDTA-anticoagulated blood samples, but not seen when others anticoagulants such as heparin, acid-citrate dextrose, or citrate, are used. The mechanism of this platelet adhesion to PMN is not understood, but there is evidence that autoantibodies directed to the glycoprotein IIb/IIIa complex of the platelet membrane, as well against the neutrophil Fc gama receptor, are involved (1). It is possible that the epitopes for those antibodies are usually hidden in leukocyte and platelet membranes and that membrane changes induced by EDTA expose them; which would explain why satellitism is observed exclusively in blood anticoagulant with EDTA. There are few citations about platelet satellitism in the medical literature. Two recent reports address this issue. The first includes an ultrastructural analysis of blood from a patient that presented pseudothrombocytopenia due to leucocyte phagocytosis of platelets (2). The other documents refer to platelet satellitism around mantle cell lymphocytes, in the first observation of these cells (3). Three cases of platelet satellitism were published in Cosa Rica, and all of them presented the typical findings described for this phenomenon, namely plalelets associated with PMN forming rosettes. The first report describes two cases: a young woman and a 12-yearold boy. Neither had any clinical symptoms/signs and it was observed during a routine analysis (4). The third case was a 21-year-old man, also asymptomatic, and was detected in a routine blood analysis. In this case, a second peripheral blood sample was collected in EDTA and kept at room temperature for 12 hours and smears were made every one to two hours during that period (5). Platelet satellitism increased in the smears made from 2 to 6 hours, until more than 90% of the PMN were seen forming rosettes with platelets. Frequency of rosette formation decreased to 50% thereafter, showing that the Is platelet satellitism an infrequent phenomenon?

The first electron microscope in Costa Rica was a donation from the government of Japan through its International Cooperation Agency (JICA) in 1974. This donation made possible the consolidation of what was to become the University of Costa Rica's Electron Microscope Unit (UME). Within three years the first scientific papers were published, dealing with ultrastructural aspects of "Corn's rayado fino virus" and rotavirus, viral agent of human diarrhea. Subsequent papers out of the UME were published for the most part in the Journal of Tropical Biology, totaling at least 50 in that journal alone by the year 2000. With the recent acquisition of Energy Dispersive Spectrometer to coupled in transmission electron microscope and scanning electron microscope to X ray analysis, the data acquisition of the UME has been greatly enhanced, making possible to analyze both structure and elemental chemical composition in a specimen. Other applications of this new technology include studies of environmental pollution with heavy metals, such as comparative analysis of residues on leaves from urban areas and those on leaves from primary forest.

Cell-free extracts from 20 strains of Clostridium tetani isolated from soil samples, were tested for tetanus toxin production using an enzyme immunoassay. All the extracts were classified as positive for the toxin presence, and eight of them showed absorbance values corresponding to tetanus toxin concentrations between 3.2 and 88 ng/ml; thus, they fell within the linear absorbance range (0.135-0.317). All dilutions of toxin used to obtain the calibration curve (0.0071 to 1.1 ng) were lethal for mice.

El método diagnóstico más frecuente para Strongyloides stercoralis sigue siendo la observación de las larvas en las heces del paciente infectado; no obstante, éstas se excretan en bajo número e interrumpidamente, por lo cual su visualización requiere el análisis de un mínimo de muestras 5 a 7 muestras colectadas en días consecutivos y procesadas mediante métodos como el Baermann (MB) o el cultivo en plato de agar (CPA); de lo contrario se estará subestimando la prevalencia de este parásito. Un ejemplo de tal subestimación se deduce del análisis de la literatura costarricense relacionada con parasitosis intestinales, pues en la mayoría de los informes que mencionan a S. stercoralis, en los cuales el análisis no se hicieron con MB ni CPA, le asignan una prevalencia menor del 0,5%, en tanto cuando se usó alguno de éstos la prevalencia fue mayor; por ejemplo del 1% en pacientes con SIDA, 5,7% en alcohólicos y 2% en ancianos. El pobre diagnóstico de esta parasitosis se refleja en el informe de casos esporádicos o series de menos de 10 casos. En la mayoría de esos pacientes el desenlace es la muerte asociada con complicaciones debidas a hiperinfec-ciones, en gran parte asociadas con tratamiento con corticosteroides. Una posible explicación para esas infecciones masivas las relaciona con un efecto modulador de la transformación en el intestino de larvas L1 a la forma infecciosa (L3) posiblemente debido a similitud entre corticosteroides y hormonas de ecdisis de este parásito. El informe frecuente de casos mortales debido a hiperinfecciones con S. stercoralis subraya la necesidad de incluir métodos como el MB o el CPA para el diagnóstico de este parásito The observation of Strongyloides stercoralis larvae in the feces of infected patients still constitutes the most frequent diagnosis method for this parasite; nevertheless, these larvae are excreted in low number and not daily. For this reason, their visualization require the analysis of at least 5 to 7 samples collected in consecutive days and processed using methods such as the Baermann method (BM) or agar plate culture (APC). If these methodologies are not used the prevalence of S. stercoralis is under estimated. An example of that under estimation, is the prevalence reported for Costa Rica, because in the majority of surveys of intestinal parasites do not included BM nor ACP and reported a frequency less than 0.5% for S. stercoralis. However when those methods are used its prevalence is higher: 1% in patients with AIDS, 5.7% in alcoholics, and 2% in older persons. The failure to diagnose this parasitosis is reflected in the frequent reports of fatal cases associated with hiperinfections, brought about by corticosteroid therapy. The similarity between corticosteroids and an ecdisis hormone of the parasite, which promotes maturation of infective larva in the intestine of the patient, is a possible explanation for this association. The frequent reports of fatal cases due to S. stercoralis underscores the need to include methods such as BM or ACP in the diagnosis of this parasite

Bacterial vaginosis is a common and often underdiagnosed condition. It is the most frequent cause of vaginal discharge, affecting 8 to 15% of women (1), and it is associated with alterations of the vaginal microbial ecosystem, loss of commensal lactobacilli and increased pH, leading to polymicrobial colonization and malodorous discharge. While a normal vaginal Gram smear shows a predominance of Gram positive bacilli, in bacterial vaginosis there is an overgrowth of aerobic and anaerobic Gram negative rods, including Gardnerella, Prevotella, Bacteroides, and Mobiluncus (1-3). We report here the finding of a previously unreported large spirochete-like bacterium in Gram smears of vaginal secretions from two patients with bacterial vaginosis. The first case was a 28 year-old-woman who presented vaginal discharge. A Gram-stained smear from a vaginal swab showed predominance of Gram negative small bacilli and curved Gram negative bacteria and in addition abundant large spirochete-like bacteria. The nurse taking the sample reported the presence of a tampon and the patient confirmed it had remained for at least 10 days in the vagina. The second case was a 8 year-old-girl with a vaginal secretion and discomfort. The attending pediatrician took a sample of the vaginal secretions and also observed some Enterobius vermicularis in the anal region. A Gram-stain of the vaginal secretion smear showed the characteristic vaginal f1ora of bacterial vaginosis and some large spirochete-like agents. The adult woman maintained a tampon for at least 10 days inside her vagina, and poor hygienic habits may have caused fecal contamination. In regards to the other patient, it must be remembered that enterobiasis can cause vulvovaginitis in children. Almost 25% of the cases are associated with anal pruritus (4), and this may have caused the child to scratch and draw fecal material towards her vagina. Thus, the possibility exists that in both cases fecal bacteria, among them the large spirochetelike agent we observed, may have colonized the A spirochete-like bacteria observed in Gram-stained vaginal smears.

artículo -- Universidad de Costa Rica. Instituto de Investigaciones en Salud, 1983 Rotaviruses, enterotoxigenic Escherichia coil, Salmonella, Shigella, and parasites were investigated in outpatient diarrheic children, and in hospitalized diarrheic and nondiarrheic children, between January 1976 and June 1979. In outpatient cases studied within 4 days of onset of symptoms, rotaviruses were the most common agents (45.3%); E. coil heatstable enterotoxin ranked second (13.4%); Shigella was third (8.1%); Salmonella was fourth (7.3%). In 63.2%, one or more enteric agents were detected. In hospitalized non-diarrheic children, asymptomatic shedding of pathogens was rarely observed. A later survey of outpatient diarrheic children revealed Campylobacter fetus jejuni in 8%. In 5.5 years of observation rotaviruses were endemic with excess frequency in the dry and cooler months of December and January. The excess occurrence of bacterial pathogens did not coincide with that of rotaviruses. Universidad de Costa Rica, Instituto de investigaciones en Salud. UCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias de la Salud::Instituto de Investigaciones en Salud (INISA)