Characterization of a leukocidin identified in Staphylococcus pseudintermedius

Bacterial infections from Staphylococcus pseudintermedius are the most common cause of skin infections (pyoderma) affecting dogs. Two component pore-forming leukocidins are a family of potent toxins secreted by staphylococci and consist of S (slow) and F (fast) components. They impair the innate immune system, the first line of defense against these pathogens. Seven different leukocidins have been characterized in Staphylococcus aureus, some of which are host and cell specific. Through genome sequencing and analysis of the S. pseudintermediussecretome using liquid chromatography mass spectrometry we identified two proteins, named “LukS-I” and “LukF-I”, encoded on a degenerate prophage contained in the genome of S. pseudintermedius isolates. Phylogenetic analysis of LukS-I components in comparison to the rest of the leukocidin family showed that LukS-I was most closely related to S. intermediusLukS-I, S. aureus LukE and LukP, whereas LukF-I was most similar to S. intermedius LukF-I S. aureus gamma hemolysin subunit B. The killing effect of recombinant S. pseudintermediusLukS-I and LukF-I on canine polymorphonuclear leukocytes was determined using a flow cytometry cell permeability assay. The cytotoxic effect occurred only when the two recombinant proteins were combined. Engineered mutant versions of the two-component pore-forming leukocidins, produced through amino acids substitutions at selected points, were not cytotoxic. Anti-Luk-I produced in dogs against attenuated proteins reduced the cytotoxic effect of native canine leukotoxin which highlights the importance of Luk-I as a promising component in a vaccine against canine S. pseudintermedius infections

M\"obius Symmetry of Discrete Time Soliton Equations

We have proposed, in our previous papers, a method to characterize integrable discrete soliton equations. In this paper we generalize the method further and obtain a $q$-difference Toda equation, from which we can derive various $q$-difference soliton equations by reductions.Comment: 21 pages, 4 figure, epsfig.st

Absolute Time Derivatives

A four dimensional treatment of nonrelativistic space-time gives a natural frame to deal with objective time derivatives. In this framework some well known objective time derivatives of continuum mechanics appear as Lie-derivatives. Their coordinatized forms depends on the tensorial properties of the relevant physical quantities. We calculate the particular forms of objective time derivatives for scalars, vectors, covectors and different second order tensors from the point of view of a rotating observer. The relation of substantial, material and objective time derivatives is treated.Comment: 26 pages, 4 figures (minor revision

Nasal carriage of methicillin-resistant coagulase-positive staphylococci among cats and dogs hospitalized in the Veterinary Teaching Hospital of the Faculty of Veterinary Medicine – Technical University of Lisbon, Portugal

Dissertação de Mestrado Integrado em Medicina VeterináriaMethicillin-resistant coagulase-positive staphylococci (MRCPS) colonization in companion animals is an emerging and significant problem in public and animal health. During one year, nasal swabs were obtained from 40 cats and 146 dogs admitted to the Teaching Hospital of the Faculty of Veterinary Medicine - Technical University of Lisbon. MRCPS colonization was screened by plating enrichment cultures on a selective medium, Chrom MRSA ID. Bacterial species and mecA were confirmed by PCR. Clonality of the isolates was assessed by pulsed-field gel electrophoresis (PFGE). All isolates were subjected to spa and SCCmec typing. They were also tested by PCR for the lukF/lukS genes encoding Panton-Valentine leukocidin (PVL) in Staphylococcus aureus and Luk-I and Staphylococcus intermedius exfoliative toxin (SIET) in Staphylococcus pseudintermedius. Methicillin-resistant S. aureus (MRSA) was found in two cats (5 %) and one dog (0.6 %). Isolates were spa type t032, SCCmec IV and shared identical PFGE profiles. These were similar to the EMRSA-15 human clone. Strains were PVL-negative. Nine dogs carried methicillin-resistant S. pseudintermedius (MRSP) (6 %), whereas none of the cats was positive. The PFGE type A strain (n=1) showed identical characteristics as the American MRSP clone strains (CC68-MRSP-V), while PFGE cluster B grouped European MRSP isolates (CC71-MRSP-III) (n=8). All isolates were SIETnegative. The 8 European MRSP isolates were positive for the lukF/lukS genes and the American MRSP isolate was negative for both genes. Strains were multidrug-resistant, which represents a major challenge for veterinarians in terms of antibiotic therapy.RESUMO - Frequência de colonização por staphylococci coagulase-positivo meticilinaresistente em cães e gatos internados no hospital escolar da Faculdade de Medicina Veterinária – Universidade Técnica de Lisboa, Portugal - A colonização por staphylococci coagulase-positivo meticilina-resistente (MRCPS) é um problema emergente e de grande importância em termos de saúde animal e pública. Durante um ano, zaragatoas nasais de 146 cães e 40 de gatos foram obtidas de animais internados no Hospital Escolar da Faculdade de Medicina Veterinária - Universidade Técnica de Lisboa. A colonização por MRCPSfoi pesquisada por inoculação de culturas de enriquecimento num meio selectivo, Chrom MRSA ID. As espécies de MRCPS e a amplificação do gene mecA por feita por PCR. A clonalidade dos isolados foi confirmada por PFGE. Todos os isolados foram sujeitos a tipagem spa e SCCmec. Os isolados de S. aureus meticilina-resistente (MRSA) e de S. pseudintermedius meticilina-resistente (MRSP) foram testados por PCR para a presença dos genes lukF/lukS que codificam, respectivamente, a leucocidina Panton-Valentine (PVL) e a leucocidina-I (Luk-I). Os isolados de MRSP foram ainda testados para a presença da toxina exfoliativa do S. intermedius (SIET). Nesta amostra, 0,6 % (n=1) dos cães testados e 5 % (n=2) dos gatos apresentaram MRSA. Os isolados de MRSA eram spa tipo t032, SCCmec IV e partilhavam padrões idênticos de PFGE. As estirpes eram idênticas ao clone humano EMRSA-15. Os 3 isolados eram PVL negativos. Nove cães apresentaram MRSP (6 %), enquanto nenhum dos gatos foi positivo. PFGE tipo A mostrou características idênticas ao clone americano de MRSP (CC68-MRSP-V) e PFGE tipo B agrupou os isolados europeus de MRSP (CC71-MRSP-III) (n=8). Os isolados de MRSP PFGE tipo B eram Luk-I positivos mas SIET negativos. Todas as estirpes de MRSP eram multirresistentes a várias classes de antibióticos, o que representa um desafio para os médicos veterinários em termos de estratégias de antibioterapia

Faktori koji utječu na oblik zavara kod elektrolučnog zavarivanja trostrukom žičanom elektrodom

The article describes the influences of welding parameters, modes of metal transfer through the arc and the number of wires applied on weld formation and final shape. Diagrams show the influence of current intensity and arc voltage while a figure shows the influence of streaming and rotating metal transfers on the final weld shape. Diagrams and macro specimens, however, show the influence of the number of wires used on the weld shape and weld formation in submerged arc welding with a triple-wire electrode.U članku je opisan utjecaj parametara zavarivanja, utjecaj načina prolaska materijala kroz električni luk i utjecaj broja žica na nastajanje zavara i njegov konačni oblik. Pomoću dijagrama su prikazani utjecaji jačine struje zavarivanja i napetosti električnog luka, a slika prikazuje utjecaj prelaska materijala tečenjem i utjecaj prelaska materijala okretanjem na završni oblik zavara. Dijagramima i pomoću makrobrušenih uzoraka prikazan je utjecaj broja žica na oblik i nastanak vara kod zavarivanja trostrukom žičanom elektrodom pod zaštitom praha

Gold substrate-induced single-mode lasing of GaN nanowires

We demonstrate a method for mode-selection by coupling a GaN nanowire laser to an underlying gold substrate. Multimode lasing of GaN nanowires is converted to single-mode behavior following placement onto a gold film. A mode-dependent loss is generated by the absorbing substrate to suppress multiple transverse-mode operation with a concomitant increase in lasing threshold of only ∼13%. This method provides greater flexibility in realizing practical single-mode nanowire lasers and offers insight into the design of metal-contacted nanoscale optoelectronics