http://hdl.handle.net/10362/3556 2013-05-23T18:37:47Z 2013-05-23T18:37:47Z Nunes, Sónia http://hdl.handle.net/10362/8593 2013-01-22T17:18:32Z 2012-11-01T00:00:00Z

Title: Epidemiological studies of Streptococcus pneumoniae carriage in the post-vaccination era among two risk groups: children and the elderly Authors: Nunes, Sónia Abstract: Streptococcus pneumoniae is a global cause of disease including pneumonia, otitis media, conjunctivitis, sepsis, and bacterial meningitis. These infections are not essential to the transmission or long-term survival of the bacterium; indeed, S. pneumoniae depends on asymptomatic colonization of the human nasopharynx for its dissemination to additional hosts. Considering this, colonization studies are a good way to monitor changes in the pneumococcal epidemiology that may result from the use of antibiotics and vaccines. The molecular characterization of pneumococci is crucial to assess these changes which highlight the need for the development and validation of easier and faster methods of molecular typing. Since 1996 our group has been monitoring the pneumococcal population colonizing children attending day care centers. However, for several years these studies have been confined to the Lisbon area. In this PhD we have addressed this situation by including other regions of Portugal in our study. In addition, we have started to study pneumococcal colonization in the elderly, the other age group where the incidence of pneumococcal infections is high. This thesis summarizes five studies conducted during this PhD. The first four studies were focused on the pneumococcal epidemiology among the two age groups where the rates of pneumococcal disease are highest: children up to six years old and adults older than 60 years. The fifth and last study describes the evaluation and validation of a new genotyping strategy for pneumococci.(...) Description: Dissertation presented to obtain the Ph.D. degree in Biology/ Molecular Biology

2012-11-01T00:00:00Z Miragaia, M de Lencastre, H Perdreau-Remington, F Chambers, HF Higashi, J Sullam, PM Lin, J Wong, KI King, KA Otto, M Sensabaugh, GF Diep, BA http://hdl.handle.net/10362/5855 2011-06-28T15:26:03Z 2009-01-01T00:00:00Z

Title: Genetic diversity of arginine catabolic mobile element in Staphylococcus epidermidis Authors: Miragaia, M; de Lencastre, H; Perdreau-Remington, F; Chambers, HF; Higashi, J; Sullam, PM; Lin, J; Wong, KI; King, KA; Otto, M; Sensabaugh, GF; Diep, BA Abstract: Background: The methicillin-resistant Staphylococcus aureus clone USA300 contains a novel mobile genetic element, arginine catabolic mobile element ( ACME), that contributes to its enhanced capacity to grow and survive within the host. Although ACME appears to have been transferred into USA300 from S. epidermidis, the genetic diversity of ACME in the latter species remains poorly characterized. Methodology/Principal Findings: To assess the prevalence and genetic diversity of ACME, 127 geographically diverse S. epidermidis isolates representing 86 different multilocus sequence types (STs) were characterized. ACME was found in 51% (65/127) of S. epidermidis isolates. The vast majority (57/65) of ACME-containing isolates belonged to the predominant S. epidermidis clonal complex CC2. ACME was often found in association with different allotypes of staphylococcal chromosome cassette mec (SCCmec) which also encodes the recombinase function that facilities mobilization ACME from the S. epidermidis chromosome. Restriction fragment length polymorphism, PCR scanning and DNA sequencing allowed for identification of 39 distinct ACME genetic variants that differ from one another in gene content, thereby revealing a hitherto uncharacterized genetic diversity within ACME. All but one ACME variants were represented by a single S. epidermidis isolate; the singular variant, termed ACME-I.02, was found in 27 isolates, all of which belonged to the CC2 lineage. An evolutionary model constructed based on the eBURST algorithm revealed that ACME-I.02 was acquired at least on 15 different occasions by strains belonging to the CC2 lineage. Conclusions/Significance: ACME-I.02 in diverse S. epidermidis isolates were nearly identical in sequence to the prototypical ACME found in USA300 MRSA clone, providing further evidence for the interspecies transfer of ACME from S. epidermidis into USA300. Description: PLos One, 4(11): ARTe7722

2009-01-01T00:00:00Z Conceição, Teresa http://hdl.handle.net/10362/5798 2011-06-15T16:18:41Z 2011-03-01T00:00:00Z

Title: Staphylococcus aureus: towards a comprehensive view on epidemiology and clonal spread Authors: Conceição, Teresa Abstract: Staphylococcus aureus is known for its extraordinary capacity of colonizing asymptomatically the anterior nares of humans. A high versatility allied to the successive accumulation of resistance to almost all clinically available antibiotics, made S. aureus a major human pathogen worldwide. Soon after the introduction of methicillin into clinical practice, methicillin resistant S. aureus (MRSA) emerged as a major pathogen in hospitals worldwide, and more recently in the community as well. Methicillin susceptible S. aureus (MSSA) are also an important problem. MSSA is responsible from mild to severe invasive infections, commonly due to enhanced virulence content, rather than accumulation of resistance determinates. However, many gaps in the knowledge of the epidemiology of MSSA remain to be clarified.(...) Description: Dissertation presented to obtain a PhD degree in Biology/ Molecular Biology by the Universidade Nova de Lisboa, Instituto de Tecnologia Química e Biológica

2011-03-01T00:00:00Z Frazão, Nelson http://hdl.handle.net/10362/5792 2011-06-15T14:12:03Z 2010-01-01T00:00:00Z

Title: Massive shift in the pneumococcal nasopharyngeal flora after the 7-valent conjugate vaccine: epidemiological studies and testing pathogenic potential in animal models Authors: Frazão, Nelson Abstract: Although it exists mostly as a commensal bacterium colonizing the human nasopharynx, particularly in children, the Gram-positive bacterium Streptococcus pneumoniae, is also a major human pathogen that can cause a wide range of diseases, which include otitis media, sinusitis, pneumonia, and such life-threatening afflictions as bloodstream infection and meningitis. Created to protect children against pneumococcal disease, the 7-valent pneumococcal conjugate vaccine (PCV7) showed high efficacy in preventing disease caused by the serotypes included in the vaccine, the so-called vaccine types (VTs). Since colonization is an essential first step to develop pneumococcal disease, it is of importance to investigate the effect of this vaccine on the degree of colonization, on changes in the composition of the nasopharyngeal flora and the virulence potential of the non vaccine type (NVT) strains.(...) Description: Dissertation presented to obtain the PhD degree in Biology/Molecular Biology by Universidade Nova de Lisboa, Instituto de Tecnologia Química e Biológica

2010-01-01T00:00:00Z