PubMed Health⌕ Search

Biomedical subjects

S Stefani

Publications and source records attributed to S Stefani.

At least 55 records · Page 3Linked to original sources
PubMed1998

Lack of consistent short sequence repeat polymorphisms in genetically homologous colonizing and invasive Candida albicans strains.

Short sequence repeats (SSRs), potentially representing variable numbers of tandem repeat (VNTR) loci, were identified for the human-pathogenic yeast species Candida albicans by computerized DNA sequence scanning. The individual SSR regions were investigated in different clinical isolates of C. albicans. Most of the C. albicans SSRs were identified as genuine VNTRs. They appeared to be present in multiple allelic variants and were demonstrated to be diverse in length among nonrelated strains. As such, these loci provide adequate targets for the molecular typing of C. albicans strains. VNTRs encountered in other microbial species sometimes participate in regulation of gene expression and function as molecular switches at the transcriptional or translational level. Interestingly, the VNTRs identified here often encode polyglutamine stretches and are frequently located within genes potentially involved in the regulation of transcription. DNA sequencing of these VNTRs demonstrated that the length variability was restricted to the CAA/CAG repeats encoding the polyglutamine stretches. For these reasons, paired C. albicans isolates of similar genotype, either found as noninvasive colonizers or encountered in an invasive state in the same individual, were studied with respect to potentially invasion-related alterations in the VNTR profiles. However, none of the VNTRs analyzed thus far varied systematically with the transition from colonization to invasion. In contrast to the situation described for some prokaryotic species, this finding suggests that VNTRs of C. albicans may not simply function as contingency loci related to straightforward on/off regulation of invasion-related gene expression.

Base Sequence↗
PubMed1998

Susceptibility survey of piperacillin/tazobactam and some beta-lactam comparators in Italy.

From September 1994 to March 1995 an Italian multicenter in vitro study to evaluate the susceptibility of piperacillin/tazobactam compared with that of imipenem, ceftazidime, ceftazidime, ceftriaxone, cefotaxime and ampicillin/sulbactam against aerobic bacterial pathogens isolated in 132 different hospitals, was undertaken. In total, 26,732 isolates were collected but only 25,266 aerobic bacteria were able to be evaluated (16,863 Gram-negative and 8,403 Gram-positive). Escherichia coli was the most frequent pathogen isolated (25.9%) followed by Staphylococcus aureus (14.9%), Pseudomonas aeruginosa (13.9%), Enterococcus faecalis (8.2%) and Klebsiella pneumoniae (5.9%). Piperacillin/tazobactam had a general spectrum of activity (84.8% susceptible strains) comparable to imipenem (87.9%), and was distinctly greater than ceftazidime (71.1%).

Anti-Bacterial Agents↗
PubMed1996

Combined differentiating therapy for myelodysplastic syndromes: a phase II study.

An in vitro synergism between different inducers of AML cell differentiation has been previously observed. Therefore, we treated 53 myelodysplastic (MDS) patients with a low dose combination of cis-retinoic acid (cRA, 20-40 mg/day) and 1,25 alpha (OH)2 cholecalciferol [(OH)2D3, 1-1.5 micrograms/day] +/- intermittent 6-thioguanine (30 mg/m2/day). The latter was reserved for patients with bone marrow (BM) blast excess (> or = 5%). The treatment was well tolerated, without major toxicity. Among 25 patients with BM blasts less than 5%, we observed one complete, eight partial and four minor responses (response rate 52%) with a median response duration of 8 months (2 +/- 24). Median survival, which did not correlate with response, is projected at 76 months. Thirty-one patients with BM blast excess (> or = 5%), including three of the previous group who progressed to refractory anemia with excess of blasts (RAEB), were treated with the three-drug protocol. One complete, 12 partial and six minor responses were obtained (response rate 61%) with a median response duration of 6 months (2-29+). A significant difference in survival (P < 0.005) was observed between the 19 responders (median 25 months) and the 12 non-responders (median 9 months). A reduction in the transfusion need was observed in 41% of the transfusion-dependent patients with blast excess and in 53% of those without blast excess. Therefore, combined differentiating therapy seems more effective than previously reported single agent treatments and should be considered for a larger randomized study to assess its actual impact on survival of MDS patients.

Aged↗
PubMed1996

[Moraxella catarrhalis: an emerging respiratory pathogen].

In the past years Moraxella (Branhamella) catarrhalis has finally gained respect as a pathogen thanks to the many reports of its causal role. The intent of this review is to provide a critical evaluation of the intent of this review is to provide a critical evaluation of the microbiological features (taxonomy, diagnosis, virulence, epidemiology and drug resistance), clinical diseases and therapy of this microorganism

English Abstract↗
PubMed1995

Molecular epidemiology of enterococci with high-level resistance to aminoglycosides.

DNA-based methodologies are considerably more powerful than other phenotype-based typing systems, providing a finer level of epidemiological discrimination, differentiating both closely and distantly related independent isolates that otherwise may appear as identical. In this study, plasmid analysis and pulsed-field gel electrophoresis were used to compare 28 isolates of Enterococci (respectively 13 strains of Enterococcus faecalis and 15 strains of Enterococcus faecium) with high-level resistance to aminoglycosides, isolated in Catania (Italy). Plasmid profile analysis resolved 20 different patterns among 24 plasmid harboring strains; many isolates showed one or two plasmids of the same size, but different plasmid content. Analysis of the PFGE-based RFLP patterns after SmaI digestion of genomic DNA resolved 26 different clones from 28 isolates: particularly, it resolved two different clones from three isolates showing identical plasmid profiles, and it identified as a single clone two isolates exhibiting different plasmid profiles. Thus, on the basis of our PFGE-based RFLP analysis data, we concluded that all the strains included in the study were genetically unrelated with two exceptions.

Aminoglycosides↗
PubMed1995

Interactions of biapenem with active-site serine and metallo-beta-lactamases.

Biapenem, formerly LJC 10,627 or L-627, a carbapenem antibiotic, was studied in its interactions with 12 beta-lactamases belonging to the four molecular classes proposed by R. P. Ambler (Philos. Trans. R. Soc. Lond. Biol. Sci. 289:321-331, 1980). Kinetic parameters were determined. Biapenem was readily inactivated by metallo-beta-lactamases but behaved as a transient inhibitor of the active-site serine enzymes tested, although with different acylation efficiency values. Class A and class D beta-lactamases were unable to confer in vitro resistance toward this carbapenem antibiotic. Surprisingly, the same situation was found in the case of class B enzymes from Aeromonas hydrophila AE036 and Bacillus cereus 5/B/6 when expressed in Escherichia coli strains.

Binding Sites↗
PubMed1995

Enterococci: susceptibility patterns and therapeutic options.

Enterococcal isolates are increasingly responsible for nosocomial infections in the last decade and they are recently cited as being the second most common pathogen isolated from hospitalized patients. Enterococcal infections can be localized at different sites: endocarditis, CNS, intrabdominal, pelvic. The epidemiological trend may be a consequence of predisposing risk factors due to hospitalization such as instrumentation, immunosuppression, long-term hospitalization. Nevertheless the most alarming aspect of the problem is the increasing detection of antibiotic resistance Enterococcal strains, especially the high level resistance (HLR) to aminoglycosides, penicillin and glycopeptides must not be underestimated. Optimal antibiotic regimes for the treatment of multiple resistant strains in severe enterococcal infections are not been defined yet and antibiotic association such as aminoglycosides + glycopeptides or glycopeptides + fluoroquinolones could be suggested.

Journal Article↗
PubMed1995

Enterococci: susceptibility patterns and therapeutic options.

Enterococci do not possess the common virulence factors found in many other bacteria, but they have a number of other characteristics which make them particularly pathogenic. These organisms are intrinsically resistant to a number of antimicrobial agents, including beta-lactams (penicillins and cephalosporins), polymyxins and the lincosamides. They are also tolerant to the bactericidal activity of penicillins and glycopeptides, and some of the group have acquired resistance to a number of other clinically important antimicrobial agents including ampicillin, aminoglycosides, chloramphenicol and erythromycin. Numerous national and international studies have demonstrated the changes in the antibiotic resistance of enterococci. Many strains now exhibit multiple drug resistance, the most important being high-level resistance to streptomycin and gentamicin. Organisms exhibiting this high-level resistance are usually resistant to all synergistic combinations of beta-lactam antibiotics and aminoglycosides. Ampicillin-resistant strains are now emerging, some of which are beta-lactamase producers. While resistance to glycopeptides remains rare, it is increasing dramatically in many areas of the world. As nosocomial isolates of enterococci have displayed resistance to essentially every useful antimicrobial agent, it is likely to become increasingly difficult to treat and control enterococcal infections. The glycopeptide antibiotics vancomycin and, particularly, teicoplanin are the only alternatives currently available. Although a bactericidal combination of antibiotics appears necessary only in endocarditis and meningitis and although knowledge of the prevalence of resistant strains can be used to guide the selection of appropriate therapy, optimal regimens for the treatment of infections caused by multiresistant strains have yet to be determined.(ABSTRACT TRUNCATED AT 250 WORDS)

Drug Resistance, Microbial↗
PubMed1994

Observations on the tolerance and the paradoxical effect in enterococci.

Enterococci, already know to be relatively unaffected by several antibiotics due to their inheritant characteristics, are increasingly resistant to some very important groups of drugs, by means of acquisition or exchange of new genetic traits of resistance. Resistance or moderate susceptibility towards penicillin is an interesting characteristic of enterococci, whose low degree of susceptibility to this drug is due to a low affinity for penicillin-binding proteins (PBP). Some strains of enterococci are not killed by the action of this drug but are "tolerant" (MIC/MBC > 32 mg/l). This kind of "resistance", in which the probability of surviving under selective pressure of the drug is increased, is probably linked to the deficiency of the cell's autolytic system. Only rarely does another form of resistance called the "paradoxical effect" appear, in which higher numbers of cells survive at high concentrations than at lower concentrations. In our study the degree of bactericidal activity of some beta-lactams was considered. Our results demonstrate that: i) the paradoxical effect appears more in cultures in exponential phase compared to aged cultures; ii) mutated strains show an increased number of cells that respond paradoxically (the behavior is genetically determined); iii) different beta-lactams induced different degrees of autolysis.

Anti-Bacterial Agents↗
PubMed1994

Survey on antibiotic resistance in gram-negative non-fermentative bacteria other than pseudomonas in Italy.

A survey was conducted to investigate the incidence and antibiotic resistance of clinical isolates of Gram-negative non-fermentative bacteria, isolated during a one-year period in Italy. Overall, these microorganisms account respectively for 11.47% and 20.5% of all Gram-negative bacteria. The most representative species isolated during the study were: Acinetobacter, Flavobacterium, Alcaligenes, Achromobacter and Xanthomonas species. As regards their antimicrobial pattern of resistance, this survey demonstrated the wide differences existing within each group. The antimicrobial agents usually active against Pseudomonas aeruginosa do not seem to be useful against these microorganisms.

Ciprofloxacin↗
PubMed1994

Incidence of lower respiratory tract infections caused by Mycoplasma, Chlamydia and Legionella: an Italian Multicenter Survey.

A collaborative retrospective study based on serologic diagnosis was conducted to assess the etiological role sustained by privileged pathogens in Italy. The results obtained indicate the Mycoplasma, Chlamydia and Legionella are important etiologic agents of lower respiratory tract infections in Italy since they account for about 31% of the cases taken into consideration in this survey. We found a high incidence of M. pneumoniae (12.3%), C. pneumoniae (10.5%) and L. pneumophila (8.3%). These results are in line with similar figures reported in the recent literature. While the data gathered in our survey do not allow us to clarify the nature of the agents involved in the etiology of the majority (70%) of the respiratory infections occurring in Italy, it seems safe to assume that after Streptococcus pneumoniae and Haemophilus influenzae, the privileged pathogens represent the most common cause of lower respiratory tract infections.

Chlamydia Infections↗
PubMed1994

Androgen responsiveness and androgen receptor gene expression in human kidney cells in continuous culture.

The effects of androgen and estrogen on cell growth and gene expression were investigated in KJ29 kidney epithelial cells. Incorporation of 3H leucine and 3H thymidine was increased by androgen at 10nM, but not by estrogen. Estrogen however, inhibited the effects induced by androgen. In addition, cell number and the proliferation marker Ki67 were increased by androgen, but not by estrogen. Levels of androgen receptor RNA, as detected by RT-PCR and Northern blot analysis, were not affected by either androgen or estrogen. Levels of estrogen receptor RNA could be detected only by RT-PCR, and disappeared after estrogen treatment. These studies show that sex steroid receptors are differently expressed in KJ29 cells, and suggest that androgen, via its canonic receptor, acts as a mitogenic factor in human kidney cells, whereas estrogen has an antiandrogenic action.

Antibodies, Monoclonal↗
PubMed1994

Analysis of polycystic kidney disease with two new microsatellite markers.

Two (CA) microsatellite polymorphisms have been studied in 209 subjects from Northern Italy, members of 27 Polycystic Kidney Disease families. Polymorphic alleles were analyzed by using a labelled PCR. Results obtained show that these markers highly improve the presymptomatic diagnosis of the disease in subjects at risk. In addition, our findings suggest that a region with a high recombination frequency should exist between PKD1 and SM7.

Base Sequence↗
PubMed1992

Susceptibility of frequent urinary pathogens to fosfomycin trometamol and eight other antibiotics: results of an Italian multicenter survey.

In order to assess the resistance profile for fosfomycin trometamol after several years of clinical use in Italy, this study has explored the susceptibility to fosfomycin and eight other antibacterial drugs of 6,021 strains isolated from 23,816 urines during 1990 in three teaching hospitals located in Genoa, Parma and Catania. Gram-negative strains, notably Escherichia coli (41.6%), were primarily involved. Amoxicillin was the least active compound with resistance in 41.4% of the isolates. Fosfomycin showed the lowest rate of resistance in both gram-negative (2.8%) and gram-positive (2.1%) pathogens. This was followed by norfloxacin with a resistance rate of 11.8% and netilmicin with 12.2%. These results indicate that fosfomycin-trometamol may continue to be used in single-dose treatment of urinary tract infections even in the absence of microbiological data since the prevalence of resistance to the drug is, at present, so low that therapeutic failure is highly improbable.

Anti-Bacterial Agents↗
PubMed1992

Microbiological considerations of the etiological agents of lower respiratory tract infections.

One hundred eight-four sputum specimens from the same number of patients with lower respiratory tract infections were examined to determine the bacterial count and the relationship between the microorganisms isolated and the presumptive pathology. The sputa were subdivided into three groups; "high probability", "low probability", and "contaminated sputa", following the criteria of the microscopic readings: sputum with more than 25 white cells and low numbers of squamous epithelial cells represents true lower respiratory tract infections (high probability); those with fewer than 25 white cells represent non-bacterial infections or non-infected sputa (low probability) while sputa with more than 25 squamous cells per field represent contaminated specimens (contaminated sputa). Statistical analysis was carried out to correlate these data. Haemophilus influenzae, Haemophilus parainfluenzae, Streptococcus pneumoniae, and Streptococcus pyogenes showed significant differences in the three groups considered.

Gram-Negative Bacteria↗
PubMed1992

In vitro activity of a new broad-spectrum, beta-lactamase-stable oral cephalosporin, cefixime, in comparison with other drugs, against Haemophilus influenzae, Haemophilus parainfluenzae, Moraxella catarrhalis and Streptococcus pneumoniae.

Cefixime, a new orally absorbed iminomethoxyaminothiazolyl cephalosporin, was tested against some microorganisms involved in upper and lower respiratory tract infections such as Haemophilus (influenzae and parainfluenzae), Moraxella catarrhalis and Streptococcus pneumoniae, isolated in the period from November 1990 to April 1991. Its activity was compared to nine other antimicrobial agents: erythromycin, trimethoprim-sulfamethoxazole, ampicillin, amoxicillin-clavulanate, cefaclor, ceftazidime, ceftriaxone, cefotaxime and ofloxacin. Cefixime inhibits 90% of S. pneumoniae, H. influenzae and H. parainfluenzae, both beta-lactamase producers (BLP) or not (NBLP) at concentrations of less than 0.25 mg/l. It inhibits 90% of M. catarrhalis (BLP and NBLP) at concentrations of less than 1 mg/l. In general, cefixime has a superior in vitro activity with respect to cefaclor and the other cephalosporins as well as erythromycin and amoxicillin (the last one in BLP strains). In the evaluation of the antibacterial activity of beta-lactam against Haemophilus and M. catarrhalis, the authors observed different indications in the guidelines for ampicillin. Cefixime is not destroyed by the plasmid-mediated beta-lactamase produced by Haemophilus sp. and M. catarrhalis (TEM and ROB in Haemophilus strains and BRO in M. catarrhalis). In view of its excellent in vitro activity against the commonly encountered respiratory tract pathogens, cefixime is indicated in the therapy of these infections.

Administration, Oral↗
PubMed1992

Simplified construction and characterization of yeast artificial chromosome libraries.

Three yeast artificial chromosome (YAC) libraries were constructed using two human cell lines and the pYAC-RC vector. The main differences from the previously described methods were: i) genomic DNA was digested in low melting point (LMP) agarose blocks with the rare cutting enzyme ClaI; ii) DNA was ligated in melted LMP agarose after agarase treatment; iii) spheroplast regeneration plating was done in calcium alginate thin layer. In addition, a panel of PCR primers was used to identify quickly the presence in the libraries of repetitive and single copy human DNA sequences.

Base Sequence↗