A molecular strategy to optimize bovine tuberculosis post-mortem diagnosis and the exposure to Mycobacterium tuberculosis variant bovis.

Bovine tuberculosis (bTB) is a zoonotic disease caused by Mycobacterium tuberculosis var. bovis, for which the definitive diagnosis is accomplished by bacterial isolation, which has biosafety issues and requires long time. Thus, diagnostic methods with potential to be faster and more efficient can represent an advance in bTB epidemiological knowledge and decrease exposure to M. tuberculosis var. bovis. This study aimed to validate a molecular test for bTB post-mortem diagnosis, as a strategy to reduce waste in bovine production. A total of 185 tissues from animals of infected herds or with suspected lesions at abattoir were evaluated through bacterial isolation, PCR and histopathology. PCR and histopathology showed sensitivities of 45.1% and 71.2%, respectively, and specificities of 83.3% and 83.0%, respectively, when compared to bacterial isolation. The combination of both tests resulted in enhanced specificity and positive predictive values.Therefore, PCR in conjunction with histopathology may be used as screening, in which concordant results can be considered conclusive, and discordant results may be submitted to bacterial isolation.

In-Situ Synthesis and Characterization of Nanocomposites in the Si-Ti-N and Si-Ti-C Systems.

The pyrolysis (1000 °C) of a liquid poly(vinylmethyl-co-methyl)silazane modified by tetrakis(dimethylamido)titanium in flowing ammonia, nitrogen and argon followed by the annealing (1000-1800 °C) of as-pyrolyzed ceramic powders have been investigated in detail. We first provide a comprehensive mechanistic study of the polymer-to-ceramic conversion based on TG experiments coupled with in-situ mass spectrometry and ex-situ solid-state NMR and FTIR spectroscopies of both the chemically modified polymer and the pyrolysis intermediates. The pyrolysis leads to X-ray amorphous materials with chemical bonding and ceramic yields controlled by the nature of the atmosphere. Then, the structural evolution of the amorphous network of ammonia-, nitrogen- and argon-treated ceramics has been studied above 1000 °C under nitrogen and argon by X-ray diffraction and electron microscopy. HRTEM images coupled with XRD confirm the formation of nanocomposites after annealing at 1400 °C. Their unique nanostructural feature appears to be the result of both the molecular origin of the materials and the nature of the atmosphere used during pyrolysis. Samples are composed of an amorphous Si-based ceramic matrix in which TiNxCy nanocrystals (x + y = 1) are homogeneously formed "in situ" in the matrix during the process and evolve toward fully crystallized compounds as TiN/Si3N4, TiNxCy (x + y = 1)/SiC and TiC/SiC nanocomposites after annealing to 1800 °C as a function of the atmosphere.

Food safety in raw milk production: risk factors associated to bacterial DNA contamination.

While human illness from milkborne pathogens may be linked to contamination of the product after pasteurization or improper pasteurization, such diseases are usually associated with consumption of raw milk or its by-products. Molecular biology tools were applied to investigate contamination by Listeria monocytogenes, Salmonella spp., some pathogenic strains of Escherichia coli, and Campylobacter jejuni in 548 raw milk samples from 125 dairy farms established in two regions from southern Brazil. Moreover, 15 variables were evaluated for their association with raw milk contamination levels, and the risk factors were determined by multiple regression analysis. Salmonella spp. were more frequently detected, followed by pathogenic E. coli. There was difference in contamination index between the regions, in which risk factors such as temporary cattle confinement, low milk production, low milking machine cleaning frequency, and milk storage area without tile walls were identified. The risk factors were specific to each region studied. Nevertheless, the data can be used to improve milk quality of dairy farms/herds with similar management practices.

Pathogenic Leptospira spp. in bats: Molecular investigation in Southern Brazil.

The present study aimed to investigate the frequency of pathogenic Leptospira spp. in Brazilian bats and to determine possible risk factors associated to it. Ninety two bats of 12 species were evaluated. Whole genomic DNA from kidneys was extracted and real-time PCR specific to pathogenic Leptospira spp. was applied. Association between the frequency of specimens positive for Leptospira spp. and sex, age, bat species or family, season of collection, geographic localization and feeding habits was evaluated. The results showed that 39.13% of analyzed bats were found positive for Leptospira spp. Nine bat species had at least one positive result. There was no association among the evaluated variables and frequency of pathogenic Leptospira spp. Although the limitations due to lack of Leptospira spp. isolation, leptospiral carriage was demonstrated in bats of different species from southern Brazil, which reinforces the need for surveillance of infectious agents in wild animals.

Detection of Mycobacterium tuberculosis and Mycobacterium avium Complexes by Real-Time PCR in Bovine Milk from Brazilian Dairy Farms.

Foodborne diseases are a public health problem worldwide. The consumption of contaminated raw milk has been recognized as a major cause of transmission of bovine tuberculosis to humans. Other mycobacteria that may be present in raw milk and may cause diseases are those belonging to the Mycobacterium avium complex. In this study, molecular biology tools were applied to investigate raw milk contamination with Mycobacterium spp. in family dairy farms from Rio Grande do Sul, southern Brazil. Furthermore, different variables related to the source of the milk, herd characteristics, and management were evaluated for their effect on milk contamination. Five hundred and two samples were analyzed, of which 354 were from the Northwest region (102 farms with samples from 93 bulk tanks and 261 animals) and 148 from the South region of the state (22 farms with samples from 23 bulk tanks and 125 animals). Among them, 10 (1.99%) and 7 (1.39%) were positive for Mycobacterium tuberculosis (9 confirmed as Mycobacterium bovis) and M. avium complexes, respectively. There was no difference in the frequencies of positive samples between the regions or the sample sources. Of the positive samples, 4 were collected from a bulk tank (1 positive for M. avium and 3 for M. tuberculosis). Moreover, 1 sample was positive concomitantly for M. tuberculosis and M. avium complexes. On risk analysis, no variable was associated with raw milk contamination by M. tuberculosis complex species. However, washing the udders of all animals and drying them with paper towels were weakly classified as risk factors for M. avium contamination. Positive samples were obtained from both animals and bulk tanks, which emphasizes the importance of tuberculosis control programs and provides evidence that milk monitoring can be used as a control practice. Moreover, the findings of this study reinforce the need for awareness of the problems of raw milk consumption among the general population.