Laboratory assessment of the efficiency of encasing materials against house dust mites and their allergens

BACKGROUND

The current recommendation to reduce mite allergen exposure for mite-sensitive individuals is to use allergen-impermeable bed coverings. As these covers are made of various kinds of materials, they vary in quality. The objective of this study was to investigate the efficiency of different covering materials against house dust mites and their allergens in vitro.

METHODS

Four types of materials including (1) plastic cover, (2) polyurethane-coated cover, (3) non-woven covers, (4) tightly woven microfiber covers and a regular cotton bed sheet (as a control) were evaluated using three methods: (i) heat escape method, (ii) Siriraj chamber method and stereomicroscopy, scanning electron microscopy and (iii) enzyme-linked immunosorbent assay (ELISA).

RESULTS

We found that there was a statistically significant difference in allergen permeability among four types of coverings (P < 0.001). In terms of the impermeability to mites and their allergens, plastic- and polyurethane-coated covers were observed to be the best, followed by non-woven, woven and cotton-based bed sheets. A regular cotton-based bed sheet allows a significant amount of leakage of mite allergens. Both woven and non-woven material are efficient barriers against mite allergen in terms of impermeability. However, with regard to mite colonization, non-woven covers have the drawback of mites being able to penetrate and colonize within the fabric fibers. Woven covers are therefore recommended because of their major advantages of not allowing the colonization of mites within the fabric, being easy to clean, and comfortable.

CONCLUSION

The three assessment methods used in this study could be useful as a primary approach to evaluate the quality of covering materials in vitro using both pore size and ability to be colonized by mites on the materials as the key factors.

Toxoplasma gondii antibodies in HIV and non-HIV infected Thai pregnant women

Serological evidence for Toxoplasma gondii infection in Thai pregnant women was investigated. One thousand six hundred and sixty-nine blood specimens were collected from 838 HIV-seropositive and 831 HIV-seronegative pregnant women attending the antenatal-care clinic at Siriraj Hospital, Bangkok, Thailand, during a two-year period. Toxoplasma IgG antibody was detected, using a solid-phase enzyme-linked immunosorbent assay in which the membrane protein p-30 was the predominant antigen. IgG positive sera were subsequently examined for IgM antibody by the capture antibody enzyme immunoassay. The IgG antibody was found in 450 (53.7%) HIV seropositive women and 44 (5.3%) non-HIV infected women, with a statistically significant difference (p < 0.0001). Three of the 450 HIV-seropositive and 2 of the 44 HIV-seronegative sera with IgG antibody were positive for IgM antibody against T. gondii. This result suggested that HIV seropositive pregnant women had a higher risk of Toxoplasma infection with increase exposure to their offspring.

Immunoblotting and enzyme linked-immunosorbent assay for diagnosis of toxoplasma infection in HIV Thai patients

Toxoplasma gondii has been recognized as an important cause of morbidity and mortality among immunocompromised persons. The diagnosis of T. gondii infection is most often based on serological tests results. Serological diagnosis can be limited in AIDS patients because of depressed antibody responses. Fifty serum samples were used in this study to investigate serological evidence of toxoplasmosis in HIV positive Thai patients by Platelia kit, the commercial enzyme-linked immunosorbent assay (ELISA) in which the membrane protein p-30 is the predominant antigen and immunoblot technique (IB). Sera of HIV positive Thai patients with Toxoplasma infection recognized the same antigenic component, the 32 kDa antigenic band, as is recognized by Toxoplasma positive sera from immunocompetent patients and it may represent a specific marker for diagnosis of Toxoplasma infection in HIV positive Thai patients.

Indirect immunoperoxidase staining of Crithidia luciliae for detecting anti-dsDNA: comparison with other serodiagnostic tests

The indirect immunoperoxidase (IIP) method was modified and improved for detecting anti-dsDNA. Using fetal calf serum to block the non-specific antibodies and staining with chromatic substrate solution at pH 6.2, the performance time is substantially decreased and the patterns of positive and negative staining are easily distinguished. IIP was compared with indirect hemagglutination (IHA), latex agglutination (LA) and the standard method indirect immunofluorescent technique (IFT). The sensitivities and specificities of the three methods were studied in 507 sera from various sources. Using IFT as the gold standard, sensitivities of IIP, IHA, LA were 98.18%, 88.18% and 50.91% respectively, and the corresponding specificities were 99.5%, 98.24% and 100%. There was a good correlation between titers of IFT and IIP (Spearman correlation coefficient = 0.77, p < 0.001) with no significant difference between the titer of both tests (Wilcoxon Matched-Pairs Signed-Rank test, p = 0.143). These results indicate that the modified IIP method is both highly sensitive and specific and only needs a light microscope to perform it.

In vitro studies on the sensitivity of local Entamoeba histolytica to anti-amoebic drugs

The in vitro activity of drugs, namely dehydroemetine, ornidazole, metronidazole and tinidazole were determined against the locally isolated strains of E. histolytica in Thailand. The test was performed in liquid monophasic medium, i.e. liver marmite serum medium. In all, locally isolated strains from thirty hosts studied, the minimal inhibitory concentration (MIC) for dehydroemetine ranged from 0.125 to 1 microgram/ml, ornidazole ranged from 0.0625 to 0.25 microgram/ml, metronidazole ranged from 0.0625 to 0.125 microgram/ml, and tinidazole ranged from 0.0625 microgram/ml to 0.25 microgram/ml. The MIC of dehydroemetine was significantly different from ornidazole, metronidazole and tinidazole. Metronidazole was superior to that of dehydroemetine but was not significantly different among ornidazole, metronidazole and tinidazole.