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J Navas

Publications and source records attributed to J Navas.

At least 19 recordsLinked to original sources
PubMed2006

Antimicrobial susceptibility patterns of Haemophilus parasuis from pigs in the United Kingdom and Spain.

A total of 30 British and 30 Spanish Haemophilus parasuis isolates were tested for their susceptibility to 19 of the antimicrobials currently used in swine practice with a broth microdilution method in order to know the emergence of resistance against these compounds in this porcine pathogen. All the British isolates were susceptible to penicillin, ceftiofur, erythromycin, tilmicosin, enrofloxacin, and florfenicol, and most of them were susceptible to the remaining antimicrobials (the highest resistance rate found was of 20% to neomycin). In contrast, all the Spanish isolates were susceptible exclusively to florfenicol, and high proportions of resistance were encountered for penicillin, ampicillin, oxytetracycline, erythromycin, tilmicosin, tiamulin and trimethoprim+sulphamethoxazole; in addition, a bimodal or multimodal distribution, or tailing of Spanish isolates over the MIC range was observed for clindamycin, sulphonamides and tylosine tartrate, suggesting the development of acquired resistance. In addition, several multiresistance patterns were found among the Spanish isolates, 23.3% of them being resistant to at least eight antimicrobials, the same rate as that encountered for those being susceptible to all antimicrobials tested. This study showed that in general British H. parasuis isolates are susceptible to antimicrobial agents routinely used for treatment of porcine respiratory diseases; however, the Spanish isolates need a more continuous surveillance of their susceptibility patterns.

Animals↗
PubMed2006

Evaluation of ALOA plating medium for its suitability to recover high pressure-injured Listeria monocytogenes from ground chicken meat.

AIMS: To evaluate a chromogenic plating medium for the isolation of sublethally injured cells of Listeria monocytogenes from processed foods. METHODS AND RESULTS: The inactivation of L. monocytogenes at pressures up to 400 MPa and 12 degrees C in ground chicken meat was employed to examine the recovery of high-pressure injured cells. Before and after different repair incubation periods at 30 degrees C in a nonselective broth, samples were plated onto a selective and differential agar [Agar Listeria according to Ottaviani and Agosti (ALOA)] and in the same medium supplemented with 4% sodium chloride (ALOA-S), and incubated at 37 degrees C. Sublethally injured cells were able to grow when directly plated onto the ALOA medium, without a previous repair incubation period. However, only uninjured cells grew on the ALOA-S medium. CONCLUSIONS: Sublethally injured cells of L. monocytogenes can be quantified by subtracting counts on ALOA-S medium from counts on ALOA medium. SIGNIFICANCE AND IMPACT OF THE STUDY: Possible applications include direct enumeration on ALOA of stressed cells of L. monocytogenes in foods with more than 100 colony forming units per gram.

Animals↗
PubMed2005

aroA gene PCR-RFLP diversity patterns in Haemophilus parasuis and Actinobacillus species.

The Haemophilus parasuis aroA gene encodes 5-enolpyruvylshikimate-3-phosphate synthase and participates in the aromatic amino acids and the folic acid universal metabolic pathway of bacteria. The application of aroA-based PCR-RFLP methodology yields a significant degree of diversity in H. parasuis and Actinobacillus species. PCR amplification of the aroA gene rendered a 1,067-bp fragment in all 15 H. parasuis serovars, and also in Actinobacillus pleuropneumoniae serotypes 1-12, Actinobacillus lignieresii, Actinobacillus equuli, Actinobacillus porcinus, Actinobacillus rossii, Actinobacillus suis, Actinobacillus ureae, Actinobacillus minor and Actinobacillus indolicus. Sau3AI and RsaI digestions of the aroA PCR products rendered seven different restriction fragment length polymorphism (RFLP) patterns: group I (H. parasuis serovars 1, 2, 4-6, and 8-15, A. porcinus and A. ureae), group II (H. parasuis serovars 3 and 7, and A. pleuropneumoniae serotypes 1, 4, 5, 9, 11 and 12), group III (A. lignieresii), group IV (A. pleuropneumoniae serotype 7), group V (A. pleuropneumoniae serotypes 2, 3, 6 and 8, A. equuli, A. rossii, A. minor and A. indolicus), group VI (A. suis) and group VII (A. pleuropneumoniae serotype 10). This is the first report describing the presence of aroA gene in H. parasuis, A. lignieresii, A. porcinus, A. rossii, A. suis, A. ureae, A. minor and A. indolicus and the data presented here demonstrates a significant degree of aroA genetic diversity in H. parasuis and species of the genus Actinobacillus.

3-Phosphoshikimate 1-Carboxyvinyltransferase↗
PubMed2005

Technical note: molecular typing of Corynebacterium bovis isolates by pulsed-field gel electrophoresis.

A typing method for Corynebacterium bovis based on pulsed-field gel electrophoresis (PFGE) is described and applied to type 162 strains isolated from mastitic milk from 57 Friesian dairy herds in northern Spain. Isolates were identified to the species level using the API-Coryne system and a polymerase chain reaction-restriction fragment length polymorphism of the 16S rDNA amplicon. Cultures in logarithmic phase were harvested, mixed with agarose, and treated with lisozyme and proteinase K to release intact genomic DNA that was digested with XbaI and submitted to PFGE. Seven different pulsotypes were identified; none of them were similar to that of the reference strain (ATCC 7715). The most frequent pulsotype was pattern I (51.9%) followed by pattern II (29.6%). The majority of the herds showed infection with one single pulsotype, but 12 herds yielded 2 pulsotypes, and one herd had 3 pulsotypes. No relationship was found between the geographical location of the herd and the pulsotype. This is the first description of a typing method for C. bovis; the technique might prove useful for epidemiological studies on this species.

Animals↗
PubMed2003

Merkel cell tumor presenting as a painful patch lesion on the right arm.

Primary small cell cutaneous neuroendocrine carcinoma (Merkel cell carcinoma) is an uncommon, highly malignant, primary cutaneous neuroendocrine carcinoma. Clinically it is seen as a 0.5- to 5.0-cm pinkish purple papule or nodule, usually not ulcerated, on the head, neck, or, less frequently, the roots of the limbs. We present the case of a woman with an atypical clinical presentation of a Merkel cell tumor.

Arm↗
PubMed2001

Identification and mutagenesis by allelic exchange of choE, encoding a cholesterol oxidase from the intracellular pathogen Rhodococcus equi.

The virulence mechanisms of the facultative intracellular parasite Rhodococcus equi remain largely unknown. Among the candidate virulence factors of this pathogenic actinomycete is a secreted cholesterol oxidase, a putative membrane-damaging toxin. We identified and characterized the gene encoding this enzyme, the choE monocistron. Its protein product, ChoE, is homologous to other secreted cholesterol oxidases identified in Brevibacterium sterolicum and Streptomyces spp. ChoE also exhibits significant similarities to putative cholesterol oxidases encoded by Mycobacterium tuberculosis and Mycobacterium leprae. Genetic tools for use with R. equi are poorly developed. Here we describe the first targeted mutagenesis system available for this bacterium. It is based on a suicide plasmid, a selectable marker (the aacC4 apramycin resistance gene from Salmonella), and homologous recombination. The choE allele was disrupted by insertion of the aacC4 gene, cloned in pUC19 and introduced by electroporation in R. equi. choE recombinants were isolated at frequencies between 10(-2) and 10(-3). Twelve percent of the recombinants were double-crossover choE mutants. The choE mutation was associated with loss of cooperative (CAMP-like) hemolysis with sphingomyelinase-producing bacteria (Listeria ivanovii). Functional complementation was achieved by expression of choE from pVK173-T, a pAL5000 derivative conferring hygromycin resistance. Our data demonstrate that ChoE is an important cytolytic factor for R. equi. The highly efficient targeted mutagenesis procedure that we used to generate choE isogenic mutants will be a valuable tool for the molecular analysis of R. equi virulence.

Alleles↗
PubMed1998

Disseminated skin infection due to Mycobacterium fortuitum in an immunocompetent patient.

Skin infections caused by atypical rapid-growing mycobacteria, which used considered to be unusual, have become more frequent, especially in immunodepressed patients. Clinical cutaneous disease with these pathogens seems to follow two patterns: in the immunocompetent host, a traumatic injury is followed by the development of localized abscess formation; but in the immunocompromised individual there is no history of trauma and the patient presents with multiple subcutaneous nodular lesions. We describe a rare case of an immunocompetent young woman with disseminated skin infection due to Mycobacterium fortuitum. We emphasize the diagnostic and therapeutic problems associated with such infections.

Adult↗
PubMed1997

Orifices at the lower neck: heterotopic salivary glands.

Heterotopic islands of salivary-gland tissue are rare and have been described in a number of sites in the head and neck. We describe a patient with salivary-gland fistulas in the lower third of the neck, without evidence of any other congenital abnormalities. The appearance of sinuses in association with heterotopic salivary-gland tissue suggests that its embryologic origin may be from the branchial clefts. Surgical treatment is recommended.

Child↗
PubMed1996

Sustained levels of ascorbic acid are toxic and immunosuppressive for human T cells.

Ascorbate (vitamin C) can protect from oxidative damage to DNA and lipids that may lead to aging, cancer, and other dysfunctions. However, we find that purified human T cells deteriorate if maintained in ascorbate in culture for 18 hrs. or more; viability and Il-2 synthesis are over 90% curtailed by ascorbate at 50 micrograms/ml. T cell proliferation and adhesion are severely suppressed at 10-25 micrograms/ml. Dihydro-ascorbate was much less toxic or suppressive. The suppressive effect of ascorbate appears irreversible, since removal of ascorbate after 18 hrs. did not restore the mitogenic response. Although moderate dietary levels of ascorbate often reach 250-1000 mg or more daily and appear beneficial, our data caution against sustained megadoses of ascorbate for treatment of patients with AIDS and cancer.

Ascorbic Acid↗
PubMed1996

Genetic tools in pathogenic nocardioform actinomycetes.

Nocardioform actinomycetes are Gram-positive bacteria with high G+C content. Several species of Mycobacterium, Corynebacterium, Nocardia and Rhodococcus are important human or animal pathogens. Transposon mutagenesis and homologous recombination are powerful genetic tools used for the identification of pathogenicity determinants. Transposable elements with potential application to mutagenize pathogenic nocardioform actinomycetes are described. Homologous recombination experiments which have been recently achieved in mycobacteria and related actinomycetes are commented on.

Actinomycetales↗
PubMed1992

Site-directed mutagenesis of conserved residues of Clostridium thermocellum endoglucanase CelC.

Four conserved residues of Clostridium thermocellum endoglucanase CelC were replaced by site-directed mutagenesis. Proteins mutated in His-90, Asn-139 and Glu-140 showed strongly reduced activity, in agreement with predictions of sequence alignments. Mutations in Glu-140 did not result in any detectable change in Km, or apparent size, suggesting that Glu-140 is directly involved in catalysis. The pH optimum of the proteins carrying the Glu-140/Ala and Glu140/Gln mutations was lower than that of the wild type, whereas the activity vs. pH profile of Glu-140/Asp CelC was similar to that of the wild type, suggesting that Glu-140 may act as a proton donor.

Amino Acid Sequence↗
PubMed1991

Inhibition of T cell mitogenesis by nitrofurans.

A group of nitrofurans (5-nitro-2-furaldehyde, nifuroxime, nitrofurazone, nitrofurantoin, 5-nitro-2-furoic acid and 2-nitrofuran) were evaluated for inhibition of mitogenesis (DNA synthesis) in human peripheral blood T cells. T cells, either triggered by phorbol myristate acetate (PMA) or in the presence of accessory cells, were activated with a specified mitogen [phytohemagglutin (PHA), concanavalin A (ConA), or anti-CD3] and the amount of tritiated thymidine incorporated into DNA was determined. The results obtained indicate that nitrofurans inhibit mitogenesis irrespective of activator. 5-Nitro-2-furaldehyde was much more inhibitory than the other compounds, while 2-nitrofuran was less inhibitory. When the aldehyde group (5-nitro-2-furaldehyde) was replaced by a carboxyl group (5-nitro-2-furoic acid), the inhibitory activity was also reduced greatly. These results show that while the nitro group alone confers inhibitory activity to the furan ring, the group at the 2 position is crucial. In general, the mitogenic response of purified T cells (lacking accessory cells) triggered by PMA (phorbol ester) was inhibited less than that of the T cell-accessory cell system. With the latter, 50% inhibition of T cell mitogenesis was achieved by nifuroxime, nitrofurazone, and nitrofurantoin at 45-51 and 34-39 microM with PHA and ConA respectively. When purified T cells were used, the values were 71-85 and 55-60 microM respectively. For a given drug concentration, mitogenesis was more inhibited when induced by ConA or anti-CD3 than by PHA. The importance of using a single cell system (purified T cells) was emphasized by the interesting finding that only this system showed enhancement of mitogenesis, up to 35-40% at low drug levels. With the exception of the nitrofuraldehyde, the nitrofurans at strongly inhibitory levels were only moderately cytotoxic, exhibiting 62-85% cell survival after exposure to drug for 68 hr. Our results suggest that nitrofurans inhibit T cell mitogenesis by a relatively non-toxic mechanism; these results are comparable to those obtained for mammalian cells under aerobic conditions.

Adult↗