Application of laser scanning cytometry followed by epifluorescent and differential interference contrast microscopy for the detection and enumeration of Cryptosporidium and Giardia in raw and potable waters

A summary of cryptosporidiosis outbreaks reported in France and overseas departments, 2017-2020

Cryptosporidium is a known foodborne pathogen, ranked fifth out of 24 among foodborne parasites in terms of importance and a cause of many cryptosporidiosis outbreaks worldwide. In France, very few outbreaks were reported before 2017, and data recently obtained by the Expert Laboratory of the Cryptosporidiosis National Reference Center (CNR-LE-Cryptosporidiosis) have shown that outbreaks are in fact common and frequently underreported. In this work, we aim to report the characteristics of outbreaks detected in France during the period 2017-2020 and present a summary of investigations carried out by the CNR-LE-Cryptosporidiosis. During the study period, there were eleven cryptosporidiosis outbreaks, including three with no identified origin. Among the eight identified outbreaks: six were due to water contamination (five tap water and one recreational water), one was due to direct contact with infected calves, and one was due to consumption of contaminated curd cheese. Among these outbreaks, five of them exceeded one hundred cases. Recent results obtained by the CNR-LE-Cryptosporidiosis revealed the multiannual occurrence of Cryptosporidium outbreaks in France. Waterborne outbreaks were more frequently detected, while foodborne outbreaks which are more difficult to detect were likely underreported.

Label-free detection of Giardia lamblia cysts using a deep learning-enabled portable imaging flow cytometer

We report a field-portable and cost-effective imaging flow cytometer that uses deep learning and holography to accurately detect Giardia lamblia cysts in water samples at a volumetric throughput of 100 mL h-1. This flow cytometer uses lens free color holographic imaging to capture and reconstruct phase and intensity images of microscopic objects in a continuously flowing sample, and automatically identifies Giardia lamblia cysts in real-time without the use of any labels or fluorophores. The imaging flow cytometer is housed in an environmentally-sealed enclosure with dimensions of 19 cm × 19 cm × 16 cm and weighs 1.6 kg. We demonstrate that this portable imaging flow cytometer coupled to a laptop computer can detect and quantify, in real-time, low levels of Giardia contamination (e.g., <10 cysts per 50 mL) in both freshwater and seawater samples. The field-portable and label-free nature of this method has the potential to allow rapid and automated screening of drinking water supplies in resource limited settings in order to detect waterborne parasites and monitor the integrity of the filters used for water treatment.

Whole cell hybridisation for monitoring harmful marine microalgae

Fluorescence in situ hybridisation (FISH) is a powerful molecular biological tool to detect and enumerate harmful microorganism in the marine environment. Different FISH methods are available, and especially in combination with automated counting techniques, the potential for a routine monitoring of harmful marine microalgae is attainable. Various oligonucleotide probes are developed for detecting harmful microalgae. However, FISH-based methods are not yet regularly included in monitoring programmes tracking the presence of harmful marine microalgae. A limitation factor of the FISH technique is the currently available number of suited fluorochromes attached to the FISH probes to detect various harmful species in one environmental sample at a time. However, coupled automated techniques, like flow cytometry or solid-phase cytometry, can facilitate the analysis of numerous field samples and help to overcome this drawback. A great benefit of FISH in contrast to other molecular biological detection methods for harmful marine microalgae is the direct visualisation of the hybridised target cells, which are not permitted in cell free formats, like DNA depending analysis methods. Therefore, an additional validation of the FISH-generated results is simultaneously given.

Detection of waterborne parasites using field-portable and cost-effective lensfree microscopy

Protection of human health and well-being through water quality management is an important goal for both the developed and the developing parts of the world. In the meantime, insufficient disinfection techniques still fail to eliminate pathogenic contaminants in freshwater as well as recreational water resources. Therefore, there is a significant need for screening of water quality to prevent waterborne outbreaks and incidents of water-related diseases. Toward this end, here we investigate the use of a field-portable and cost-effective lensfree holographic microscope to image and detect pathogenic protozoan parasites such as Giardia Lamblia and Cryptosporidium Parvum at low concentration levels. This compact lensless microscope (O. Mudanyali et al., Lab Chip, 2010, 10, 1417-1428), weighing approximately 46 grams, achieves a numerical aperture of approximately 0.1-0.2 over an imaging field of view that is more than an order of magnitude larger than a typical 10X objective lens, and therefore may provide an important high-throughput analysis tool for combating waterborne diseases especially in resource limited settings.

Detection and surveillance of waterborne protozoan parasites

The majority of the world's population still live without access to healthy water and the contamination of drinking water with protozoan pathogens poses a serious threat to millions of people in the developing world. Even in the developed world periodic outbreaks of diarrhoeal diseases are caused by the protozoan parasites Cryptosporidium sp., Giardia duodenalis and Entamoeba histolytica. Thus, surveillance of drinking water is imperative to minimize such contaminations and ensure continuous supplies of healthy water world-wide. This article reviews the progress in technology for detection and surveillance of these important waterborne parasites.

Pilot-scale evaluation of UV reactors' efficacy against in vitro infectivity of Cryptosporidium parvum oocysts

An experimental protocol was developed to assess the efficacy of two UV reactors (medium-pressure UVaster), and a low-pressure reactor) on the infectivity of Cryptosporidium parvum oocysts under conditions mimicking small- or medium-size water distribution units. The protocol included purification of large amounts of viable oocysts from experimentally infected calf feces, pilot spiking, sample concentration and purification after UV radiation, oocyst quantification and in vitro evaluation of oocyst infectivity on HCT-8 cells. Water samples were collected at intervals upstream and downstream from the UV reactor after spiking. Oocysts were concentrated by centrifugation, purified by immunomagnetic capture and quantified using laser-scanning cytometry. An enhanced in vitro infectivity test on HCT-8 cells was developed, where oocysts were pretreated in order to obtain maximized in vitro infectivity, and infectious foci were enumerated after immunofluorescence staining after 3 days of culture. This method was superior to viability measured by excystation for assessing oocyst infectivity. The infectivity rate of untreated oocysts ranged between 9% and 30% in replicate experiments. The method allowed us to determine inactivation rates >4.92 (log) with UVaster and >4.82 with the LP reactor after exposition of oocysts to an effective dose of 400 J m(-2) at flow rates of 15 and 42 m(3) h(-1), respectively.

Comparative study between two laser scanning cytometers and epifluorescence microscopy for the detection ofCryptosporidium oocysts in water

BACKGROUND

Cryptosporidium detection in water and environmental samples has increased during the last years, largely due to an increase in the number of reported waterborne outbreaks of cryptosporidiosis and the implementation of new regulations about Cryptosporidium monitoring in water supplies. The aim of this study was to validate and compare the capacity of two laser scanning cytometers commercially available (LSC and ChemScanRDI), against manual microscopic enumeration of Cryptosporidium oocysts in surface water and reference material samples.

METHODS

Reference material and surface water samples were analysed by two laser scanning cytometers methodologies and by manual epifluorescence microscopy. Two mAbs from commercial suppliers were used to evaluate background reduction.

RESULTS

Highly significant correlations were obtain between both cytometers (R(2) = 0.99) and with manual microscopy (R(2) = 0.98), showing that oocysts counts made by cytometers were equivalent to those obtained with conventional methods. We observed a variability in oocysts counts when different antibodies where used with laser scanning cytometers and manual microscopy.

CONCLUSIONS

This study showed the efficacy of the laser scanning technology (LSC and ChemScanRDI), as an automated and a more standardized alternative to manual epifluorescence microscopy examination, for Cryptosporidium detection in water samples. High quality antibodies are needed for automated enumeration as well as for manual microscope observations.

Detection of Cryptosporidium, Giardia and Enterocytozoon bieneusi in surface water, including recreational areas: a one-year prospective study

Accidental ingestion of natural waters while bathing carries a risk of infection by waterborne protozoa such as Cryptosporidium, Giardia and, possibly, microsporidia. In order to evaluate this risk, we conducted a one-year prospective study of two recreational lakes and three river sites located near Paris, where bathing and boating are frequent. Twenty-litre water samples were collected monthly from each site. Concentrated samples were submitted to immunomagnetic separation followed by immunofluorescence (IMS-IF) for Cryptosporidium and Giardia detection. PCR and PCR restriction fragment length polymorphism (PCR-RFLP) were used for the genetic characterization of Cryptosporidium species on IMS-IF-positive samples. PCR were systematically performed to detect Enterocytozoon bieneusi. Bacteria counts were also determined. IMS-IF revealed low counts of Giardia cysts and Cryptosporidium oocysts in the recreational lakes, with occasional peaks (max. 165 cysts/10 L and 9 oocysts/10 L). By contrast, the river sites were consistently and sometimes heavily contaminated throughout the year. Enterocytozoon bieneusi was found in only two river samples. PCR-RFLP genotyping showed the presence of C. hominis and C. parvum. No correlation was found between the presence or counts of parasites and bacteria, except between the presence of Giardia and high counts of Escherichia coli and enterococci. Based on a previously developed model for quantitative risk assessment of waterborne parasitic infections, we estimated that the mean risk of infection by Cryptosporidium and Giardia associated with swimming was <10(-4) in the recreational lakes, and frequently higher at the river sites.

Occurrence of Cryptosporidium spp. oocysts in raw and treated sewage and river water in north-eastern Spain

AIMS

To determine the occurrence and levels of Cryptosporidium parvum oocysts in wastewater and surface waters in north-eastern Spain.

METHODS AND RESULTS

Samples from five sewage treatment plants were taken monthly and quarterly during 2003. In addition, water was collected monthly from the River Llobregat (NE Spain) during the period from 2001 to 2003. All samples were analysed by filtration on cellulose acetate filters or through Envirocheck using EPA method 1623, followed by immunomagnetic separation and examination by laser scanning cytometry. All raw sewage, secondary effluent and river water samples tested were positive for Cryptosporidium oocysts. Of the tertiary sewage effluents tested, 71% were positive for Cryptosporidium oocysts. The proportion of viable oocysts varied according to the sample.

CONCLUSIONS

Two clear maxima were observed during spring and autumn in raw sewage, showing a seasonal distribution and a correlation with the number of cryptosporidiosis cases and rainfall events.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study provides the first data on the occurrence of Cryptosporidium oocysts in natural waters in north-eastern Spain.

Nondestructive measurement of an optical fiber refractive-index profile by a transmitted-light differential interference contact microscope

A novel transmitted-light differential interference contrast (DIC) system is used for nondestructive measurement of the refractive-index profile (RIP) of an optical fiber. By means of this system the phase of a measured light beam can be modulated with an analyzer, and the phase distribution of a fiber is obtained by calculation of the various interference patterns. The measurement theory and structure and some typical applications of this system are demonstrated. The results of measuring RIPs in graded-index fiber are presented. Both the experimental results and theoretical analysis show that the system takes the advantage of high index resolution and of sufficient measurement accuracy for measuring the refractive index of the optical fiber. The system has strong ability to overcome environmental disturbance because of its common-path design. Moreover, one can use the system to measure the RIP along the fiber axis and acquire an image of the three-dimensional RIP of the fiber.