Last data update: May 13, 2024. (Total: 46773 publications since 2009)
Records 1-4 (of 4 Records) |
Query Trace: Villegas EN[original query] |
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Differences in staining intensities affects reported occurrences and concentrations of Giardia spp. in surface drinking water sources
Alderisio KA , Villegas LF , Ware MW , McDonald LA , Xiao L , Villegas EN . J Appl Microbiol 2017 123 (6) 1607-1613 AIM: USEPA Method 1623, or its equivalent, is currently used to monitor for protozoan contamination of surface drinking water sources worldwide. At least three approved staining kits used for detecting Cryptosporidium and Giardia are commercially available. This study focuses on understanding the differences among staining kits used for Method 1623. METHODS AND RESULTS: Merifluor and EasyStain labeling kits were used to monitor Cryptosporidium oocyst and Giardia cyst densities in New York City's raw surface water sources. In the year following a change to the approved staining kits for use with Method 1623, an anomaly was noted in the occurrence of Giardia cysts in New York City's raw surface water. Specifically, Merifluor-stained samples had higher Giardia cyst densities as compared with those stained with EasyStain. Side by side comparison revealed significantly lower fluorescence intensities of Giardia muris as compared with G. duodenalis cysts when labeled with EasyStain. CONCLUSIONS: This study showed very poor fluorescence intensity signals by EasyStain on G. muris cysts results in lower cyst counts, while Merifluor, with its broader Giardia cyst staining specificity, results in higher cyst counts, when using Methods 1623. SIGNIFICANCE AND IMPACT OF STUDY: These results suggest that detected Giardia cyst concentrations are dependent on the staining kits used, which can result in a more or less conservative estimation of occurrences and densities of zoonotic Giardia cysts by detecting a broader range of Giardia species/Assemblages. |
Human infective potential of Cryptosporidium spp., Giardia duodenalis and Enterocytozoon bieneusi in urban wastewater treatment plant effluents.
Ma J , Feng Y , Hu Y , Villegas EN , Xiao L . J Water Health 2016 14 (3) 411-423 Cryptosporidiosis, giardiasis, and microsporidiosis are important waterborne diseases. In the standard for wastewater treatment plant (WWTP) effluents in China and other countries, the fecal coliform count is the only microbial indicator, raising concerns about the potential for pathogen transmission through WWTP effluent reuse. In this study, we collected 50 effluent samples (30 L/sample) from three municipal WWTPs in Shanghai, China, and analyzed for Cryptosporidium spp., Giardia duodenalis and Enterocytozoon bieneusi by microscopy and/or polymerase chain reaction (PCR). Moreover, propidium monoazide (PMA)-PCR was used to assess the viability of oocysts/cysts. The microscopy and PCR-positive rates for Cryptosporidium spp. were 62% and 40%, respectively. The occurrence rates of G. duodenalis were 96% by microscopy and 92-100% by PCR analysis of three genetic loci. Furthermore, E. bieneusi was detected in 70% (35/50) of samples by PCR. Altogether, 10 Cryptosporidium species or genotypes, two G. duodenalis genotypes, and 11 E. bieneusi genotypes were found, most of which were human-pathogenic. The chlorine dioxide disinfection employed in WWTP1 and WWTP3 failed to inactivate the residual pathogens; 93% of the samples from WWTP1 and 83% from WWTP3 did not meet the national standard on fecal coliform levels. Thus, urban WWTP effluents often contain residual waterborne human pathogens. |
Conference report: The 6th International Symposium on Waterborne Pathogens
Rochelle PA , Klonicki PT , Di Giovanni GD , Hill VR , Akagi Y , Villegas EN . J Am Water Works Assoc 2015 107 (10) 24-32 There have been substantial improvements in preventing waterborne disease and outbreaks in developed countries over the past two decades. Consequently, it can be easy to get complacent about pathogens in drinking water in the absence of large, well-publicized waterborne disease outbreaks such as Milwaukee, Wis., in 1993 and Clark County, Nev., in 1994 (Goldstein et al. 1996, MacKenzie et al. 1994). However, waterborne microbial diseases are still a cause of substantial morbidity (and some mortality), even in developed countries; for example, an estimated 4 million to 16 million cases of waterborne gastroenteritis occur annually in the United States (Colford et al. 2006, Messner et al. 2006). Therefore, persistent vigilance is required to continue controlling the risks posed by waterborne pathogens. | Pathogens in drinking water have received considerable media attention recently in the United States. Over the past 10 years, Legionella has become the most frequent cause of waterborne disease outbreaks in the United States, as shown in Figure 1 (Beer et al. 2015). Also, a cryptosporidiosis outbreak in Oregon in 2013 (Oregon Health Authority 2014) was the first time since Clark County, Nev., over 20 years ago in which a US disease outbreak was linked to municipal drinking water. And setting an unwelcome precedent, the first cases of fatal primary amoebic meningoencephalitis (caused by N. fowleri) linked to treated municipal drinking water were reported in 2012 in Louisiana (Yoder et al. 2012). Therefore, it is not surprising that all three of these pathogens were discussed in detail at the 6th ISWP. This symposium, which is organized every three to five years by AWWA’s Organisms in Water Committee, provides a forum to discuss all aspects of pathogen occurrence, detection, and treatment in water. | The 2015 meeting hosted 141 attendees from six countries—the United States, Japan, the United Kingdom, Canada, the Netherlands, and New Zealand; attendees represented water utilities, academia, public health and other government agencies, equipment manufacturers, and environmental consulting firms. Speaker affiliations and locations are shown in Table 1. In addition to sessions and discussions about the three pathogens noted here, two days of intense, single-track sessions covered P. aeruginosa, Norovirus, toxigenic E. coli, fecal indicator bacteria, pathogen risk modeling, water reuse, pathogens in wastewater, and antibiotic-resistant bacteria. |
Development and Evaluation of Three Real-time PCR Assays for Genotyping and Source Tracking Cryptosporidium in Water.
Li N , Neumann NF , Ruecker N , Alderisio KA , Sturbaum GD , Villegas EN , Chalmers R , Monis P , Feng Y , Xiao L . Appl Environ Microbiol 2015 81 (17) 5845-54 The occurrence of Cryptosporidium oocysts in drinking source water can present a serious public health risk. To rapidly and effectively assess the source and human-infective potential of Cryptosporidium oocysts in water, sensitive detection and correct identification of oocysts to the species level (genotyping) are essential. In this study, we developed three real-time PCR genotyping assays, two targeting the small subunit (SSU) rRNA gene (18S-LC1 and 18S-LC2 assays) and one targeting the 90 kDa heat shock protein (hsp90) gene (hsp90 assay), and evaluated the sensitivity and Cryptosporidium species detection range of these assays. Using fluorescence resonance energy transfer probes and melt curve analysis, the 18S-LC1 and hsp90 assay could differentiate common human-pathogenic species (C. parvum, C. hominis, and C. meleagridis), while the 18S-LC2 assay was able to differentiate non-pathogenic species (such as C. andersoni) from human-pathogenic ones commonly found in source water. In sensitivity evaluations, the 18S-LC2 and hsp90 genotyping assays could detect as few as one Cryptosporidium oocyst per sample. Thus, the 18S-LC2 and hsp90 genotyping assays might be used in environmental monitoring, whereas the 18S-LC1 genotyping assay could be useful for genotyping Cryptosporidium spp. in clinical specimens or wastewater samples. |
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