Unraveling Antimicrobial Resistance Genes and Phenotype Patterns among Enterococcus faecalis Isolated from Retail Chicken Products in Japan

Multidrug-resistant enterococci are considered crucial drivers for the dissemination of antimicrobial resistance determinants within and beyond a genus. These organisms may pass numerous resistance determinants to other harmful pathogens, whose multiple resistances would cause adverse consequences. Therefore, an understanding of the coexistence epidemiology of resistance genes is critical, but such information remains limited. In this study, our first objective was to determine the prevalence of principal resistance phenotypes and genes among Enterococcus faecalis isolated from retail chicken domestic products collected throughout Japan. Subsequent analysis of these data by using an additive Bayesian network (ABN) model revealed the co-appearance patterns of resistance genes and identified the associations between resistance genes and phenotypes. The common phenotypes observed among E. faecalis isolated from the domestic products were the resistances to oxytetracycline (58.4%), dihydrostreptomycin (50.4%), and erythromycin (37.2%), and the gene tet(L) was detected in 46.0% of the isolates. The ABN model identified statistically significant associations between tet(L) and erm(B), tet(L) and ant(6)-Ia, ant(6)-Ia and aph(3’)-IIIa, and aph(3’)-IIIa and erm(B), which indicated that a multiple-resistance profile of tetracycline, erythromycin, streptomycin, and kanamycin is systematic rather than random. Conversely, the presence of tet(O) was only negatively associated with that of erm(B) and tet(M), which suggested that in the presence of tet(O), the aforementioned multiple resistance is unlikely to be observed. Such heterogeneity in linkages among genes that confer the same phenotypic resistance highlights the importance of incorporating genetic information when investigating the risk factors for the spread of resistance. The epidemiological factors that underlie the persistence of systematic multiple-resistance patterns warrant further investigations with appropriate adjustments for ecological and bacteriological factors.     

Pr-SNTX,a short-chain three-finger toxin from Papuan pigmy mulga snake,is an antagonist of muscle-type nicotinic acetylcholine receptor (α2βδε)

Three-finger toxins (3FTxs) are one of the major components in snake venoms. In this study, we isolated a cDNA encoding a short-chain 3FTx, Pr-SNTX, from Pseudechis rossignolii. The amino acid sequence of Pr-SNTX is nearly identical to that of its ortholog in Pseudechis australis. Pr-SNTX protein inhibited muscle-type (α₂βδε), but not neuronal α7 nicotinic acetylcholine receptor (nAChR) activity.     

Age-Related Changes of Myelin Proteins in the Rat Peripheral Nervous System

Age-related changes in amounts of myelin proteins from rat sciatic nerve or spinal root were analyzed by sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis (PAGE). In the aged peripheral nerve myelin, the relative amounts of band 105K and proteins X and Y increased, whereas those of proteins P0 and P1 and band 190K decreased. Band 105K purified by preparative SDS-PAGE exhibited three bands of 105K, 28K, and 21K at the second electrophoresis. A repeated SDS-PAGE did not improve the purity of bank 105K, but increased the ratio of 21K to 28K. Compared with P0 protein, band 105K has a very similar peptide map pattern and amino acid composition, as well as the identical NH2 terminal residue, isoleucine. These findings suggest that band 105K is an aggregate form of P0 protein and its fragment, 21K. The 21K protein is a distinct entity from X protein. The quantitative and qualitative alterations in myelin proteins, as we report here, may reflect continuing demyelination and remyelination in aged peripheral nerves.     

Distribution of Acid Proteinase Activity in Molluscs

Acid proteinases with an optimum around pH 3 were demontrated in various tissues of 12 molluscan species. Enzymes strongly inhibited by pepstatin were predominant and the molecular weights of those from two species were in the region of 38,000–68,000, suggesting that they were cathepsin D-type proteinases.     

Regulation of rat brainstem tryptophan 5-monooxygenase. Calcium-dependent reversible activation by ATP and magnesium.

Tryptophan 5-monooxygenase in rat brainstem cytosol was activated about twofold by incubation with 0.5 mm ATP and 5 mm MgCl₂. The activation required micromolar concentrations of Ca²⁺ but was not dependent on either cyclic AMP or cyclic GMP. Rat brain cytosol was shown to possess an endogenous protein kinase which was markedly stimulated by the addition of Ca²⁺ using endogenous protein substrates. Following activation by ATP and Mg²⁺ in the presence of Ca²⁺, tryptophan 5-monooxygenase was reversibly deactivated to the original level by incubation at 30 °C after removal of Ca²⁺ by adding ethylene glycol bis(β-aminoethyl ether)N,N′-tetraacetic acid and was then reactivated by incubation at 30 °C after subsequent addition of Ca²⁺ and ATP. The deactivation was markedly inhibited by the omission of Mg²⁺ or by the addition of NaF.     

N-type Calcium Channel in the Pathogenesis of Experimental Autoimmune Encephalomyelitis

One of the family of voltage-gated calcium channels (VGCC), the N-type Ca²⁺ channel, is located predominantly in neurons and is associated with a variety of neuronal responses, including neurodegeneration. A precise mechanism for how the N-type Ca²⁺ channel plays a role in neurodegenerative disease, however, is unknown. In this study, we immunized N-type Ca²⁺ channel α_1B-deficient (α_1B^−/−) mice and their wild type (WT) littermates with myelin oligodendrocyte glycoprotein 35–55 and analyzed the progression of experimental autoimmune encephalomyelitis (EAE). The neurological symptoms of EAE in the α_1B^−/− mice were less severe than in the WT mice. In conjunction with these results, sections of the spinal cord (SC) from α_1B^−/− mice revealed a reduction in both leukocytic infiltration and demyelination compared with WT mice. No differences were observed in the delayed-type hypersensitivity response, spleen cell proliferation, or cytokine production from splenocytes between the two genotypes. On the other hand, Western blot array analysis and RT-PCR revealed that a typical increase in the expression of MCP-1 in the SC showed a good correlation with the infiltration of leukocytes into the SC. Likewise, immunohistochemical analysis showed that the predominant source of MCP-1 was activated microglia. The cytokine-induced production of MCP-1 in primary cultured microglia from WT mice was significantly higher than that from α_1B^−/− mice and was significantly inhibited by a selective N-type Ca²⁺ channel antagonist, ω-conotoxin GVIA or a withdrawal of extracellular Ca²⁺. These results suggest that the N-type Ca²⁺ channel is involved in the pathogenesis of EAE at least in part by regulating MCP-1 production by microglia.