The clones of Listeria monocytogenes detected in food depend on the method used

S. LONCAREVIC, W. THAM AND M.-L. DANIELSSON-THAM. 1996. Restriction enzyme analysis (REA) with pulsed-field gel electrophoresis (PFGE) has been used to characterize and compare Listeria monocytogenes strains isolated from foods by two methods, an enrichment procedure and a direct plating procedure. In total 151 isolates from nine foods were investigated. In six of the foods (101 strains investigated) only one clone of L. monocytogenes was found irrespective of the method used. In three foods (50 strains investigated) the direct plating procedure yielded more clones than the enrichment procedure. At the most, five clones were detected in the same food. The results presented here indicate that direct plating from the food reveals more L. monocytogenes clones than revealed by an enrichment procedure.     

Emergence and kinetics of simian immunodeficiency virus-specific CD8(+) T cells in the intestines of macaques during primary infection

In this report, three Mamu-A*01(+) rhesus macaques were examined to compare the emergence of simian immunodeficiency virus (SIV)-specific CD8(+) T cells in the intestines and blood in early SIV infection using a major histocompatibility complex class I tetramer complexed with the Gag(181-189) peptide. Fourteen days after intravenous inoculation with SIVmac251, large numbers of SIV Gag(181-189)-specific CD8(+) T cells were detected in the intestinal mucosa (3.1 to 11.5% of CD3(+) CD8(+) lymphocytes) as well as in the blood (3.1 to 13.4%) of all three macaques. By 21 days postinoculation, levels of tetramer-binding cells had dropped in both the intestines and blood. At day 63, however, levels of SIV Gag(181-189)-specific CD8(+) T cells in the intestines had rebounded in all three macaques to levels that were higher (8.6 to 18.7%) than those at day 21. In contrast, percentages of tetramer-binding cells in the peripheral blood remained comparatively stable (2.5 to 4.5%) at this time point. In summary, SIV Gag(181-189)-specific CD8(+) T cells appeared in both the intestinal mucosa and peripheral blood at a comparable rate and magnitude in primary SIV infection. Given that the intestine is a major site of early viral replication as well as the site where most of the total body lymphocyte pool resides, these data indicate that it is also an early and important site of development of antiviral immune responses.     

Responses ofGanoderma lucidum to heavy metals

The lelvels of seven heavy metals and their toxicity towardGanoderma lucidum under various cultivation conditions were assessed. The contents of Mn, Cu, Zn, Cd, Hg, Pb and U in the fruitbodies of cultivatedG. lucidum, and sawdust substrates were determined to be at trace levels for U, 0.01–0.1 μg/g for Cd and Hg, and 1–5 μg/g for Pb, 10–120 μg/g for Mn, Cu and Zn. The effects of heavy metals, on the growth of mycelia ofG. lucidium in pure cultures were examined over a wide range of concentrations (10–3,000 μg/ml), and their toxicities were found to decrease in the order: Hg>Cd>Cu>U>Pb>Mn=Zn. The translocation and accumulation of Zn from contaminated substrates (at 10 μg/g) in fruitbodies were investigated by using⁶⁵Zn tracer, andG. lucidum was found to take up Zn with an efficiency of >60%, leading to accumulation of >100 μ/g, in fruitbodies and >80 μ/g Zn in basidiospores.     

Growth and fruitbody formation ofGanoderma lucidum on media supplemented with vanadium, selenium and germanium

Responses of mycelia ofGanoderma lucidum to vanadium, selenium and germanium were examined over a wide range of concentrations (10–1, 120 μg/ml) in pure culture. Se and V were found to be highly toxic, but Ge was not toxic at the levels tested.Ganododerma lucidum cultivated on substrates of sawdust with V (30–80 μg/g) developed mature fruitbodies, but the bioaccumulation of V was quite low (2.5–7 μg/g in pileus, 12.5–21.5 μg/g in stipe and <1 μg/g in basidiospores). Se as Na₂SeO₄ labeled with⁷⁵Se was effectively taken up from substrates and accumulated in fruitbodies (mainly in pileus), then depleted by discharge of basidiospores. Ge as GeCl₄ labeled with⁷⁷Ge was easily uptaken and translocated into fruitbodies.     

Household environmental microbiota influences early-life eczema development

Exposure to a diverse microbial environment during pregnancy and early postnatal period is important in determining predisposition towards allergy. However, the effect of environmental microbiota exposure during preconception, pregnancy and postnatal life on development of allergy in the child has not been investigated so far. In the S-PRESTO (Singapore PREconception Study of long Term maternal and child Outcomes) cohort, we collected house dust during all three critical window periods and analysed microbial composition using 16S rRNA gene sequencing. At 6 and 18 months, the child was assessed for eczema by clinicians. In the eczema group, household environmental microbiota was characterized by presence of human-associated bacteria Actinomyces, Anaerococcus, Finegoldia, Micrococcus, Prevotella and Propionibacterium at all time points, suggesting their possible contributions to regulating host immunity and increasing the susceptibility to eczema. In the home environment of the control group, putative protective effect of an environmental microbe Planomicrobium (Planococcaceae family) was observed to be significantly higher than that in the eczema group. Network correlation analysis demonstrated inverse relationships between beneficial Planomicrobium and human-associated bacteria (Actinomyces, Anaerococcus, Finegoldia, Micrococcus, Prevotella and Propionibacterium). Exposure to natural environmental microbiota may be beneficial to modulate shed human-associated microbiota in an indoor environment.     

Hydrolysis and resynthesis of sucrose and related sugars in the developing stem tissues of Eucalyptus regnans trees

Summary When cambial tissues are removed from tree stems of Eucalyptus regnans F. Muell. and incubated in vitro with [¹⁴C]glucose, [¹⁴C]galactose and [¹⁴C]fructose in the presence of sufficient PVP (polyvinylpyrrolidone) radioactive sucrose, members of the raffinose family and related sugars are synthesized. These results suggest that PVP inactivates substances which, in in vitro experiments, inhibit the action of enzymes which are essential to the resynthesis of nutrient sugars (sucrose, raffinose and stachyose). In living trees, such enzyme inhibition is less likely to occur.     

Early induction of functional SARS-CoV-2-specific T cells associates with rapid viral clearance and mild disease in COVID-19 patients

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