Methicillin-Susceptible Staphylococcus aureus as a Predominantly Healthcare-Associated Pathogen: A Possible Reversal of Roles?

Methicillin-resistant Staphylococcus aureus (MRSA) strains have become common causes of skin and soft tissue infections (SSTI) among previously healthy people, a role of methicillin-susceptible (MSSA) isolates before the mid-1990s. We hypothesized that, as MRSA infections became more common among S. aureus infections in the community, perhaps MSSA infections had become more important as a cause of healthcare-associated infection.We compared patients, including children and adults, with MRSA and MSSA infections at the University of Chicago Medical Center (UCMC) from all clinical units from July 1, 2004-June 30, 2005; we also compared the genotypes of the MRSA and MSSA infecting bacterial strains.Compared with MRSA patients, MSSA patients were more likely on bivariate analysis to have bacteremia, endocarditis, or sepsis (p = 0.03), to be an adult (p = 0.005), to be in the intensive care unit (21.9% vs. 15.6%) or another inpatient unit (45.6% vs. 40.7%) at the time of culture. MRSA (346/545) and MSSA (76/114) patients did not differ significantly in the proportion classified as HA-S. aureus by the CDC CA-MRSA definition (p = 0.5). The genetic backgrounds of MRSA and MSSA multilocus sequence type (ST) 1, ST5, ST8, ST30, and ST59 comprised in combination 94.5% of MRSA isolates and 50.9% of MSSA isolates. By logistic regression, being cared for in the Emergency Department (OR 4.6, CI 1.5-14.0, p = 0.008) was associated with MRSA infection.Patients with MSSA at UCMC have characteristics consistent with a health-care-associated infection more often than do patients with MRSA; a possible role reversal has occurred for MSSA and MRSA strains. Clinical MSSA and MRSA strains shared genotype backgrounds

An Antireflective Nanostructure Array Fabricated by Nanosilver Colloidal Lithography on a Silicon Substrate

An alternative method is presented for fabricating an antireflective nanostructure array using nanosilver colloidal lithography. Spin coating was used to produce the multilayered silver nanoparticles, which grew by self-assembly and were transformed into randomly distributed nanosilver islands through the thermodynamic action of dewetting and Oswald ripening. The average size and coverage rate of the islands increased with concentration in the range of 50–90 nm and 40–65%, respectively. The nanosilver islands were critically affected by concentration and spin speed. The effects of these two parameters were investigated, after etching and wet removal of nanosilver residues. The reflection nearly disappeared in the ultraviolet wavelength range and was 17% of the reflection of a bare silicon wafer in the visible range

Monocyte Scintigraphy in Rheumatoid Arthritis: The Dynamics of Monocyte Migration in Immune-Mediated Inflammatory Disease

Background: Macrophages are principal drivers of synovial inflammation in rheumatoid arthritis (RA), a prototype immune-mediated inflammatory disease. Conceivably, synovial macrophages are continuously replaced by circulating monocytes in RA. Animal studies from the 1960s suggested that macrophage replacement by monocytes is a slow process in chronic inflammatory lesions. Translation of these data into the human condition has been hampered by the lack of available techniques to analyze monocyte migration in man. Methods/Principal Findings: We developed a technique that enabled us to analyze the migration of labelled autologous monocytes in RA patients using single photon emission computer tomography (SPECT). We isolated CD14+ monocytes by CliniMACS in 8 patients and labeled these with technetium-99m (99m-Tc-HMPAO). Monocytes were re-infused into the same patient. Using SPECT we calculated that a very small but specific fraction of 3.4x10(-3) (0.95-5.1x10(-3)) % of re-infused monocytes migrated to the inflamed joints, being detectable within one hour after re-infusion. Conclusions/Significance: The results indicate monocytes migrate continuously into the inflamed synovial tissue of RA patients, but at a slow macrophage-replacement rate. This suggests that the rapid decrease in synovial macrophages that occurs after antirheumatic treatment might rather be explained by an alteration in macrophage retention than in monocyte influx and that RA might be particularly sensitive to treatments targeting inflammatory cell retention

Geohelminth Infections among Pregnant Women in Rural Western Kenya; a Cross-Sectional Study

In rural western Kenya, both malaria and intestinal infections with worms are common. Pregnant women are particularly vulnerable to infection with malaria, but the effect on pregnancy of intestinal infections with worms is not clear and may depend both on how heavy the worm infection is and on the type of worm. Additionally, it is not clear whether infections with worms may affect malaria infections. In this article, we begin to disentangle some of these issues. Intestinal infections with worms were diagnosed in three-quarters of 390 pregnant women in western Kenya who provided a stool sample. In these women, intestinal worm infections caused a modest decrease both in haemoglobin levels and indicators of nutritional status. Women in their second and third pregnancies who were diagnosed with one particular type of worm infection (Ascaris lumbricoides) were less likely to have malaria than other women in their second or third pregnancies who did not have this type of worm infection. Although our results suggest that it would be good advice to treat women with drugs for intestinal worm infections during their pregnancy in this area, the effect on maternal and infant health and malaria infection needs further study

Inhibition of PbGP43 expression may suggest that gp43 is a virulence factor in Paracoccidioides brasiliensis

ABSTARCT: Glycoprotein gp43 is an immunodominant diagnostic antigen for paracoccidioidomycosis caused by Paracoccidioides brasiliensis. It is abundantly secreted in isolates such as Pb339. It is structurally related to beta-1,3-exoglucanases, however inactive. Its function in fungal biology is unknown, but it elicits humoral, innate and protective cellular immune responses; it binds to extracellular matrix-associated proteins. In this study we applied an antisense RNA (aRNA) technology and Agrobacterium tumefaciens-mediated transformation to generate mitotically stable PbGP43 mutants (PbGP43 aRNA) derived from wild type Pb339 to study its role in P. brasiliensis biology and during infection. Control PbEV was transformed with empty vector. Growth curve, cell vitality and morphology of PbGP43 aRNA mutants were indistinguishable from those of controls. PbGP43 expression was reduced 80-85% in mutants 1 and 2, as determined by real time PCR, correlating with a massive decrease in gp43 expression. This was shown by immunoblotting of culture supernatants revealed with anti-gp43 mouse monoclonal and rabbit polyclonal antibodies, and also by affinity-ligand assays of extracellular molecules with laminin and fibronectin. In vitro, there was significantly increased TNF-α production and reduced yeast recovery when PbGP43 aRNA1 was exposed to IFN-γ-stimulated macrophages, suggesting reduced binding/uptake and/or increased killing. In vivo, fungal burden in lungs of BALB/c mice infected with silenced mutant was negligible and associated with decreased lung ΙΛ-10 and IL-6. Therefore, our results correlated low gp43 expression with lower pathogenicity in mice, but that will be definitely proven when PbGP43 knockouts become available.

Role of mprF1 and mprF2 in the Pathogenicity of Enterococcus faecalis

Aujourd hui, Enterococcus faecalis est considéré comme l un des plus importants agents pathogènes causant des maladies nosocomiales. En raison de sa résistance innée et acquise aux antibiotiques, l identification de nouvelles cibles pour le traitement de cette bactérie est une grande priorité. Le facteur Multiple Peptide Résistance (MprF), qui a été décrit en premier chez Staphylococcus aureus, modifie le phosphatidylglycérol avec de la lysine et réduit ainsi la charge négative de l enveloppe cellulaire. Ceci a comme conséquence d augmenter la résistance aux peptides antimicrobiens cationiques (PAC). Deux gènes paralogues putatifs (mprF1 et mprF2) ont été identifiés chez E. faecalis par recherche BLAST en utilisant le gène décrit chez S. aureus. Une caractérisation de ces deux gènes d E. faecalis ainsi que des mécanismes conduisant à une résistance aux PAC, pourrait aider à développer des nouvelles stratégies thérapeutiques contre ce pathogène. Deux mutants de délétion et un double mutant ont été construits par recombinaison homologue chez E. faecalis. L analyse des phospholipides des membranes cytoplasmiques des deux mutants mprF1 et mprF2 par chromatographie sur couche mince a montré que seule l inactivation de mprF2 inhibe la synthèse de trois amino-phosphatidlyglycérol distincts (comme la Lysine-PG, l Alanine-PG et l Arginine-PG). De plus, le mutant mprF2 est également plus sensible aux PAC que la souche sauvage. La capacité de formation d un biofilm est généralement considérée comme un facteur important de virulence, ce qui est également le cas pour les entérocoques. Le mutant mprF2 montre une capacité accrue dans ce phénomène. Ceci semble être du à une augmentation de la concentration d ADN extracellulaire dans le biofilm formé par ce mutant. Curieusement, cette augmentation est indépendante d une autolyse. Le mutant mprF2 est également plus résistant à l opsonophagocytose. Cependant, le gène mprF2 ne joue aucun rôle dans les bactériémies de souris et les endocardites de rats.En revanche, aucun phénotype n a été trouvé pour un mutant mprF1 jusqu à présent. Cette mutation ne modifie ni la synthèse de l aminoacyl-PG en condition de laboratoire ni la résistance aux PAC et à l opsonophagocytose. Par conséquent, il semble que mprF2 soit le seul gène mprF fonctionnel chez E. faecalis. Néanmoins, contrairement à d autres bactéries, mprF2 ne semble pas être un facteur de virulence majeur pour cette espèce.Enterococcus faecalis is regarded nowadays as one of the most important nosocomial pathogens. Due to its innate and acquired resistance to antibiotics, identification of new targets for antimicrobial treatment of E. faecalis is a high priority. The multiple peptides resistance factor (MprF), which was first described in Staphylococcus aureus, modifies phosphatidylglycerol with lysine and reduces the negative charge of the membrane, thus increasing resistance to cationic antimicrobial peptides (CAMPs). Two putative mprF paralogs (mprF1 and mprF2) were identified in E. faecalis by Blast search using the well-described S. aureus gene as a lead. A better understanding of these two genes and mechanisms leads to enterococcal resistance to CAMPs might help designing therapeutic strategies against this bacteria. Two single deletion mutants and double mutant in E. faecalis were created by homologues recombination. Analysis of cell membrane phospholipids from both mutants by thin-layer chromatography showed that inactivation of mprF2 abolished the synthesis of three distinct amino-phosphatidylglycerol (mostly likely Lysin-PG, Alanine-PG and Argine-PG). The CAMPs testing assay demonstrated that the deletion mutant of mprF2 was more susceptible to CAMPs than the wild type. Biofilm formation is usually regarded as a virulence factor which provides an important way for enterococci to cause infections. Inactivation of mprF2 led to increase the biofilm formation which we showed that it was due to the accumulation of eDNA in the biofilm, but the release of eDNA is independent from autolysis. The mprF2 mutant was resistance to killing by opsonophagocytosis more than wild type. However, the mprF2 gene plays no role in bacteremia in mice and rat endocarditis. Our results showed that non polar effect mprF1 mutant does not affect in the synthesis of aminoacyl-PG in the laboratory condition. It also has no effect on susceptible to CAMPs, opsonic killing and autolysis. Therefore, it seems that mprF2 is the only functional mprF gene in E. faecalis in the laboratory condition. Unlike mprF found in other bacteria, mprF does not seem to be a major virulence factor in enterococci.CAEN-BU Sciences et STAPS (141182103) / SudocSudocFranceF