Pherotypes are driving genetic differentiation within Streptococcus pneumoniae

<p>Abstract</p> <p>Background</p> <p>The boundaries of bacterial species and the mechanisms underlying bacterial speciation are matters of intense debate. Theoretical studies have shown that recombination acts as a strong cohesive force preventing divergence in bacterial populations. <it>Streptococcus pneumoniae </it>populations have the telltale signs of high recombination with competence implicated as the major driving force behind gene exchange. Competence in <it>S. pneumoniae </it>is triggered by a quorum-sensing mechanism controlled by the competence-stimulating peptide pheromone.</p> <p>Results</p> <p>We studied the distribution of the two major pherotypes in the pneumococcal population and their association with serotype, antimicrobial resistance and genetic lineage. Using multilocus sequence data we evaluated pherotype influence on the dynamics of horizontal gene transfer. We show that pherotype is a clonal property of pneumococci. Standard population genetic analysis and multilocus infinite allele model simulations support the hypothesis that two genetically differentiated populations are defined by the major pherotypes.</p> <p>Conclusion</p> <p>Severe limitations to gene flow can therefore occur in bacterial species in the absence of geographical barriers and within highly recombinogenic populations. This departure from panmixia can have important consequences for our understanding of the response of pneumococci to human imposed selective pressures such as vaccination and antibiotic use.</p

Genotypic Characterization of Streptococcus canis Isolated from Distinct Hosts with Special Emphasis on Multilocus Sequence Typing

Background: The animal pathogen Streptococcus canis is increasingly being noticed in human infections. Our aim was to develop a new multilocus sequence typing (MLST) scheme for Streptococcus canis and to compare isolates recovered from house pets and humans, in order to define the clonal structure of the S. canis population and explore the zoonotic potential of distinct S. canis genetic lineages. Methods: Eighty-five S. canis isolates recovered from infections in animals (n = 78, recovered from 2000 to 2010 in three European countries, mainly from house pets) and humans (n = 7, recovered from 2006 to 2010 in Portugal) were studied. Isolates were identified by API 20 Strep, 23S rRNA gene targeted PCR and 16S rRNA gene sequencing, and characterized by MLST, pulsed-field gel electrophoresis (PFGE) and emm typing. Results: All isolates were successfully typed with the proposed MLST scheme, indicating its applicability to S. canis from distinct sources. The MLST analysis showed a polyclonal structure of the S. canis population, where the same genetic lineages are found infecting house pets and humans and are disseminated in distinct geographic locations. PFGE confirmed the MLST findings, as it identified the same prevailing lineages and further strengthened the similarity between animal and human isolates. Phylogenetic analysis conducted with the 16S rRNA and MLST loci sequence data indicated that S. canis was a divergent taxon of the sister species Streptococcus pyogenes and Streptococcus dysgalactiae subsp. equisimilis, and found evidence of acquisition of genetic material by S. canis from the latter species. The presence of emm-like genes was restricted to a few isolates and correlated with MLST defined genetic lineages. Conclusion: Our data shows that S. canis isolated from house pets and humans are a single population, and demonstrates that isolates belonging to the main genetic lineages identified are able to infect the human host, providing strong evidence for the zoonotic nature of S. canis infection in humans. A MLST database for S. canis was established at http://pubmlst.org/scanis/ (hosted by the Department of Zoology, University of Oxford, United Kingdom), constituting a valuable tool for future studies on the molecular epidemiology of this pathogen

Beta-hemolytic Streptococcus dysgalactiae strains isolated from horses are a genetically distinct population within the Streptococcus dysgalactiae taxon

The pathogenic role of beta-hemolytic Streptococcus dysgalactiae in the equine host is increasingly recognized. A collection of 108 Lancefield group C (n = 96) or L (n = 12) horse isolates recovered in the United States and in three European countries presented multilocus sequence typing (MLST) alleles, sequence types and emm types (only 56% of the isolates could be emm typed) that were, with few exceptions, distinct from those previously found in human Streptococcus dysgalactiae subsp. equisimilis. Characterization of a subset of horse isolates by multilocus sequence analysis (MLSA) and 16S rRNA gene sequence showed that most equine isolates could also be differentiated from S. dysgalactiae strains from other animal species, supporting the existence of a horse specific genomovar. Draft genome information confirms the distinctiveness of the horse genomovar and indicates the presence of potentially horse-specific virulence factors. While this genomovar represents most of the isolates recovered from horses, a smaller MLST and MLSA defined sub-population seems to be able to cause infections in horses, other animals and humans, indicating that transmission between hosts of strains belonging to this group may occur

Beta-hemolytic Streptococcus dysgalactiae strains isolated from horses are a genetically distinct population within the Streptococcus dysgalactiae taxon

The pathogenic role of beta-hemolytic Streptococcus dysgalactiae in the equine host is increasingly recognized. A collection of 108 Lancefield group C (n=96) or L (n=12) horse isolates recovered in the United States and in three European countries presented multilocus sequence typing (MLST) alleles, sequence types and emm types (only 56% of the isolates could be emm typed) that were, with few exceptions, distinct from those previously found in human Streptococcus dysgalactiae subsp. equisimilis. Characterization of a subset of horse isolates by multilocus sequence analysis (MLSA) and 16S rRNA gene sequence showed that most equine isolates could also be differentiated from S. dysgalactiae strains from other animal species, supporting the existence of a horse specific genomovar. Draft genome information confirms the distinctiveness of the horse genomovar and indicates the presence of potentially horse-specific virulence factors. While this genomovar represents most of the isolates recovered from horses, a smaller MLST and MLSA defined sub-population seems to be able to cause infections in horses, other animals and humans, indicating that transmission between hosts of strains belonging to this group may occur

Pneumococcal Serotypes Colonise the Nasopharynx in Children at Different Densities.

Prevalence of pneumococcal serotypes in carriage and disease has been described but absolute serotype colonisation densities have not been reported. 515 paediatric nasal swab DNA extracts were subjected to lytA qPCR and molecular serotyping by microarray. Absolute serotype densities were derived from total pneumococcal density (qPCR cycle threshold and standard curve) and relative abundance (microarray) and varied widely. Compared to all serotype densities observed, the strongest evidence of differences was seen for serotypes 21 and 35B (higher) and 3, 38 and non-typeables (lower) (p<0.05) with a similar hierarchy when only a single serotype carriage was assessed. There was no evidence of any overall density differences between children with single or multiple serotypes detected but serotypes with mid-range densities were more prevalent. The hierarchy of distinct pneumococcal serotype carriage densities described here for the first time, may help explain the dynamics of transmission between children

Адаптация гидравлической модели водостока к бассейнам рек Дунай и Днестр

Гидравлическая модель водостока адаптирована к бассейну рек Дунай и Днестр. По данным орографии, атмосферных осадках или поверхностном стоке она позволяет рассчитывать объемы, расходы и уровни воды с пространственным разрешением 1 км. В модели возможно использование данные об экосистемах на земной поверхности, типах почвы. По данным наблюдений стока оценены среднемесячные величины расходов рек, которые соответствуют наблюдениям, что позволяет применять модель в дальнейших оценках стока, наносов и т.д.Hydraulic model of water inflow is adapted to the Danube and the Dniester rivers basin. According to the orography, precipitation and surface inflow data it permits to calculate water volumes, discharges and levels with spatial resolution 1 km. It is possible to use the data on ecosystems on the ground surface, types of soil in the model. According to the observations data of the inflow the average monthly values of river discharges corresponding to the observations are estimated. It permits to apply the model in the further estimations of inflow, alluvia e t.c

Survey of extended-spectrum beta-lactamases in Escherichia coli isolates from a Portuguese hospital and characterisation of a novel class 1 integron (In60A) carrying the bla(CTX-M-9) gene

Between November 2001 and November 2004, 231 Escherichia coli isolates resistant to P-lactam antibiotics were identified. In 14 isolates, bla(TEM-24) (2 isolates), bla(TEM-52) (5 isolates) and bla(TEM-26) (7 isolates) were identified. In 145 E. coli isolates with the same M13 fingerprinting profile and the same resistance phenotype, the bla(CTX-M-15) gene was found in association with an insertion sequence ISEcp1. The bla(CTX-M-2) gene was identified in one E. coli isolate (290HSM), and in other E. coli isolate (246HSM) the bla(CTX-M-9) gene was contained in a new complex sull-type class 1 integron (named In60A). This is the first report of three cefotaximases (CTX-M-15, CTX-M-2 and CTX-M-9) in E. coli isolates from a Portuguese hospital. (c) 2006 Elsevier B.V. and the International Society of Chemotherapy. All rights reserved

Pediatric Complicated Pneumonia Caused by Streptococcus pneumoniae Serotype 3 in 13-Valent Pneumococcal Conjugate Vaccinees, Portugal, 2010–2015

Despite use of 7-valent pneumococcal conjugate vaccine, incidence of pleural effusion and empyema (pediatric complicated pneumococcal pneumonia [PCPP]) is reportedly increasing globally. We cultured and performed PCR on 152 pleural fluid samples recovered from pediatric patients in Portugal during 2010–2015 to identify and serotype Streptococcus pneumoniae. We identified only 17 cases by culture, but molecular methods identified S. pneumoniae in 68% (92/135) of culture-negative samples. The most frequent serotypes were 3, 1, and 19A, together accounting for 62% (68/109) of cases. Nineteen cases attributable to 13-valent pneumococcal conjugate vaccine (PCV13) serotypes (mostly serotype 3) were detected among 22 children age-appropriately vaccinated with PCV13. The dominance of the additional serotypes included in PCV13 among PCPP cases in Portugal continues, even with PCV13 available on the private market (without reimbursement) since 2010 and with average annual coverage of 61% among age-eligible children. Our data suggest reduced effectiveness of PCV13 against serotype 3 PCPP

Beta-hemolytic Streptococcus dysgalactiae strains isolated from horses are a genetically distinct population within the Streptococcus dysgalactiae taxon

The pathogenic role of beta-hemolytic Streptococcus dysgalactiae in the equine host is increasingly recognized. A collection of 108 Lancefield group C (n = 96) or L (n = 12) horse isolates recovered in the United States and in three European countries presented multilocus sequence typing (MLST) alleles, sequence types and emm types (only 56% of the isolates could be emm typed) that were, with few exceptions, distinct from those previously found in human Streptococcus dysgalactiae subsp. equisimilis. Characterization of a subset of horse isolates by multilocus sequence analysis (MLSA) and 16S rRNA gene sequence showed that most equine isolates could also be differentiated from S. dysgalactiae strains from other animal species, supporting the existence of a horse specific genomovar. Draft genome information confirms the distinctiveness of the horse genomovar and indicates the presence of potentially horse-specific virulence factors. While this genomovar represents most of the isolates recovered from horses, a smaller MLST and MLSA defined sub-population seems to be able to cause infections in horses, other animals and humans, indicating that transmission between hosts of strains belonging to this group may occur