Revista latinoamericana de microbiologia最新文献

Bacillary dysentery (shigellosis) is a severe human disease caused by Shigellae. In recent years, a large amount of information has been generated regarding the host, pathogen and environmental factors that impact the pathogenesis of shigellosis at the cellular and molecular level. This review summarizes what is currently known about Shigella, detailing those factors that contribute to pathogenesis and examining the current progress in the development of a vaccine.

The principal aim of this work was to detect the bacteriocinogenic capacity of S. flexneri strains on members of the human intestinal flora. A total of 49 bacteriocinogenic S. flexneri strains were isolated from individuals of both sexes and different ages. The bacteriocins were detected by means of the drop method using E. coli and B. fragilis as target strains. The serotypes of the S. flexneri were determined. The producer capacity of bacteriocins was analysed in 10 different colonies of the same cellular clone and also the arbitrary units were determined. The highest number of bacteriocinogenic S. flexneri strains were obtained from diarrhoeal individuals from 0-10 years old and the S. flexneri serotype 2a was the most abundant. It was demonstrated that E. coli and B. fragilis isolated from the normal intestinal flora of healthy individuals were susceptible to the bacteriocinogenic S. flexneri strains. By means of the determination of arbitrary units per ml of the bacteriocin, it was demonstrated that colonies from a single colony isolate of a same clone of bacteriocinogenic S. flexneri produce different quantities of bacteriocin.

The word "quinoprotein" describes four groups of different enzymes which have cofactors containing o-quinones. Pyrrolo-quinoline quinone (PQQ) is not covalently attached. PQQ is the cofactor of several quinoprotein bacterial dehydrogenases including glucose dehydrogenase (G-DH), alcohol dehydrogenase (A-DH) and aldehyde dehydrogenase (AL-DH). These dehydrogenases are located in the periplasm of Gram-negative bacteria. This report summarises the structural properties of quinoprotein dehydrogenases, such as the biological functions and biotechnological aspects more important.

All living organisms are subject to changing environmental conditions, to which they must adapt in order to survive. Recently, there have been significant advances leading to the comprehension of the different mechanisms implicated in the responses to stressful situations in the yeast S. cerevisiae. In nature, as well as in laboratory conditions or industrial processes, this yeast is subjected to different adverse environmental situations, such as osmotic, thermal and oxidative stresses. A general stress response pathway, mediated by protein kinase A, allows S. cerevisiae to cope with these three stressful conditions. However, there are also specific response pathways that include the HOG kinase for osmotic stress, the Heat Shock Factor for thermal stress and Yap1p and Yap2p transcription factors that regulate the oxidative stress response, among other enzymatic and non-enzymatic mechanisms. In this review, we describe the perception and signal transduction pathways that regulate gene expression leading to the adaptation to most common types of stress in S. cerevisiae. We also include information regarding the interaction between the signal transduction pathways involved in the different responses that allow this organism to coordinate its various physiological processes for optimal adaptation to the changing environment.

Yolk sac infection (YSI) is a major cause of mortality of broilers during the first week post-hatching. The aim of the present-study was to analyze the possible sources of fertile egg contamination and to establish the etiology of YSI. Sixty fertile eggs, sixty sawdust samples from the nest, sixty nonfertile 19 to 21 day old incubation eggs and liver and yolk sac samples from 216 dead, 1 to 7 day old chicks, were cultured. Five hundred and eighty eight colonies were isolated and further characterized using biochemical tests. Escherichia coli was the most common bacterium recovered from all samples except the sawdust and fertile eggs collected from the nest. Fertile egg contamination at breeder farm level was found to be minimal. In broilers, both mortality and the rate of E. coli isolation were increased with the time. These results suggest that egg contamination does not occur at the breeders farm, as previously has been reported. Bacterial contamination causing YSI in vertically integrated operations can occur at a latter stage. It can be considered that the main etiologic agent of YSI is E. coli, since YSI mortality was highly correlated with E. coli isolation.

Secretory and systemic antibody response in mice against enteropathogenic Escherichia coli (EPEC) was evaluated. Groups of mice were immunized with formalin inactivated EPEC 0127:H6 strain by intranasal, peroral, intragastric and intrarectal route, with and without cholera toxin (CT) used as mucosal adjuvant. Mice immunized subcutaneously and a non treated control group were included. Other groups of mice were immunized intranasally with different EPEC strains and a non pathogenic E. coli K12 strain. Antibody response tested by ELISA assay showed that specific anti EPEC 0127:H6 antibodies were induced in serum by intranasal, subcutaneous and intragastric routes. A strong increase of antibody response against EPEC 0127:H6 strain was observed in saliva after intranasal delivery, while a lower response was detected by peroral and intrarectal immunization. Only the intranasal route increased IgA anti EPEC 0127:H6 antibody titers in feces. Specific and cross reactive antibodies to EPEC 0127:H6 were seen in mice immunized intranasally with different EPEC strains. Some control mice showed a background of anti EPEC 0127:H6 antibodies in feces. CT had a negative effect as adjuvant. We showed that nasal mucosa rendered the strongest antibody response in serum and secretions. These results might contribute to optimize the protective effect of enteric vaccines against infections associated to EPEC.

The intestinal flora plays an important role in health and wellbeing of different organisms. Indigenous microflora can be innocuous or pathogenic. Consumption of food supplemented with beneficial microorganisms as probiotics provides a good health state and this can be maintained and recovered. Currently, probiotic strains of Bifidobacterium and Lactobacillus are widely used in humans as well as animals. Swine industry would benefit with the application of probiotics, mainly to overcome diarrheal diseases produced by different causes, as a pathogenic E. coli K88. The aim of this work was to isolate strains of Enterococcus from gastrointestinal tract of pigs to use them as probiotic. Two strains of E. faecalis, 2 of E. mundii and 7 of E. faecium were isolated with characteristics of resistance to acid pH, tolerance to biliary salts and a high antagonistic activity (>80%) against E. coli K88. Based on their characteristics and species affinity, we believe that these strains could be administered to pigs as a probiotic.

At present, the genomes of various microorganisms have been completely sequenced, and many others are in progress. The availability of this level of information and the computational analysis of the described sequences have led to the development of new genomic areas such as: analysis in silico, comparative genomics, functional genomics, transcriptomics, proteomics, and pharmacogenomics. Microarray technology is a powerful tool for analyzing the expression profile of thousands of genes in a global way and can be applied to the study of various biological systems. Using the complete sequences for both the H. pylori and human genome that are available in the data bases, a number of researchers have revealed important information. Some of these data offer a glimpse into the great genetic diversity of H. pylori, the differential genetic expression between the strains that shows the complexity of the response of microorganisms to different conditions of development, and into the association of gene cluster expression with clinical outcome. Other groups have examined the global transcriptional response of gastric epithelial cells to H. pylori. The majority of these studies report an alteration in gene expression related to transcription functions, transduction signals, cell cycle regulation and differentiation, development factors, proliferation/apoptosis balance, expression of membrane proteins, and inflammatory response.

Kombucha is a sour beverage reported to have potential health effects prepared from the fermentation of black tea and sugar with a "tea fungus", a symbiotic culture of acetic acid bacteria and yeasts. Although black tea is the preferred substrate for Kombucha fermentation, other beverages have also been tested as substrates with fair results. Cheese whey is a by-product with a good amount of fermentable lactose that has been used before in the production of beverages, so the objective of this study was to test three types of whey (fresh sweet, fresh acid and reconstituted sweet) in the elaboration of a fermented beverage using a kombucha culture as inoculum. The isolation and identification of bacteria and yeasts from the fermented tea and wheys was done along with the study of the rates of change in sugar consumption, acid production and pH decrease. Several species of acetic acid bacteria (Acetobacter aceti subsp. aceti, Gluconobacter oxydans subsp. industrius, subsp. oxydans and Gluconoacetobacter xylinus) were isolated from the different kombuchas along with the yeasts Saccharomyces cerevisiae, Kluyveromyces marxianus, and Brettanomyces bruxelensis. The main metabolic products in the fermented wheys included ethanol, lactic and acetic acids. A good growth was obtained in both sweet wheys in which a pH of 3.3 and a total acid content (mainly lactic and acetic acids) of 0.07 mol/l was reached after 96 h. The sweet whey fermented beverages contained a relatively low lactose concentration (< 12 g/l). The final ethanol content was low (5 g/l) in all the fermented wheys. The whey products were strongly sour and salty non sparkling beverages.

Blastocystis hominis is a pathogenic protozoon that lives in the human bowel and causes diarrhea: the mode of transmission is a passive one, through the ingestion of stool-contaminated water or foods that contain infective forms of the parasite. The purpose of this study is to report the prevalence of Blastocystis hominis among food vendors in the markets within the Xochimilco jurisdiction, Mexico City, Mexico. A cross-sectional study was conducted in which food vendors answered an epidemiological questionnaire and underwent a serial stool culture. The frequency of the intestinal parasitoses reported was estimated and an analysis was carried out associating the presence of Blastocystis hominis with socio-economic and hygienic factors using the odds ratio at a 95% confidence interval. The frequency of intestinal parasites and commensals was 50.4%; Blastocystis hominis was found in 48 (41.7%) food vendors. The risk analysis showed that Blastocystis hominis was associated with: male gender, poor personal hygiene habits, personal history of parasitosis, and family history of parasitosis. The prevalence reported is high when compared with other populations studied. The relevance of this report lies on the fact that food vendors handle foods and could transmit the infection to consumers.