Intralaboratory validation according to the EN ISO 16 140 Standard of the Vidas SET2 detection kit for use in official controls of staphylococcal enterotoxins in milk products

AIM: Immunological tools used to detect staphylococcal enterotoxins (SEs) in foods are numerous. The aim of this study was to evaluate, on naturally contaminated milk product samples, the performance of the Vidas SET2, in comparison to the Transia plate SET. METHODS AND RESULTS: The Vidas SET2 was compared with the Transia plate SET on supernatants of Staphylococcus aureus isolates and on naturally contaminated milk products. It is noteworthy that when using IgG rabbit treatment, both kits can be considered as equivalent to detect enterotoxins in naturally contaminated milk products. CONCLUSIONS: This study demonstrated that the Vidas SET2 performance is similar to that of Transia plate SET kit, when a rabbit IgG treatment step is used before detection step. This additional treatment significantly decreased, from 42% to 8%, the rate of positive deviations observed using the Transia plate SET detection kit. SIGNIFICANCE AND IMPACT OF THE STUDY: The Vidas SET2 was clearly found as more specific, when no preliminary rabbit IgG treatment was used, and which results in a better workflow when a large number of samples have to be analysed within a few days. Considering the results obtained, the Vidas SET2 detection kit can be used to assess the safety of milk products for SEs.     

Recovery of Flavobacterium psychrophilum viable cells using a charcoal-based solid medium

AIMS: Flavobacterium psychrophilum is the etiological agent of the cold-water disease in salmonids. This micro-organism is somewhat fastidious being difficult to isolate and culture. The aim of this study was to develop a new solid medium which improves the recovery of viable cells from a sample. METHODS AND RESULTS: Six different media [nutrient agar (NA), NA + charcoal (NAC), enriched Anacker Ordal serum (EAOS), EAOS supplemented with aromatic compounds (EAOSa), EAOS with activated charcoal (EAOC) and EAOC supplemented with aromatic compounds (EAOCa)], three of them containing activated charcoal, were used to recover isolated colonies from a diluted sample of Fl. psychrophilum THC02-90. Pair wise comparisons between different media were carried out using the test of bootstrap to determine the best solid medium and if the presence of activated charcoal increased the number of colonies. The results showed that activated charcoal improved the recovery of viable cells in all the cases and NAC was slightly better than EAOCa but more variable. CONCLUSIONS: Activated charcoal has a great capacity of absorption of toxic compounds and it has no nutritional value, so the problems to culture and isolate Fl. psychrophilum are in part due to an inhibition phenomenon. The use of EAOCa can overcome some of these problems. SIGNIFICANCE AND IMPACT OF THE STUDY: The improvement in Fl. psychrophilum cultivation will facilitate physiological, biochemical and genetic studies with this bacterium.     

The biogeography and population genetics of neotropical vector species

Phylogenetic and population genetic data support the Pliocene or Pleistocene divergences of the co-distributed hematophagous insect vectors, the sand fly Lutzomyia longipalpis s.l., the mosquitoes Anopheles darlingi and A. albitarsis s.l., and the triatomines Rhodnius prolixus and R. robustus. We examined patterns of divergence and distribution in relation to three hypotheses of neotropical diversification: Miocene/Pliocene marine incursion, Pliocene/Pleistocene riverine barriers and Pleistocene refugia. Only R. prolixus has a pattern concordant with the refugia hypothesis, and R. robustus conforms to the marine incursion predictions. A. darlingi partially fits the refugia hypothesis. For L. longipalpis s.l. and A. albitarsis s.l., elements of both incursion and refugia hypotheses seem to fit, suggesting perhaps an interaction of factors determining their distribution patterns.     

Aerenchyma development and elevated alcohol dehydrogenase activity as alternative responses to hypoxic soils in the Piriqueta caroliniana complex

The ability of plants to make morphological or physiological adjustments in response to environmental cues allows them to survive and reproduce under a wide range of conditions. One stress that plants are often exposed to is soil oxygen depletion due to flooding. Plants can respond to hypoxic soils by producing oxygen-conducting aerenchymous tissue or through induction of enzymes in the ethanolic fermentation pathway. Here we use greenhouse experiments to examine flood responses in plants of the Piriqueta caroliniana (Turneraceae) complex, which occupy a range of moisture regimes. Morphotypes and hybrids in this complex exhibited contrasting responses to hypoxic conditions. Genotypes from flooded habitats developed aerenchyma and did not substantially elevate levels of alcohol dehydrogenase (ADH) activity, an enzyme associated with anaerobic respiration. Plants from drier sites, on the other hand, did not develop aerenchyma but had much higher levels of ADH activity. Plants with aerenchymous tissue had substantially higher rates of growth under sustained flooding. Results are consistent with the hypothesis that aerenchyma development is an effective strategy in habitats subject to persistent flooding, while elevating activity of enzymes for ethanolic fermentation is effective only under ephemeral flooding. The range of phenotypic responses observed illustrates contrasting adaptive strategies that can lead to habitat isolation and evolutionary divergence.     

Expression profiling of candidate genes for abdominal fat mass in domestic chicken <Emphasis Type="Italic">Gallus gallus</Emphasis>

The quantitative traits of mass and percentage of abdominal fat in chicken and various types of obesity in mammals are homologous and functionally similar. Therefore, the genes involved in obesity development in humans and laboratory rodents as well as those responsible for pig lard thickness could be involved in abdominal fat deposition in broilers. Expression of candidate genes FABP1, FABP2, FABP3, HMGA1, MC4R, PPARG, PPARGC1A, POMC and PTPN1 was studied in fat, liver, colon, muscle, pituitary gland, and brain in chicken (broilers) using real-time PCR. Significant difference in the HMGA1 gene expression in the liver of broiler chicken with high (3.5 ± 0.18%) and low (1.9 ± 0.56%) abdominal fat concentration has been revealed. The expression of this gene was been shown to correlate with the amount (0.7, P ≤ 0.01) and mass (0.7, P ≤ 0.01) of abdominal fat. The PPARG gene expression in liver in the same chicken subsets was also significantly different. Correlation coefficients of the gene expression with the abdominal fat amount and mass were respectively 0.55 (P ≤ 0.05) and 0.57 (P ≤ 0.01). Based on these results, we suggest that the HMGA1 and PPARG genes are involved in abdominal fat deposition. The search for single nucleotide polymorphisms (SNPs) in the HMGA and PPARG regulatory regions could facilitate identifying genetic markers for broiler breeding according to the mass and percentage of abdominal fat.     

The population structure of Mycobacterium tuberculosis in Mongolia as assessed using large sequence polymorphism analysis

112 strains of M. tuberculosis isolated from lung tuberculosis patients in Mongolia were genotyped using RD9, RD7, TbD1, RD105, and RD750 loci. The genotypes of all the strains studied were characterized using the conservation of RD7, RD9, and RD750 loci and the presence of the deletion in the locus TbD1. RD105 was detected in 65 isolates (58%). The isolate was classified into two groups--East-Asian and Euro-American.     

Role of the JNK pathway in NMDA-mediated excitotoxicity of cortical neurons

Excitotoxic insults induce c-Jun N-terminal kinase (JNK) activation, which leads to neuronal death and contributes to many neurological conditions such as cerebral ischemia and neurodegenerative disorders. The action of JNK can be inhibited by the D-retro-inverso form of JNK inhibitor peptide (D-JNKI1), which totally prevents death induced by N-methyl-D-aspartate (NMDA) in vitro and strongly protects against different in vivo paradigms of excitotoxicity. To obtain optimal neuroprotection, it is imperative to elucidate the prosurvival action of D-JNKI1 and the death pathways that it inhibits. In cortical neuronal cultures, we first investigate the pathways by which NMDA induces JNK activation and show a rapid and selective phosphorylation of mitogen-activated protein kinase kinase 7 (MKK7), whereas the only other known JNK activator, mitogen-activated protein kinase kinase 4 (MKK4), was unaffected. We then analyze the action of D-JNKI1 on four JNK targets containing a JNK-binding domain: MAPK-activating death domain-containing protein/differentially expressed in normal and neoplastic cells (MADD/DENN), MKK7, MKK4 and JNK-interacting protein-1 (IB1/JIP-1).     

Diatomic ligand discrimination by the heme oxygenases from Neisseria meningitidis and Pseudomonas aeruginosa

Heme oxygenases have an increased binding affinity for O2 relative to CO. Such discrimination is critical to the function of HO enzymes because one of the main products of heme catabolism is CO. Kinetic studies of mammalian and bacterial HO proteins reveal a significant decrease in the dissociation rate of O2 relative to other heme proteins such as myoglobin. Here we report the kinetic rate constants for the binding of O2 and CO by the heme oxygenases from Neisseria meningitidis (nmHO) and Pseudomonas aeruginosa (paHO). A combination of stopped-flow kinetic and laser flash photolysis experiments reveal that nmHO and paHO both maintain a similar degree of ligand discrimination as mammalian HO-1 and the HO from Corynebacterium diphtheriae. However, in addition to the observed decrease in dissociation rate for O2 by both nmHO and paHO, kinetic analyses show an increase in dissociation rate for CO by these two enzymes. The crystal structures of nmHO and paHO both contain significant differences from the mammalian HO-1 and bacterial C. diphtheriae HO structures, which suggests a structural basis for ligand discrimination in nmHO and paHO.