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L Calegari

Publications and source records attributed to L Calegari.

At least 19 recordsLinked to original sources
PubMed2000

Artificial neural network based identification of environmental bacteria by gas-chromatographic and electrophoretic data.

Chemotaxonomic identification techniques are powerful tools for environmental micro-organisms, for which poor diagnostic schemes are available. Whole cellular fatty acid methyl esters (FAME) content is a stable bacterial profile, the analysis method is rapid, cheap, simple to perform and highly automated. Whole-cell protein is an even more powerful tool because it yields information at or below the species level. The description of new species and genera and subsequent continuous rearrangement provide large amounts of data, resulting in large databases. In order to set up suitable software tools to work on such large databases artificial neural network (ANN) based programs have been used to classify and identify marine bacteria at genus and species levels, starting from the fatty acid profiles and protein profiles respectively. We analysed 50 certified strains belonging to Halomonas, Marinomonas, Marinospirillum, Oceanospirillum and Pseudoalteromonas genera. Both supervised and unsupervised ANNs provide a correct classification of the marine strains analyzed. Moreover, a set of 73 marine fresh isolates were used as an example of identification using ANNs. We propose supervised and unsupervised ANNs as a reliable tool for classification of bacteria by means of their FAME and of whole-protein analyses and as a sound basis for a comprehensive artificial intelligence based system for polyphasic taxonomy.

Bacteria↗
PubMed1999

An integration system to rapidly identify aquatic bacteria.

An identification system for aquatic bacteria which would be useful for aspects ranging from pollution monitoring to health care, is described. It contains relevant information concerning the nature, taxonomy and activity of aquatic bacteria and allows to identify fresh isolates by means of their chemotaxonomic profiles. The system is simple and user friendly, so that it can be used by people not familiar with computers and has a modular interface that allows an easy interaction with laboratory instruments. The system is also connected with artificial neural network based programs to identify strains starting from the considered chemotaxonomic features.

Bacteria↗
PubMed1997

Artificial neural network identification of heterotrophic marine bacteria based on their fatty-acid composition.

The traditional approach to biochemical identification of marine fresh isolates requires considerably long culture preparation times and large quantities of expensive materials and reagents, and the results are not reliable. On the other hand, taxonomy tests based on DNA composition, although sensitive and reliable, require long execution time and high costs. A method is presented for the classification of fatty-acid profiles, extracted from marine bacteria strains, at genus level based on supervised artificial neural networks. The proposed method allows the correct identification of all patterns belonging to the test set. Moreover, a quantitative measure of the importance of each fatty acid for bacterial classification is also achieved. This measure allows the determination of a cluster of fatty acids to be controlled with greater care. The results show that the proposed method is reproducible and rapid, so that it can be routinely used in the marine microbiology laboratory to identify fresh isolates.

Algorithms↗
PubMed1996

Automated systems for identification of heterotrophic marine bacteria on the basis of their Fatty Acid composition.

The fatty acid methyl ester composition of a total of 71 marine strains representing the genera Alteromonas, Deleya, Oceanospirillum, and Vibrio was determined by gas-liquid chromatographic analysis. Over 70 different fatty acids were found. The predominant fatty acids were 16:0, 16:1 cis 9, summed-in-feature (SIF) 4 (15:0 iso 2OH and/or 16:1 trans 9) and SIF 7 (18:1 cis 11, 18:1 trans 9, and/or 18:1 trans 6) for all the strains considered, but minor quantitative variations could be used to distinguish the different genera. In addition to a conventional statistical processing method to analyze the data and draw comparison between species and genera, an approach involving neutral network-based elaboration is applied. The statistical analysis and dendrogram representation gave a comparison of the species considered, while the neural network computation provided a more accurate assignment of species to their genera. Moreover, by using neural networks, it was possible to conclude that only 22 fatty acids were important for the identification of the marine genera considered. A database of Alteromonas, Deleya, Oceanospirillum, and Vibrio fatty acid methyl ester profiles was generated and is now routinely used to identify fresh marine isolates.

Journal Article↗
PubMed1991

Enterococcus faecalis: specific and non-specific interactions with human polymorphonuclear leukocytes.

In previous studies we have demonstrated that the ability of Enterococcus faecalis to adhere to and to be internalized in human urinary tract epithelial cells, Girardi Heart cells and human polymorphonuclear leukocytes (PMNs), was dependent on whether the strain had been isolated from urinary tract infections (UTI) or endocarditis (EN) respectively. These properties were further modified by growth of the organism in human serum. In the present report, using competition assays we show that adhesins containing a D-glucose moiety play a role in mediating the interactions between human PMNs and E. faecalis strains isolated from UTI and grown in brain-heart infusion broth (BHIB). On the other hand, adhesins containing both D-glucose and D-galactose moieties were involved in the interactions between PMNs and serum grown UTI isolates or EN isolates grown in either BHIB or human serum. Moreover, the impairment in the association between both UTI and EN strains after growth in serum appears to be at least partially related to a decrease in enterococcal surface hydrophobicity.

Adult↗
PubMed1991

Serum dependent expression of Enterococcus faecalis adhesins involved in the colonization of heart cells.

Our previous studies have shown that the adhesive ability of Enterococcus faecalis is dependent on the strain and is further modified by growth in serum. The data reported here demonstrate that E. faecalis adherence is mediated by carbohydrate residues present on the bacterial cell surface. Some of these (D-mannose and D-glucose) are expressed by strains isolated from both urinary tract infections (UTI) and endocarditis (EN) when the cells are grown in brain-heart infusion broth (BHIB), and mediate adherence to either urinary tract epithelial cells or the Girardi Heart (GH) cell line. Other residues are present only on EN strains (D-galactose and L-fucose) and mainly mediate adherence to GH cells. These ligands can also be expressed by UTI isolates after growth in serum. D-galactose-bearing adhesins also seem to be involved in internalization of serum grown UTI strains and BHIB or serum grown EN isolates into GH cells.

Bacterial Adhesion↗
PubMed1989

Impairment of phagocytosis by the Klebsiella pneumoniae mannose-inhibitable adhesin-T7 receptor.

It has been previously shown that Klebsiella pneumoniae K59 carrying the mannose-inhibitable adhesin-T7 receptor (MIAT) efficiently binds to polymorphonuclear leukocytes (PMNs) incubated at 4 degrees C but is not efficiently bound and internalized by phagocytes incubated at 37 degrees C. Pretreatment of K59 with compounds that bind the MIAT ligand (D-mannose, UV-inactivated T7 phages, and pepsin-digested anti-MIAT antibodies) enables PMNs to phagocytize and kill these bacteria. In this article, we show that the incubation temperature has no direct effect on expression of either the MIAT or the PMN receptors. These receptors were always expressed at 37 degrees C when PMNs were treated with substances that impaired their ability to rearrange their surfaces (glutaraldehyde and cytochalasins B and D). Pretreatment of inert PMNs with concanavalin A or succinyl concanavalin A drastically reduced binding of K59 to phagocytes at both 4 and 37 degrees C. The same pretreatment carried out with metabolically active PMNs enabled them to efficiently phagocytize the MIAT-positive strain. When phagocytes were treated with K59 bacteria, they became unable to ingest and kill a K59 mutant not expressing the MIAT which was sensitive to phagocytosis. If this pretreatment was performed in the presence of D-mannose, UV-inactivated T7 phages, and pepsin-digested anti-MIAT antibodies, PMNs maintained their phagocytic activity against the MIAT-negative strain. In the presence of K59 bacteria, a very low chemiluminescence response was generated; in contrast, a significant response was observed when bacteria were previously absorbed with UV-inactivated T7 phages and pepsin-digested anti-MIAT antibodies. These results support our previous suggestion that the MIAT adhesin triggers changes in the cell surface, inhibiting further binding and phagocytosis.

Bacterial Adhesion↗
PubMed1989

Role of adherence in pathogenesis of Enterococcus faecalis urinary tract infection and endocarditis.

Enterococcus faecalis strains isolated from urinary tract infections (UTIs) and endocarditis were analyzed for their ability to adhere to urinary tract epithelial cells (ECs) and Girardi heart (GH) and human embryonic kidney (HEK) cell cultures. UTI isolates adhered to urinary tract ECs more efficiently than to the cultured cells, at the same time showing the least affinity for GH cells. In contrast, endocarditis isolates adhered to GH cell cultures more readily than to urinary tract ECs. Moreover, although strains isolated from endocarditis adhered to GH cells more efficiently than those derived from UTI, the latter strains adhered to urinary tract cells better than the former. Studies of the ability of GH and HEK cells to internalize E. faecalis showed that for UTI isolates, 9 to 74% of adhered bacteria were internalized, while for endocarditis isolates, the percentage varied from 76 to 82%. All strains were able to associate with human neutrophils; endocarditis strains, however, associated less efficiently than UTI isolates. Growth in serum raised the adherence of all tested strains by at least 1.5- to 3-fold, with the greatest increase being observed in UTI strain adherence to GH cells (8-fold). In contrast, the association of serum-grown cells with polymorphonuclear leukocytes was reduced by two- to fivefold. In both cases, the observed serum-dependent alterations were cancelled by a few subcultures in brain heart infusion broth. These results indicate that adhesive properties are important virulence factors in the pathogenesis of UTI and endocarditis and also suggest that UTI strains showing the highest invasion and adhesive potential invade the kidneys, cause bacteremia, and, after having expressed the serum-dependent surface modification, colonize the heart.

Adult↗
PubMed1989

[Seroprevalence of antibodies against Trypanosoma cruzi in 13 departments of Uruguay].

In 1985 a study was undertaken of the prevalence of Trypanosoma cruzi antibodies in 13 departments of Uruguay where transmission of the parasite by the vector Triatoma infestans persists. A total of 5,924 serum samples were selected using a probabilistic method--3,840 from individuals over the age of 12 (sample I) and 2,084 from subjects who were 12 years old (sample II). The population was classified according to place of residence (capital city, non-capital city, suburban area, and rural area). The percentage of positive sera detected by indirect immunofluorescence in the different departments ranged from 1 to 11%, and overall seroprevalence for the area was 3.4%. Based on the results obtained, it was possible to distinguish three areas: A, with seroprevalence from 6 to 11%; B, 2 to 3.2%, and C, 1 to 1.4%. In sample II from the Departments of Paysandú, Soriano, Flores, Florida, and Durazno, no cases of Chagas' disease were detected, which suggests that there is no active transmission of T. cruzi in this age group in the area studied. The number of persons estimated to have the disease was 36,952, or 1.3% of the total population of Uruguay and 4% of the population in the area surveyed. These seroprevalence figures are similar to those recorded in the province of Entre Ríos, Argentina, and in the neighboring municipalities of Rio Grande do Sul, Brazil.

Adolescent↗
PubMed1987

A waterborne outbreak of leptospirosis.

During the period from July 10-26, 1984, 33 cases of serologically confirmed leptospirosis occurred in a small town in central Italy. The fatality rate, including the deaths of two unconfirmed cases, was 8.6% (3 of 35). Based on serologic evidence, the infection was caused by leptospires of the serogroup Australis. Epidemiologic study showed that the patients contracted the infection by drinking water from a fountain. The source of leptospiral contamination was probably a hedgehog trapped in a reservoir of water not in use but still connected to the water system of the fountain.

Adult↗
PubMed1987

[Pitted keratolysis of hyperkeratotic form and isolation of the etiologic agent: Corynebacterium sp].

Two cases of "pitted keratolysis" with a very accentuated plantar hyperkeratosis, and the isolation on chocolate thelurite agar of the presumptive etiologic agent, Corynebacterium sp., is presented. In order to keep permanently in mind, for a proper diagnosis, the original description of the disease as "keratoma plantare sulcatum" (Castellani, 1910), we are proposing to distinguish two different clinical forms: The hyperkeratotic one and the common or usual form of "pitted keratolysis" with keratolysis as the main sign. The prosecution of our biochemical studies with a significant number of strains isolated from both "pitted keratolysis" and from classical erythrasma cases, will surely permit us to definitively determine if all of them should or not be assimilated to Corynebacterium minutissimum.

Adolescent↗
PubMed1985

Plasmid-specified aminoglycoside-modifying enzymes in clinical isolates of Klebsiella pneumoniae.

In 106 clinical isolates of multiresistant Klebsiella pneumoniae strains, we found that aminoglycoside-resistance was due mostly to two adenylating enzymes: AAD (2") (56.6%), that modifies gentamicin, kanamycin, tobramycin and sissomicin, and AAD (3") 9 (56.6% + 19.8%) that modifies streptomycin and spectinomycin. The identification of these enzymes was possible by MICs determination against a set of aminoglycosides antibiotics. AAD (2") + AAD (3")9 were coded by conjugative plasmid of about 120 Md.

Aminoglycosides↗
PubMed1984

A hospital epidemic caused by a multiple antibiotic resistant Klebsiella pneumoniae: implication of a conjugative R plasmid.

A R-plasmid of about 65 X 10(6) Md was found in several Klebsiella pneumoniae strains, responsible for an outbreak at the Lancisi Cardiological Hospital in Ancona. This plasmid was self-transferable and carried a "core" of resistance markers to ampicillin, carbenicillin and streptomycin; to this "core" the resistance markers to chloramphenicol, tetracycline, kanamycin and gentamicin can individually link, without appreciable changes in the molecular weight. We think that these Klebsiella pneumoniae strains are a potential reservoir of plasmid-mediated antibiotic resistance.

Anti-Bacterial Agents↗
PubMed1984

Modulation of production of hepatitis B surface antigen by a human hepatoma cell line.

Three drugs were assayed for their capacity to inhibit hepatitis B surface antigen (HBsAg) production by the PLC/PRF/5 human hepatoma cell line. The effect on cell growth and HBsAg production of Cordycepin, 6-azauridine, and Hygromicin B is reported. Hygromicin B, a translation inhibitor unable to penetrate normal cells, greatly reduced HBsAg production by growing and confluent cells.

Anti-Bacterial Agents↗
PubMed1984

Insulin reduces HBsAg production by PLC/PRF/5 human hepatoma cell line. Brief report.

Although its action at the molecular level is not completely understood, insulin, as well as its antagonist glucagon, certainly plays an important role in the modulation of protein synthesis. In order to observe whether insulin is involved in virus gene expression, we studied its effect on PLC/PRF/5 human hepatoma cell line, which posses HBV DNA sequences integrated at several sites. While human insulin had no effect on cell growth and increased the production of two plasma proteins, a selective inhibitory effect on HBsAg production could be detected. This observation might be useful for further studies both on virus gene expression and insulin action at the molecular level.

Carcinoma, Hepatocellular↗