Contribution of enhanced efflux to reduced susceptibility of Salmonella enterica serovar Choleraesuis to fluoroquinolone and other antimicrobials

We examined antimicrobial susceptibility and efflux systems in laboratory-derived mutants of Salmonella enterica serovar Choleraesuis selected by culture on fluoroquinolone-containing plates. The mutants exhibited decreased susceptibilities to quinolones and several other antimicrobials. Mutations in the gyrA gene were not always found in the mutants. Accumulation assays revealed that intracellular enrofloxacin concentrations were significantly lower in the mutants compared with parent isolates. Increased expression of acrB mRNA can explain the decreased susceptibilities to several antimicrobials but not in the case of carbonyl cyanide m-chlorophenylhydrazone (CCCP). Decreased susceptibility to CCCP may result from the increased expression of emrA mRNA. These results suggest that the enhancement of multiple efflux pumps is responsible for decreased susceptibilities to several antimicrobials in the laboratory-derived mutants.     

Nitrogen and oxygen isotope enrichment factors of nitrate at different denitrification rates in an agricultural soil

ABSTRACT

Quantitative evaluation of denitrification by the dual isotope approach, which measures the stable isotope ratios of nitrogen (δ¹⁵N) and oxygen (δ¹⁸O) in nitrate, has been hampered by the wide range of values reported for the ratio of enrichment factors for ¹⁵N and ¹⁸O (¹⁵ε and ¹⁸ε, respectively) during denitrification. The objectives of this study were to determine ¹⁵ε and ¹⁸ε values at different denitrification rates under controlled conditions, and to infer possible mechanisms by which the ¹⁸ε/¹⁵ε ratio is influenced under different conditions. Column experiments were conducted at 25, 15, and 10°C, which enabled determination of ¹⁵ε and ¹⁸ε at different denitrification rates, in the absence of nitrate replenishment from ammonium oxidation and other sources. The values of ¹⁵ε and ¹⁸ε ranged from ?11.8 to ?14.9‰ and from ?8.4 to ?15.9‰, respectively, with ¹⁵ε less sensitive to changes in the denitrification rates. The resultant ¹⁸ε/¹⁵ε ratio, ranging from 0.70 to 1.17, was close to the values reported for sediment incubations, and larger than those for groundwater systems. These results are consistent with the explanations that ¹⁸ε/¹⁵ε value itself is close to unity during denitrification, and that at smaller denitrification rates, concurrent reactions including re-oxidation of nitrite to nitrate lead to smaller apparent fractionation of ¹⁸O and smaller ¹⁸ε/¹⁵ε ratios. This suggests that while linear relationships between δ¹⁸O and δ¹⁵N give a strong evidence of denitrification, apparent ¹⁸ε/¹⁵ε values are site specific and depend on the ambient conditions. In evaluating denitrification in such systems, we suggest the use of ¹⁵ε in preference to ¹⁸ε because ¹⁵ε is less sensitive to denitrification rates.     

Antigen-binding and protein G-binding abilities of immunoglobulin G in hyperimmunized cow's milk treated under various conditions

Skim milk and whey prepared from milk secreted by cows that had been injected with bacteria were kept under various conditions, and the antigen‐binding and protein G‐binding abilities of immunoglobulin G (IgG) in the milk samples were investigated. More than 85% of the original antigen‐binding and protein G‐binding abilities remained when the skim milk was heated at 63°C for 60 min or kept at a pH range of 4–10 for 24 h at 37°C. Both of the high abilities were maintained on pepsin treatment above pH 4 and intestinal proteinase treatments. Little antigen‐binding and protein G‐binding abilities decreased upon storage of the powdered skim milk for 12 months at room temperature. In contrast, at least half, and more than 70% of their respective abilities, were lost upon incubation at pH 2 in the absence and presence of pepsin, respectively, for 1 h at 37°C. These results suggest that most of the biological activities of the Fab‐region and Fc‐region of bovine milk IgG can be maintained during processing or storage, and both of the inactivation degrees mainly depend on the stomach condition after oral ingestion of the IgG preparation.     

Slip systems in MgSiO3 post-perovskite: implications for D' anisotropy

Understanding deformation of mineral phases in the lowermost mantle is important for interpreting seismic anisotropy in Earth's interior. Recently, there has been considerable controversy regarding deformation-induced slip in MgSiO(3) post-perovskite. Here, we observe that (001) lattice planes are oriented at high angles to the compression direction immediately after transformation and before deformation. Upon compression from 148 gigapascals (GPa) to 185 GPa, this preferred orientation more than doubles in strength, implying slip on (001) lattice planes. This contrasts with a previous experiment that recorded preferred orientation likely generated during the phase transformation rather than deformation. If we use our results to model deformation and anisotropy development in the D' region of the lower mantle, shear-wave splitting (characterized by fast horizontally polarized shear waves) is consistent with seismic observations.     

Identification of a high-affinity binding site for dinotefuran in the nerve cord of the American cockroach

The binding of the neonicotinoid insecticide dinotefuran to insect nicotinic acetylcholine receptors (nAChRs) was examined by a centrifugation method using the nerve cord membranes of American cockroaches and [3H]dinotefuran (78 Ci mmol-1). The Kd and Bmax values of [3H]dinotefuran binding were estimated to be 13.7 nM and 14.8 fmol 40 microg-1 protein respectively by Scatchard analysis. Epibatidine, an nAChR agonist, showed a rather lower affinity to the dinotefuran binding site (IC50=991 nM) than dinotefuran (IC50=5.02 nM). Imidacloprid and nereistoxin displayed lower potencies than dinotefuran but higher potencies than epibatidine. The potencies of five dinotefuran analogues in inhibiting the specific binding of [3H]dinotefuran to nerve cord membranes were determined. A good correlation (r2=0.970) was observed between the -log IC50 values of the tested compounds and their piperonyl butoxide-synergised insecticidal activities (-log LD50 values) against German cockroaches. The results indicate that a high-affinity binding site for dinotefuran is present in the nerve cord of the American cockroach and that the binding of ligands to the site leads to the manifestation of insecticidal activity.     

Determining competitive nitrate and chloride adsorption in an andisol by the unsaturated transient flow method

Abstract

Activated sludge from a sewage disposal plant was labeled with ¹⁵N in the laboratory. The labeled sludge (dewatered cake) was then incubated under aerobic conditions for 30 days with four kinds of cultivated soils: volcanic ash soil, red-yellow soil, paddy soil, and sandy dune soil. The nitrogen mineralization of the soil organic matter was remarkable only in the case of the paddy soil. In this soil, a priming effect caused by the addition of the sludge was observed. After 30 days of incubation, the ¹⁵N organic fractions remaining in the red-yellow soil were determined. It was found that the amino acid and the unidentified fractions in the hydrolyzable nitrogen forms of the sludge contributed mainly to the amount of nitrogen mineralized. Finally, using sludges which originated from the same organic matter source, the lnftuence of a generally-used inorganic coagulator Oime and ferric chloride) of sludge on the nitrogen cycle was clarified. This coagulator caused a reduction in the amount of inorpnic nitrogen mineralized in the soil and also accelerated the nitrification process.     

Contrast-enhanced CT features of pyloric lesions in 17 dogs: Case series

Pyloric outflow obstructions can be caused by several types of lesions. When a thickened gastric wall and pyloric mass are detected, malignant neoplasia must be differentiated from chronic hypertrophic pyloric gastropathy. CT can characterize gastric tumors. However, based on the authors’ review of the literature, there is limited information about the CT findings of pyloric lesions. The purpose of this retrospective case series study was to assess the CT findings of canine pyloric lesions. The following CT parameters were recorded: anatomical area, involved area, lesion shape, growth patterns of wall thickening lesions, enhancement pattern of the lesion in the early and delayed phases, lymphomegaly, and pulmonary metastasis. Seventeen dogs were included in this study and had the following final diagnoses: hyperplasia (five dogs), adenoma (five dogs), adenocarcinoma (three dogs), gastrointestinal stromal tumor (GIST; two dogs), polyposis (one dog), and pyogenic granuloma (one dog). Hyperplasia, adenoma, and polyposis formed mass lesions that involved the mucosal layer. Lymphomegaly was detected in two Jack Russell terriers with hyperplasia; however, the causes were unknown because we did not perform biopsies. All adenocarcinomas formed wall-thickened lesion that involved the outer layer, with lymphomegaly. All GISTs formed mass lesion that involved the outer layer. The pyogenic granulomas formed symmetric wall-thickened lesion that involved the mucosal and outer layers. CT facilitated the characterization of canine pyloric lesions using contrast enhancement, based on the involved area and lesion shape. However, polyposis may require caution in diagnosis based on CT findings alone.     

Acute myelomonocytic leukemia (AML-M4) in a dog with the extradural lesion

A two-year-old dog having presented with neurological signs showed marked leukocytosis and appearance of blast cells in the peripheral blood. Hematological and bone marrow examination showed an increase in blasts having both myeloid and monocytic cells characteristics. The dog was diagnosed with acute myelomonocytic leukemia (AML-M4) on the basis of bone marrow findings. Although the dog was treated with a multi-combination chemotherapy, the neurological abnormalities progressed and the dog was euthanized. Myelographic examination and necropsy revealed the extradural lesion formed by AML-M4 around the cervical spinal cord and this lesion was considered as a cause of the neurological signs.     

Dicyema sphyrocephalum (Phylum Dicyemida: Dicyemidae) isolated from Korean common octopus Callistoctopus minor in Korea

BackgroundDicyemids are parasites found in the renal sac of cephalopods. The first species of dicyemid was found from kidneys of the Korean common octopus Callistoctopus minor.ObjectivesThis study aimed to identify the dicyemid and investigate the effect on renal sac of host.MethodsIn this study, we compared the morphological characteristics of isolate to dicyemids (Dicyema sphyrocephalum, Dicyema clavatum, and Dicyema dolichocephalum) reported from C. minor in Japan. We compared the 18S ribosomal RNA (rDNA) and cytochrome c oxidase subunit I (COI) sequences of isolate to the sequences of D. shyrocephalum and D. clavatum. The infected octopuses renal tissues were histologically compared with the tissues of uninfected individuals.ResultsThe morphological characteristic of this isolated species corresponds to D. sphyrocephalum. The sequences similarities of 18S rDNA and COI gene of isolate are 99.7% and 98.1% with D. sphyrocephalum. We observed morphological changes in the epithelia folds of kidney at the dicyemids attached areas.ConclusionsThe present study identified the isolate as D. sphyrocephalum and this is the first report of dicyemid species from Republic of Korea. Further studies on the effects of dicyemids on growth and health status of cephalopods will be needed.