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Ehrlichia canis has gained importance over the years as a zoonotic bacterium, nevertheless in Mexico is unknown the extent of the problem in animals and public health. The country had a few studies carried out locally using serology and molecular tests as diagnostic methods. Ehrlichiosis is not considered endemic in the central valley of Mexico, because the climatic conditions in the region have not allowed the vector (Rhipicephalus sanguineus) to establish itself adequately, therefore, diagnosis is not used in clinical practice in this area. A nested PCR (nPCR) offers rapid results with high sensitivity and specificity regardless of cost. The use of a recombinant positive control provides the advantage of timely diagnosis, follow-up treatment and allows the clinician to decide. In this work, the nPCR reported by Wen et al. (J Clin Microbiol 35(7):1852–2185, 1997) was used for the diagnosis of E. canis by modifying the reaction conditions to improve the detection of the test. We constructed a recombinant positive control to nPCR as diagnostic technique for E. canis, also we modified the reaction conditions to improve detection of the test which allowed the diagnosis of E. canis in dogs in the Mexican Republic using 53 samples from dogs with positive serological diagnosis of Ehrlichiosis, some of them from the valley of Mexico. Currently, this nPCR is offered to public at the Faculty of Veterinary Medicine and Zootechnics of the National Autonomous University of Mexico at an accessible cost and allows to begin to generate epidemiological information to know distribution of the bacterium. [ABSTRACT FROM AUTHOR]

In this communication, we report the presence of RNA of bovine viral diarrhea virus (BVDV) as a contaminant of different biological products used in Mexico for veterinary vaccine production. For this purpose, six batches of monovalent vaccines, eight cell line batches used for vaccine production, and 10 fetal bovine serum lots (FBS) commercially available in Mexico from different suppliers were tested by reverse transcription polymerase chain reaction (RT-PCR). Viral RNA was detected in 62.5% of the samples analyzed. Phylogenetic analysis revealed the presence of the subgenotypes BVDV-1a, 1b, and BVDV-2a in the tested samples. Collectively, these findings indicate that contamination by BVDV RNA occurs in commercial vaccines and reagents used in research and production of biological products. The ramifications of this contamination are discussed. [ABSTRACT FROM AUTHOR]

Escherichia coli strains are part of the normal biota of humans and animals; however, several clinical reports have implicated E. coli as the etiological agent of diarrhea in humans and companion animals. Thus, the aim of the present study was to know if companion dogs in the city of San Luis Potosi are colonized with virulent potentially harmful E. coli strains. Rectal swabs from 30 dogs, 13 with and 17 without diarrhea were analyzed. Phylogenetic and virulence genes analysis was performed to the E. coli isolates. Additionally, the Kirby-Bauer test was used to analyze the sensitivity to 32 different antimicrobials from 14 families. Eighty-five isolates were identified as E. coli and detected in 97% of healthy and diarrheic dog samples. E. coli isolates from healthy dogs carried several virulence genes, in contrast with those from diarrheic animals that presented only eaeA. In healthy dogs, phylogenetic analysis showed that 57% and 43% of E. coli isolates belonged to commensal (A and B1) and virulent (B2 and D) groups respectively. Meanwhile, diarrheic dogs showed that 69% of the isolates were identified as virulent B2 and D phylogroups. Moreover, E. coli resistant to β-lactams, aminoglycosides, tetracycline, quinolones, and folate inhibitors were detected in both groups of dogs. The presence of E. coli with eaeA virulence gene in diarrheic dogs, suggest that these strains are associated with the animal´s condition. Finally, major attention must be drawn to the careful handling of dogs because of their capability to harbor and disseminate virulent E. coli strains. [ABSTRACT FROM AUTHOR]

Brucellosis is an infectious disease that affects practically all species of mammals, including human, and is a major zoonosis worldwide. Brucella spp. are facultative intracellular pathogens that have the ability to survive and multiply in phagocytic and nonphagocytic cells such as trophoblast and epithelial cells. Among the six recognized species of the genus Brucella, Brucella melitensis is the main etiological agent involved in goat brucellosis and is also the most pathogenic for human. It causes significant losses in livestock production as a result of abortions, metritis, infertility, and birth of weak animals. Outer membrane proteins (OMPs) are exposed on the bacterial surface and are in contact with cells and effectors of the host immune response, whereby they could be important virulence factors of Brucella species. To evaluate this hypothesis, the gene encoding for the major outer membrane protein Omp31 was amplified, cloned into pUC18 plasmid, and inactivated by inserting a kanamycin cassette, rendering pLVM31 plasmid which was transformed into B. melitensis wild-type strain to obtain LVM31 mutant strain. The Outer membrane (OM) properties of the mutant strain were compared with B. melitensis Bm133 wild-type and B. melitensis Rev1 vaccine strains, in assessing its susceptibility to polymyxin B, sodium deoxycholate, and nonimmune serum. The mutant strain was assessed in vitro with survival assays in murine macrophages J774.A1 and HeLa cells. Our results demonstrate that LVM31 mutant is more susceptible to polymyxin B, sodium deoxycholate, and nonimmune serum than control strains; moreover, Omp31 mutation caused a decrease in the internalization and a significant decrease in the intracellular survival compared with the reference strains in both cell lines. These results allow us to conclude that Omp31 is important for maintaining OM integrity, but also it is necessary for bacterial internalization, establishment and development of an optimal replication niche, and essential for survival and intracellular multiplication. [ABSTRACT FROM AUTHOR]

Salmonella gallinarum is the causative agent of fowl typhoid. Being a Gram-negative bacteria, its outer membrane proteins (OMP) can be regulated by different microenvironments. S. gallinarum was cultured under the following conditions: nutrient broth (NB), NB supplemented with serum from specific pathogen-free birds (NBS) and NB with serum incubated at 56 °C prior to incubation with the bacteria (NBSD); OMP were subsequently extracted. Several changes were observed in the apparent expression of OMP, mainly a decrease in an OMP with a size of 30 kDa, approximately, under the NBS condition. In contrast, the same event was not observed in NB and NBSD when using one- and two-dimensional polyacrylamide gels (SDS-PAGE). Using the OMP with a size of 30 kDa, approximately, as antigen in indirect ELISA, we were able to differentiate serum from healthy and vaccinated birds, as well as birds infected with S. gallinarum and S. enteritidis. The amino-terminal of this protein was sequenced, showing 100 % identity with OmpA of S. typhimurium. Subsequently, we designed primers to amplify the gene by PCR. The partial sequence of the amplified gene showed 100 % identity with OmpA of S. gallinarum. (1) Heat-labile serum components influence the presence of OmpA in the OM of S. gallinarum; (2) by the way of ELISA, OmpA allows to specifically differentiate healthy from diseased birds. [ABSTRACT FROM AUTHOR]

An enzyme immunoassay (EIA) for detection of serum antibodies in patients with typhoid fever was developed using Salmonella typhi outer membrane protein (OMP) preparations as antigen. Acute phase (first week) sera from adult typhoid fever patients were tested as well as sera from the following control groups: adult travellers with diarrhea caused by enterotoxigenic Escherichia coli, children infected with Campylobacter jejuni, healthy Mexican adult blood donors, and adults with septicemia caused by other organisms. At a 1:3,125 serum dilution, the mean absorbance values were 1.41 in the typhoid fever patients, and 0.57, 0.55, 0.51 and 0.52 in the respective control groups. Inhibition EIA studies using OMP preparations or lipopolysaccharide (LPS) as free antigen indicated that proteins can play an important role in the detection of antibodies in early typhoid fever. This EIA may be useful for the diagnosis of typhoid fever since results were obtained within about five hours and in an endemic area antibodies against Salmonella typhi OMP preparations appear early in the course of the disease. [ABSTRACT FROM AUTHOR]