Phase transformation B1 to B2 in TiC, TiN, ZrC and ZrN under pressure

Phase stability of various phases of MX (M = Ti, Zr; X = C, N) at equilibrium and under pressure is examined based on first-principles calculations of the electronic and phonon structures. The results reveal that all B1 (NaCl-type) MX structures undergo a phase transition to the B2-structures under high pressure in agreement with the previous total-energy calculations. The B1-MX structures are dynamically stable under very high pressure (210-570 GPa). The pressure-induced B2 (CsCl-type) MC phases are dynamically unstable even at high pressures, and TiN and ZrN are found to crystallize with the B2-structure only at pressures above 55 GPa. The first-order B1-to-B2 phase transition in these nitrides is not related to the softening of phonon modes, and the dynamical instability of B2-MX is associated with a high density of states at the Fermi level.Comment: 9 pages, 4 figure

Low Level of Colistin Resistance and mcr Genes Presence in Salmonella spp.: Evaluation of Isolates Collected between 2000 and 2020 from Animals and Environment

Salmonellosis is one of the most important zoonoses in Europe and the world. Human infection may evolve in severe clinical diseases, with the need for hospitalization and antimicrobial treatment. Colistin is now considered an important antimicrobial to treat infections from multidrugresistant Gram-negative bacteria, but the spreading of mobile colistin-resistance (mcr) genes has limited this option. We aimed to evaluate colistin minimum inhibitory concentration and the presence of mcr (mcr-1 to mcr-9) genes in 236 Salmonella isolates previously collected from different animals and the environment between 2000 and 2020. Overall, 17.79% of isolates were resistant to colistin; no differences were observed in relation to years of isolation (2000–2005, 2009–2014, and 2015–2020), Salmonella enterica subspecies (enterica, salamae, diarizonae, and houtenae), origin of samples (domestic animals, wildlife, and environment), or animal category (birds, mammals, and reptiles); only recently isolated strains from houseflies showed the most resistance. Few isolates (5.93%) scored positive for mcr genes, in particular for mcr-1, mcr-2, mcr-4, mcr-6, and mcr-8; furthermore, only 2.54% of isolates were mcr-positive and colistin-resistant. Detected resistance to colistin was equally distributed among all examined Salmonella isolates and not always related to the presence of mcr genes

Phenotypic and genotypic resistance to colistin in E. coli isolated from wild boar (Sus scrofa) hunted in Italy

The One Health approach is not only focused on diseases and zoonosis control but also on antimicrobial resistance. As concern this important issue, the problem of plasmid-mediated colistin resistance recently emerged. Few studies reported data about colistin resistance and mcr genes in bacteria from wildlife. In this manuscript, 168 Escherichia coli isolated from hunted wild boar were tested; colistin resistance was evaluated by MIC microdilution method, and the presence of mcr-1 and mcr-2 genes was evaluated by PCR. Overall, 27.9% of isolates resulted resistant to colistin, and most of them showed a MIC value > 256 μg/mL. A percentage of 44.6% of tested E. coli scored positive for one or both genes. In details, 13.6% of isolated harbored mcr-1 and mcr-2 in combination; most of them exhibiting the highest MIC values. Interestingly, 19.6% of mcr-positive E. coli resulted phenotypically susceptible to colistin. Wild boar could be considered a potential reservoir of colistin-resistant bacteria. In the light of the possible contacts with domestic animals and humans, this wild species could play an important role in the diffusion of colistin resistance. Thus, the monitoring programs on wildlife should include this aspect

Listeria monocytogenes contamination of Tenebrio molitor larvae rearing substrate: Preliminary evaluations

Today, edible insects represent a hot topic as an emerging and eco-friendly source of protein. The mealworm (Tenebrio molitor L.) is among the most employed insects for human consumption and feed purposes. So far Listeria monocytogenes, have never been detected either in products sold on the market or during the rearing process. In this study, the substrate employed for mealworm rearing was deliberately contaminated with L. monocytogenes and the bacterium was enumerated during the rearing period and after technological treatments of the larvae. L. monocytogenes persisted during the rearing period. Washing the larvae did not produce any significant effect, while fasting the larvae for 24 or 48 h reduced the L. monocytogenes load (P < 0.001). Oven cooking eliminated L. monocytogenes cells from the product, reducing the risk associated to this foodborne pathogen to zero

Caciotta della Garfagnana cheese: selection and evaluation of autochthonous mesophilic lactic acid bacteria as starter cultures

The aim of this study was to isolate, identify and select, with respect to acidification and proteolytic activities, the autochthonous mesophilic lactic acid bacteria (LAB) present in milk and Caciotta della Garfagnana, a cheese produced either with raw or thermised cow's milk in small dairies and family plants of Garfagnana (Tuscany), to obtain LAB strains with attributes suitable to be employed as starter cultures in this type of cheese, particularly when thermised milk is used to control spoilage microflora. Samples of raw milk, curd and cheese were collected from three representative farmers of the production area and used to isolate autochthonous LAB. Phenotypic and genotypic (species-specific PCR assay) identification of isolated LAB was done. Twenty-eight strains of LAB isolated from milk, curd and cheese were screened for acidifying and proteolytic activities. LAB strains with the better attributes were used as mesophilic starter cultures in technological trials: experimental cheeses manufactured with the addition of autochthonous LAB and control cheeses were compared for LAB and pH evolution. Experimental cheeses presented a significant increase in the mesophilic lactic acid microflora up to 14 days of ripening and significantly lower pH values up to seven days of ripening. The use of wild selected mesophilic lactic acid bacteria, together with thermisation of milk, for the Caciotta della Garfagnana looks very promising and could help to both standardise the production and improve quality and traditional characteristics of this type of cheese

Nalaz leptospira u nutrije (Myocastor coypus) i štakora selca (Rattus norvegicus) koji nastanjuju zaštićeno močvarno područje u Toskani u Italiji.

From September 2009 to February 2011, 122 coypus (Myocastor coypus) and 74 rats (Rattus norvegicus) were captured employing cage traps in a protected wetland in Tuscany (central Italy). Blood serum samples were collected from the animals and successively examined by the microagglutination test for several serovars of Leptospira: Bratislava, Ballum, Bataviae, Grippothyphosa, Icterohaemorrhagiae, Copenhageni, Mini, Pomona, Zanoni, Sejroe, Hardjo and Tarassovi. Kidney samples were collected from each animal and tested by bacteriological methods and submitted to Polymerase Chain Reaction. Thirty-four (27.87 %) coypu sera were positive to Leptospira interrogans serovar Bratislava, with antibody titers ranging from 1:100 to 1:400; no strain was isolated from coypu by bacteriological examination, while 12 (9.83 %) subjects were positive to PCR. All rats resulted seronegative; thirty-seven (50 %) Leptospira strains were isolated from rat kidneys; 30 were classified as Leptospira interrogans serovar Icterohaemorrhagiae and 7 as Leptospira interrogans serovar Ballum by the cross-agglutination test. Forty-five (60.81 %) rats resulted positive to PCR: 37 subjects positive to bacteriological examination and there were eight from which no strain were isolated from kidneys. These results would seem to suggest the minor zooepidemiological role of coypu in leptospirosis, which is widespread according to literature.Od rujna 2009. do veljače 2011. u zamke su bile uhvaćene 122 nutrije (Myocastor coypus) i 74 štakora selca (Rattus norvegicus) u zaštićenoj močvari u Toskani u središnjoj Italiji. Prikupljeni uzorci krvnog seruma bili su pretraženi mikroaglutinacijskim testom na nekoliko serovarova leptospira: Bratislava, Ballum, Bataviae, Grippothyphosa, Icterohaemorrhagiae, Copenhageni, Mini, Pomona, Zanoni, Sejroe, Hardjo i Tarassovi. Uzorci tkiva bubrega, uzeti od svake životinje, bili su pretraženi bakteriološki i lančanom reakcijom polimerazom. Tridesetčetiri (27,87 %) uzorka seruma nutrije bila su pozitivna na vrstu Leptospira interrogans serovar Bratislava s titrom protutijela od 1:100 do 1:400. Bakteriološkom pretragom iz nutrija nije bio izdvojen nijedan izolat, dok je 12 uzoraka (9,83 %) bilo pozitivno PCR-om. Svi štakori bili su serološki negativni, ali je 37 (50 %) izolata leptospira bilo izdvojeno iz tkiva njihovih bubrega. Od toga je 30 izolata pripadalo vrsti Leptospira interrogans serovaru Icterohaemorrhagiae, a 7 serovaru Ballum pretragom križnim aglutinacijskim testom. Ukupno su 45 štakora (60,81 %) bila pozitivna pretragom PCR-om, a 37 bakteriološkom pretragom. Od osam štakora nije bio izdvojen nijedan izolat leptospira iz bubrega. Ti rezultati upućuju na neznatnu zooepidemiološku ulogu nutrija u širenju leptospiroze

Characterization of salmonella spp. Isolates from swine: Virulence and antimicrobial resistance

Salmonella is one of the most important zoonotic pathogens worldwide. Swine represent typical reservoirs of this bacterium and a frequent source of human infection. Some intrinsic traits make some serovars or strains more virulent than others. Twenty-nine Salmonella spp. isolated from pigs belonging to 16 different serovars were analyzed for gastric acid environment resistance, presence of virulence genes (mgtC, rhuM, pipB, sopB, spvRBC, gipA, sodCI, sopE), antimicrobial resistance and presence of antimicrobial resistance genes (blaTEM, blaPSE-1, aadA1, aadA2, aphA1-lab, strA-strB, tetA, tetB, tetC, tetG, sul1, sul2, sul3). A percentage of 44.83% of strains showed constitutive and inducible gastric acid resistance, whereas 37.93% of strains became resistant only after induction. The genes sopB, pipB and mgtC were the most often detected, with 79.31%, 48.28% and 37.93% of positive strains, respectively. Salmonella virulence plasmid genes were detected in a S. enterica sup. houtenae ser. 40:z4,z23:-strain. Fifteen different virulence profiles were identified: one isolate (ser. Typhimurium) was positive for 6 genes, and 6 isolates (3 ser. Typhimurium, 2 ser. Typhimurium monophasic variant and 1 ser. Choleraesuis) scored positive for 5 genes. None of the isolates resulted resistant to cefotaxime and ciprofloxacin, while all isolates were susceptible to ceftazidime, colistin and gentamycin. Many strains were resistant to sulfonamide (75.86%), tetracycline (51.72%), streptomycin (48.28%) and ampicillin (31.03%). Twenty different resisto-types were identified. Six strains (4 ser. Typhimurium, 1 ser. Derby and 1 ser. Typhimurium monophasic variant) showed the ASSuT profile. Most detected resistance genes sul2 (34.48%), tetA (27.58%) and strA-strB (27.58%). Great variability was observed in analyzed strains. S. ser. Typhimurium was confirmed as one of the most virulent serovars. This study underlines that swine could be a reservoir and source of pathogenic Salmonella strains

STABILITY AND ORDERING PROPERTIES OF FCC ALLOYS BASED ON RH, IR, PD, AND PT

Stability properties and ordering trends for the six face-centered cubic binary combinations of the four transition metals Rh, Ir, Pd, and Pt are examined in the context of electronic structure calculations. The method is based on a Green function description of the electronic structure of random alloys. Configurational order is treated within the generalized perturbation method. On one hand, the three alloys, Pd-Rh, Pd-Ir and Pt-Ir that have been studied experimentally are confirmed to behave like phase separating systems. On the other hand, the other three mixtures, Pd-Pt, Rh-Ir, and Pt-Rh for which phase separating trends have been inferred from experiments are found to display chemical order with ordering of the (1 0 0), (1 1/2 0) family-types and a mixture of both, respectively. The origin of these results is discussed in terms of electronic structure properties

Occurrence of Coxiella burnetii in goat and ewe unpasteurized cheeses: Screening and genotyping

Q fever is a zoonosis caused by Coxiella burnetii which infects humans as well as several animal species; sheep, goats and cattle are the primary animal reservoir. The main route of human exposure to Coxiella burnetii is inhalation of contaminated aerosols from excreta, especially birth products, while the role of unpasteurized dairy products in the transmission of Q fever to humans remains still controversial. The aim of this work was to evaluate the presence of Coxiella burnetii in unpasteurized cheese samples (n=84) by PCR and to genotype the circulating strains by Multispacer sequence typing (MST) analysis. Coxiella burnetii DNA was detected in 27/84 (32.14%) cheeses and positivity rate of handicraft cheeses reached 17.24%, while positivity rate of non-handicraft cheeses reached 65.38%. In addition, the MST profile of Coxiella burnetii detected in 5 cheese samples have shown the circulation of ST12 and ST32 genotypes in Tuscany