Construction of an inducible expression shuttle vector for Laribacter hongkongensis, a novel bacterium associated with gastroenteritis

An Escherichia coli-Laribacter hongkongensis shuttle vector (pPW380) was constructed by ligating the 4701-bp EcoRI digested fragment of pHLHK8 to EcoRI digested pBK-CMV. An E. coli-L. hongkongensis inducible expression shuttle vector was further constructed by ligating a 2105-bp fragment that contains the tetracycline repressor and tetracycline-inducible promoter region of pALC2084 to the 8897-bp fragment of pPW380, deletion of the green fluorescent protein gene, and insertion of a multiple cloning site. This inducible expression system was able to express two commonly used reporter genes, the green fluorescent protein gene and the glutathione S-transferase gene, efficiently in E. coli and L. hongkongensis.     

不同来源株香港海鸥形菌药敏试验结果分析

目的对分离自社区获得性胃肠炎患者及淡水鱼肠道内的香港海鸥形菌(Laribacter hongkongensis,LH)进行药敏试验,为临床合理使用抗菌药物提供依据。方法2005年至2006年杭州市第一人民医院肠道门诊从社区获得性胃肠炎患者中分离到4株及2种淡水鱼体内10株LH菌株,计14株,按美国CLSI推荐的纸片扩散法进行药敏试验。结果药敏结果显示,14株LH菌株对24种常用抗菌药物中的15种药物,分别表现出不同程度的耐药性,耐药率达62.5%;尤其对青霉素、头孢唑啉和头孢哌酮等3种药物,14株LH菌株均为耐药,耐药率为100.0%;其中人体株LHHZ26,对12种药物耐药、1种为中介。LH对3代头孢表现为较高的耐药性,3种头孢药物的耐药率为71.43%~100%;14株LH株对头孢吡肟及头孢哌酮/舒巴坦均为敏感。对氨曲南(14.29%)、庆大霉素(7.14%)、复方新诺明(7.14%)的耐药率较低;喹诺酮类、氯霉素、阿米卡星、美罗培南、亚胺培南等药物均敏感。结论LH菌株对β-内酰胺类药物表现出耐药性,对青霉素类、头孢菌素类药物广泛耐药。建议对LH感染患者喹诺酮类为首选治疗用药。     

Isolation of Laribacter hongkongensis from Little Egrets (Egretta garzetta) in Hangzhou, China

Aims: Laribacter hongkongensis is well adapted to diverse freshwater environments and is associated with human community‐acquired gastroenteritis and traveller’s diarrhoea. The study intended to investigate whether L. hongkongensis could be detected in Little Egrets (Egretta garzetta, a widespread aquatic bird) in Hangzhou, China. Methods and Results: A total of 176 faecal specimens from three habitats in Hangzhou were obtained for this study. L. hongkongensis was isolated from 12 (6·8%) specimens. Identification of the 12 L. hongkongensis isolates was achieved through a combination of phenotypic characterization and 16S rRNA gene sequence analysis. Conclusions: The results illustrate that L. hongkongensis is present in the faeces of Little Egrets from three different habitats in Hangzhou, China. Significance and Impact of the Study: This study suggests the possibility that Little Egrets serve as mechanical carriers of L. hongkongensis, thus potentially transmitting the organism between bodies of water.     

A biological survey of ballast water in container ships entering Hong Kong

The role of ballast water in the introduction of exotic species has recently received extensive attention. The aim of this study is to assess the importance of ballast water discharge as a vector for the introduction of exotic species into Hong Kong waters. Twelve ballast water samples were collected from 5 container ships entering Hong Kong between June1994 and October 1995. The ballast water originated from ports on both sides of the Pacific Ocean. At least 81 species from 8 animal phyla and 5 protist phyla were found. Most of the major marine taxonomic groups were represented and many planktonic larval stages were included. Species richness in the ballast tanks decreased with the age of ballast water. Copepoda was the most diverse and abundant taxonomic group. The density of calanoid and cyclopoid copepods decreased with the age of ballast water, but that of harpacticoid copepods did not change significantly with time. Bivalve, crustacean, polychaete and ascidian larvae from ballast water samples were observed to settle in laboratory culture tanks. The mussel Mytilopsis sallei which was introduced to Hong Kong in 1980, was one of the bivalves that settled readily. Results of this study indicate that ballast water can be a major source for the introduction of exotic species to Hong Kong waters. Regulatory guidelines on the discharge of ballast water should be established. This revised version was published online in August 2006 with corrections to the Cover Date.     

Study of phytoplankton characteristics in Tolo Harbour,Hong Kong,by HPLC analysis of chemotaxonomic pigments

Spatial and seasonal characteristics of phytoplankton in Tolo Harbour, Hong Kong, were studied by microscopic observation of phytoplankton samples and HPLC analysis of chemotaxonomic pigments. Diatoms dominated the phytoplankton. Common diatoms included Skeletonema costatum and species of Cerataulina, Leptocylindrus, Pseudo-nitzschia and Thalassiosira. Dinoflagellates occurred sporadically and mainly in the inner part of the harbour. The dinoflagellate Scrippsiella trochoidea was the causative organism for the red tide occurrences in March, April and September 2001. Significant positive correlations between fucoxanthin and diatoms and between peridinin and dinoflagellates suggested that fucoxanthin and peridinin were valuable chemotaxonomic markers for diatoms and dinoflagellates, respectively. Analysis of pigment ratios revealed that red tide events caused by dinoflagellates were marked by increase in the value of PERI:chl a and decrease in the value of FUCO:chl a. Increase in the value of FUCO:chl a also revealed the presence of a dense population of Pseudo-nitzschia that was not indicated by increase in chlorophyll a and fucoxanthin concentrations. Pigment analysis also revealed the presence of cyanobacteria, silicoflagellates, cryptophytes and green algae in the surface waters of Tolo Harbour.     

Research Integrity in Greater China: Surveying Regulations,Perceptions and Knowledge of Research Integrity from a Hong Kong Perspective

In their 2010 article ‘Research Integrity in China: Problems and Prospects’, Zeng and Resnik challenge others to engage in empirical research on research integrity in China. Here we respond to that call in three ways: first, we provide updates to their analysis of regulations and allegations of scientific misconduct; second, we report on two surveys conducted in Hong Kong that provide empirical backing to describe ways in which problems and prospects that Zeng and Resnik identify are being explored; and third, we continue the discussion started by Zeng and Resnik, pointing to ways in which China's high‐profile participation in international academic research presents concerns about research integrity. According to our research, based upon searches of both English and Chinese language literature and policies, and two surveys conducted in Hong Kong, academic faculty and research post‐graduate students in Hong Kong are aware of and have a positive attitude towards responsible conduct of research. Although Hong Kong is but one small part of China, we present this research as a response to concerns Zeng and Resnik introduce and as a call for a continued conversation.     

喜盐草属在中国香港特别行政区的新记录及分类补注

报道小喜盐草Halophila minor (Zoll.) den Hartog在香港的首次记录, 同时也是除沿海岛屿(海南及南沙群岛)以外中国大陆的首次记录。喜盐草属在中国最早的记录可追溯至1856年(香港九龙湾), 包括喜盐草H. ovalis及贝克喜盐草H. beccarii在内, 目前已知3种喜盐草属植物分布香港。尽管从前小喜盐草及圆叶喜盐草H. ovata曾作同种处理, 现已有最新证据清楚区别这两种喜盐草(本文证实圆叶喜盐草不产香港)。因本属的世界分布及分类最近已被全面修订, 使得准确鉴别各种喜盐草成为可能。香港的海岸面对高速发展, 海草的保育尤需关注。     

饮用水系统硝化微生物分布规律、环境影响因素及调控应用的研究进展

硝化微生物广泛存在于饮用水系统中。水处理过程中,硝化微生物对含氮污染物的去除有突出贡献;而输配水过程中,硝化微生物会加剧消毒剂氯胺的降解,造成一系列饮用水微生物安全问题。本文介绍了常用硝化微生物检测方法,综述了硝化微生物在滤池、市政主管网、二次供水系统中的分布特征和规律,分析了环境因子及工程条件对硝化微生物的影响机制,探讨了硝化微生物强化应用及管控的实际工程措施,展望了未来饮用水系统中硝化微生物的研究重点与应用前景。     

The population dynamics of some freshwater carideans (Crustacea: Decapoda) in Hong Kong,with special reference to Neocaridina serrata (Atyidae)

During a 15-month investigation of the population dynamics of three caridean shrimp species in the Lam Tsuen River, New Territories, Hong Kong, the numbers of the commonest species, Neocaridina serrata (Stimpson)(Atyidae), were reduced as water temperatures fell. By contrast, Caridina lanceifrons Yu became more numerous during the winter. The relatively scarce Macrobrachium hainanense (Parisi)(Palaemonidae) tended to be more abundant during the summer, and the abundance of this species was directly correlated with that of N. serrata. The population size of these two species was positively correlated with water temperatures prevailing one and two months prior to the collection of samples, but there was no significant relationship between C. lanceifrons abundance and water temperature.All species exhibited similar growth patterns with an inflection at the attainment of sexual maturity, occurring after the (presumed) 14th moult for N. serrata and in the (presumed) 13th and 18th stadium for C. lanceifrons and M. hainanensis respectively. Ovigerous shrimps of all species were only recorded when water temperatures exceeded 20 °C and the % incidence of ovigerous N. serrata was positively correlated with prevailing temperatures. It is suggested that restriction of freshwater caridean breeding periods by low temperatures may be common in the subtropics while perennial breeding is more likely to be typical of tropical regions.The mean carapace length of N. serrata populations was negatively correlated with prevailing temperatures, but more strongly correlated with temperatures recorded one and two months prior to sampling when gametogenesis may have taken place. Smallest mean sizes were recorded in late summer upon the cessation of juvenile recruitment. N. serrata has a maximum longevity of approximately 12 months and reproduction occurs in the 7th month of life or later. The hatchlings are well developed and clutch size is not related to the size of the brooding female. An annual life cycle, as seen in N. serrata, may be typical of many small freshwater carideans.Department of Zoology, The University of Hong Kong     

Spatial distribution of toxic metals in drinking water sources and their associated health risk in district buner,Northern Pakistan

Vigorous knowledge on the occurrence and distribution of toxic metals (TMs) in theenvironment is needed to assess their toxicological impacts on human health especially in developing countries like Pakistan. For the first time, the concentrations of TMs like Ni, Zn, Pb, Cr, and Cd in both ground and surface water and their potential health risk in the district Buner (Pakistan) were determined using Inductive Coupled Plasma Mass Spectrometry (ICP-MS, Agilent Technologies, 7500 CX, USA) and their results were compared with their safe limits defined by Pakistan Environmental Protection Agency (Pak-EPA) and World Health Organization WHO (2008 WHO (World Health Organization). 2008. Guidelines for drinking water quality, First Addendum to third ed. Recommendations, vol 1. Geneva, Switzerland [Google Scholar]). The concentrations of TMs, like Pb (43% and 86%), Ni (63% and 32%), Cr (41%), and Cd (1% and 20%) in drinking water samples exceeded their respective permissible limits set by Pak-EPA and WHO (2008), respectively. The mean concentrations of TMs were found in decreasing order Ni > Pb > Cr > Cd > Zn. The HRI values of TMs in drinking water samples for both adults and children were observed <1 indicating no health risk to the local population. Excessive marble industries are present in the study area; therefore, it is necessary to reduce metal contamination via proper disposal and treatment of marble wastewater, for which the government should take serious action in the study area.     

Distribution of six virulence factors in Aeromonas species isolated from US drinking water utilities: a PCR identification

AIMS: To examine whether Aeromonas bacteria isolated from municipally treated water had virulence factor genes. METHODS AND RESULTS: A polymerase chain reaction-based genetic characterization determined the presence of six virulence factors genes, elastase (ahyB), lipase (pla/lip/lipH3/alp-1) flagella A and B (flaA and flaB), the enterotoxins, act, alt and ast, in these isolates. New primer sets were designed for all the target genes, except for act. The genes were present in 88% (ahyB), 88% (lip), 59% (fla), 43% (alt), 70% (act) and 30% (ast) of the strains, respectively. Of the 205 isolates tested only one isolate had all the virulence genes. There was a variety of combinations of virulence factors within different strains of the same species. However, a dominant strain having the same set of virulence factors, was usually isolated from any given tap in different rounds of sampling from a single tap. CONCLUSIONS: These results show that Aeromonas bacteria found in drinking water possess a wide variety of virulence-related genes and suggest the importance of examining as many isolates as possible in order to better understand the health risk these bacteria may present. SIGNIFICANCE AND IMPACT OF THE STUDY: This study presents a rapid method for characterizing the virulence factors of Aeromonas bacteria and suggests that municipally treated drinking water is a source of potentially pathogenic Aeromonas bacteria.     

Impact of solar radiation in disinfecting drinking water contaminated with Giardia duodenalis and Entamoeba histolytica/dispar at a point-of-use water treatment

Aims:  To determine the impact of natural sunlight in disinfecting water contaminated with cysts of Giardia duodenalis and Entamoeba histolytica/dispar using plastic containers.
Methods and Results:  Known quantities of Giardia duodenalis and Entamoeba histolytica/dispar cysts in sterile water were exposed to the sun. Containers were made of polyethylene terephthalate, eight painted black on one side, one not painted and another cut open at the top and the last was a high density polypropylene container. Viability testing was performed using vital and fluorescent dyes. The same assays were conducted under cloudy conditions. Thermal control tests were also performed using heat without ultra violet light from the sun. Results show that 99·9% of parasites was inactivated when water temperatures reached 56°C after sunlight exposure.
Conclusion:  Both solar radiation and heat produced by the sun have a synergistic effect in killing cysts of Giardia duodenalis and Entamoeba histolytica/dispar when temperatures rise above 50°C, with complete death at 56°C, using painted 2-l PET containers.
Significance and Impact of the Study:  Solar disinfection system using PET containers painted black on one side can be used to disinfect water against Giardia duodenalis and Entamoeba histolytica/dispar using natural sunlight.     

Prevalence of Haplorchis taichui and Haplorchoides sp. metacercariae in freshwater fish from water reservoirs, Chiang Mai, Thailand

A parasitological investigation on trematode metacercariae was made on 62 freshwater fishes of 13 species in northern Thailand; Cyclocheilichthys apogon, Puntioplites proctozysron, Labiobarbus siamensis, Barbodes gonionotus, Barbodes altus, Henicorhynchus siamensis, Osteochilus hasselti, Notopterus notopterus, Mystacoleucus marginatus, Anabas testudineus, Systomus orphoides, Morulius chrysophykadian, and Hampala macrolepidota. The fish were caught over the summer period (February-May 2007) from 2 Chiang Mai water reservoirs, i.e., the Mae Ngad (UTM 47Q E 503200, 47Q N 2119300) and the Mae Kuang Udomtara (UTM 47Q E 513000, 47Q N 2092600) Reservoirs in Chiang Mai province, Thailand. The prevalence of heterophyid (Haplorchis taichui and Haplorchoides sp.) metacercariae in these fish was 83.9% and 74.2% in the Mae Ngad and Mae Kuang Udomtara Reservoirs, respectively. The highest intensity of heterophyid metacercariae in H. siamensis in the Mae Ngad was 120.4 and that in P. proctozysron in the Mae Kuang Udomtara was 180.0. The fish, A. testudineus, C. apogon, and M. chrysophykadian, were not found to be infected with H. taichui metacercariae. The results show that the freshwater fish in Chiang Mai water reservoirs are heavily infected with H. taichui and Haplorchoides sp. metacercariae.     

Hunger rapidly overrides the risk of predation in the subtidal scavenger Nassarius siquijorensis (Gastropoda: Nassariidae): an energy budget and a comparison with the intertidal Nassarius festivus in Hong Kong

This study shows that, as with its intertidal counterpart, Nassarius festivus, the rate at which subtidal Nassarius siquijorensis moves towards food bait is similar for starved and well-fed individuals. This study also investigates another facet of nassariid nutrition related to the degree of hunger, i.e. the effect of simulated predation upon a feeding assemblage. Individuals which fed within 7 days, cease feeding and depart palatable food if crushed conspecifics are added. Between 7 and 13 days since its last meal, however, N. siquijorensis will feed when food is available, despite the possibility of predation. For the intertidal N. festivus, the critical time for hunger to override the risk of predation is between 14 and 21 days. The difference between subtidal and intertidal species may be due to a difference, in terms of days, that a meal can provide for their energy expenditure, particularly with regard to respiration. The bigger, subtidal, N. siquijorensis needs to feed more frequently than the smaller, intertidal, N. festivus.     

Environmental factors associated with toxic cyanobacterial blooms across 20 drinking water reservoirs in a semi-arid region of Brazil

Cyanobacteria are known to produce a wide variety of bioactive, toxic secondary metabolites generally described as hepatotoxins, neurotoxins, cytotoxins, or dermatoxins. In Brazil, the regular monitoring of cyanobacterial toxins has intensified after the death of 65 patients in a hemodialysis clinic in Caruaru in the state of Pernambuco due to microcystin exposure. The primary objective of this study was to use multivariate statistics that incorporated environmental parameters (both biotic and abiotic) to forecast blooms of cyanobacteria and their toxic secondary metabolites in 20 drinking water reservoirs managed by the Water Treatment Company of Ceará (CAGECE) in the semi-arid region of Ceará, Brazil. Across four years (January 2013 to January 2017), 114 different phytoplankton taxa were identified, including 24 cyanobacterial taxa. In general, Ceará reservoirs were dominated by cyanobacteria due to eutrophication but also because of the dry and warm climate found throughout the region. Interestingly, specific cyanobacterial taxa were influenced by different biotic and abiotic factors. For example, nitrogen-to-phosphorus (N:P) and evaporation were positively related to saxitoxin-producing taxa, especially Raphidiopsis raciborskii, while temperature, electrical conductivity, total phosphorus, and transparency (measured as Secchi depth) were positively associated with microcystin-producing taxa, such as Microcystis aeruginosa. Climate forecasts predict higher evaporation and temperatures in the semi-arid Ceará region, which will likely magnify droughts and water scarcity as well as promote toxic cyanobacterial blooms in reservoirs in the future. Therefore, understanding the factors associated with algal blooms dominated by specific taxa is paramount for water resource management.     

浙江饮用水源地浮游动物群落特征及环境响应

2010年1月至2011年10月,对浙江省16个饮用水源地(H1—H8为河网型,K1—K8为水库型)的浮游动物群落进行季节调查。共记录浮游动物优势种(属)21种(轮虫8种、枝角类5种、剑水蚤5种和哲水蚤3种),各类群第一优势种分别为针簇多肢轮虫(Polyarthra trigla)、长额象鼻溞(Bosmina longirostris)、粗壮温剑水蚤(Thermocyclops dybowskii)和汤匙华哲水蚤(Sinocalanus dorrii)。2年间,河网和水库浮游动物平均密度分别为345.2 L-1和199.4 L-1,生物量分别为0.667 mg/L和0.421mg/L。各类群密度百分比例均以轮虫和桡足类无节幼体为主,甲壳动物以剑水蚤为主。经逐步回归分析表明,浮游动物群落密度(生物量)与河网水质因子(P0.01)之间相关性比水库(P0.05)更密切,总磷和氨氮分别入选了河网和水库所有有效的回归方程中。通径分析和决策系统分析表明,河网的总磷和叶绿素a含量对浮游动物群落变动具有正效应,溶解氧具有负效应;总磷含量是影响河网群落变动的最重要因子,叶绿素a含量则是影响群落增长最主要的限制因子。河网剑水蚤、无节幼体和轮虫群落的密度(生物量)与水体综合营养指数TLIc密度(TLIc生物量)之间有显著的线性回归关系(P0.001),无节幼体密度构成了TLIc密度变动的限制因子,轮虫生物量成为TLIc生物量变动的限制因子,而剑水蚤是一类最重要、稳定的水质指示群落,这对于筛选浮游动物群落的一些拓展性监测指标具有重要的参考作用。     

Seasonal occurrence of freshwater medusa Limnocnida indica annandale (Cnidaria: Limnomedusae) in a lake associated with the river Yamuna, India

A freshwater medusa, Limnocnida indica Annandale, 1912 was observed in the month of April and May of two consecutive years 1994, 1995 in a lake having free connection with the river Yamuna in Delhi. Medusae in the lake were abundant in those areas where the vegetation of Hydrilla sp. was moderately dense, whereas it was absent in areas with Potamogeton sp. The composition of planktonic community in the lake was different before and during the occurrence of medusae and after their disappearance. Moina sp. and Keratella sp. were totally absent and Mesocyclops sp. and nauplii were reduced in number during the occurrence of medusae which were either present or more in number before the occurrence of the latter. Dinophyceae was maximum in number during this period. These zooplankters reappeared after the disappearance of medusae. It is likely that ecological conditions which prevailed during April and May favour the seasonal occurrence of freshwater medusae.     

Metal pollution in water environment and the associated human health risk from drinking water: A case study of Sukinda chromite mine,India

Sukinda is one of the most polluted regions of the globe due to chromium pollution. The study sheds light into the heavy metal pollution around the mining area and its effect on the health of the resident populace. The Cr(VI) was in the range of 0.027–2.48 mg/L in surface water and BDL–1.35 mg/L in the groundwater. Multivariate analysis revealed that mining activity was the main source of TCr, Cr(VI), and Zn in the surface water that warrants attention. Heavy metal evaluation index showed high levels of Fe, Mn, and Cr in groundwater that can pose serious threat to the exposed population. Cancer and non-cancer risk of Cr(VI) was higher than other metals in groundwater. The results revealed that the total cancer risk was 1.21E-03 and 1.05E-03 in adults and children, respectively, which exceeded the USEPA acceptable cancer health risk. High health risk was observed through oral intake of water, while both cancer and non-cancer risks were negligible through dermal contact. This study strongly advocates proper periodic assessment of drinking as well as surface water in the area and regulation to restrict the use of contaminated water for daily use.