Community-associated methicillin-resistant Staphylococcus aureus transmission in households of infected cases: a pooled analysis of primary data from three studies across international settings.

Diverse strain types of methicillin-resistant Staphylococcus aureus (MRSA) cause infections in community settings worldwide. To examine heterogeneity of spread within households and to identify common risk factors for household transmission across settings, primary data from studies conducted in New York (USA), Breda (The Netherlands), and Melbourne (Australia) were pooled. Following MRSA infection of the index patient, household members completed questionnaires and provided nasal swabs. Swabs positive for S. aureus were genotyped by spa sequencing. Poisson regression with robust error variance was used to estimate prevalence odds ratios for transmission of the clinical isolate to non-index household members. Great diversity of strain types existed across studies. Despite differences between studies, the index patient being colonized with the clinical isolate at the home visit (P < 0·01) and the percent of household members aged <18 years (P < 0·01) were independently associated with transmission. Targeted decolonization strategies could be used across geographical settings to limit household MRSA transmission.

Title: Obesogenic microbial signatures and the development of obesity in childhood acute lymphoblastic leukemia.

Childhood acute lymphoblastic leukemia (ALL) is the most common childhood cancer with survival exceeding 90% for standard-risk groups. A debilitating side-effect of treatment is the development of overweight/obesity (OW/OB), which develops in approximately 40% of children by the end of treatment. The microbiome has been associated with the development of OW/OB. We examined fluctuations in the microbiome with the development of OW/OB during the first six months of treatment at diagnosis, and two subsequent timepoints (N = 62). Shotgun metagenomic sequencing was performed on Illumina Nextseq system, and taxa and functional pathways were extracted from sequences using kraken2 and humann2, respectively. An association of increased presence of several species (e.g., Klebsiella pneumoniae, Escherichia coli) was observed in children with OW/OB, while lean-promoting species (Veillonella, Haemophilus, and Akkermansia) were increased in children who maintained a normal weight. Pathway analysis revealed purine nucleotide biosynthesis, sugar nucleotide biosynthesis, and enzyme cofactor biosynthesis were positively correlated with Bacteroides spp. among children with OW/OB. We identified several taxa and functional pathways that may confer increased risk for the development of OW/OB. The associations observed in this pilot are preliminary and warrant further research in the microbiome and the development of OW/OB in childhood ALL.

Molecular characterization of Staphylococcus aureus from outpatients in the Caribbean reveals the presence of pandemic clones.

Staphylococcus aureus infections continue to pose a global public health problem. Frequently, this epidemic is driven by the successful spread of single S. aureus clones within a geographic region, but international travel has been recognized as a potential risk factor for S. aureus infections. To study the molecular epidemiology of S. aureus infections in the Caribbean, a major international tourist destination, we collected methicillin-susceptible S. aureus (MSSA) and methicillin-resistant S. aureus (MRSA) isolates from community-onset infections in the Dominican Republic (n = 112) and Martinique (n = 143). Isolates were characterized by a combination of pulsed-field gel electrophoresis (PFGE), spa typing, and multilocus sequence typing (MLST) typing. In Martinique, MRSA infections (n = 56) were mainly caused by t304-ST8 strains (n = 44), whereas MSSA isolates were derived from genetically diverse backgrounds. Among MRSA strains (n = 22) from the Dominican Republic, ST5, ST30, and ST72 predominated, while ST30 t665-PVL+ (30/90) accounted for a substantial number of MSSA infections. Despite epidemiological differences in sample collections from both countries, a considerable number of MSSA infections (~10%) were caused by ST5 and ST398 isolates at each site. Further phylogenetic analysis suggests the presence of lineages shared by the two countries, followed by recent genetic diversification unique to each site. Our findings also imply the frequent import and exchange of international S. aureus strains in the Caribbean.

Antimalarial multi-drug resistance in Asia: mechanisms and assessment.

The emergence and spread of drug-resistant parasites poses a major problem for management of Plasmodium falciparum malaria in endemic areas. Nowhere is this more apparent than in southeast Asia, where multi-drug resistance to chloroquine and sulfadoxine-pyrimethamine was exacerbated when mefloquine monotherapy began failing in the 1980s. A better understanding of mechanisms of (multi-) drug resistance is urgently warranted to monitor and guide antimalarial chemotherapy regimens more efficiently. Here we review recent advances on identification of molecular markers that can be employed in predicting in vitro and in vivo resistance in southeast Asia. Examples include amplification of PfMDR1 (P. falciparum multi-drug resistant gene 1) and mefloquine, K76T PfCRT and chloroquine, as well as mutations in the dihydroperoate synthase and dihydrofolate reductase genes and the antifolate class of drugs.

Properties of the Plasmodium falciparum homologue of a protective vaccine candidate of Plasmodium yoelii.

We describe an unusual tryptophan-rich protein of Plasmodium falciparum that contains threonine-rich repeats. The protein is encoded by a 2.5 kb gene with a two-exon structure including a short AT-rich intron that is spliced out of the mature message. The 5' end of the gene encodes a hydrophobic region, which is assumed to be a signal peptide. The peptide sequence is characterised by a tryptophan-rich region and a block of degenerate threonine repeats. The protein is synthesised throughout the asexual life cycle and has an apparent molecular weight of approximately 94 kDa. It has a variable molecular weight in different strains of P. falciparum. Length polymorphisms can be found in the intron region and the second exon. Four single nucleotide mutations are localised in the tryptophan-rich region and two were found in the threonine-repeat block. Homology searches based on gene structure and amino acid sequence revealed a relationship with a P. yoelii antigen that has been used successfully in vaccine studies. Thus, this P. falciparum antigen should be considered an additional candidate for assessment in vaccination against the asexual blood-stages of P. falciparum.

Semiautomated and simultaneous analysis of the interleukin-10 gene microsatellites IL-10G and IL-10R by fluorescence-based polymerase chain reaction reveals significant differences in allele distributions between Caucasians (Germany) and Africans (Gabon).

Interleukin-10 (IL-10) is an important immunoregulatory cytokine influencing many aspects of the adaptive and inflammatory immune response. Two dinucleotide repeats have been identified in the 5'-UTR of IL-10 and shown to be useful genetic markers in several diseases. A simple, two-colour fluorescence assay was developed for determination of microsatellite fragment length by an automatic sequencer. Using this method polymorphisms at the IL-10G and IL-10R loci of the 5' flanking region of the IL-10 gene can be identified simultaneously. A unified standard nomenclature was applied to the known IL-10G and IL-10R microsatellites. The multiplex PCR approach was used to compare the allele frequencies in two independent donor groups from Germany (Caucasian), comprising 112 and 106 cases, respectively, and one group from Gabon (African) including 91 donors. Significant differences in the allele distribution were found. Both Caucasian populations tested showed no significant differences in their allele and genotype distribution. Whereas in Africans, allele IL-10G25 is rare at 3% compared to 21% in Caucasian, alleles IL-10G22 and G23 are more prevalent in Africans than in Caucasians (22% versus 10% and 26% versus 7%, respectively). Within the IL-10R locus, the allele R13 was observed at 88% in the African group compared to 69% in Caucasians. These data may help immunogenetic studies in diseases, where IL-10 is thought to be deregulated.

Inhibition of CD95/Fas-induced DNA degradation by osmotic cell shrinkage.

Apoptosis (programmed cell death) is an active physiological mechanism from which removal of abundant or potentially harmful cells follows. Apoptosis of lymphocytes is critical for the development of the immune system and during the immune response. As we have shown previously, moderate osmotic cell shrinkage interferes with CD95(Fas/Apo-1)-induced cell death. The present study has been performed to further elucidate the underlying mechanisms. To this end, apoptosis in Jurkat T-lymphocytes was elicited by triggering the CD95-receptor with monoclonal CD95/Fas-antibody. Osmotic cell shrinkage which was induced by the addition of 100 mM NaCl, did not significantly interfere with CD95-induced phosphatidylserine exposure nor the activation of caspase 3 activity as determined by PARP cleavage, DEVD-AMC consumption, or the activation of PAK2-kinase. However, osmotic cell shrinkage almost abolished CD95-induced DNA fragmentation (as revealed by propidium iodide staining) and the activation of a DNase as evidenced from SDS-PAGE gel assay. Western blot analysis showed CD95-induced tyrosine phosphorylation of a nuclear protein of ca. 20 kD which comigrated with nuclease activity. This tyrosine phosphorylation was almost completely abolished by the addition of 100 mM NaCl. Furthermore, osmotic cell shrinkage blunted the CD95-induced activation of the Src-like kinase p56lck. It is concluded that different signaling pathways mediate FITC-Annexin-V binding and DNase activation. Only the latter is sensitive to osmotic cell shrinkage.

Stimulation of TK1 lymphoma cells via alpha 4 beta 7 integrin results in activation of src-tyrosine- and MAP-kinases.

The lymphocyte integrin alpha 4 beta 7 is a cell surface adhesion receptor involved in initiating lymphocyte homing to gut-associated/mucosal lymphoid tissues by binding the mucosal addressin cell adhesion molecule-1 (MAdCAM-1). Other known ligands are vascular cell adhesion molecule-1, fibronectin, and the alpha 4 integrin chain itself. Here, we demonstrate that stimulation of the alpha 4 beta 7 integrin through its alpha 4 subunit (mAb R1-2), beta 7 subunit (mAb M293), or the combinatory epitope (mAb DATK32) enhances tyrosine phosphorylation of several cellular proteins in the murine TK1 lymphoma cell line. The two src-kinases p56lck and p59fyn were identified as possible mediators and substrates of the detected tyrosine phosphorylation. Furthermore, we observed activation of the MAP-kinases ERK1/2.

Cellular taurine release triggered by stimulation of the Fas(CD95) receptor in Jurkat lymphocytes.

One of the hallmarks of apoptosis is cell shrinkage which appears to be important for cell death. The mechanisms mediating cell volume decrease have, however, not been addressed. Mechanisms employed by swollen cells to decrease their cell volume include activation of ion transport pathways, such as ion channels and KCl cotransport, and release of cellular osmolytes, such as taurine, sorbitol, betaine and inositol. The present study has been performed to test for release of taurine. To this end Jurkat human T-lymphocytes were loaded with [3H]taurine and apoptotic cell death induced by triggering the Fas(CD95) receptor with monoclonal crosslinking antibody. Triggering the Fas(CD95) receptor led to a release of 60+/-5% of cellular taurine within 90 min. The release did not occur prior to 45 min. The release coincided with cell shrinkage as evidenced from forward scatter in FACS analysis and preceeded DNA fragmentation according to propidium iodide staining. The delay of taurine release was not influenced by exchange of medium and thus was not due to extracellular accumulation of a stimulator. The Fas(CD95)-induced taurine release, cell shrinkage and DNA fragmentation were blunted by lowering of ambient temperature to 23 degreesC. Following pretreatment of cells with Fas(CD95) antibody at 23 degreesC rewarming led to rapid taurine release, cell shrinkage and DNA fragmentation, indicating that the temperature-sensitive step is distal to the mechanisms accounting for the delay. Osmotic cell swelling led to an immediate release of taurine. In conclusion, Fas(CD95) triggering leads to delayed taurine release through a temperature-sensitive mechanism.

Cell volume regulatory mechanisms in apoptotic cell death.

One of the hallmarks of apoptosis is cell shrinkage, which--at constant extracellular osmolarity--requires a decrease of cellular osmolarity. Moreover, apoptosis can be elicited by increase of extracellular osmolarity and the resistance of cells towards apoptosis correlates with their ability to regulate their volume in hypertonic environment. On the other hand, CD95-receptor-mediated apoptosis is blunted at moderate increases of extracellular osmolarity. Given the role of cell volume alterations it is not surprising that apoptosis is paralleled by marked alterations of cell volume regulatory mechanisms. Stimulation of the CD95-receptor, which confers apoptosis to a variety of cells, leads to activation of cell volume regulatory anion channel ORCC. However, activation of ORCC is paralleled by inhibition of cell volume regulatory K+ channel Kv1.3. It is only 40 to 60 minutes after triggering of the CD95-receptor when the cells release the organic osmolyte taurine and shrink.