Biomedical subjects

Liliana Vitorino

Publications and source records attributed to Liliana Vitorino.

6 recordsLinked to original sources

PubMed2007

Rickettsiae phylogeny: a multigenic approach.

The development of molecular taxonomic methods has provided a large amount of data in the reorganization of Rickettsiae taxonomy. Nevertheless, phylogenetic relationships among some groups and species delimitation remain unclear. To clarify rickettsial phylogeny, a multigenic approach was used for the first time for the genus Rickettsia, based on simultaneous analyses of eight loci: atpA, recA, virB4, dnaA, dnaK, rrl-rrf internal transcribed spacer, ompA and gltA. Concatenation of different nucleotide sequences resulted in an improvement in phylogenetic resolution when compared to single gene data. This multigenic approach has enabled the differentiation of many groups, including the spotted fever group which includes a great number of closely related species. The reliability of some previously recognized groups was evaluated.

Animals↗

PubMed2006

Automated method based in VNTR analysis for Rickettsiae genotyping.

A genetic locus named Rc-65, which is 5' adjacent to gene dksA and 3' adjacent to xerC gene, has previously been demonstrated to contain a VNTR with high discriminatory power in several rickettsial strains and thus, potentially useful for genetically similar strains identification. In this work, we present an automated molecular identification method based on capillary electrophoresis separation of VNTRs amplicons. The resulting electropherograms were in agreement with the sequence data obtained in a previous work. The presented genotyping method is fast and suitable for full automation, being a powerful tool for epidemiological surveillance in a large number of samples and enables the detection co-infected samples. The combination of other VNTR loci should improve the discriminatory capacity of this typing system, providing greater resolution and contributing to a more accurate VNTR-based assay. To our knowledge, this is the first automated assay for rickettsial strains identification.

Bacterial Typing Techniques↗

PubMed2006

Rickettsia sibirica isolation from a patient and detection in ticks, Portugal.

We report the first isolation of Rickettsia sibirica (strain mongolotimonae) from the blood of a patient and detection by polymerase chain reaction (PCR) of the rickettsia in a Rhipicephalus pusillus tick collected from a dead mongoose (Herpestes ichneumon) in the Alentejo region, Portugal. We describe also the first PCR detection of a new Rickettsia strain that is related to R. sibirica.

Aged↗

PubMed2005

Characterization of a tandem repeat polymorphism in Rickettsia strains.

Mediterranean spotted fever (MSF) is a tick-borne rickettsiosis caused by 'Rickettsia conorii complex' strains. In Portugal, R. conorii and Israeli tick typhus (ITT) are the aetiological agents of this disease. A novel 65 bp tandem repeat was identified by the analysis of the R. conorii Malish 7 whole genome sequence with an appropriate algorithm for searching for repeated sequences. The variable number tandem repeat (VNTR) was named VNTR Rc-65 and this locus was amplified by PCR and sequenced in order to characterize the repeat diversity within different rickettsial strains including Portuguese strains isolated from clinical and vector samples. The VNTR Rc-65 has seven alleles within the rickettsial strains studied and a diversity index value of 0.71, meaning that this locus has a great discriminatory capacity and therefore can be used for identification of closely related strains. PCR amplification of the Rc-65 locus can be used to differentiate between the Portuguese R. conorii Malish-like and Israeli tick typhus strains, enabling a more accurate and rapid identification of these rickettsial isolates.

Animals↗

PubMed2005

The presence of eschars, but not greater severity, in Portuguese patients infected with Israeli spotted fever.

In Portugal, Mediterranean spotted fever (MSF) is caused by R. conorii Malish and Israeli spotted fever (ISF) strains. It has been suggested that the ISF strain isolated from patients with MSF causes different clinical manifestations compared to those caused by Malish strain, namely the absence of eschar and greater severity. The aim of this study was to analyze the presence or absence of eschar and of fatality in Portuguese patients infected with either Malish or ISF strain. Of 94 patients with a clinical diagnosis of MSF between 1994 to 2004, 47 were infected with Malish strain and 47 with ISF strain. Eschars were reported in 20 patients (49%) infected with Malish strain, and in 17 (39%) with ISF strain. The presence of eschar is not statistically associated to a greater extent with either R. conorii strain (P=0.346). A total of 22 patients died, 9 infected with Malish strain and 13 infected with ISF strain, and no statistically significant difference was found (P=0.330). This study showed that the concepts of absence of the eschar and greater severity in Israeli spotted fever infection should be revised.

Animals↗

PubMed2003

rRNA intergenic spacer regions for phylogenetic analysis of Rickettsia species.

Species of the genus Rickettsia are responsible for several human diseases, namely epidemic typhus, Rocky Mountain spotted fever, and tick-borne typhus transmitted by arthropod vectors. The rrl-rrf intergenic spacer region (rrl-rrf ITS) was sequenced for 12 Rickettsia strains, including R. typhi, 6 untested species, R. aeschlimannii, Bar29, R. helvetica, R. honei, R. massilae, and R. slovaca as well as 5 Portuguese isolates. Phylogenetic trees inferred from rrl-rrf spacer sequences using maximum-parsimony and distance methods provided largely congruent tree topologies, supported by significant bootstrap values, enabling the identification of five distinct rickettsiae clusters.

Animals↗