Biomedical subjects

Fatima Bacellar

Publications and source records attributed to Fatima Bacellar.

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

Boutonneuse fever and climate variability.

Researchers have long appreciated the role of climate in vector-borne diseases, including the resurgence of boutonneuse fever (BF). Portugal usually is classified as having temperate Mediterranean climate. In this new century, in analyzing the data from the Meteorology Institute, this pattern has changed and an accentuated variability in climate is being observed. BF (febre escaro nodular) is endemic and high season is from late spring and summer. The brown dog tick Rhipicephalus sanguineus. is the vector and reservoir of Rickettsia conorii complex strains: R. conorii Malish and Israeli spotted fever strain. To assess the influence of climate change in BF seasonality our aim was to compare the human sera samples received at CEVDI-INSA for laboratory diagnosis of MSF for 5 months per year from October to February, ("off-season") from 2000 to 2005. Of 1,299 sera samples in persons with suspected clinical diagnosis of MSF, 45 (3.4%) were considered positive cases and the number of positive cases has doubled in the last 2 years. BF epidemiology clearly appears to be associated with climate change, especially with low precipitation values. Physicians should be aware of increasing off-season BF cases.

Boutonneuse Fever↗

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

Molecular detection of Rickettsia felis, Rickettsia typhi and two genotypes closely related to Bartonella elizabethae.

A total of 56 fleas were collected from mice, rats, and one hedgehog in national parks of mainland Portugal and the Madeira Island. All fleas were tested for the presence of bacteria of the genera Rickettsia and Bartonella using PCR assays. In fleas from mainland Portugal, we detected Rickettsia felis in one Archaeopsylla erinacei maura flea and in one Ctenophtalmus sp. In five Leptopsylla segnis fleas taken from rats in the Madeira Island, we identified Rickettsia typhi. In addition, in four fleas from the genera Ornithophaga and Stenoponia collect from mice and a rat in mainland Portugal, we detected the presence of two new Bartonella genotypes closely related to Bartonella elizabethae. Our findings emphasize the potential risk of flea-transmitted infections in mainland Portugal and the Madeira archipelago, and extend our knowledge of the potential flea vectors of human pathogens.

Animals↗

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↗

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↗