Tinción de Gram de tejido: alcances y limitaciones / Gram stain of tissue biopsy: scope and pitfalls

La identificación de microorganismos en tejido es esencial para reconocer un proceso infeccioso. Inicialmente, mediante la coloración de hematoxilina-eosina, se puede identificar el patrón de inflamación asociado y luego, a través de tinciones basadas en plata y la tinción de Gramde tejido se visualizan los microorganismos. La tinción de Gram no solo sirve para bacterias, sino también para algunos hongos y parásitos; no obstante, esta técnica tiene algunos inconvenientes, como la contaminación con otros microorganismos y la imposibilidad de visualizar algunas bacterias, entre ellas Legionella pneumophila, Leptospira spp y Bartonella spp. En este artículode revisión se describirán los fundamentos del Gram de tejido, su contribución en el diagnóstico de infecciones como herramienta adicional para el reconocimiento de microorganismos, y sus limitaciones.

The identification of microorganisms in tissue is pivotal to recognize infectious processes.At first, the hematoxylin-eosin stain is used to identify the pattern of inflammation associated; after that, microorganisms are seen through Gram or silver stains. Gram Stain of tissue biopsy not only stains bacteria, but also a number of fungus and parasites. However, this technique has some disadvantages, such as contamination with other microorganisms, and lack of stain of some bacteria, including Legionella pneumophila, Leptospira spp and Bartonella spp. This review articleaims to describe the fundamentals of Gram stain of tissue biopsy and its assistance in infectious diagnosis as an additional tool for recognition of microorganisms, as well as its limitations.

Bacterial diversity in soil in response to different plants, phosphate fertilizers and liming

The diversity of bacterial isolates from soil in response to different plants (control, Brachiaria ruziziensis and Cajanus cajan), fertilization (control, simple superphosphate and rock phosphate) and liming (with and without lime) was evaluated. Phenotypic and physiological characteristics of the isolates were recorded and organized in a file to identify the bacteria. Among the isolates, 95 percent were Gram-positive and 5 percent Gram-negative rods. Soil cultivated with B. ruziziensis favored the nonsporing Gram-positive and Gram-negative rods compared to soil with C. cajan or uncultivated. Number of spore-forming Gram-positive rods were higher in plots with superphosphate than in unfertilized soil or soil fertilized with rock phosphate. In unfertilized plots, larger number of Gram-positive cocci and Gram-negative rods was obtained than in fertilized plots. Unlimed plots favored spore-forming Gram-positive rods, Gram-positive cocci and Gram-negative rods, while liming a larger proportion of nonsporing Gram-positive rods was found. From 7 to 86 percent of the total isolates utilized different carbohydrates. The recording data used in this experiment was effective in the isolates identification, and might be useful for diagnosis of soil bacteria. Bacillus, Cellulomonas, Rhodococcus, Enterobacter, Flavobacterium, Micrococcus and Arthrobacter were the genera more commonly found. Bacterial diversity was enhanced in limed, unfertilized and plant cultivated plots.