[Comparison study of HBV-P mutation detection by MALDI-TOF Ms and direct PCR sequencing].

OBJECTIVE: To compare the sensitivities of MALDI-TOF MS and direct PCR sequencing on gene mutations detection of hepatitis B virus. METHODS: 100 serum samples from chronic hepatitis B patients were collected, which consisted of 90 serum samples (study group) from 90 chronic hepatitis B patients received nucleoside analogues (NA) therapy for more than 1 year and HBV DNA titer still higher than 500 copies/ml and 10 serum samples (blank group) from 10 chronic hepatitis B patients never treated with antiviral therapy and HBV-DNA titer higher than 1 x 10(5) copies/ml. 9 known mutations associated with HBV P gene in these samples were detected by MALDI-TOF MS and direct PCR sequencing at the same time, TYPE4.0 software and Sequence Navigator software were used to analyze the results separately. RESULTS: (1) In study group, mutations were detected in 53 samples and the total mutation sites were 86 by MALDI-TOF MS with a positive detection rate of 58.89%, whereas only 19 samples were found with mutations and totally 28 mutation sites were detected by direct PCR sequencing, the positive detection rate was 21.11%. The positive detection rate by MALDI-TOF MS was higher than that by direct PCR sequencing and the difference was statistically significant (P < 0.05). In blank group, no mutations were detected by any method. (2) In study group, when the HBV DNA titers were at 500-1000 copies/ml, 10(3)-10(4) copies/ml and 10(4)-10(5) copies/ml, the positive mutation detection rates by MALDI-TOF MS were 50%, 52.08% and 77.27% respectively, higher than that by direct PCR sequencing, which were only 0%, 8.33% and 45.45%. The difference was still statistically significant (P < 0.05). CONCLUSIONS: MALDI-TOF MS had higher detection sensitivity for known mutation sites as compared to direct PCR sequencing method.

[Mites in mattress dust and relevant environmental factors in student dormitories in Shenzhen].

Three hundred and eight mattress dust samples were collected from college dormitories in Shenzhen with a mite prevalence of 88% (271/308). From the samples, 6163 mites were isolated and identified. Dermatophagoides farinae, D. pteronyssinus and Blomia tropicalis were three most abundant species, occupying 29.7%, 21.7% and 17.9%, respectively. It was found that sex of the students, mattress cover (bamboo mat or bed sheet), with or without air conditioner installation, and daily using of air conditioner (<2 h, 2-8 h and >8 h) had no significant influence on the mite prevalence (P>0.05). However, logistic regression analysis revealed that the risk of mite sensitization in male student dormitory was significantly lower than that in female dormitory (OR=0.55, P=0.038), and the risk of using bed sheets was significantly higher than using bamboo mats (OR=2.13, P=0.040). Both mite prevalence and the risk of mite sensitization significantly decreased with higher floor of the dormitory building.