Revista latinoamericana de microbiologia最新文献

A study was conducted in order to detect the presence of Salmonella spp in fattening pigs, to identify the serogroups present and to determine the sensibility to the antibiotics more used in the region. The farm was a breeding farm of a multiple-site system. Of the total farrowings of a week, 55 sows and one piglet from each sow were selected. All pigs were negative to Salmonella spp. at the star of the study. Piglets were monitored from day two of age (six times; every 23 days approximately) up to finishing (23 weeks of age). Samples of feces (1 g/animal) were collected directly from the pig's rectum. The first positive pig was found at the second sampling (25 days) and the highest number of positive cases in the fifth sampling (117 days). The cumulative incidence was 52.7%. Thirty-four out of the 40 Salmonellas isolated corresponded to the B serogroup and 6 to the C2 serogroup. The serotypes found in the B serogroup were: S. typhimurium (28/34) and S. agona (6/34). Regarding serogroup C2 these were: S. romanby and S ajiobo. Salmonella spp B serogroup included three of the serotypes more commonly isolated in humans: S. typhimurium, S. agona and S. heidelberg.

When nutrients become scarce E. coli cells enter into a non-growth phase known as stationary and develop a multiple-stress resistance state analogue to sporulation in B. subtilis. Morphological changes are observed, including rounded shape, loss of flagella and thickening of the cell wall. General metabolism is redirected, macromolecular degradation is increased, and storage and osmoprotection compounds are synthesized. The reorganization of the nucleoid is accompanied by an overall repression of gene expression, but a subset of genes required for starvation survival become transcribed in a manner dependent on the stationary phase-specific subunit of RNA polymerase (RpoS or sigma(s)). The regulatory function of sigma(s) seems to be central to a global gene network that is beginning to be understood. Also, stationary phase populations are highly heterogeneous in properties as viability, genotype, and mutability. The emergence of mutant subpopullations capable of using nutrient traces suggest survival strategies during long term starvation. This review focuses on the major characteristics of E. coli during stationary phase and on the regulatory gene network responsible of such characteristics.

Saccharomyces cerevisiae Sc47 (Biosaf) is a commercially available baker's yeast strain (Lesaffre, France) that has been used as a probiotic in animal nutrition. It has been previously reported that animals fed with the yeast showed an improved resistance to several enteric infectious diseases. Some of the S. cerevisiae strains adhere potentially pathogenic bacteria such as Escherichia coli and Salmonella spp. This could be a mechanism through which animals fed with the yeast may become more resistant to infections caused by these microorganisms. In this paper, the adhesion of forty-five Salmonella spp. isolates to Sc47 was assessed by sedimentation and agglutination tests, and by light and electron microscopy. Results showed that 57.7% (26/45) of the isolates and 66.6% (6/9) of the Salmonella serovars tested adhered to the Sc47 cell wall.

The lipopolysaccharides (LPS) are major components of the outer membrane of Gram negative bacteria and, because of their location, are important mediators in the interaction between these bacteria and their environment and other organisms. The alpha-Proteobacterial family Rhizobiaceae includes the rhizobia and agrobacteria, microorganisms which establish symbiotic or parasitic relationships with plants. Mutants deficient in LPS biosynthesis show anomalous interactions with their hosts. The agronomical relevance of the relationship between rhizobia and agrobacteria with plants has promoted a large number of studies on the LPS from these bacteria. The complete structures of one or several domains of LPS from Rhizobiaceae have been determined in the last years. Additionally, several metabolic steps in the biosynthesis of these molecules have been elucidated. This review aims at the description of the more recent findings on the structure and biosynthesis of LPS in Rhizobium, Sinorhizobium and Agrobacterium.

The availability of multiple bacterial genome sequences has led to the discovery of several conserved domains of proteins. Recently, GGDEF and EAL domains have been described as domains responsible for the synthesis and degradation of c-di-GMP, a second messenger in bacteria. c-di-GMP has been involved in cellulose production and identified as a global regulator of several processes such as biofilm formation, motility and virulence, presumibly through a modification of the cell surface properties.

Onchocerciasis is one of the major causes of blindness in the World, with about 17.7 million infected, particularly in West Africa. In Mexico, onchocerciasis is also present and has been subjected to control since 1923. The standard diagnosis of onchocerciasis is by the detection of microfilariae by skin biopsy and transmission is evaluated by detection of Onchocerca volvulus larvae in the vector. Classically, this was carried out by manual dissection of Simuliumn ochraceun s.l. However, with the use of ivermectin, a drug that kills microfilariae but not the adult worms, the skin biopsy is becoming no longer useful for detecting microfilariae levels and due to the reduced transmission, fly dissection is no longer viable. The subject of this paper is to present the immunological and molecular techniques developed to supersede the skin biopsy and fly dissection, and their diagnostic ability to assess the impact of multiple bi-annual mass ivermectin treatments on O. volvulus transmission in Mexico.

A multitude of different polymerase chain reactions (PCRs) have been described for detection and typing of Herpes simplex virus (HSV). This paper compares two PCRs coupled to enzymatic restriction (PCR/RFLP) to detect and type HSV. A primers set was designed to amplify a HSV DNA fragment from UL30 and UL 15 genes. Typing was done by restriction of the UL30 and UL15 amplicons with Ava II and Hpa II enzymes, respectively. This strategy was tested with two reference strains (HSV-1 McIntyre, and HSV-2 G), and 47 clinical HSV isolates. Both PCRs produced the expected amplicons (a 492 bp UL30, and 305 bp UL15). The restriction of both amplicons clearly differentiated HSV- from HSV-2, and produced equal results. Thirty one (66%) of the isolates were identified as HSV-1, and the other 16 (34%), as HSV-2. Most of the HSV-1 isolates (27/31) were from orofacial and thoracic lesions; and also, one half of the HSV-2 isolates (8/16) were from the same anatomical regions. Our results showed that either of the two PCR/RFLP could be used to detect and type HSV. Furthermore, our results of the anatomical site of HSV-1 and HSV-2 infections are consistent with previous reports which have shown changes in the classical anatomical localization of herpesvirus infections.

Enteroaggregative Escherichia coli (EAEC) is an emergent bacterial pathogen. The first studies in developing countries with EAEC strains, showed that this bacterium was associated with persistent diarrhea. However, new studies showed that EAEC may be associated also with acute diarrhea, with both nosocomial and community outbreaks worldwide, and as an important pathogen of diarrheal disease in human immunodeficiency virus-infected adults. EAEC strains are recognized by their characteristic aggregative adherence or "stacked-brick" pattern to epithelial cells. Although the pathogenesis of EAEC infection is not well understood, cellular changes observed in animal models and in vitro assays, suggested that the alterations in the intestinal mucosa during EAEC infection are associated with adherence factors and toxins production. The damage has been associated with the release of inflammatory mediators, which may contribute also to the intestinal illness. The dissemination of the high pathogenicity island from Yersinia pestis evolutionary group to EAEC has been show; different studies suggest that it may contribute to the virulence of EAEC strains. Molecular methods to investigate the presence of plasmid and chromosomal EAEC-associated virulence markers, have been used for the characterization and epidemiological studies of EAEC strains. Although the clinical and epidemiological importance of EAEC have been demonstrated in different studies, Escherichia coli strains with adherent agreggative phenotype are commonly isolated from healthy children and environmental sources. This support the necessity to study virulence factors no related with the cells adherence pattern, that show the specific EAEC pathogenic clones associated whit intestinal disease.

In countries such as Mexico, brucellosis is still an important public health problem due to the consumption of non-pasteurized milk and dairy products, contaminated with Brucella spp. The aim of this study was to look into the survival of Brucella abortus during fermentation of milk with a yoghurt starter culture and storage at refrigeration temperature. Sterile skim milk was inoculated with B. abortus at two concentrations, 10(5) and 10(8) CFU/ml simultaneously with a yoghurt starter culture of lactic acid bacteria (Streptococcus thermophilus and Lactobacillus delbrueckii subspecie bulgaricus). Inoculated flasks were incubated at 42 degrees C, followed by refrigeration at 4 degrees C. Samples were taken during fermentation and during storage and viable count of B. abortus and lactic acid bacteria and pH were determined. Results showed that after 10 days of storage at 4 degrees C, B. abortus was recovered in fermented milk at a level of 10(5) CFU/ml, despite the low pH below 4.0. Therefore B. abortus is able to survive in fermented milk. This finding may imply that non-pasteurized fermented milk contaminated with Brucella abortus could be a means of transmission of these bacteria.

Lactoferrin (Lf) is an iron binding multifunctional glycoprotein that is present in several mucosal secretions like milk, tears and saliva. Lf is also an abundant component of the specific granules of neutrophils and can be released into the serum upon neutrophil degranulation. One of the functions of this protein is the transport of metals, but it is also an important component of the non-specific immune system. Human and bovine Lfs display a broad antimicrobial spectrum against Gram positive and Gram negative bacteria, fungi and several viruses. While the iron-binding properties were originally believed to be solely responsible for the host defense properties ascribed to lactoferrin, it is now known that other mechanisms contribute to the antimicrobial role of this glycoprotein. This review gives an overview of the knowledge of these mechanisms and the potential clinical applications of Lf against infections