Seasonal Assessment of Opportunistic Premise Plumbing Pathogens in Roof-Harvested Rainwater Tanks

A seasonal study on the occurrence of six opportunistic premise plumbing pathogens (OPPPs) in 24 roof-harvested rainwater (RHRW) tanks repeatedly sampled over six monthly sampling events (n = 144) from August 2015 to March 2016 was conducted using quantitative qPCR. Fecal indicator bacteria (FIB) Escherichia coli (E. coli) and Enterococcus spp. were enumerated using culture-based methods. All tank water samples over the six events were positive for at least one OPPP (Legionella spp., Legionella pneumophila, Mycobacterium avium, Mycobacterium intracellulare, Pseudmonas aeruginosa, or Acanthamoeba spp.) during the entire course of the study. FIB were positively but weakly correlated with P. aeruginosa (E. coli vs P. aeruginosa τ = 0.090, p = 0.027; Enterococcus spp. vs P. aeruginosa τ = 0.126, p = 0.002), but not the other OPPPs. FIBs were more prevalent during the wet season than the dry season, and L. pneumophila was only observed during the wet season. However, concentrations of Legionella spp., M. intracellulare, Acanthamoeba spp., and M. avium peaked during the dry season. Correlations were assessed between FIB and OPPPs with meteorological variables, and it was determined that P. aeruginosa was the only OPPP positively associated with an increased antecedent dry period, suggesting stagnation time may play a role for the occurrence of this OPPP in tank water. Infection risks may exceed commonly cited benchmarks for uses reported in the rainwater usage survey such as pool top-up, and warrant further exploration through quantitative microbial risk assessment (QMRA).

Comparison of sputum microbiome of legionellosis-associated patients and other pneumonia patients: indications for polybacterial infections

Bacteria of the genus Legionella cause water-based infections resulting in severe pneumonia. Here we analyze and compare the bacterial microbiome of sputum samples from pneumonia patients in relation to the presence and abundance of the genus Legionella. The prevalence of Legionella species was determined by culture, PCR, and Next Generation Sequencing (NGS). Nine sputum samples out of the 133 analyzed were PCR-positive using Legionella genus-specific primers. Only one sample was positive by culture. Illumina MiSeq 16S rRNA gene sequencing analyses of Legionella-positive and Legionella-negative sputum samples, confirmed that indeed, Legionella was present in the PCR-positive sputum samples. This approach allowed the identification of the sputum microbiome at the genus level, and for Legionella genus at the species and sub-species level. 42% of the sputum samples were dominated by Streptococcus. Legionella was never the dominating genus and was always accompanied by other respiratory pathogens. Interestingly, sputum samples that were Legionella positive were inhabited by aquatic bacteria that have been observed in an association with amoeba, indicating that amoeba might have transferred Legionella from the drinking water together with its microbiome. This is the first study that demonstrates the sputum major bacterial commensals and pathogens profiles with regard to Legionella presence.

Environmental Free-Living Amoebae Isolated from Soil in Khon Kaen, Thailand, Antagonize Burkholderia pseudomallei

Presence of Burkholderia pseudomallei in soil and water is correlated with endemicity of melioidosis in Southeast Asia and northern Australia. Several biological and physico-chemical factors have been shown to influence persistence of B. pseudomallei in the environment of endemic areas. This study was the first to evaluate the interaction of B. pseudomallei with soil amoebae isolated from B. pseudomallei-positive soil site in Khon Kaen, Thailand. Four species of amoebae, Paravahlkampfia ustiana, Acanthamoeba sp., Naegleria pagei, and isolate A-ST39-E1, were isolated, cultured and identified based on morphology, movement and 18S rRNA gene sequence. Co-cultivation combined with a kanamycin-protection assay of B. pseudomallei with these amoebae at MOI 20 at 30°C were evaluated during 0–6 h using the plate count technique on Ashdown’s agar. The fate of intracellular B. pseudomallei in these amoebae was also monitored by confocal laser scanning microscopy (CLSM) observation of the CellTracker^™ Orange-B. pseudomallei stained cells. The results demonstrated the ability of P. ustiana, Acanthamoeba sp. and isolate A-ST39-E1 to graze B. pseudomallei. However, the number of internalized B. pseudomallei substantially decreased and the bacterial cells disappeared during the observation period, suggesting they had been digested. We found that B. pseudomallei promoted the growth of Acanthamoeba sp. and isolate A-ST39-E1 in co-cultures at MOI 100 at 30°C, 24 h. These findings indicated that P. ustiana, Acanthamoeba sp. and isolate A-ST39-E1 may prey upon B. pseudomallei rather than representing potential environmental reservoirs in which the bacteria can persist.

Molecular detection of Acanthamoeba spp., Naegleria fowleri and Vermamoeba (Hartmannella) vermiformis as vectors for Legionella spp. in untreated and solar pasteurized harvested rainwater

Background

Legionella spp. employ multiple strategies to adapt to stressful environments including the proliferation in protective biofilms and the ability to form associations with free-living amoeba (FLA). The aim of the current study was to identify Legionella spp., Acanthamoeba spp., Vermamoeba (Hartmannella) vermiformis and Naegleria fowleri that persist in a harvested rainwater and solar pasteurization treatment system.

Methods

Pasteurized (45 °C, 65 °C, 68 °C, 74 °C, 84 °C and 93 °C) and unpasteurized tank water samples were screened for Legionella spp. and the heterotrophic plate count was enumerated. Additionally, ethidium monoazide quantitative polymerase chain reaction (EMA-qPCR) was utilized for the quantification of viable Legionella spp., Acanthamoeba spp., V. vermiformis and N. fowleri in pasteurized (68 °C, 74 °C, 84 °C and 93 °C) and unpasteurized tank water samples, respectively.

Results

Of the 82 Legionella spp. isolated from unpasteurized tank water samples, Legionella longbeachae (35 %) was the most frequently isolated, followed by Legionella norrlandica (27 %) and Legionella rowbothamii (4 %). Additionally, a positive correlation was recorded between the heterotrophic plate count vs. the number of Legionella spp. detected (ρ = 0.710, P = 0.048) and the heterotrophic plate count vs. the number of Legionella spp. isolated (ρ = 0.779, P = 0.0028) from the tank water samples collected. Solar pasteurization was effective in reducing the gene copies of viable V. vermiformis (3-log) and N. fowleri (5-log) to below the lower limit of detection at temperatures of 68–93 °C and 74–93 °C, respectively. Conversely, while the gene copies of viable Legionella and Acanthamoeba were significantly reduced by 2-logs (P = 0.0024) and 1-log (P = 0.0015) overall, respectively, both organisms were still detected after pasteurization at 93 °C.

Conclusions

Results from this study indicate that Acanthamoeba spp. primarily acts as the vector and aids in the survival of Legionella spp. in the solar pasteurized rainwater as both organisms were detected and were viable at high temperatures (68–93 °C).

Public health implications of Acanthamoeba and multiple potential opportunistic pathogens in roof-harvested rainwater tanks

A study of six potential opportunistic pathogens (Acanthamoeba spp., Legionella spp., Legionella longbeachae, Pseudomonas aeruginosa, Mycobacterium avium and Mycobacterium intracellulare) and an accidental human pathogen (Legionella pneumophila) in 134 roof-harvested rainwater (RHRW) tank samples was conducted using quantitative PCR (qPCR). All five opportunistic pathogens and accidental pathogen L. pneumophila were detected in rainwater tanks except Legionella longbeachae. Concentrations ranged up to 3.1×10(6) gene copies per L rainwater for Legionella spp., 9.6×10(5) gene copies per L for P. aeruginosa, 6.8×10(5) gene copies per L for M. intracellulare, 6.6×10(5) gene copies per L for Acanthamoeba spp., 1.1×10(5) gene copies per L for M. avium, and 9.8×10(3) gene copies per L for L. pneumophila. Among the organisms tested, Legionella spp. (99% tanks) were the most prevalent followed by M. intracellulare (78%). A survey of tank-owners provided data on rainwater end-uses. Fecal indicator bacteria (FIB) Escherichia coli and Enterococcus spp. were enumerated using culture-based methods, and assessed for correlations with opportunistic pathogens and L. pneumophila tested in this study. Opportunistic pathogens did not correlate well with FIB except E. coli vs. Legionella spp. (tau=0.151, P=0.009) and E. coli vs. M. intracellulare (tau=0.14, P=0.015). However, M. avium weakly correlated with both L. pneumophila (Kendall's tau=0.017, P=0.006) and M. intracellulare (tau=0.088, P=0.027), and Legionella spp. also weakly correlated with M. intracellulare (tau=0.128, P=0.028). The presence of these potential opportunistic pathogens in tank water may present health risks from both the potable and non-potable uses documented from the current survey data.

Isolation of thermotolerant Vermamoeba vermiformis strains from water sources in Lanzarote Island, Canary Islands, Spain

In this study, twenty water samples were collected in the island of Lanzarote, Canary Islands, Spain in order to check for the presence of V. vermiformis strains in these samples. Water samples were cultured on 2% Non-Nutrient Agar (NNA) plates covered with a thin layer of heat killed E. coli and checked daily for the presence of Vermamoeba. After a week, V. vermiformis amoebae were observed in 2 of the 20 processed samples (10%) incubated at room temperature and 37°C. Molecular characterization was carried out by amplifying the 18S rDNA gene and DNA sequencing in order to confirm the identity of the isolated amoebic strains. To the best of our knowledge, this is the first report on the presence of FLA in environmental sources in Lanzarote Island and the first report of Vermamoeba vermiformis in water sources in this island. Furthermore, the two strains isolated in this study were collected in recreational areas with close contact with humans and thus awareness should be raised.

Environmental factors shaping cultured free-living amoebae and their associated bacterial community within drinking water network

Free-living amoebae (FLA) constitute an important part of eukaryotic populations colonising drinking water networks. However, little is known about the factors influencing their ecology in such environments. Because of their status as reservoir of potentially pathogenic bacteria, understanding environmental factors impacting FLA populations and their associated bacterial community is crucial. Through sampling of a large drinking water network, the diversity of cultivable FLA and their bacterial community were investigated by an amplicon sequencing approach, and their correlation with physicochemical parameters was studied. While FLA ubiquitously colonised the water network all year long, significant changes in population composition were observed. These changes were partially explained by several environmental parameters, namely water origin, temperature, pH and chlorine concentration. The characterisation of FLA associated bacterial community reflected a diverse but rather stable consortium composed of nearly 1400 OTUs. The definition of a core community highlighted the predominance of only few genera, majorly dominated by Pseudomonas and Stenotrophomonas. Co-occurrence analysis also showed significant patterns of FLA-bacteria association, and allowed uncovering potentially new FLA - bacteria interactions. From our knowledge, this study is the first that combines a large sampling scheme with high-throughput identification of FLA together with associated bacteria, along with their influencing environmental parameters. Our results demonstrate the importance of physicochemical parameters in the ecology of FLA and their bacterial community in water networks.

Pseudomonas aeruginosa in premise plumbing of large buildings

Pseudomonas aeruginosa is an opportunistic bacterial pathogen that is widely occurring in the environment and is recognized for its capacity to form or join biofilms. The present review consolidates current knowledge on P. aeruginosa ecology and its implication in healthcare facilities premise plumbing. The adaptability of P. aeruginosa and its capacity to integrate the biofilm from the faucet and the drain highlight the role premise plumbing devices can play in promoting growth and persistence. A meta‐analysis of P. aeruginosa prevalence in faucets (manual and electronic) and drains reveals the large variation in device positivity reported and suggest the high variability in the sampling approach and context as the main reason for this variation. The effects of the operating conditions that prevail within water distribution systems (disinfection, temperature, and hydraulic regime) on the persistence of P. aeruginosa are summarized. As a result from the review, recommendations for proactive control measures of water contamination by P. aeruginosa are presented. A better understanding of the ecology of P. aeruginosa and key influencing factors in premise plumbing are essential to identify culprit areas and implement effective control measures.

In vitro anti-Acanthamoeba synergistic effect of chlorhexidine and cationic carbosilane dendrimers against both trophozoite and cyst forms

Acanthamoeba sp. are the causative agents of severe illnesses in humans such as Acanthamoeba keratitis (AK) and granulomatous amoebic encephalitis (GAE). Medical therapy is not yet well established. Treatments of AK last for several months and generate toxicity, resistances appear due to the cysts stage and recurrences can occur. In this study has been demonstrated that the combination of chlorhexidine digluconate (CLX) and carbosilane dendrimers containing ammonium or guanidine moieties has in vitro synergistic effect against Acanthamoeba polyphaga. This synergy provokes an important reduction in the minimal trophozoite amoebicidal concentration (MTAC) of CLX, which means a reduction of their toxic effects on human cells. Moreover, some CLX/dendrimer combinations show important activity against the cyst resistance stage.

Optimized methods for Legionella pneumophila release from its Acanthamoeba hosts

BACKGROUND

Free-living amoebae (FLA) and particularly acanthamoebae serve as vehicles and hosts for Legionella pneumophila, among other pathogenic microorganisms. Within the amoebae, L. pneumophila activates a complex regulatory pathway that enables the bacteria to resist amoebal digestion and to replicate. Moreover, the amoebae provide the bacteria protection against harsh environmental conditions and disinfectants commonly used in engineered water systems. To study this ecological relationship, co-culture and infection models have been used. However, there is a lack of data regarding the effectiveness of the different methods used to release intracellular bacteria from their amoebal hosts. The aim of this study was to evaluate the impact of the methods used to release intracellular L. pneumophila cells on the culturability of the bacteria. Furthermore, the standard method ISO 11731:1998 for the recovery and enumeration of Legionella from water samples was evaluated for its suitability to quantify intracellular bacteria.

RESULTS

The effectiveness of the eight release treatments applied to L. pneumophila and Acanthamoeba strains in a free-living state varied between bacterial strains. Moreover, the current study provides numerical data on the state of co-culture suspensions at different time points. The release treatments enhanced survival of both microorganisms in co-cultures of L. pneumophila and Acanthamoeba. Passage through a needle (21G, 27G) and centrifugation at 10,000 × g showed the highest bacterial counts when releasing the bacteria from the intracellular state. Regarding the ISO 11731:1998 method, one of the tested strains showed no differences between the recovery rates of associated and free-living L. pneumophila. However, a reduced bacterial recovery rate was observed for the second L. pneumophila strain used, and this difference is likely linked to the survival of the amoebae.

CONCLUSIONS

Mechanical release treatments were the most effective methods for providing bacterial release without the use of chemicals that could compromise further study of the intracellular bacteria. The current results demonstrated that the recovery of L. pneumophila from water systems may be underestimated if protozoal membranes are not disrupted.

Sanitation in constructed wetlands: A review on the removal of human pathogens and fecal indicators

Removal of human pathogens from wastewater is a critical factor with linkage to human health. Constructed Wetlands (CWs) are environmental friendly ecosystems that are applicable not only for chemical pollution control, but also for the reduction of pathogens from wastewater. Yet the knowledge on the fate and removal of such indicator bacteria in CWs is still not sufficient due to the complexity of removal mechanisms and influencing factors. This review serves to provide a better understanding of this state-of-the-art technology, which is necessary for further investigations and design development. The fecal indicator bacteria in CWs mainly come from three sources, namely, influent wastewaters, regrowth within the CWs, and animal activities. The properties of microbial contamination vary depending on the different sources. The removal of pathogens is a complex process that is influenced by operational parameters such as hydraulic regime and retention time, vegetation, seasonal fluctuation, and water composition. The most frequent and well-validated removal mechanisms include natural die-off due to starvation or predation, sedimentation and filtration, and adsorption. The concentration of the main fecal indicator bacteria in the effluent was found to be exponentially related to the loading rate. Generally, horizontal subsurface flow CWs have better reduction capacity than free water surface flow CWs, and hybrid wetland systems were found to be the most efficient due to a longer retention time. Further improvement of fecal indicator bacteria removal in CWs is needed, however, levels in CW effluents are still higher than most of the regulation standards for reuse.

Extreme weather events: Should drinking water quality management systems adapt to changing risk profiles?

Among the most widely predicted and accepted consequences of global climate change are increases in both the frequency and severity of a variety of extreme weather events. Such weather events include heavy rainfall and floods, cyclones, droughts, heatwaves, extreme cold, and wildfires, each of which can potentially impact drinking water quality by affecting water catchments, storage reservoirs, the performance of water treatment processes or the integrity of distribution systems. Drinking water guidelines, such as the Australian Drinking Water Guidelines and the World Health Organization Guidelines for Drinking-water Quality, provide guidance for the safe management of drinking water. These documents present principles and strategies for managing risks that may be posed to drinking water quality. While these principles and strategies are applicable to all types of water quality risks, very little specific attention has been paid to the management of extreme weather events. We present a review of recent literature on water quality impacts of extreme weather events and consider practical opportunities for improved guidance for water managers. We conclude that there is a case for an enhanced focus on the management of water quality impacts from extreme weather events in future revisions of water quality guidance documents.

Protozoan Cysts Act as a Survival Niche and Protective Shelter for Foodborne Pathogenic Bacteria

The production of cysts, an integral part of the life cycle of many free-living protozoa, allows these organisms to survive adverse environmental conditions. Given the prevalence of free-living protozoa in food-related environments, it is hypothesized that these organisms play an important yet currently underinvestigated role in the epidemiology of foodborne pathogenic bacteria. Intracystic bacterial survival is highly relevant, as this would allow bacteria to survive the stringent cleaning and disinfection measures applied in food-related environments. The present study shows that strains of widespread and important foodborne bacteria (Salmonella enterica, Escherichia coli, Yersinia enterocolitica, and Listeria monocytogenes) survive inside cysts of the ubiquitous amoeba Acanthamoeba castellanii, even when exposed to either antibiotic treatment (100 μg/ml gentamicin) or highly acidic conditions (pH 0.2) and resume active growth in broth media following excystment. Strain- and species-specific differences in survival periods were observed, with Salmonella enterica surviving up to 3 weeks inside amoebal cysts. Up to 53% of the cysts were infected with pathogenic bacteria, which were located in the cyst cytosol. Our study suggests that the role of free-living protozoa and especially their cysts in the persistence and epidemiology of foodborne bacterial pathogens in food-related environments may be much more important than hitherto assumed.

Environmental (Saprozoic) Pathogens of Engineered Water Systems: Understanding Their Ecology for Risk Assessment and Management

Major waterborne (enteric) pathogens are relatively well understood and treatment controls are effective when well managed. However, water-based, saprozoic pathogens that grow within engineered water systems (primarily within biofilms/sediments) cannot be controlled by water treatment alone prior to entry into water distribution and other engineered water systems. Growth within biofilms or as in the case of Legionella pneumophila, primarily within free-living protozoa feeding on biofilms, results from competitive advantage. Meaning, to understand how to manage water-based pathogen diseases (a sub-set of saprozoses) we need to understand the microbial ecology of biofilms; with key factors including biofilm bacterial diversity that influence amoebae hosts and members antagonistic to water-based pathogens, along with impacts from biofilm substratum, water temperature, flow conditions and disinfectant residual—all control variables. Major saprozoic pathogens covering viruses, bacteria, fungi and free-living protozoa are listed, yet today most of the recognized health burden from drinking waters is driven by legionellae, non-tuberculous mycobacteria (NTM) and, to a lesser extent, Pseudomonas aeruginosa. In developing best management practices for engineered water systems based on hazard analysis critical control point (HACCP) or water safety plan (WSP) approaches, multi-factor control strategies, based on quantitative microbial risk assessments need to be developed, to reduce disease from largely opportunistic, water-based pathogens.

Opportunistic Premise Plumbing Pathogens: Increasingly Important Pathogens in Drinking Water

Opportunistic premise plumbing pathogens are responsible for a significant number of infections whose origin has been traced to drinking water. These opportunistic pathogens represent an emerging water borne disease problem with a major economic cost of at least $1 billion annually. The common features of this group of waterborne pathogens include: disinfectant-resistance, pipe surface adherence and biofilm formation, growth in amoebae, growth on low organic concentrations, and growth at low oxygen levels. Their emergence is due to the fact that conditions resulting from drinking water treatment select for them. As such, there is a need for novel approaches to reduce exposure to these pathogens. In addition to much-needed research, controls to reduce numbers and human exposure can be instituted independently by utilities and homeowners and hospital- and building-operators.

Sensitivity of Vermamoeba (Hartmannella) vermiformis cysts to conventional disinfectants and protease

Vermamoeba vermiformis is a free-living amoeba (FLA) widely distributed in the environment, known to colonize hot water networks and to be the reservoir of pathogenic bacteria such as Legionella pneumophila. FLA are partly resistant to biocides, especially in their cyst form. The control of V. vermiformis in hot water networks represents an important health issue, but there are very few data on their resistance to disinfection treatments. The sensitivity of cysts of two strains of V. vermiformis to three disinfectants frequently used in hot water networks (chlorine, heat shock, peracetic acid (PAA) mixed with hydrogen peroxide (H2O2)) was investigated. In vitro, several concentrations of biocides, temperatures and exposure times according to the French regulation were tested. Cysts were fully inactivated by the following conditions: 15 mg/L of chlorine for 10 min; 60 °C for 30 min; and 0.5 g/L equivalent H2O2 of PAA mixed with H2O2 for 30 min. For the first time, the strong efficacy of subtilisin (0.625 U/mL for 24 h), a protease, to inactivate the V. vermiformis cysts has been demonstrated. It suggests that novel approaches may be efficient for disinfection processes. Finally, V. vermifomis cysts were sensitive to all the tested treatments and appeared to be more sensitive than Acanthamoeba cysts.

Isolation and molecular characterization of free-living amoebae from different water sources in Italy

Free-living amoebae (FLA) are protozoa ubiquitous in Nature, isolated from a variety of environments worldwide. In addition to their natural distribution, some species have been found to be pathogenic to humans. In the present study a survey was conducted in order to evaluate the presence and to characterize at molecular level the isolates of amoebic organisms collected from different water sources in Italy. A total of 160 water samples were analyzed by culture and microscopic examination. FLA were found in 46 (28.7%) of the investigated water samples. Groundwater, well waters, and ornamental fountain waters were the sources with higher prevalence rates (85.7%, 50.0%, and 45.9%, respectively). Identification of FLA species/genotypes, based on the 18S rDNA regions, allowed to identify 18 (39.1%) Acanthamoeba isolates (genotypes T4 and T15) and 21 (45.6%) Vermamoeba vermiformis isolates. Other FLA species, including Vahlkampfia sp. and Naegleria spp., previously reported in Italy, were not recovered. The occurrence of potentially pathogenic free-living amoebae in habitats related to human population, as reported in the present study, supports the relevance of FLA as a potential health threat to humans.

Campylobacter-Acanthamoeba interactions

Campylobacter jejuni is a foodborne pathogen recognized as the major cause of human bacterial enteritis. Undercooked poultry products and contaminated water are considered as the most important sources of infection. Some studies suggest transmission and survival of this bacterial pathogen may be assisted by the free-living protozoa Acanthamoeba. The latter is known to play the role of a host for various pathogenic bacteria, protecting them from harsh environmental conditions. Importantly, there is a similarity between the mechanisms of bacterial survival within amoebae and macrophages, making the former a convenient tool for the investigation of the survival of pathogenic bacteria in the environment. However, the molecular mechanisms involved in the interaction between Campylobacter and Acanthamoeba are not well understood. Whilst some studies suggest the ability of C. jejuni to survive within the protozoa, the other reports support an extracellular mode of survival only. In this review, we focus on the studies investigating the interaction between Campylobacter and Acanthamoeba, address some reasons for the contradictory results, and discuss possible implications of these results for epidemiology. Additionally, as the molecular mechanisms involved remain unknown, we also suggest possible factors that may be involved in this process. Deciphering the molecular mechanisms of pathogen-protozoa interaction will assist in a better understanding of Campylobacter lifestyle and in the development of novel antibacterial drugs.

Microbial Contamination of Drinking Water and Human Health from Community Water Systems

A relatively short list of reference viral, bacterial and protozoan pathogens appears adequate to assess microbial risks and inform a system-based management of drinking waters. Nonetheless, there are data gaps, e.g. human enteric viruses resulting in endemic infection levels if poorly performing disinfection and/or distribution systems are used, and the risks from fungi. Where disinfection is the only treatment and/or filtration is poor, cryptosporidiosis is the most likely enteric disease to be identified during waterborne outbreaks, but generally non-human-infectious genotypes are present in the absence of human or calf fecal contamination. Enteric bacteria may dominate risks during major fecal contamination events that are ineffectively managed. Reliance on culture-based methods exaggerates treatment efficacy and reduces our ability to identify pathogens/indicators; however, next-generation sequencing and polymerase chain reaction approaches are on the cusp of changing that. Overall, water-based Legionella and non-tuberculous mycobacteria probably dominate health burden at exposure points following the various societal uses of drinking water.

Potent antimicrobial peptides against Legionella pneumophila and its environmental host, Acanthamoeba castellanii

Legionella pneumophila, the major causative agent of Legionnaires' disease, is most often found in the environment in close association with free-living amoebae, leading to persistence, spread, biocide resistance, and elevated virulence of the bacterium. In the present study, we evaluated the anti-Legionella and anti-Acanthamoeba activities of three alpha-helical antimicrobial peptides (AMPs), namely, NK-2, Ci-MAM-A24, and Ci-PAP-A22, already known for the extraordinary efficacy against other microbes. Our data represent the first demonstration of the activity of a particular AMP against both the human facultative intracellular pathogen L. pneumophila and its pathogenic host, Acanthamoeba castellanii. Interestingly, the most effective peptide, Ci-MAM-A24, was also found to reduce the Legionella cell number within amoebae. Accordingly, this peptide was immobilized on gold surfaces to assess its antimicrobial activity. Surfaces were characterized, and activity studies revealed that the potent bactericidal activity of the peptide was conserved after its immobilization. In the frame of elaborating anti-Legionella surfaces, Ci-MAM-A24 represents, by its direct and indirect activity against Legionella, a potent peptide template for biological control of the bacterium in plumbings.

Nuclease activity of Legionella pneumophila Cas2 promotes intracellular infection of amoebal host cells

Legionella pneumophila, the primary agent of Legionnaires' disease, flourishes in both natural and man-made environments by growing in a wide variety of aquatic amoebae. Recently, we determined that the Cas2 protein of L. pneumophila promotes intracellular infection of Acanthamoeba castellanii and Hartmannella vermiformis, the two amoebae most commonly linked to cases of disease. The Cas2 family of proteins is best known for its role in the bacterial and archeal clustered regularly interspaced short palindromic repeat (CRISPR)-CRISPR-associated protein (Cas) system that constitutes a form of adaptive immunity against phage and plasmid. However, the infection event mediated by L. pneumophila Cas2 appeared to be distinct from this function, because cas2 mutants exhibited infectivity defects in the absence of added phage or plasmid and since mutants lacking the CRISPR array or any one of the other cas genes were not impaired in infection ability. We now report that the Cas2 protein of L. pneumophila has both RNase and DNase activities, with the RNase activity being more pronounced. By characterizing a catalytically deficient version of Cas2, we determined that nuclease activity is critical for promoting infection of amoebae. Also, introduction of Cas2, but not its catalytic mutant form, into a strain of L. pneumophila that naturally lacks a CRISPR-Cas locus caused that strain to be 40- to 80-fold more infective for amoebae, unequivocally demonstrating that Cas2 facilitates the infection process independently of any other component encoded within the CRISPR-Cas locus. Finally, a cas2 mutant was impaired for infection of Willaertia magna but not Naegleria lovaniensis, suggesting that Cas2 promotes infection of most but not all amoebal hosts.

Effect of UV irradiation (253.7 nm) on free Legionella and Legionella associated with its amoebae hosts

Water systems are the primary reservoir for Legionella spp., where the bacteria live in association with other microorganisms, such as free-living amoebae. A wide range of disinfection treatments have been studied to control and prevent Legionella colonization but few of them were performed considering its relation with protozoa. In this study, the effectiveness of UV irradiation (253.7 nm) using low-pressure lamps was investigated as a disinfection method for Legionella and amoebae under controlled laboratory conditions. UV treatments were applied to 5 strains of Legionella spp., 4 strains of free-living amoeba of the genera Acanthamoeba and Vermamoeba, treating separately trophozoites and cysts, and to two different co-cultures of Legionella pneumophila with the Acanthamoeba strains. No significant differences in the UV inactivation behavior were observed among Legionella strains tested which were 3 logs reduced for fluences around 45 J/m(2). UV irradiation was less effective against free-living amoebae; which in some cases required up to 990 J/m(2) to obtain the same population reduction. UV treatment was more effective against trophozoites compared to cysts; moreover, inactivation patterns were clearly different between the genus Acanthamoeba and Vermamoeba. For the first time data about Vermamoeba vermiformis UV inactivation has been reported in a study. Finally, the results showed that the association of L. pneumophila with free-living amoebae decreases the effectiveness of UV irradiation against the bacteria in a range of 1.5-2 fold. That fact demonstrates that the relations established between different microorganisms in the water systems can modify the effectiveness of the UV treatments applied.

Detection of free-living amoebae using amoebal enrichment in a wastewater treatment plant of Gauteng Province, South Africa

Free-living amoebae pose a potential health risk in water systems as they may be pathogenic and harbor potential pathogenic bacteria known as amoebae resistant bacteria. Free-living amoebae were observed in 150 (87.2%) of the environmental water samples. In particular, Acanthamoeba sp. was identified in 22 (12.8%) using amoebal enrichment and confirmed by molecular analysis. FLA were isolated in all 8 stages of the wastewater treatment plant using the amoebal enrichment technique. A total of 16 (9.3%) samples were positive for FLA from influent, 20 (11.6%) from bioreactor feed, 16 (9.3%) from anaerobic zone, 16 (9.3%) from anoxic zone, 32 (18.6%) from aerators, 16 (9.3%) from bioreactor effluent, 11 (6.4%) from bioreactor final effluent, and 45 (26.2%) from maturation pond. This study provides baseline information on the occurrence of amoebae in wastewater treatment plant. This has health implications on receiving water bodies as some FLA are pathogenic and are also involved in the transmission and dissemination of pathogenic bacteria.

Stenotrophomonas maltophilia and Vermamoeba vermiformis relationships: bacterial multiplication and protection in amoebal-derived structures

Stenotrophomonas maltophilia, a bacteria involved in healthcare-associated infections, can be found in hospital water systems. Other microorganisms, such as Free Living amoebae (FLA), are also at times recovered in the same environment. Amongst these protozoa, many authors have reported the presence of Vermamoeba vermiformis. We show here that this amoeba enhances S. maltophilia growth and harbors the bacteria in amoebal-derived structures after 28 days in harsh conditions. These results highlight the fact that particular attention should be paid to the presence of FLA in hospital water systems, because of their potential implication in survival and growth of pathogenic bacterial species.

First evidence of amoebae-mycobacteria association in drinking water network

Free-living amoebae are protozoa ubiquitously found in water systems. They mainly feed on bacteria by phagocytosis, but some bacterial species are able to resist or even escape this lethal process. Among these amoeba resistant bacteria are numerous members of the genus Mycobacterium. Nontuberculous Mycobacteria (NTM) are opportunistic pathogens that share the same ecological niches as amoebae. While several studies have demonstrated the ability of these bacteria to colonise and persist within drinking water networks, there is also strong suspicion that mycobacteria could use amoebae as a vehicle for protection and even replication. We investigated here the presence of NTM and FLA on a drinking water network during an all year round sampling campaign. We observed that 87.6% of recovered amoebal cultures carried high numbers of NTM. Identification of these amoeba and mycobacteria strains indicated that the main genera found in drinking water networks, that is, Acanthamoeba, Vermamoeba, Echinamoeba, and Protacanthamoeba are able to carry and likely to allow replication of several environmental and potentially pathogenic mycobacteria including M. llatzerense and M. chelonae. Direct Sanger sequencing as well as pyrosequencing of environmental isolates demonstrated the frequent association of mycobacteria and FLA, as they are part of the most represented genera composing amoebae's microbiome. This is the first time that an association between FLA and NTM is observed in water networks, highlighting the importance of FLA in the ecology of NTM.

The novel Legionella pneumophila type II secretion substrate NttC contributes to infection of amoebae Hartmannella vermiformis and Willaertia magna

The type II protein secretion (T2S) system of Legionella pneumophila secretes over 25 proteins, including novel proteins that have no similarity to proteins of known function. T2S is also critical for the ability of L. pneumophila to grow within its natural amoebal hosts, including Acanthamoeba castellanii, Hartmannella vermiformis and Naegleria lovaniensis. Thus, T2S has an important role in the natural history of legionnaires' disease. Our previous work demonstrated that the novel T2S substrate NttA promotes intracellular infection of A. castellanii, whereas the secreted RNase SrnA, acyltransferase PlaC, and metalloprotease ProA all promote infection of H. vermiformis and N. lovaniensis. In this study, we determined that another novel T2S substrate that is specific to Legionella, designated NttC, is unique in being required for intracellular infection of H. vermiformis but not for infection of N. lovaniensis or A. castellanii. Expanding our repertoire of amoebal hosts, we determined that Willaertia magna is susceptible to infection by L. pneumophila strains 130b, Philadelphia-1 and Paris. Furthermore, T2S and, more specifically, NttA, NttC and PlaC were required for infection of W. magna. Taken together, these data demonstrate that the T2S system of L. pneumophila is critical for infection of at least four types of aquatic amoebae and that the importance of the individual T2S substrates varies in a host cell-specific fashion. Finally, it is now clear that novel T2S-dependent proteins that are specific to the genus Legionella are particularly important for L. pneumophila infection of key, environmental hosts.

Your garden hose: a potential health risk due to Legionella spp. growth facilitated by free-living amoebae

Common garden hoses may generate aerosols of inhalable size (≤10 μm) during use. If humans inhale aerosols containing Legionella bacteria, Legionnaires' disease or Pontiac fever may result. Clinical cases of these illnesses have been linked to garden hose use. The hose environment is ideal for the growth and interaction of Legionella and free-living amoebae (FLA) due to biofilm formation, elevated temperatures, and stagnation of water. However, the microbial densities and hose conditions necessary to quantify the human health risks have not been reported. Here we present data on FLA and Legionella spp. detected in water and biofilm from two types of garden hoses over 18 months. By culturing and qPCR, two genera of FLA were introduced via the drinking water supply and reached mean densities of 2.5 log10 amoebae·mL(-1) in garden hose water. Legionella spp. densities (likely including pathogenic L. pneumophila) were significantly higher in one type of hose (3.8 log10 cells·mL(-1), p < 0.0001). A positive correlation existed between Vermamoebae vermiformis densities and Legionella spp. densities (r = 0.83, p < 0.028). The densities of Legionella spp. identified in the hoses were similar to those reported during legionellosis outbreaks in other situations. Therefore, we conclude that there is a health risk to susceptible users from the inhalation of garden hose aerosols.

Improved axenization method reveals complexity of symbiotic associations between bacteria and acanthamoebae

Bacteria associated with free-living amoebae have attracted considerable attention because of their role in human disease and as models for studying endosymbiosis. However, the identification and analysis of such novel associations are hindered by the limitations of methods for isolation and axenization of amoebae. Here, we replaced the heat-inactivated Escherichia coli, which is typically used as food source during axenization, with a live E. coli tolC knockout mutant strain hypersensitive to antibiotics. Together with the addition of otherwise sublethal amounts of ampicillin, this approach tripled the success rate and reduced the time required for axenization by at least 3 days. Using this method for two environmental samples, 10 Acanthamoeba strains were isolated, seven of which contained bacterial symbionts. In three cases, amoebae harbouring two phylogenetically distinct symbionts were recovered, supporting a more widespread occurrence of multi-partner symbiotic associations among free-living amoebae.

Impact of drinking water conditions and copper materials on downstream biofilm microbial communities and Legionella pneumophila colonization

AIMS

This study examined the impact of pipe materials and introduced Legionella pneumophila on downstream Leg. pneumophila colonization and microbial community structures under conditions of low flow and low chlorine residual.

METHODS AND RESULTS

CDC biofilm(™) reactors containing either unplasticized polyvinylchloride (uPVC) or copper (Cu) coupons were used to develop mature biofilms on Norprene(™) tubing effluent lines to simulate possible in-premise biofilm conditions. The microbial communities were characterized through 16S and 18S rRNA gene clone libraries and Leg. pneumophila colonization was determined via specific qPCR assays. The Cu significantly decreased downstream microbial diversity, approximately halved bacterial and eukaryotic abundance, with some groups only detected in uPVC-reactor tubing biofilms. However, some probable amoeba-resisting bacteria (ARB) like Mycobacterium spp. and Rhodobacteraceae were significantly more abundant in the Cu than uPVC-reactor tubing biofilms. In particular, Leg. pneumophila only persisted (postinoculation) within the Cu-reactor tubing biofilms, and the controlled low chlorine residue and water flow conditions led to a general high abundance of possible free-living protozoa in all tubing biofilms. The higher relative abundance of ARB-like sequences from Cu-coupons vs uPVC may have been promoted by amoebal selection and subsequent ARB protection from Cu inhibitory effects.

CONCLUSIONS

Copper pipe and low flow conditions had significant impact on downstream biofilm microbial structures (on plastic pipe) and the ability for Leg. pneumophila colonization post an introduction event.

SIGNIFICANCE AND IMPACT OF THE STUDY

This is the first report that compares the effects of copper and uPVC materials on downstream biofilm communities grown on a third (Norprene(™)) surface material. The downstream biofilms contained a high abundance of free-living amoebae and ARB, which may have been driven by a lack of residual disinfectant and periodic stagnant conditions. Given the prevalence of Cu-piping in buildings, there may be increased risk from drinking water exposures to ARB following growth on pipe/fixture biofilms within premise drinking water systems.

Free-living ciliates as potential reservoirs for eukaryotic parasites: occurrence of a trypanosomatid in the macronucleus of Euplotes encysticus

Background

Flagellates of the family Trypanosomatidae are obligate endoparasites, which can be found in various hosts. Several genera infect insects and occur as monoxenous parasites especially in representatives of Diptera and Hemiptera. These trypanosomatid flagellates probably share the worldwide distribution of their hosts, which are often infested by large numbers of endoparasites. Traditionally, their taxonomy was based on morphology, host origin, and life cycle. Here we report the characterization of a trypanosomatid infection detected in a protozoan, a ciliate collected from a polluted freshwater pond in a suburb of New Delhi (India).

Methods

Live observations and morphological studies applying light, fluorescence and transmission electron microscopy were conducted. Molecular analyses of host and parasite were performed and used for phylogenetic reconstructions and species (host) or genus level (parasite) identification.

Results

Although the morphological characteristics were not revealing, a high similarity of the trypanosomatids 18S rRNA gene sequence to Herpetomonas ztiplika and Herpetomonas trimorpha (Kinetoplastida, Trypanosomatidae), both parasites of biting midges (Culicoides kibunensis and Culicoides truncorum, respectively) allowed the assignment to this genus. The majority of the host population displayed a heavy infection that significantly affected the shape of the host macronucleus, which was the main site of parasite localization. In addition, the growth rate of host cultures, identified as Euplotes encysticus according to cell morphology and 18S rRNA gene sequence, was severely impacted by the infection.

Conclusions

The host-parasite system described here represents a recent example of free-living protists acting as environmental reservoirs for parasitic eukaryotic microorganisms.

Encystment of Vermamoeba (Hartmannella) vermiformis: Effects of environmental conditions and cell concentration

Vermamoeba vermiformis is a free-living amoeba (FLA) which is widely distributed in the environment. It is known to colonize water systems and to be a reservoir of pathogenic bacteria, such as Legionella pneumophila. For these reasons the control of V. vermiformis represents an important health issue. However, FLA may be resistant to disinfection treatments due to the process of encystment. Thereby, it is important to better understand factors influencing this process. In this aim, we investigated the effect of temperature, pH, osmotic pressure and cell concentration on the encystment of two V. vermiformis strains. Encystment was quite fast, with a 100% encystment rate being observed after 9h of incubation. For the two strains, an optimal encystment was obtained at 25 and 37°C. Concerning pH and osmotic pressure, there were different effects on the encystment according to the tested strains. For the reference strain (ATCC 50237), the patterns of encystment were similar for pH comprised between 5 and 9 and for KCl concentrations ranging from 0.05 to 0.2 mol L(-1). For the environmental strain (172A) an optimal encystment was obtained for basic pH (8 and 9) and for a concentration in KCl of 0.1 mol L(-1). The results also clearly demonstrated that the encystment rate increased with cell concentration, suggesting that there is an inter-amoebal communication. The present study establish for the first time environmental conditions favoring encystment and would lay the foundations to better control the encystment of V. vermiformis.

Endosymbiotic Mycobacterium chelonae in a Vermamoeba vermiformis strain isolated from the nasal mucosa of an HIV patient in Lima, Peru

In March 2010, a 35 year-old HIV/AIDS female patient was admitted to hospital to start treatment with Highly Active Antiretroviral Therapy (HAART) since during a routine control a dramatic decrease in the CD4(+) levels was detected. At this stage, a nasal swab from each nostril was collected from the patient to include it in the samples for the case study mentioned above. Moreover, it is important to mention that the patient was diagnosed in 2009 with invasive pneumococcal disease, acute cholecystitis, pancreatitis and pulmonary tuberculosis. The collected nasal swabs from both nostrils were positive for Vermamoeba vermiformis species which was identified using morphological and PCR/DNA sequencing approaches. Basic Local Alignment Search Tool (BLAST) homology and phylogenetic analysis confirmed the amoebic strain to belong to V.vermiformis species. Molecular identification of the Mycobacterium strain was carried out using a bacterial universal primer pair for the 16S rDNA gene at the genus level and the rpoB gene was amplified and sequenced as previously described to identify the Mycobacterium species (Shin et al., 2008; Sheen et al., 2013). Homology and phylogenetic analyses of the rpoB gene confirmed the species as Mycobacterium chelonae. In parallel, collected swabs were tested by PCR and were positive for the presence of V.vermiformis and M.chelonae. This work describes the identification of an emerging bacterial pathogen,M.chelonae from a Free-Living Amoebae (FLA) strain belonging to the species V.vermiformis that colonized the nasal cavities of an HIV/AIDS patient, previously diagnosed with TB. Awareness within clinicians and public health professionals should be raised, as pathogenic agents such as M.chelonae may be using FLA to propagate and survive in the environment.

[Sources and fate of pathogenic microorganisms in aquatic environments]

Un grand nombre d’infections humaines d’origine hydrique sont causées par des micro-organismes qu’il s’agisse de virus, de bactéries ou encore de protozoaires. Ces micro-organismes sont soit naturellement présents dans les environnements aquatiques, soit transférés au sein de ces derniers via des sources d’origine fécale. Ils séjournent dans ces environnements pendant un temps plus ou moins long avant de contaminer un nouvel hôte. Les environnements aquatiques sont soumis à une forte variabilité de leurs paramètres physicochimiques et abritent une vaste communauté microbienne plus ou moins adaptée à ces changements environnementaux. Ainsi les interactions entre les micro-organismes, qu’ils soient pathogènes ou non, sont nombreuses et certaines d’entre elles sont encore aujourd’hui méconnues. L’objectif de cet article est de présenter les interactions connues entre certains micro-organismes pathogènes et le milieu naturel en abordant notamment la diversité des sources de contamination, leur contribution dans la pollution microbiologique des milieux aquatiques, et le devenir des pathogènes dans des environnements notamment au travers des stratégies de survie que certains sont capables de développer.

Prevalence of Acanthamoeba spp. in Tasmanian intensive care clinical specimens

BACKGROUND

Acanthamoebae are ubiquitous free-living environmental amoebae that may occasionally cause keratitis, granulomatous encephalitis, cutaneous lesions and systemic disease in humans. Acanthamoeba spp. have been implicated as a vehicle by which a number of common bacterial causes of healthcare-associated pneumonia may enter the lungs. Limited evidence has been found implicating Acanthamoeba spp. as a primary cause of pneumonia and urinary catheter colonization in intensive care patients.

AIM

To explore the possibility of colonization of the respiratory and urinary tracts of intensive care patients with free-living amoebae.

METHODS

Thirty-nine catheter urines, 50 endotracheal trap sputa and one general ward sputum sample from 45 patients and nine intensive care unit (ICU) environmental water samples were collected during a four-and-half-month period in the Royal Hobart Hospital from August 2011.

FINDINGS

Acanthamoebae were isolated by culture and detected by polymerase chain reaction in two sputum samples from a single patient, taken one week apart. A single Acanthamoeba species isolate was detected by culture only from the ICU environment.

CONCLUSION

Colonization of ICU patients' respiratory tracts with Acanthamoeba spp. does occur. This may have significance for the role of acanthamoebae as a source of bacterial pathogens in intensive therapy patients' respiratory tracts.

Microbiome of free-living amoebae isolated from drinking water

Free-living amoebae (FLA) are protozoa that can be found in water networks where they prey on bacteria within biofilms. Most bacteria are digested rapidly by phagocytosis, however some are able to survive within amoebae and some are even able to multiply, as it is the case for Legionella pneumophila. These resisting bacteria are a potential health problem as they could also resist to macrophage phagocytosis. Several publications already reported intra-amoebal bacteria but the methods of identification did not allow metagenomic analysis and are partly based on co-culture with one selected amoebal strain. The aim of our study was to conduct a rRNA-targeted metagenomic analysis on amoebae and intra-amoebal bacteria found in drinking water network, to provide the first FLA microbiome in environmental strains. Three sites of a water network were sampled during four months. Culturable FLA were isolated and total DNA was prepared, allowing purification of both amoebal and bacterial DNA. Metagenomic studies were then conducted through 18S or 16S amplicons sequencing. Hartmannella was by far the most represented genus of FLA. Regarding intra-amoebal bacteria, 54 genera were identified, among which 21 were newly described intra-amoebal bacteria, underlying the power of our approach. There were high differences in bacterial diversity between the three sites. Several genera were highly represented and/or found at least in two sites, underlying that these bacteria could be able to multiply within FLA. Our method is therefore useful to identify FLA microbiome and could be applied to other networks to have a more comprehensive view of intra-amoebal diversity.

Effect of thermal treatment on free-living amoeba inactivation

AIMS

To evaluate the effect of temperature on two amoeba strains of the genera Acanthamoeba and two amoeba strains of the genera Hartmannella separately treated depending on their life stage, trophozoite or cyst, when cells are directly exposed under controlled conditions.

METHODS AND RESULTS

For thermal treatments, three temperatures were selected 50, 60 and 70°C, and a microcosm was designed using dialysis bags. The inactivation of each strain was determined using a method based on the most probable number quantification on agar plates. The results showed that for all amoeba strains, thermal treatment was more effective against trophozoites compared with cyst stages. The inactivation patterns showed statistical differences between the two genera analysed at temperatures above 50°C. The effectiveness of the thermal treatments at 60 and 70°C was higher for both life stages of Hartmannella vermiformis strains compared with Acanthamoeba strains, being the most resistant Acanthamoeba cysts.

CONCLUSIONS

Free-living amoebae have been isolated in a wide range of environments worldwide due to their capacity to survive under harsh conditions. This capacity is mainly based on the formation of resistant forms, such as double-walled cysts, which confers a high level of resistance as shown here for thermal treatments.

SIGNIFICANCE AND IMPACT OF STUDY

Free-living amoebae survival can promote a rapid recolonization of drinking water systems and is a likely source of emerging opportunistic pathogens such as Legionella. Because of that a better understanding of the factors that affect micro-organism inactivation in water systems would allow more efficient application of disinfection treatments.

Discovery of new intracellular pathogens by amoebal coculture and amoebal enrichment approaches

Intracellular pathogens such as legionella, mycobacteria and Chlamydia-like organisms are difficult to isolate because they often grow poorly or not at all on selective media that are usually used to cultivate bacteria. For this reason, many of these pathogens were discovered only recently or following important outbreaks. These pathogens are often associated with amoebae, which serve as host-cell and allow the survival and growth of the bacteria. We intend here to provide a demonstration of two techniques that allow isolation and characterization of intracellular pathogens present in clinical or environmental samples: the amoebal coculture and the amoebal enrichment. Amoebal coculture allows recovery of intracellular bacteria by inoculating the investigated sample onto an amoebal lawn that can be infected and lysed by the intracellular bacteria present in the sample. Amoebal enrichment allows recovery of amoebae present in a clinical or environmental sample. This can lead to discovery of new amoebal species but also of new intracellular bacteria growing specifically in these amoebae. Together, these two techniques help to discover new intracellular bacteria able to grow in amoebae. Because of their ability to infect amoebae and resist phagocytosis, these intracellular bacteria might also escape phagocytosis by macrophages and thus, be pathogenic for higher eukaryotes.

Behavior of Yersinia enterocolitica in the presence of the bacterivorous Acanthamoeba castellanii

Free-living protozoa play an important role in the ecology and epidemiology of human-pathogenic bacteria. In the present study, the interaction between Yersinia enterocolitica, an important food-borne pathogen, and the free-living amoeba Acanthamoeba castellanii was studied. Several cocultivation assays were set up to assess the resistance of Y. enterocolitica to A. castellanii predation and the impact of environmental factors and bacterial strain-specific characteristics. Results showed that all Y. enterocolitica strains persist in association with A. castellanii for at least 14 days, and associations with A. castellanii enhanced survival of Yersinia under nutrient-rich conditions at 25°C and under nutrient-poor conditions at 37°C. Amoebae cultivated in the supernatant of one Yersinia strain showed temperature- and time-dependent permeabilization. Intraprotozoan survival of Y. enterocolitica depended on nutrient availability and temperature, with up to 2.8 log CFU/ml bacteria displaying intracellular survival at 7°C for at least 4 days in nutrient-rich medium. Transmission electron microscopy was performed to locate the Yersinia cells inside the amoebae. As Yersinia and Acanthamoeba share similar ecological niches, this interaction identifies a role of free-living protozoa in the ecology and epidemiology of Y. enterocolitica.

First report of a Chinese PFOS alternative overlooked for 30 years: its toxicity, persistence, and presence in the environment

This is the first report on the environmental occurrence of a chlorinated polyfluorinated ether sulfonate (locally called F-53B, C8ClF16O4SK). It has been widely applied as a mist suppressant by the chrome plating industry in China for decades but has evaded the attention of environmental research and regulation. In this study, F-53B was found in high concentrations (43-78 and 65-112 μg/L for the effluent and influent, respectively) in wastewater from the chrome plating industry in the city of Wenzhou, China. F-53B was not successfully removed by the wastewater treatments in place. Consequently, it was detected in surface water that receives the treated wastewater at similar levels to PFOS (ca. 10-50 ng/L) and the concentration decreased with the increasing distance from the wastewater discharge point along the river. Initial data presented here suggest that F-53B is moderately toxic (Zebrafish LC50-96 h 15.5 mg/L) and is as resistant to degradation as PFOS. While current usage is limited to the chrome plating industry, the increasing demand for PFOS alternatives in other sectors may result in expanded usage. Collectively, the results of this work call for future assessments on the effects of this overlooked contaminant and its presence and fate in the environment.