[Seasonal changes of ammonia-oxidizing bacterial communities during tropical forest restoration]. / 热带森林恢复过程中氨氧化细菌群落的季节变化.

In this study, we used a high-throughput sequencing technology to survey the dry-wet seasonal change characteristics of soil ammonia-oxidizing bacteria (AOB) communities in the three restoration stages [i.e., Mallotus paniculatus community (early stage), Millettia leptobotrya community (middle stage), and Syzygium oblatum community (later stage)] of Xishuangbanna tropical forest ecosystems. We analyzed the effects of soil physicochemical characteristics on AOB community composition and diversity during tropical forest restoration. The results showed that tropical forest restoration significantly affected the relative abundance of dominant AOB phyla and their dry-wet seasonal variation. The maximum relative abundance of Proteobacteria (71.3%) was found in the early recovery stage, while that of Actinobacteria was found in the late recovery stage (1.0%). The abundances of Proteobacteria and Actinobacteria had the maximum ranges of dry-wet seasonal variation in the early and late stages, respectively. The abundance of dominant AOB genera and its dry-wet seasonal variation varied across tropical forest restoration stages. The maximum average relative abundance of Nitrosospira and Nitrosomonas in the late recovery stage was 66.2% and 1.5%, respectively. In contrast, the abundance of Nitrosovibrio reached its maximum (25.6%) in the early recovery stage. The maximum dry-wet seasonal variation in relative abundance of Nitrosospira and Nitrosomonas occurred in the early recovery stage, while that of Nitrosovibrio occurred in the middle recovery stage. The Chao1, Shannon, and Simpson diversity indices of AOB communities increased along the restoration stages, which were significantly higher in the wet season than in the dry season. The results of canonical correspondence analysis showed that soil easily oxidized carbon was the main factor controlling AOB community diversity and Actinobacteria abundance. Soil bulk density and temperature were the main factors affecting Proteobacteria abundance. Soil pH, microbial biomass carbon, water content, ammonium nitrogen, bulk density, and temperature were the main factors controlling the abundances of Nitrosospira, Nitrosomonas, and Nitrosovibrio. Therefore, tropical forest restoration can regulate the change of relative abundance of dominant AOB taxa via mediating the changes of soil temperature, bulk density, and readily oxidized carbon, leading to an increase in soil AOB community diversity.

Trends and disease burden of enteric fever in Guangxi province, China, 1994-2004.

OBJECTIVE: To determine the burden of enteric fever through trends in morbidity and mortality, bacterial species and antimicrobial resistance in Guangxi, a southern, subtropical, coastal province of China with a disproportionally large burden of enteric fever. METHODS: Data on morbidity and mortality caused by enteric fever between 1994 and 2004 were extracted from the Guangxi Center for Disease Control and Prevention. Laboratory-based surveillance and outbreak investigations were integrated with reports of notifiable infectious diseases to estimate the bacterial species-specific incidence of enteric fever. To adjust for underreporting, survey data were collected from three prefectures that represent the hyper-, moderate- and low-endemic regions of Guangxi province. FINDINGS: In Guangxi province, enteric fever incidence rate varied over the study period, with a peak of 13.5 cases per 100 000 population in 1995 and a low of 6.5 in 2003. The disease occurred most frequently during the summer and autumn months and in the group aged 10-49 years. The incidence of enteric fever varied by region within Guangxi province. During the 11-year period covered by the study, 61 outbreaks of enteric fever were reported, and Salmonella paratyphi A (SPA) became the predominant causative agent in the province. CONCLUSION: Prospective studies may provide a better understanding of the reason for the shifting epidemiology of enteric fever in Guangxi province. Given the emergence of resistance to first- and second-line antimicrobials for the treatment of enteric fever, a bivalent vaccine against both SPA and S. typhi would facilitate for disease control.

[Application of cluster randomization method on typhoid Vi vaccine trails].

OBJECTIVE: To describe the design and application of cluster randomized controlled method on typhoid Vi vaccine trial, and to assess the effect of implementation. METHODS: Simple size calculation of cluster-randomized trial was used to determine the sample size of the two groups and a vaccination campaign was conducted. The study group was given typhoid Vi vaccine and the control group was given meningococcal A vaccine. RESULTS: According to sample size calculation, a total sample of 96,121 participants was required and the study areas were divided into 108 clusters. In practice, 53 study clusters with 44,054 participants and 54 control clusters with 48,422 participants were stratified and matched according to size, location (urban or rural), characteristics (school, department, factory, demography) were randomized respectively. Confounding factors of two groups including age, sex, resident area, income, level of education were compared. It was found that the ratio of all confounding factors between the two groups were comparable and balanced. CONCLUSION: Confounding factors can be better controlled between study group and the control group by applying cluster-randomized method on vaccine trail which enabled the intervention to be more scientifically evaluated; The implementation of cluster randomization trial was simple and easy to be accepted.

A mass vaccination campaign targeting adults and children to prevent typhoid fever in Hechi; expanding the use of Vi polysaccharide vaccine in southeast China: a cluster-randomized trial.

BACKGROUND: One of the goals of this study was to learn the coverage, safety and logistics of a mass vaccination campaign against typhoid fever in children and adults using locally produced typhoid Vi polysaccharide (PS) and group A meningococcal PS vaccines in southern China. METHODS: The vaccination campaign targeted 118,588 persons in Hechi, Guangxi Province, aged between 5 to 60 years, in 2003. The study area was divided into 107 geographic clusters, which were randomly allocated to receive one of the single-dose parenteral vaccines. All aspects regarding vaccination logistics, feasibility and safety were documented and systematically recorded. Results of the logistics, feasibility and safety are reported. RESULTS: The campaign lasted 5 weeks and the overall vaccination coverage was 78%. On average, the 30 vaccine teams gave immunizations on 23 days. Vaccine rates were higher in those aged < or = 15 years (90%) than in adolescents and young adults (70%). Planned mop-up activities increased the coverage by 17%. The overall vaccine wastage was 11%. The cold chain was maintained and documented. 66 individuals reported of adverse events out of all vaccinees, where fever (21%), malaise (19%) and local redness (19%) were the major symptoms; no life-threatening event occurred. Three needle-sharp events were reported. CONCLUSION: The mass immunization proved feasible and safe, and vaccine coverage was high. Emphasis should be placed on: injection safety measures, community involvement and incorporation of mop-up strategies into any vaccination campaign. School-based and all-age Vi mass immunizations programs are potentially important public health strategies for prevention of typhoid fever in high-risk populations in southern China.