Mupirocin is a bacteriostatic antibiotic that is used to decolonize people who carry methicillin-resistant staphylococci, primarily methicillin-resistant Staphylococcus aureus (MRSA). Mupirocin reversibly binds to bacterial isoleucyl tRNA synthetase to disrupt protein synthesis. Resistance to mupirocin is due either to a point mutation to the ileS gene that encodes the isoleucyl tRNA synthetase, classified as low-level mupirocin resistance; or, bacteria may obtain a plasmid that carries the ileS2 gene encoding an alternate isoleucyl tRNA synthetase, conferring high-level resistance. Mupirocin resistance plasmids contain insertion sequence (IS) 257 repeats, into which the ileS2 gene is inserted. Such plasmids have been characterized by their IS257-ileS2 junctions in both S. aureus and, recently, in Staphylococcus pseudintermedius in a dog from Croatia. The primary goals of this study were to determine the prevalence of mupirocin resistance in isolates of S. pseudintermedius in Texas, to determine whether resistance was due to point mutations in the native ileS or due to carriage of mupirocin resistance plasmids, and to characterize the structure of the mupirocin resistance genes carried on plasmids. In this study, 572 S. pseudintermedius isolates, collected from veterinary patients from across Texas were screened for their susceptibility to low levels of mupirocin. Of these isolates, only one out of 572 (0.17%) tested positive for mupirocin resistance and was found by polymerase chain reaction (PCR), using previously published primers mupA and mupB, to have a 458 bp fragment and, with primers M1 and M2 to have a 237 bp fragment, indicating the presence of the high-level mupirocin resistance gene, ileS2. The arrangement of the IS257-ileS2 junctions was then analyzed by PCR and the products, bands at 1816 bp for primers ileS2-5’ and IS257R and at 1127 bp for primers ileS2-3’ and IS257F, which are consistent with the amplification pattern for an S2 plasmid, were cloned into a plasmid, pT7Blue, and sequenced for comparison to published sequences in GenBank. BLAST analyses in NCBI, comparing the isolate to recently published sequences for mupirocin-resistant S. pseudintermedius isolated from a dog with pyoderma in Croatia, indicate a 100% similarity to the upstream junction, JX186508, and 97% to the downstream junction, JX186509.

No description available.

La mammite bovine (inflammation des glandes mammaires), est la maladie la plus fréquente chez les vaches laitières et la plus coûteuse pour les producteurs laitiers. Plusieurs microorganismes peuvent causer la mammite mais Staphylococcus aureus en est le plus souvent responsable. En exprimant une panoplie de gènes de virulence, la bactérie est capable d’éviter l’action du système immunitaire. Sa capacité à résister au traitement antibiotique, soit en exprimant des gènes de résistance ou en se localisant à l’intérieur des cellules hôtes, est également documentée. Toutes ses raisons font que S. aureus peut causer des mammites chroniques et que le besoin de trouver de nouvelles stratégies thérapeutiques est bien réel. Beaucoup d’études ont été menées pour trouver de nouvelles molécules ou des vaccins pour traiter cette pathologie. La plupart d’entre elles ont été réalisées in vitro ou dans des modèles murins, lesquels ne représentent pas exactement la réalité d’une infection de glande mammaire de vache laitière. Le présent projet de doctorat a proposé une approche davantage reliée à la réalité de cette infection. Nous avons donc voulu identifier les gènes exprimés par S. aureus durant la mammite bovine afin de mieux orienter la recherche de cibles thérapeutiques. Pour y parvenir, nous avons effectué des infections expérimentales de vaches laitières, développé une méthode d’isolement des bactéries du lait, procédé aux analyses transcriptomiques et identifié des gènes exprimés par la bactérie lors de l’infection. Cette approche n’avait encore jamais été tentée dans le contexte de la mammite bovine à cause des nombreux défis techniques que nous avons relevés. Les gènes de S. aureus identifiés lors du présent projet ont mené à différentes découvertes. D’abord, nous avons pu vérifier l’importance de deux de ces gènes pour la virulence de la bactérie lors de l’infection. Ensuite, c’est cette analyse transcriptomique qui est à la base du développement d’un vaccin dont l’efficacité est en cours d’analyse, et du développement d'une nouvelle classe d’antibiotique qui vise un gène exprimé lors de la mammite. Ces deux dernières percées font chacune l’objet d’un brevet d’invention. Nous sommes donc partis de l’hypoThèse que les gènes exprimés par S. aureus lors de la mammite bovine sont essentiels ou importants pour sa virulence ou sa survie et que ceux-ci représentent de bons candidats au développement de nouvelles stratégies thérapeutiques. Cette Thèse rapporte précisément un tel constat.

Staphylococcus aureus (S. aureus) is a bacterium commonly found on the skin and associated with minor skin and soft tissue infections. It is possible for S. aureus to infect the bloodstream, which can lead to serious illness and possibly death. Endothelial cells line all blood vessels in the body and serve as the last defense against pathogens attempting to invade the bloodstream. We have found that S. aureus requires a cellular pathway, called the phosphoinositide 3-kinase (PI3K) pathway, to be active in order to invade endothelial cells. PI3K has multiple isoforms and we hypothesize that one isoform, p1 l Oa, is specifically utilized for infection. We have gathered strong evidenceto suggest that p 1 l Oa plays a significant role in the infection process of S. aureus; however more experiments are needed to conclude that our hypothesis is supported. / Department of Biology

Abstract Sepsis is a serious clinical condition that is characterized by a systemic inflammatory response syndrome resulting from a known or suspected infection. The major clinical symptoms involve an abnormal WBC count, elevated body temperature, respiration and pulse rate. Reported cases with high mortality rate range between 13 - 20 million. In order to treat Sepsis, the detection of bacteria in blood culture is extremely crucial. Treating patients with broad spectrum antibiotics is usually related to adverse effects, drug resistance, increased mortality, and high cost. In the past decades, researches had detected that E. coli and S. aureus are the major role players that cause sepsis. These microbes are molecularly tested by methods like MALDI TOF, FISH and Microarrays.   In this analysis, DNA fluorescence in situ hybridization (FISH) assessment for the identification of S. aureus, one of the most frequent blood pathogens, was optimized in the labs of Högskolan i Skövde. As a result, the growth of S. aureus was observed very carefully, optimizing the FISH procedure for gram positive bacteria was done and the sensitivity, stability and specificity of the DNA probe were examined under variant conditions like the continuous decrease in the bacteria cells number and utilizing a mixture of different types of bacteria cells. / Data mining strategies and molecular techniques for microbial detection in severe sepsis

No description available.

Bacterial contamination of platelet concentrates (PCs) poses the major transfusion-associated infectious risk. Coagulase negative staphylococci (CoNS), the predominant platelet contaminants, are recognized as one of the leading causes of hospital-acquired infections due to their ability to form biofilms (surface-attached aggregates). In this study, 29 CoNS strains were characterized for their growth and biofilm formation abilities in media and PCs. Twenty-five strains were aerobic including Staphylococcus epidermidis, S. capitis, and S. chromogenes, while four were identified as the anaerobe S. saccharolyticus. Biofilm-associated icaA and icaD genes were amplified from eight strains. Interestingly, only six of those strains were biofilm-positive. Sequencing of S. capitis icaD revealed no mutations that could explain differences in biofilm phenotypes. Growth of CoNS in PCs varied significantly between strains. This study provides preliminary evidence that slow-growing biofilm-positive S. epidermidis are more likely to be missed during platelet culture, highlighting the need for improved screening methods.

xiv, 131 leaves : ill. ; 28 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Biochemistry, 1975

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniv., 2004. / Härtill 4 uppsatser.

Thesis (M.P.H.) -- University of Adelaide, Dept. of Public Health, 1999. / Bibliography: leaves 117-136.