Biomedical subjects
Publications and source records attributed to M E Alvarez.
36 episodes (25 nosocomial and 11 community-acquired) of infections caused by Hafnia alvei showed that this bacterium is responsible for serious infections in adults, specially in hospitalized patients with underlying chronic diseases, subjected to invasive procedures or even under antibiotic treatment.
AIMS: The objective of the present study was to determine the potential of promoter sequences from the cfp gene of Neurospora crassa to drive the expression of transgenes in filamentous fungi. METHODS AND RESULTS: Northern blot analyses showed that the mRNA levels of cfp were rapidly modified in response to either inducing or repressing culture conditions. The hygromycin phosphotransferase (hph) and S-adenosylmethionine synthetase (eth-1) genes were fused to a minimal cfp promoter fragment (Pcfp) and used as reporter genes. These constructs were highly expressed in transformant N. crassa strains grown in media containing glucose or sucrose and repressed in media containing ethanol or ethanol plus glucose. A gene fusion of the cfp promoter to the beta-glucuronidase gene (cfp-uidA) showed identical patterns of expression in the heterologous filamentous fungus Aspergillus nidulans. CONCLUSIONS: Our results show that the levels of expression of the native cfp gene, as well as reporter genes driven by cfp promoter sequences, can be rapidly modified in response to different carbon sources. These modified levels of expression are maintained by continuous growth in the presence of the corresponding carbon source. SIGNIFICANCE AND IMPACT OF THE STUDY: We propose that the cfp promoter can be used to control the expression of transgenes in filamentous fungi in a carbon source-dependent fashion.
Mortality due to invasive mold infections in solid organ transplant recipients is very high despite therapy with amphotericin B, including lipid formulations. Voriconazole is a triazole with a good activity against molds, including Aspergillus spp. and Scedosporium spp. Experience with voriconazole is limited, but preliminary results in patients with these infections are promising. Reported here is the experience with voriconazole administered on a compassionate-use basis to five patients with invasive mold infections: four solid organ recipients and one patient with an autoimmune disorder. Four patients had invasive Aspergillus fumigatus infection (3 lung infections, 1 abdominal infection) and one had invasive ocular Scedosporium apiospermum infection. The MIC of voriconazole was < or =1 microg/ml for all isolates (NCCLS performance standards for microdilution assay, proposed standard M38-P). Voriconazole was administered as primary therapy in a patient with Scedosporium infection and, in patients with Aspergillus infections, after persistence of positive culture despite a cumulative dose of 3 g of a lipid formulation of amphotericin B. Voriconazole was administered for a median time of 80 days (range, 60-90 days). No visual disturbances were observed, but one patient presented a moderate increase in liver enzymes. An increase in the levels of immunosuppressive drugs (tacrolimus or cyclosporine) was detected in all patients during coadministration with voriconazole. A clinical response was observed in all patients (complete response, n=3; partial response, n=2), and a microbiological response was observed in all but one patient. Furthermore, a good relationship between the MIC of voriconazole and outcome was observed. Voriconazole is an effective and safe therapy for treatment of invasive mold infections in solid organ recipients. To avoid toxicity with this drug, however, the dosing of immunosuppressive drugs must be reduced.
The effects of Clematis montevidensis Spreng. (Ranunculaceae) on urinary excretion of water, sodium and potassium were investigated in rats loaded with isotonic saline solution. The data reported in the present work indicate that the infusions of the root and aerial part of Clematis montevidensis showed a moderate diuretic activity. This effect could be due, at least in part, to the presence of oleanolic acid isolated from this plant.
A pharmacological evaluation of the diuretic activity of Fabiana patagonica Speg. (Solanaceae) was carried out in isotonic saline loaded rats. The data reported in the present work indicate that the acetone extract and infusion of the aerial part of Fabiana patagonica showed a moderate diuretic activity. This activity could be due, in part, to the presence of oleanolic acid isolated as the major metabolite of F. patagonica.
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BACKGROUND: Invasive aspergillosis (IA) is an important cause of mortality in liver transplant patients. Clinical and microbiological diagnosis is difficult, and it is frequently achieved only after autopsy. Early diagnosis and antifungal therapy could improve the survival of these patients. METHODS: A retrospective case-control study of IA in liver transplant recipients (OLT) was performed to determine the value of the detection of galactomannan Aspergillus antigen in serum using a sandwich-ELISA test (Platelia, Sanofi Diagnostic Pasteur). Stored frozen serum specimens obtained during the posttransplantation period were used. RESULTS: Fourteen cases of IA were diagnosed in 240 OLT recipients (IA incidence: 5.8%) during 5 years with 13 deaths (mortality: 93%). Nine case patients and 33 control patients met the criteria required for being considered "valid" for antigenemia analysis. In five of the nine case patients, a serum sample was positive for Aspergillus antigenemia detection. The median value was 5.7 ng/ml (range: 1.6-6.6). Sensitivity of the test was 55.6%, specificity was 93.9%, the positive predictive value was 71.4%, and the negative predictive value was 88.6%. The likelihood ratio of a positive test was 9.2. CONCLUSIONS: Galactomannan detection in serum could be useful for an early diagnosis of IA in OLT recipients.
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BACKGROUND: The diagnostic profile of patients with rheumatic diseases admitted to a general hospital is variable. AIM: To report the epidemiological profile of patients with rheumatic diseases admitted to a tertiary care hospital. MATERIAL AND METHODS: All admissions to a Medicine ward of a general hospital and seen by the Rheumatology team were prospectively registered during one year in 1999. Patients were classified as primarily admitted for a rheumatic disease or admitted for other cause that required a consultation with the Rheumatology team. RESULTS: One hundred forty five admissions due to rheumatic diseases were registered. Of these, 82 were due to primary rheumatic diseases. Systemic lupus erythematosus, rheumatoid arthritis and vasculitis were the main diagnoses and the mean hospital stay was 18.5 days. Sixty three patients required a consultation with the Rheumatology team specially due to osteoarthritis and crystal induced diseases. CONCLUSIONS: Admissions due to rheumatic diseases are prolonged, correspond to 0.46% of all admissions and the main responsible disease is systemic lupus erythematosus.
Although extensive data has described the key role of salicylic acid (SA) in signaling pathogen-induced disease resistance, its function in physiological processes related to cell death is still poorly understood. Recent studies have explored the requirement of SA for mounting the hypersensitive response (HR) against an invading pathogen, where a particular cell death process is activated at the site of attempted infection causing a confined lesion. Biochemical data suggest that SA potentiates the signal pathway for HR by affecting an early phosphorylation-sensitive step preceding the generation of pro-death signals, including those derived from the oxidative burst. Accordingly, the epistatic relationship between cell death and SA accumulation, analyzed in crosses between lesion-mimic mutants (spontaneous lesion formation) and the transgenic nahG line (depleted in SA) places the SA activity in a feedback loop downstream and upstream of cell death. Exciting advances have been made in the identification of cellular protective functions and cell death suppressors that might operate in HR. Moreover, the spatio-temporal patterns of the SA accumulation (non-homogeneous distribution, biphasic kinetics) described in some HR lesions, may also reveal important clues for unraveling the complex cellular network that tightly balances pro- and anti-death functions in the hypersensitive cell death.
Since temperature affects the inactivation rate of viruses in natural water systems, the aim of this study was to determine if a temperature shift could influence the structural integrity of model viruses. When crude lysates of MS-2 phage were seeded into groundwater microcosms and incubated at 27 degrees C, complete virus inactivation took place in eight days. The temperature was then shifted to 4 degrees C. Three days after the temperature shift, a two-log increase in virus titer (reactivation) occurred. However, when purified MS-2 lysates were added to groundwater microcosms, no reactivation was obtained. No reactivation of poliovirus took place when similar microcosm experiments were done. The sedimentation coefficients of MS-2 shifted from 80S to 58S, 48S, 37S, 32S, and 18S as inactivation proceeded in groundwater and distilled water controls. Similarly, the sedimentation coefficients of polioviruses changed from 156S to 142S, 135S, 117S, 105S, 95S, and 80 S as inactivation took place. There was no correlation between % virus inactivation and % decrease in virions with intact sedimentation coefficients, as reported earlier for poliovirus inactivated by chlorine. The results presented support our hypothesis that virus inactivation proceeds gradually, involving the rearrangement and (or) loss of capsomere components that may eventually lead to the ejection of nucleic acids. The intermediate particles generated as inactivation proceeds may be in a reversibly inactivated state, and may revert back to a fully infectious state when chemical components stabilize the virus particle.
The clinical picture of primary systemic vasculitis, that cause inflammation and necrosis of vessel walls, depend on the type, size and location of involved vessels. Frequently, their clinical presentation does not reflect the specific type of vasculitis and its prognosis. Moreover, the correct diagnosis, early and adequate treatment have an important prognostic value. Recently, new diagnostic methods for systemic vasculitis have been devised. This article critically reviews and provides information for the rational use of these new imaging techniques and laboratory procedures for the diagnosis and follow up of systemic vasculitis.
Recognition of an avirulent pathogen stimulates an oxidative burst generating O2- and H2O2, and these reactive oxygen intermediates (ROIs) cue the induction of defense genes and cell death in the development of a restricted lesion. This localized hypersensitive response (HR) is accompanied by the development of systemic acquired resistance to virulent pathogens. Here we show that inoculation of Arabidopsis leaves with avirulent Pseudomonas syringae induces secondary oxidative bursts in discrete cells in distant tissues, leading to low-frequency systemic micro-HRs. The primary oxidative burst induces these systemic responses, and both the primary burst and the secondary microbursts are required for systemic immunity. Hence, ROIs mediate a reiterative signal network underlying systemic as well as local resistance responses.
The antimicrobial susceptibility profile of 77 oropharyngeal viridans streptococci isolates from 34 cystic fibrosis (CF) patients and 58 isolates from 43 healthy non-CF patients were studied by the E-test and the standard disk diffusion methods. Overall penicillin and cefotaxime resistances (intermediate plus resistant isolates) were significantly higher (p < 0.05) among CF isolates (72.7% and 45.5%, respectively) than among non-CF isolates (51.7% and 15.5%, respectively). No significant difference was observed in overall (intermediate plus resistant) erythromycin resistance rates, although high-level erythromycin resistance (> or =32 microg/mL) was more frequently found in CF isolates (24.6%) than in non-CF isolates (12.1%). An unexpected high percentage of isolates showed low level erythromycin resistance (MIC range, 0.5-15 microg/mL): 41.5% in cystic fibrosis and 46.5% in non-CF isolates. No significant differences were observed regarding the percentage of colonized patients with at least one penicillin-resistant isolate. On the contrary, colonization with cefotaxime (p < 0.001) or erythromycin (p = 0.014) resistant isolates were significantly more prevalent in CF patients. Similar tetracycline and chloramphenicol resistance rates were observed for both groups. Viridans isolates resistant to a single antibiotic were more prevalent among non-CF patients and multiple resistance was higher among CF patients. Prior antibiotic exposure could result in differences in beta-lactam resistance and colonization rates with resistant isolates between both groups. None of the non-CF patients was previously treated with antimicrobials for a period of three months before sampling. In contrast, 94.1% of CF patients were treated with antimicrobials within the same period; 65.6% with beta-lactam antibiotics. Patients with CF disease, frequently exposed to antimicrobials, may be a reservoir of viridans streptococci isolates with resistance determinants, particularly to beta-lactam antibiotics.
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BACKGROUND: Avirulent pathogens elicit a battery of plant defenses, often accompanied by collapse of the challenged cells. In soybean cells, sustained accumulation of H2O2 from an oxidative burst cues localized host cell death. Such hypersensitive cell death appears to be an active process, but little is known about the mechanisms underlying cellular collapse. RESULTS: We show that H2O2 stimulates a rapid influx of Ca2+ into soybean cells, which activates a physiological cell death program resulting in the generation of large (approximately 50 kb) DNA fragments and cell corpse morphology--including cell shrinkage, plasma membrane blebbing and nuclear condensation--characteristic of apoptosis. In contrast, H2O2 induction of the cellular protectant gene glutathione S-transferase is Ca(2+)-independent. Apoptosis in soybean cells and leaf tissue was induced by avirulent Pseudomonas syringae pv. glycinea but was not observed at comparable stages of the compatible interaction with the isogenic virulent strain, which fails to elicit a hypersensitive response. Apoptosis was also observed at the onset of the hypersensitive response in Arabidopsis leaves inoculated with avirulent P. syringae pv. tomato and in tobacco cells treated with the fungal peptide cryptogein, which is involved in the induction of non-host resistance to Phytophthora cryptogea. CONCLUSIONS: These observations establish a signal function for Ca2+ downstream of the oxidative burst in the activation of a physiological cell death program in soybean cells that is similar to apoptosis in animals. That the characteristic cell corpse morphology is also induced in Arabidopsis and tobacco by different avirulence signals suggests that apoptosis may prove to be a common, but not necessarily ubiquitous, feature of incompatible plant-pathogen interactions. Emerging similarities between facets of hypersensitive disease resistance and the mammalian native immune system indicate that apoptosis is a widespread defence mechanism in eukaryotes.
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