The utilisation of arginine by oral streptococci grown glucose-limited in a chemostat

Abstract Legionella pneumophila occurring in drinking water was subjected to environmental stress through holding tests at ambient and elevated temperatures and by chemical disinfection. The bacterium in its native environment was more resistant to adverse conditions, as compared with laboratory-grown organisms. Of the several chemical disinfectants acceptable to drinking water treatment and tested for Legionella inactivation, ozonation was the most efficient method. The C · t ' products indicated that free chlorine was superior to mono- and dichloramines.     

Distribution of legionellae in a hospital water system: prevalence of immunologically and genetically related Legionella pneumophila serogroup 6 isolates

A hospital warm water system was monitored for the presence and distribution of legionellae. Subtyping of ten selected Legionella pneumophila isolates, originating from four different sites in the system by using serogroup specific antisera in an indirect immunofluorescence test, revealed that nine of the ten isolates belong to serogroup 6, while the remaining one was serogroup 10. Two monoclonal antibodies (mAbs) specific for a subgroup of serogroup 6 strains were further used for characterization. None of the strains reacted with these mAbs. Genome analysis by elaborating NotI profiles using the pulsed field gel electrophoresis (PFGE) technique revealed that nearly all serogroup 6 isolates derived from different sites, including a new building connected by a ring pipe, were identical according to restriction fragment patterns. The patterns were distinguishable from those of the two L. pneumophila serogroup 6 reference strains, and from that of the L. pneumophila serogroup 10 isolate. These data argue for a relatively homogeneous L. pneumophila serogroup 6 population in the entire water system.     

辽宁省2006-2016年集中空调冷却水中 嗜肺军团菌毒力岛基因组携带情况

摘要:目的 了解2006?2016年辽宁地区集中空调冷却水中军团菌携带毒力岛基因情况及其致病性。方法 根据GenBank公布的嗜肺军团菌核苷酸序列设计和合成嗜肺军团菌种和毒力岛基因鉴定引物,采用PCR法对2006?2016年辽宁省各大公共场所委托及抽样检测中分离到的军团菌,进行了毒力岛基因组检测,并与血清型进行比较分析,其中嗜肺军团菌15株、非嗜肺军团菌8株。结果 标准菌株ATCC（33152）12个毒力岛基因全阳性;9株LP1型嗜肺军团菌分别检出9~11个毒力岛基因,6株LP2-14型嗜肺军团菌分别检出6~9个毒力岛基因,8株非嗜肺军团菌分别检出2~11个毒力岛基因。结论 辽宁地区军团菌广泛存在公共环境集中空调冷却系统中,以LP1型嗜肺军团菌居多,LP2-14型嗜肺军团菌与非嗜肺军团菌也普遍存在,而且所测菌株均携带毒力岛基因,是细菌感染性肺炎的重要隐患病源之一。     

Multiresistant waterborne pathogens isolated from water reservoirs and cooling systems

Aims:  To determine the incidence of multiple antibiotic-resistant strains of the emergent human pathogens Legionella pneumophila , Pseudomonas aeruginosa and mesophilic Aeromonas species among those isolated from water reservoirs and industrial cooling systems.
Methods and Results:  Water from four natural water reservoirs and four industrial cooling towers was sampled for 1 year period. The total heterotrophs, mesophilic Aeromonas , Pseudomonas spp. and Legionella spp. counts were performed as recommended by standard procedures, and the sensitivity of the isolates to 27 antibiotics was tested. A total of 117 Aeromonas , 60 P. aeruginosa and 15  L. pneumophila strains were isolated and identified by means of biochemical tests and DNA probes. 46·4% of Aeromonas , and 100% of P. aeruginosa isolates presented multiple resistance. Legionella pneumophila strains were generally sensitive to the drugs used.
Conclusions:  Antibiotic-resistant pathogenic bacteria belonging to P. aeruginosa and mesophilic Aeromonas species are common in natural aquatic environments. Thus, the risk of waterborne diseases owing to domestic and industrial uses of freshwater should be re-examined from the increase of bacterial resistance point of view.
Significance and Impact of the Study:  These data confirm the emergence of bacteria resistant to antibiotics in aquatic environments.     

Legionella pollution in cooling tower water of air-conditioning systems in Shanghai, China

Aims:  To determine Legionella pollution prevalence, describe the amount of Legionellae with respect to temperature in Shanghai cooling tower water (CTWs) in various types of public sites.
Methods and Results:  Six urban districts were selected as the study fields, adopting multiple-phase sampling methods. Routine culture was used to identify Legionellae. Of the samples, 58·9% (189/321) were observed to be positive, 19·9% were isolated over 100 CFU ml⁻¹. Legionella pneumophila serogroup 1 was the most frequently isolated species (155/189, 82·0%), followed by Leg. micdadei that was at the second place (44/189, 23·3%). The mean CFU ml⁻¹ of Legionellae in CTWs reached its peak from July to September. Over all 15·4% of the samples exceeding 100 CFU ml⁻¹ were observed in a hospital setting.
Conclusions:  The prevalence of Legionella pollution in CTWs, especially in CTWs of subway stations and hospitals, is worrying, and the positive rate and CFU ml⁻¹ of Legionellae in CTWs have a close relationship with air temperature.
Significance and Impact of the Study:  The study demonstrates pollution prevalence rates in different types of sites and various seasons, and provides a proportion of different serogroups of Legionellae . It illuminates an urgent need for dealing with the potential risk of legionellosis in Shanghai, through improved control and prevention strategies.     

Rapid quantification of viable legionellae in water and biofilm using ethidium monoazide coupled with real‐time quantitative PCR

Aims: To optimize ethidium monoazide (EMA) coupled with real‐time quantitative PCR (qPCR) and to evaluate its environmental applicability on quantifying viable legionellae in water and biofilm of cooling towers and hot water systems. Methods and Results: EMA (0·9–45·5 μg ml^?1) and propidium monoazide (PMA, 0·9 and 2·3 μg ml^?1) combined with qPCR (i.e. EMA‐qPCR and PMA‐qPCR, respectively) were applied to unheated and heated (70°C for 30 min) Legionella pneumophila to quantify viable cells, which was also simultaneously determined by BacLight Bacterial Viability kit with epifluorogenic microscopic enumeration (BacLight‐EM). The effects of nontarget microflora and sample matrix on the performance of EMA‐qPCR were also evaluated. In comparison with BacLight‐EM results, qPCR with EMA at 2·3 μg ml^?1 was determined as the optimal EMA‐qPCR assay, which performed equally well as PMA‐qPCR for unheated Leg. pneumophila but better than PMA‐qPCR for heated Leg. pneumophila (P < 0·05). Moreover, qPCR with EMA at 2·3 μg ml^?1 accurately quantified viable Leg. pneumophila, Legionella anisa and Legionella‐like amoebal pathogens 6 (LLAP 6) without interferences by heated legionellae, unheated nonlegionellae cells and cooling tower water matrix (P > 0·05). As for water and biofilm samples collected from cooling towers and hot water systems, the viable legionellae counts determined by EMA‐qPCR were mostly greater than the culturable counts by culture assay but consistently lower than the total cell counts quantified by qPCR. Conclusions: The qPCR with EMA at 2·3 μg ml^?1 may accurately quantify viable legionellae (including fastidious LLAP 6) and Leg. pneumophila pretreated with superheating and is applicable for water and biofilm samples obtained from cooling towers and hot water systems. Significance and Impact of the Study: The EMA‐qPCR assay may be useful in environmental surveillance for viable legionellae and in evaluation of superheating efficacy against legionellae.     

High‐affinity binding of phosphatidylinositol 4‐phosphate by Legionella pneumophila DrrA

The DrrA protein of Legionella pneumophila is involved in mistargeting of endoplasmic reticulum‐derived vesicles to Legionella‐containing vacuoles through recruitment of the small GTPase Rab1. To this effect, DrrA binds specifically to phosphatidylinositol 4‐phosphate (PtdIns(4)P) lipids on the cytosolic surface of the phagosomal membrane shortly after infection. In this study, we present the atomic structure of the PtdIns(4)P‐binding domain of a protein (DrrA) from a human pathogen. A detailed kinetic investigation of its interaction with PtdIns(4)P reveals that DrrA binds to this phospholipid with, as yet unprecedented, high affinity, suggesting that DrrA can sense a very low abundance of the lipid.     

广州地区嗜肺军团菌环境分离株的基因序列分型分析

摘要:【目的】研究广州市嗜肺军团菌的基因特征,对来自不同水域环境的嗜肺军团菌进行分子分型研究。【方法】选择嗜肺军团菌的7个基因flaA、asd、mip、pilE、mompS、proA和neuA 作为目的基因, 对在2006-2009年间广州地区分离的44株嗜肺军团菌进行PCR扩增和测序,并将核苷酸序列上传至欧洲军团菌病感染工作组（EWGLI）数据库进行比对,得到基因型别（Sequence type, ST）,对结果进行基因序列分型（Sequence-Based Typing, SBT）和系统进化分析。【结     

粤蓝链霉菌榴菌素生物合成基因orf20的功能

【目的】在大肠杆菌中,转录因子SoxR作为胞内氧化还原感应器,参与抗氧化胁迫的全局性调控。粤蓝链霉菌榴菌素生物合成基因簇内存在一个类soxR基因orf20,但其生理功能仍不清楚。【方法】将orf20基因在大肠杆菌中进行表达,分析携带重组质粒的大肠杆菌对百草枯抗性的变化。同时通过修改后的PCR-targeting方法构建粤蓝链霉菌orf20删除的突变株,分析突变株的表型变化和对百草枯抗性水平的变化。【结果】重组ORF20在羧基端含有组氨酸标签,并在大肠杆菌中获得可溶性表达,携带重组质粒pET28b-orf20的大肠杆菌对百草枯的抗性水平显著提高。粤蓝链霉菌orf20删除突变株仍具有产孢能力,生长特性没有改变,对百草枯的抗性水平也没有变化,但榴菌素的产量大幅提高,是野生株的3.3倍。【结论】在大肠杆菌中,orf20基因的编码产物能够被百草枯激活,替代SoxR参与抗氧化胁迫的调控。在粤蓝链霉菌中,orf20基因不参与抗氧化胁迫,而对榴菌素的产生有负调控效应。     

Incidence of Legionella and heterotrophic bacteria in household rainwater tanks in Azumino,Nagano prefecture,Japan

Many administrative agencies in Japan are encouraging installation of household rainwater‐storage tanks for more effective use of natural rainwater. Water samples were collected periodically from 43 rainwater tanks from 40 households and tested for the presence of Legionella species and the extent of heterotrophic bacteria in Azumino city, Nagano prefecture, Japan. PCR assays indicated the presence of Legionella spp. in 12 (30%) of the 43 tank water samples. Attempts were made to identify correlations between PCR positive samples, topography, pH, chemical oxygen demand (COD), atmospheric temperature and the numbers of heterotrophic bacteria. Between June and October, 2012, the numbers of heterotrophic bacteria in rainwater tanks and the values of COD positively correlated with the presence of Legionella species. In most of the Legionella‐positive cases, heterotrophic bacterial cell counts were >10⁴ CFU/mL. Moreover, Legionella species were less frequently detected when the COD value was >5 mg KMnO₄/L. Therefore, at least in Azumino, Japan between June and October 2012, both heterotrophic bacterial counts and COD values may be considered index parameters for the presence of Legionella cells in rainwater tanks. Much more accumulation of such data is needed to verify the accuracy of these findings.