How to diagnose mould allergy? Comparison of skin prick tests with specific IgE results.

BACKGROUND: Diagnosis of mould allergy is complicated due to the heterogeneity of the test material and the decrease in the number of commercial mould skin test solutions that are currently available. OBJECTIVES: The aim of this study was to compare skin prick tests (SPT) from different manufacturers to one another and concurrently with sIgE tests for Aspergillus fumigatus (Asp f), Cladosporium herbarum (Cla h), Penicillium chrysogenum (Pen ch), Alternaria alternata (Alt a) and Aspergillus versicolor (Asp v) to ascertain a feasible diagnostic procedure for mould sensitization. METHODS: In this multi-centre study, 168 patients with mould exposure and/or mould-induced respiratory symptoms were included. Mould SPT solutions were analysed biochemically and tested in duplicate on patients' arms. Specific IgE (sIgE) concentrations to corresponding mould species and mould mix (mx1) were measured by ImmunoCAP. SPTs in accordance with one another and with sIgE were further considered. The test efficiency was calculated using receiver-operating characteristic (ROC) analysis. RESULTS: Mould sensitization was more frequently detected by the SPT (90 of 168) than by the sIgE tests (56 of 168). Concordances of double SPT positives were only sufficient (≥ 80%) for environmental allergens, two Asp f and three Alt a SPT solutions, whereas all other mould solutions revealed concordances < 80%. The antigen content of SPT solutions was positively associated with concordant SPT double values as well as with sIgE. Taking sIgE as the 'positive standard', all mould SPT solutions revealed test efficiencies > 80%, but varied up to 20% in sensitivity and positive predictive value with the exception of Alt a. CONCLUSIONS: SPT solutions are sensitive and essential diagnostic tools for the detection of mould sensitization. Our recommendation for diagnosis would be to test at least Alt a, Asp f and Pen ch using SPT and additional sIgE test to mx1.

Effects of pulsed electric fields on inactivation and metabolic activity of Lactobacillus plantarum in model beer.

AIMS: Inactivation and sublethal injury of Lactobacillus plantarum at different pulsed electric field (PEF) strengths and total energy inputs were investigated to differentiate reversible and irreversible impacts on cell functionality. METHODS AND RESULTS: Lactobacillus plantarum was treated with PEF in model beer (MB) to determine critical values of field strength and energy input for cell inactivation. Below critical values, metabolic activity and membrane integrity were initially reduced without loss of viability. Above critical values, however, irreversible cell damage occurred. Presence of nisin or hop extract, during PEF treatment, resulted in an additional reduction of cell viability by 1;5 log cycles. Also, addition of the hop extract resulted in an additional two log cycles of sublethal injury. Partial reversibility of membrane damage was observed using propidium iodide (PI) uptake and staining. Inoculated MB containing hops was stored after PEF to evaluate the efficacy of such treatment for beer preservation. CONCLUSION: Cells were inactivated only above critical values of 13 kV x cm(-1) and 64 kJ x kg(-1); below these values cell damage was reversible. Storage experiments revealed that surviving cells were killed after 15 h storage in MB containing hops. SIGNIFICANCE AND IMPACT OF THE STUDY: Both reversible and irreversible cell damage due to PEF treatment was detected, depending on specific treatment conditions. The combination of PEF and hop addition is a promising nonthermal method of preservation for beer.

Effects of pressure-induced membrane phase transitions on inactivation of HorA, an ATP-dependent multidrug resistance transporter, in Lactobacillus plantarum.

The effects of pressure on cultures of Lactobacillus plantarum were characterized by determination of the viability and activity of HorA, an ATP-binding cassette multidrug resistance transporter. Changes in the membrane composition of L. plantarum induced by different growth temperatures were determined. Furthermore, the effect of the growth temperature of a culture on pressure inactivation at 200 MPa was determined. Cells were characterized by plate counts on selective and nonselective agar after pressure treatment, and HorA activity was measured by ethidium bromide efflux. Fourier transform-infrared spectroscopy and Laurdan fluorescence spectroscopy provided information about the thermodynamic phase state of the cytoplasmic membrane during pressure treatment. A pressure-temperature diagram for cell membranes was established. Cells grown at 37 degrees C and pressure treated at 15 degrees C lost >99% of HorA activity and viable cell counts within 36 and 120 min, respectively. The membranes of these cells were in the gel phase region at ambient pressure. In contrast, cells grown at 15 degrees C and pressure treated at 37 degrees C lost >99% of HorA activity and viable cell counts within 4 and 8 min, respectively. The membranes of these cells were in the liquid crystalline phase region at ambient pressure. The kinetic analysis of inactivation of L. plantarum provided further evidence that inactivation of HorA is a crucial step during pressure-induced cell death. Comparison of the biological findings and the membrane state during pressure treatment led to the conclusion that the inactivation of cells and membrane enzymes strongly depends on the thermodynamic properties of the membrane. Pressure treatment of cells with a liquid crystalline membrane at 0.1 MPa resulted in HorA inactivation and cell death more rapid than those of cells with a gel phase membrane at 0.1 MPa.

Effects of high pressure on survival and metabolic activity of Lactobacillus plantarum TMW1.460.

The application of high pressure (HP) for food preservation requires insight into mechanisms of HP-mediated cell injury and death. The HP inactivation in model beer of Lactobacillus plantarum TMW1.460, a beer-spoiling organism, was investigated at pressures ranging from 200 to 600 MPa. Surviving cells were characterized by determination of (i) cell viability and sublethal injury, (ii) membrane permeability to the fluorescent dyes propidium iodide (PI) and ethidium bromide (EB), (iii) metabolic activity with tetrazolium salts, and (iv) the activity of HorA, an ATP binding cassette-type multidrug resistance transporter conferring resistance to hop compounds. HP inactivation curves exhibited a shoulder, an exponential inactivation phase, and pronounced tailing caused by a barotolerant fraction of the population, about 1 in 10(6) cells. During exponential inactivation, more than 99.99% of cells were sublethally injured; however, no sublethal injury was detected in the barotolerant fraction of the culture. Sublethally injured cells were metabolically active, and loss of metabolic activity corresponded to the decrease of cell viability. Membrane damage measured by PI uptake occurred later than cell death, indicating that dye exclusion may be used as a fail-safe method for preliminary characterization of HP inactivation. An increase of membrane permeability to EB and a reduction of HorA activity were observed prior to the loss of cell viability, indicating loss of hop resistance of pressurized cells. Even mild HP treatments thus abolished the ability of cells to survive under adverse conditions.