Human IgMCD300a B Cells Are Circulating Marginal Zone Memory B Cells That Respond to Pneumococcal Polysaccharides and Their Frequency Is Decreased in People Living with HIV.

CD300a is differentially expressed among B cell subsets, although its expression in immunoglobulin (Ig)M B cells is not well known. We identified a B cell subset expressing CD300a and high levels of IgM (IgMCD300a). The results showed that IgMCD300a B cells were CD10CD27CD25IgDCD21CD23CD38CD1c, suggesting that they are circulating marginal zone (MZ) IgM memory B cells.

Characterization of recombinant fluoroquinolone-resistant pneumococcus-like isolates.

Fourteen fluoroquinolone-resistant streptococcal isolates with recombinant DNA topoisomerase genes, preliminarily identified as pneumococci, were further characterized using phenotypic and genotypic approaches. Phenotypic tests classified them as atypical pneumococci. Phylogenetic relationships were analyzed by using the sequences of seven housekeeping alleles from these isolates and from isolates of Streptococcus pneumoniae, Streptococcus mitis, Streptococcus oralis, and Streptococcus pseudopneumoniae.

Nonoptimal DNA topoisomerases allow maintenance of supercoiling levels and improve fitness of Streptococcus pneumoniae.

Fluoroquinolones, which target gyrase and topoisomerase IV, are used for treating Streptococcus pneumoniae infections. Fluoroquinolone resistance in this bacterium can arise via point mutation or interspecific recombination with genetically related streptococci. Our previous study on the fitness cost of resistance mutations and recombinant topoisomerases identified GyrAE85K as a high-cost change.

New species genetic approach to identify strains of mitis group streptococci that are donors of rifampin resistance to Streptococcus pneumoniae.

Eight rifampin-resistant streptococci of the mitis group were identified at the species level by using a concatenated 16S rRNA gene-sodA-rpoB-hlpA sequence. Characterization of their rpoB alleles showed single amino acid changes involved in rifampin resistance. Comparison of RpoB sequences from pneumococcal recombinant isolates, viridans isolates, and type strains revealed a species-specific amino acid signature, which allowed it to be ascertained that recombinant RpoBs were originated in genetic interchanges with Streptococcus mitis and Streptococcus oralis.

Changes in fluoroquinolone-resistant Streptococcus pneumoniae after 7-valent conjugate vaccination, Spain.

Among 4,215 Streptococcus pneumoniae isolates obtained in Spain during 2006, 98 (2.3%) were ciprofloxacin resistant (3.6% from adults and 0.

Fitness of Streptococcus pneumoniae fluoroquinolone-resistant strains with topoisomerase IV recombinant genes.

The low prevalence of ciprofloxacin-resistant (Cp r) Streptococcus pneumoniae isolates carrying recombinant topoisomerase IV genes could be attributed to a fitness cost imposed by the horizontal transfer, which often implies the acquisition of larger-than-normal parE-parC intergenic regions. A study of the transcription of these genes and of the fitness cost for 24 isogenic Cp r strains was performed. Six first-level transformants were obtained either with PCR products containing the parC quinolone resistance-determining regions (QRDRs) of S.

Molecular characterization of disease-associated streptococci of the mitis group that are optochin susceptible.

Eight optochin-susceptible (Opt(s)) alpha-hemolytic (viridans) streptococcus isolates were characterized at the molecular level. These isolates showed phenotypic characteristics typical of both viridans streptococci and Streptococcus pneumoniae. Comparison of the sequence of housekeeping genes from these isolates with those of S.

Fluoroquinolone resistance in penicillin-resistant Streptococcus pneumoniae clones, Spain.

Among 2,882 Streptococcus pneumoniae sent to the Spanish Reference Laboratory during 2002, 75 (2.6%) were ciprofloxacin-resistant. Resistance was associated with older patients (3.

Genetic characterization of optochin-susceptible viridans group streptococci.

Two clinical isolates of viridans group streptococci (VS) with different degrees of susceptibility to optochin (OPT), i.e., fully OPT-susceptible (Opt(s)) VS strain 1162/99 (for which the MIC was equal to that for Streptococcus pneumoniae, 0.

Viridans group streptococci are donors in horizontal transfer of topoisomerase IV genes to Streptococcus pneumoniae.

A total of 46 ciprofloxacin-resistant (Cip(r)) Streptococcus pneumoniae strains were isolated from 1991 to 2001 at the Hospital of Bellvitge. Five of these strains showed unexpectedly high rates of nucleotide variations in the quinolone resistance-determining regions (QRDRs) of their parC, parE, and gyrA genes. The nucleotide sequence of the full-length parC, parE, and gyrA genes of one of these isolates revealed a mosaic structure compatible with an interspecific recombination origin.

Occurrence of yeasts in municipal wastes and their behaviour in presence of cadmium, copper and zinc.

Seven yeasts strains have been isolated from sewage sludge. Also six samples of compost with different sieving, composting times and origins, have been analysed. Apparently, composting processes negatively affect the viability of yeasts, as none could be isolated from the compost samples.

Feasibility of copper uptake by the yeast Pichia guilliermondii isolated from sewage sludge.

Copper is one of the most abundant toxic heavy metals in municipal wastewaters and, in consequence, in sewage sludge and compost. The ability of a strain of the yeast Pichia guilliermondii, which was isolated from sewage sludge, to eliminate copper has been evaluated, using both viable and nonviable biomass. It has been found that raising concentrations of copper affected both morphology and physiological parameters of the viable yeast, and it is thought that a process of bioaccumulation may be involved in its copper uptake.