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Biomedical subjects

Marcello Valassina

Publications and source records attributed to Marcello Valassina.

7 recordsLinked to original sources
PubMed2003

Increasing diversity within Chlamydiae.

In recent years, 16S ribosomal DNA analyses has allowed the recognition of new chlamydia organisms, requiring the creation of new species, genera, and families within this unique, deep lineage of prokaryotes. The trachoma and psittaci groups chlamydiae are now recognized as separate genera, Chlamydia and Chlamydophila, respectively, and biovars of each group have been elevated to the species rank. Simkania and Parachlamydia have been associated with human respiratory infections, while Waddlia seems to be implicated in abortion in bovins. DNA amplification studies targeting the 16S rDNA have revealed a richer diversity within chlamydiae, identifying new lineages from both environmental and clinical samples. Further studies will be of interest to both examine the ecology and evaluate the clinical importance of these novel chlamydiae. Herein, we provide a summary of literature and our data about the novel chlamydial lineages.

Chlamydia↗
PubMed2003

Serological survey of Toscana virus infections in a high-risk population in Italy.

Toscana virus is the most important agent responsible for meningitis in central Italy. We report a serosurveillance study, using an immunoenzymatic assay, of 360 serum samples harvested from a high-risk population occupationally exposed to Toscana virus in two regions of Italy, Tuscany and Piedmont. The results indicates a seroprevalence of Toscana virus of 77.2% in the forestry workers, particularly in the Tuscany region. This fact is strictly correlated with the ecological niches specific for the survival of Toscana virus arthropod vector.

Arboviruses↗
PubMed2002

Fast duplex one-step RT-PCR for rapid differential diagnosis of entero- or toscana virus meningitis.

Acute meningitis is the most common neurologic disease that involves the central nervous system. The spectrum of infectious agents that cause neurologic infection is remarkably broad and numerous viruses are the most frequent cause of the aseptic meningitis syndrome. We applied a multiplex one-step method for the rapid detection of the genomic RNA of different neurotropic viruses: particles in the genus Enterovirus and Toscana virus, which are the most representative aetiologic agents in our country during the spring-summer period. We have evaluated the sensitivity and the specificity of the multiplex one-step test on positive controls and on RNA extracted from clinical samples harvested from 475 patients with meningitis hospitalized during the 1996-2001 period. The multiplex one-step RT-nPCR protocol allows for the detection of enterovirus and Toscana virus RNA in a single sample, by using, at the same time, a very small clinical sample volume. In our study we were able to diagnose 192 cases of meningitis by Toscana virus and 31 cases by enteroviruses out of 475 cases of meningitis utilizing the described one-step multiplex method.

Adolescent↗
PubMed2002

New parachlamydial 16S rDNA phylotypes detected in human clinical samples.

Chlamydiales are important intracellular bacterial pathogens, causing a wide variety of diseases in vertebrates, including humans. Besides the well-known species in the family Chlamydiaceae, new chlamydial organisms have recently been discovered, forming three new families: Parachlamydiaceae, Simkaniaceae and Waddliaceae. Parachlamydia acanthamoebae and Simkania negevensis are currently investigated as emerging human respiratory pathogens. Additional chlamydial lineages have been discovered by 16S rDNA-based molecular studies, and their implication in human infections is poorly known. By using a pan-chlamydia 16S rDNA PCR, we have searched for the presence of chlamydiae in 228 clinical samples that all previously had been shown to be PCR-negative for Chlamydophila pneumoniae: 170 respiratory samples, 45 atheromatic plaques and 13 peripheral blood mononuclear cell samples. Nine respiratory samples tested positive. Sequence analysis has allowed us to assign four sequences to Chlamydophila psittaci, three sequences to Chlamydophila felis, and two sequences to two novel phylotypes belonging to the Parachlamydiaceae. These latter sequences showed similarity values of more than 93% with each other and with the P. acanthamoebae sequence, thus belonging to novel, unrecognized species. In conclusion, this report showed that a variety of non-C. pneumoniae chlamydial respiratory infection is present in humans, and that new parachlamydiae distinct from P. acanthamoebae may be detected in human clinical samples. Future studies will be of interest in order to estimate the diversity of these novel chlamydiae in both clinical and environmental samples, as well as their possible clinical implication in human and animal infections.

Adolescent↗
PubMed2001

Search for Chlamydia pneumoniae genes and their expression in atherosclerotic plaques of carotid arteries.

Samples of atherosclerotic tissue from 58 patients undergoing carotid surgery were analysed by tissue culture and PCR for Chlamydia pneumoniae; PCR was performed to detect Omp1, 16S rRNA and HSP-70 genes. To understand the active pathogenic role of C. pneumoniae, a reverse transcriptase-PCR (RT-PCR) assay was applied to detect the specific RNAs expressed either in the replicative form, or in the cryptic form found in chronic infection. The C. pneumoniae omp1 gene, encoding the major outer-membrane protein (MOMP), was detected in 13 of 58 samples. Among these, the result was confirmed in 11 samples after amplification of a further target, the 16S rRNA, and the presence of the HSP-70 gene, encoding heat-shock protein 70, was revealed in only five cases. All the samples were negative for evidence of specific RNAs by RT-PCR. The presence of genomic DNA and absence of specific RNAs in atherosclerotic tissue samples suggests a lack of an active metabolic or persistent infective role for C. pneumoniae. Thus, traces of C. pneumoniae DNA in these samples could be due to a degradative pathway of the host defensive cellular and biochemical mechanisms.

Adult↗