Risk factors associated with St. Louis encephalitis seroprevalence in two populations from Córdoba, Argentina

St. Louis encephalitis virus (SLEV) is endemic in Argentina. The first outbreak was recorded in Córdoba during the late summer of 2005. This study analyzes the association between social and demographic factors and other variables related to exposure to mosquitoes with SLEV infection in 264 individuals who attended two health centers in the city of Córdoba during the period December 2004-January 2005. Multiple logistic regression models were used to estimate the risk coefficients. The seroprevalence was 12.9%, similar to that in previous reports. Risks of infection were associated with the presence of garbage dumps near dwellings, the practice of outdoor activities at night and place of residence. Risk for older people (60-80 years old) was moderate. The identification of risk factors related to SLEV infection would be useful to improve programs for vector control and community health.

Effects of baclofen on temperature perception in humans

The aim of this study was to evaluate the effect of chronic consumption of the GABAB agonist baclofen on temperature perception in humans. We investigated temperature perception thresholds to detect warm and cold stimuli in a group of 21 patients with spinal cord injury, who were chronically consuming oral baclofen at different daily doses to treat spasticity. Temperature perception thresholds were assessed above the level of the lesion, using a psychophysical approach based on the ability of the subjects to perceive precisely quantified sensory stimuli (quantitative sensory testing, QST). The data were compared with a control group of healthy subjects, not receiving baclofen. We found that chronic baclofen consumption increased temperature perception thresholds for both cold and warm stimuli in a dose-dependent manner. Temperature perception thresholds did not depend on the level of the lesion nor on the duration of baclofen treatment, suggesting that our finding represent normal GABAB-mediated modulation in spared nervous structures. We conclude that GABAB therefore plays a role in temperature perception in humans.

Effect of chronic treatment with three varieties of Lepidium meyenii (Maca) on reproductive parameters and DNA quantification in adult male rats

The aim of this study was to evaluate the chronic effect of different varieties of Lepidium meyenii (Red Maca, Yellow Maca and Black Maca). Male rats were treated by gavage with aqueous extract of each variety of maca equivalent to 1 g hypocotyl kg(-1) body weight (BW) for 84 days. At the end of the treatment, daily sperm production (DSP), epididymal sperm count (ESC) and sperm count in vas deferens (SCVD) were assessed. In addition, testis DNA quantification was also determined. Any toxic effect was assessed in liver and spleen by histological studies. The results indicate that Yellow Maca and Black Maca improved ESC and that three varieties of maca increased the SCVD without affecting DSP. Moreover, testis DNA levels were not affected by treatment with any of the three varieties of maca. Histological picture of the liver in animals treated with the three varieties of maca was similar to that observed in controls. In conclusion, Yellow and Black Maca increased epididymal sperm count after 84 days of treatment without affecting DSP. Maca seems to act as a modulator of sperm count at the reproductive tract level.

Microbial and clinical determinants of time-to-positivity in patients with bacteraemia

Time-to-positivity is useful in the diagnosis of catheter-related bacteraemia and as a predictor of an endovascular source in patients with Staphylococcus aureus bacteraemia. However, this parameter has been evaluated for only a limited number of microorganisms. In the present study, time-to-positivity was recorded for 1872 episodes of significant monomicrobial bacteraemia diagnosed at a teaching hospital during a 2-year period, and the associated microbial and clinical variables were investigated. According to multivariate analysis, Streptococcus pneumoniae, beta-haemolytic streptococci, Escherichia coli, Klebsiella, Enterobacter, Citrobacter and Aeromonas were characterised by fast growth, with an endovascular source, shock, liver cirrhosis and neutropenia also predicting a short time-to-positivity. For patients not receiving appropriate antibiotics, detection of Gram-positive cocci in clusters within 14 h was predictive of Staph. aureus; a time-to-positivity of >21 h ruled out the possibility that a Gram-positive organism in chains was a beta-haemolytic streptococcus or Strep. pneumoniae, and a time-to-positivity of < or =12 h meant that it was very unlikely that a Gram-negative bacillus was a non-fermenter. A time-to-positivity of < or =8 h was predictive of a non-urinary tract source in patients with E. coli bacteraemia, and detection of growth within 13 h predicted an endovascular source in those with Staph. aureus bacteraemia. In conclusion, time-to-positivity depended on the microorganism, original source and clinical variables involved. Although this measurement may provide some early clues concerning the microorganisms involved and the source of bacteraemia, its clinical impact remains to be defined.

Role of secreted glyceraldehyde-3-phosphate dehydrogenase in the infection mechanism of enterohemorrhagic and enteropathogenic Escherichia coli: Interaction of the extracellular enzyme with human plasminogen and fibrinogen

Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) (EC 1.2.1.12) is an anchorless, multifunctional protein displayed on the surface of several fungi and Gram-positive pathogens, which contributes to their adhesion and virulence. To date a role for extracellular GAPDH in the pathogenesis of Gram-negative bacteria has not been described. The aim of this study was to analyze the extracellular localization of GAPDH in enterohemorrhagic (EHEC) and enteropathogenic (EPEC) Escherichia coli strains and to examine its interaction with host components that could be related to the infection mechanism. Recombinant E. coli GAPDH was purified and polyclonal antibodies were obtained. Western blotting and immunoelectron microscopy showed that GAPDH is located on the bacterial surface and released to the culture medium of EHEC and EPEC strains. GAPDH export in these Gram-negative pathogens depends on the external medium, is not mediated by vesicles and leads to an extracellular active enzyme. Non-pathogenic E. coli strains do not secrete GAPDH. Two-dimensional electrophoresis analysis showed that in E. coli GAPDH is present at least in two major forms with different isoelectric points. Of these forms, the more basic is secreted. Purified GAPDH was found to bind human plasminogen and fibrinogen in Far-Western blot and ELISA-based assays. In addition, GAPDH remained associated with colonic Caco-2 epithelial cells after adhesion of EHEC or EPEC. These observations indicate that exported GAPDH may act as a virulence factor which could contribute to EHEC and EPEC pathogenesis. This is the first description of an extracellular localization for this enzyme, with a function other than its glycolytic role in Gram-negative pathogens.

Temporal relationship between proliferating and apoptotic hormone-producing and endothelial cells in the equine corpus luteum

The temporal relationship between endothelial cell death, vascular regression and the death of hormone-producing cells in the mare has not been established. To determine the dynamics of cell proliferation and death throughout the luteal phase, corpora lutea were studied at the early, mid- and late luteal phase, and after treatment with cloprostenol in the mid-luteal phase to induce premature luteolysis. Changes in cell proliferation and apoptosis were investigated utilising specific markers (phosphorylated histone-3 and activated caspase-3 respectively). Histone-3 positive cells were most abundant during the early luteal phase, and were mainly present in endothelial cells. Histone-3 activity significantly increased in hormone-producing cells 36 h after cloprostenol treatment. Frequency of activated caspase-3 staining peaked on day 14, and was induced by 36 h after cloprostenol administration in mid-luteal phase. However, cell death occurred simultaneously in the endothelial and hormone-producing cells. These results show that a subset of hormone-producing cells enter the early stages of cell division around luteolysis, while the majority of cells are undergoing cell death. Natural and induced functional and structural luteal regression in the mare can be at least partially attributed to simultaneous apoptosis of endothelial and hormone-producing cells. However, there is no evidence that endothelial cell death is the trigger for naturally occurring luteolysis.

Cost-effectiveness analysis of lamivudine and adefovir dipivoxil in the treatment of patients with HBeAg-negative chronic hepatitis B

AIM

To estimate the cost-effectiveness over a 4-year duration of lamivudine and adefovir dipivoxil for patients with hepatitis B 'e' antigen-negative chronic hepatitis B.

METHODS

A decision analysis model has been used to perform a cost-effectiveness analysis of lamivudine and adefovir dipivoxil from the perspective of the Spanish Public Health System. Data were obtained from clinical trials.

RESULTS

For the base-case, the total estimated cost per patient treated with lamivudine or adefovir dipivoxil for 4 years was 11,457 and 21,939 respectively. Virological response at year 4 for the lamivudine arm was 40.4% and 78.0% for the adefovir dipivoxil arm. The average cost-effectiveness ratio (cost per responding patient at year 4) was 28,375 for the lamivudine arm and 28,132 for the adefovir dipivoxil arm. The incremental cost-effectiveness ratio of adefovir dipivoxil vs. lamivudine (cost per additional responding patient with adefovir dipivoxil) was 27,872, demonstrating that this cost was slightly lower than the average cost-effectiveness ratios of adefovir dipivoxil or lamivudine. The sensitivity analysis demonstrated that the factors that most influence the cost-effectiveness were the response to adefovir dipivoxil and lamivudine at year 4.

CONCLUSION

Long-term treatment with adefovir dipivoxil is a cost-effective strategy in patients with chronic hepatitis B 'e' antigen-negative hepatitis.

Influence of analytical and biological variation on the clinical interpretation of seminal parameters

Quality assurance in semen analysis has been questioned recently in this journal. Based on the limited capacity of seminal parameter in the determination of fertility, the authors advocated abandoning methods of quality assurance in semen analysis for clinical situations. In this article, we explore arguments as to why quality assurance in semen analysis for clinical use is not 'a waste of time'. Imprecision and within-subject biological variations are the two major components involved in the dispersion of seminal parameter results obtained by analysis of a semen sample from an individual. As within-subject biological variation is constant across geography, time and population, imprecision is a very important factor in the quality of laboratory test results. We analyse this influence on various seminal parameters and observe that there is an amount of error that can be tolerated without invalidating the medical usefulness of seminal parameter determination. However, there is a maximum allowable analytical error above which the medical usefulness of seminal parameter results is invalidated. The level of performance required to facilitate clinical decision-making is termed quality specification. We comment on different strategies to define the maximum allowable analytical error.

Treatment of hepatitis C virus with interferon in hemodialysis patients awaiting kidney transplant

INTRODUCTION

Hepatitis C virus (HCV) infection is associated with worsening disease progression after renal transplant, and to date there is no available treatment for use at this stage. It has therefore been recommended to treat HCV infection with interferon (IFN) during the dialysis period while the patient is on the waiting list for transplantation.

METHODS

We analyzed data from 27 patients on hemodialysis awaiting transplant, who were under IFN treatment for chronic HCV infection (dominant genotype, 1b). The starting regime was IFN alpha-2b, 3 MU x 3/week (n = 20) or pegylated IFN alpha-2a, 135 mg/week (n = 7). If there was clearance of HCV RNA in the first 3 to 6 months, we attempted to prolong IFN treatment for 1 year, although in many patients the dose had to be reduced. A sustained response was defined as viral clearance for at least 12 months after the end of treatment.

RESULTS

Viremia was negative in 13 patients (48.1%) at the end of treatment, but two of these patients relapsed, to give an overall long-term response rate of 11 patients (40.7%) and incomplete follow-up in three patients. Viral clearance was not achieved in 11 patients. In three patients (12%), IFN had to be suspended before finishing the third month of therapy due to side effects (mainly pancytopenia and intolerance of a previous kidney graft). Seven patients showing a sustained response underwent transplant, maintaining a negative viremia result.

CONCLUSIONS

IFN treatment was effective in a high proportion of dialysis patients with HCV infection, with response rates possibly even higher than for the general population. However, its use is restricted by a high incidence of side effects.

Quality specifications for seminal parameters based on the state of the art

BACKGROUND

The aim of this study was to calculate the analytical goal for seminal parameters based on the state of the art, and then to compare these specifications with those previously obtained by our group based on biological variation.

METHODS

All data used for analysis were derived from the Spanish programme of external quality control on semen analysis. Over 90 laboratories participated from 1999 to 2003. Using graphs of the state of the art, we also determined the numbers of laboratories that achieved quality specifications.

RESULTS

The total allowable error calculated using state of the art graphs is similar to that calculated using biological variation for concentration and total motility. However, it is much higher for morphology and rapidly progressive motility. Over 80% of the laboratories achieved the minimum quality specification based on biological variation for concentration, total and progressive motility. However, only approximately 30% of the laboratories achieved the minimum quality specification based on biological variation for morphology and rapidly progressive motility.

CONCLUSIONS

The study enabled us to identify the state of the art of analytical performance for seminal parameters, and revealed the difficulty inherent in meeting the quality specifications based on biological variation.

Interaction of limestone grains and acidic solutions from the oxidation of pyrite tailings

To characterise the coatings formed and to analyse element partitioning between the aqueous and solid phase, suspensions were prepared with four grain sizes of limestone and three different amounts of acidic solution from oxidized pyrite tailings. In all cases, red coatings with three different layers covered the grain surface, sealing off the acidic solution. The inner layer was composed mainly of basaluminite, the middle layer of schwertmannite, and the outer layer of gypsum and jarosite. Zn, Cd and Tl were co-precipitated by Fe and Al; As and Pb were co-precipitated almost completely by Fe; and Cu formed mainly Cu sulphates. All trace elements reached almost total precipitation at pH 6.3, but the precipitation of As and Pb tended to decrease as the pH rose. Consequently, liming should be calculated so that the soil pH does not exceed 6.3. This calculation should take into account that the armouring of the limestone grains can cause underestimations in the amount of liming material needed.

Predictors of eating behaviors in a sample of Mexican women

The aim of the study was to develop a model of potential risk factors associated to the development of eating behaviors in Mexican women. A structural equation model was carried out on a sample of 425 women: high school and college students (N=425) with a mean age of 19.1 years (SD=3.8). The variables selected for the model were those that obtained significant correlations with the variable "eating behaviors": criticism by father/mother, depressed mood, body mass index, attitudes and beliefs concerning obesity and dissatisfaction with figure. The model fitted the data well, with a non-significant Chi-square. The proportion of variance explained for eating behavior by the other variables was 59, the direct effects of all the variables were significant, while the total effect of all the variables on eating behavior were also significant, particularly the effects of the "dissatisfaction with figure" and, "attitudes and beliefs concerning obesity". The model yielded similar data to the findings in international literature, since they revealed the influence exerted by social pressure on thinness, the internalization of the socio-cultural ideal of thinness and the role of excess weight in increasing the risk of body dissatisfaction and therefore with the development of eating disorders.

Soil pollution by a pyrite mine spill in Spain: evolution in time

Soil pollution was studied after the spill of the Aznalcóllar pyrite mine between 1998 and 2001, analyzing As, Zn, Cd, Cu and Pb both in total concentrations as well as in soluble and bioavailable forms. The main remediation measures were: clean-up of the tailings and polluted soils, plus application of amendment materials (liming). The results indicate that, after three years, 50-70% of the acidic soils and 25-30% of the basic soils are still highly polluted in total arsenic. The limit of 0.04 mg kg(-1) for water-soluble arsenic is exceeded in 15-20% of all soils. The EDTA-extractable arsenic (bioavailable) exceeds the limit of 2 mg kg(-1) only in the acidic sectors. After clean-up, the homogenization of the upper 20-25 cm of the soils appears to be the most recommended measure in the reduction of pollution.

Evaluation of the BCR sequential extraction procedure applied for two unpolluted Spanish soils

The procedure of BCR sequential extraction has been applied to five samples from two unpolluted soils in southern Spain. Total concentrations of different elements have been calculated as the sum of the three fractions of BCR and the residue has been measured for each. Also, a total analysis based on INAA or total-digestion techniques has been performed for the same samples. BCR and total analysis closely agreed for As, Pb and Cd. For Cu, Co, Cr and Zn the comparison of the results did not provide definitive conclusions concerning the capability of BCR in measuring total concentrations. On the other hand, in these cases, a certain correlation was found between the concentrations measured and some soil characteristics, especially the clay, organic-matter and CaCO(3) contents. BCR proved incapable of providing accurate measurements for Ni.

Migration of trace elements from pyrite tailings in carbonate soils

In the carbonate soils contaminated by a toxic spill from a pyrite mine (Aznalcóllar, southern Spain), a study was made of a thin layer (thickness = 4 mm) of polluted soil located between the pyrite tailings and the underlying soil. This layer, reddish-yellow in color due to a high Fe content, formed when sulfates (from the oxidation of sulfides) infiltrated the soil, causing acidification (to pH 5.6 as opposed to 8.0 of unaffected soil) and pollution (in Zn, Cu, As, Pb, Co, Cd, Sb, Bi, Tl, and In). The less mobile elements (As, Bi, In, Pb, Sb, and Tl) concentrated in the uppermost part of the reddish-yellow layer, with concentration decreasing downward. The more mobile elements (Co, Cd, Zn, and Cu) tended to precipitate where the pH was basic, toward the bottom of the layer or in the upper part of the underlying soil. The greatest accumulations occurred within the first 6 mm in overall soil depth, and were negligible below 15 mm. In addition, the acidity of the solution from the tailings degraded the minerals of the clay fraction of the soils, both the phyllosilicates as well as the carbonates. Also, within the reddish-yellow layer, gypsum formed autigenically, together with complex salts of sulfates of Fe, Al, Zn, Ca, and Mn, jarosite, and oxihydroxides of Fe.

[Comparison of different detection methods for methicillin resistance in Staphylococcus aureus]

The investigation of methicillin resistance in Staphylococcus aureus (MRSA) is a serious problem for the physician and microbiologist. Accurate and rapid detection is essential for the use of appropriate antimicrobial therapy and for the control of nosocomial spread of the resistant strain. The performance characteristics of the MicroScan Overnight Conventional Pos Combo 12 panels (MOCP), BBL Crystal MRSA ID (CR), E-test and agar screen plate (Muller Hinton agar with oxacillin 6 micrograms/ml and 4% NaCl) (AS) were evaluated for the detection of oxacillin resistance. Thirty S. aureus clinically significant strains with different PFGE (Pulse Field Gel Electrophoresis) banding pattern were tested, and 22 of them were mecA positive by PCR. These strains were also analyzed by mecA and Tn554 polymorphism. All mecA positive strains were classified as methicillin resistant by MOCP and E-test. CR and AS failed to detect oxacillin resistance in 2 strains. One false positive was only detected by E-test. Accurate testing for the presence of MRSA may reduce the need for empiric therapy with vancomycin for patients with staphylococcal infections. According to our results the best performance was obtained with MOCP. However, as a rapid method, CR gave acceptable sensitivity for clinical purposes.

Soil pollution by oxidation of tailings from toxic spill of a pyrite mine

On the 25th April 1998, toxic water and tailings from a pyrite mine of Aznalcóllar (southern Spain) spilled into the Agrio and Guadiamar River Basin affecting some 40 km2. In five sectors throughout the basin, we monitored the physical and chemical properties of the tailings as well as the degree of pollution in the soils on four different sampling dates: 5 May, 20 May, 4 June and 22 July 1998. The characteristics of the tailings deposited on the soils are shown to be related to distance from the spill. The oxidation rate of the tailings and the solubilization of the pollutant elements were more pronounced in the middle and lower sectors of the basin, where the particle size was finer, the sulfur content higher and the bulk density less. The increases in water-soluble sulfates, Zn. Cd and Cu were very rapid (the highest values being reached 25 days after the spill) and intense (reaching 45% of the total Cu, 65% of the total Zn and Cd). Meanwhile, the increases in water-soluble As, Bi, Sb, Pb and Tl were far lower (ranging between 0.002% of the total Tl and 2.5% of the total As) and less rapid in the case of As, Bi and Pb (the highest values for these elements being reached 40 days after the spill). These soluble elements infiltrated the soils with the rainwater, swiftly augmenting the soil pollution. Twenty-five days after the spill, when the rainfall ranged between 45 and 63 mm, the first 10-cm of the soils in the middle and lower sectors of the basin exceeded the maximum concentration permitted for agricultural soils in Zn, Cu and Tl. At 40 days after the spill, when the rainfall ranged between 60 and 89 mm, all the soils reached or exceeded the maximum permitted concentrations for As and Tl. Nevertheless, the pollutants tended to concentrate in the first 10 cm of the soils without seriously contaminating either the subsoil or the groundwaters. Consequently, a rapid removal of the tailings and the ploughing of the first 25-30 cm of the soils would be urgent measures to diminish pollutant concentration in the soils affected by the spill.

An indirect immunofluorescence assay to detect antibodies against St. Louis Encephalitis virus

An in house indirect immmunofluorescence assay ( IFA ) in relation to neutralization (NT) reference test, was assessed as a fast and cheap method to carry out serological surveys for St. Louis Encephalitis virus (SLE). Sera obtained from 213 blood donors were analyzed by both tests. The prevalence of seropositivity obtained with IFA was lower than (30.98%) that observed on NT (41.78%). The relative specificity rate of IFA was 96.77% whereas its relative sensitivity rate was 69.66%. Kappa index showed a good correlation between both tests. The results indicate that neutralization assay is still the serological test with the highest sensitivity and specificity relative rates for detecting antibodies against SLE virus. Nevertheless, the IFA could be useful as an alternative test in order to learn the circulation of the Flavivirus genus in a certain area.