Effects of glass bead size, vortexing speed and duration on Eimeria acervulina oocyst excystation

Multicenter comparative study of Enterocytozoon bieneusi DNA extraction methods from stool samples, and mechanical pretreatment protocols evaluation

Nowadays, the use of qPCR for the diagnosis of intestinal microsporidiosis is increasing. There are several studies on the evaluation of qPCR performance but very few focus on the stool pretreatment step before DNA extraction, which is nevertheless a crucial step. This study focuses on the mechanical pretreatment of stools for Enterocytozoon bieneusi spores DNA extraction. Firstly, a multicenter comparative study was conducted evaluating seven extraction methods (manual or automated) including various mechanical pretreatment. Secondly, several durations and grinding speeds and types of beads were tested in order to optimize mechanical pretreatment. Extraction methods of the various centers had widely-varying performances especially for samples with low microsporidia loads. Nuclisens® easyMAG (BioMérieux) and Quick DNA Fecal/Soil Microbe Microprep kit (ZymoResearch) presented the best performances (highest frequencies of detection of low spore concentrations and lowest Ct values). Optimal performances of mechanical pretreatment were obtained by applying a speed of 30 Hz during 60 s with the TissueLyser II (Qiagen) using commercial beads of various materials and sizes (from ZymoResearch or MP Biomedicals). Overall, the optimal DNA extraction method for E. bieneusi spores contained in stool samples was obtained with a strong but short bead beating using small-sized beads from various materials.

Comparative Study of Eleven Mechanical Pretreatment Protocols for Cryptosporidium parvum DNA Extraction from Stool Samples

Nowadays, many commercial kits allow the polymerase chain reaction (PCR) detection of Cryptosporidium deoxyribonucleic acid (DNA) in stool samples, the efficiency of which relies on the extraction method used. Mechanical pretreatment of the stools using grinding beads has been reported to greatly improve this extraction step. However, optimization of this key step remains to be carried out. Indeed, many parameters could influence the pretreatment performances, among which the modulation of the speed and duration of the grinding step, in addition to the physicochemical features of the grinding beads, have never been evaluated to date. In this study, eleven commercial mechanical pretreatment matrixes (Lysis matrix tubes^®, MP Biomedical, Irvine, CA, USA) composed of beads with different sizes, shapes, and molecular compositions, were evaluated for their performances in improving Cryptosporidium parvum oocyst DNA extraction before amplification by using our routinely used real-time PCR method. As expected, the eleven commercial mechanical pretreatment matrixes showed varying performances depending on the composition, size, and shape. All in all, the best performances were obtained when using the Lysing matrix, including ceramic beads with a median size (diameter of 1.4 mm).

Autophagy induced by monensin serves as a mechanism for programmed death in Eimeria tenella

Monensin (Mon), the first ionophoric antibiotic has widely been used for the treatment and prevention of coccidiosis in poultry until recently, however, at present; its efficacy has been compromised with the emergence of many Mon-resistant strains. Knowledge of the mode of the action of anti-parasitic agents is as important as for other antimicrobials, especially for discovery and long term use of the existing drugs. However, little is known about anti-parasitic drug: monensin's, mechanism of action and physiological alteration in Eimeria tenella. In this study, we explored Mon effects on the viability of Mon-Sensitive GZ (MonS-GZ) and Mon-Resistant GZ (MonR-GZ) Eimeria tenella strains using trypan blue staining and investigated Mon-induced autophagy using Western blotting, indirect immunofluorescence assay, and transmission electron microscopy. The results showed that monensin leads to programmed death of E. tenella parasites by inducing autophagy as a mechanism of anticoccidial action. Mon-induced autophagy was indicated by the decreased sporozoites survival rate, ATG8 over expression and localization, and intracellular vacuolar structures and autophagosomes formation in MonS-GZ strain while in MonR-GZ strains autophagy pathway was not triggered. The autophagy inhibitor 3-methyladenine (3-MA) effectively blocked programmed cell death and saved the MonS-GZ sporozoites. These findings indicated that autophagy serves as a potentially important mechanism of E. tenella cell death in response to Mon and disruption of the autophagy pathway may lead to emergence of drug resistance against this anti-parasitic drug.

Multicenter Comparative Study of Six Cryptosporidium parvum DNA Extraction Protocols Including Mechanical Pretreatment from Stool Samples

BACKGROUND

Nowadays, many commercial kits allow the detection of Cryptosporidium sp. in stool samples after deoxyribonucleic acid (DNA) extraction. Protocols of stool pretreatment have been proposed to optimize oocysts' DNA extraction. Among them, mechanical grinding was reported to improve the performance of Cryptosporidium oocysts' DNA extraction.

METHODS

A multicenter comparative study was conducted within the framework of the French National Reference Center-Expert Laboratory for Cryptosporidiosis. Six extraction systems (i.e., manual or automated) associated with various mechanical pretreatment protocols, were compared for the Cryptosporidium parvum oocyst' DNA extraction, before amplification using the same real-time PCR method targeting.

RESULTS

The sensitivity of real-time PCR assay was unequally impacted by the pretreatment/extraction protocol. We observed significant differences for the lowest concentrations of C. parvum oocysts (i.e., 0-94.4% and 33.3-100% respectively for 10 and 50 oocysts/mL). All in all, the protocol using Quick DNA Fecal/Soil Microbe-Miniprep® manual kit showed the best performances. In addition, optimal performances of mechanical pretreatment were obtained by combining a grinding duration of 60 s with a speed of 4 m/s using Fastprep24® with Lysing Matrix E®.

CONCLUSIONS

Sample pretreatment, as well as the extraction method, needs to be properly adapted to improve the diagnostic performances of the C. parvum DNA amplification methods.

Effect of different floatation solutions on E. tenella oocyst purification and optimization of centrifugation conditions for improved recovery of oocysts and sporocysts

Saturated salt floatation method is widely used for coccidian oocyst purification. However, the repeated procedures and inefficient oocysts recovery rate are a continuous challenge. This study aimed to investigate the best suitable floatation solution, along with optimal centrifugation speed and time for Eimeria tenella (E. tenella) oocyst and sporocyst purification. Different floatation solutions i-e, saturated salt, Sheather's sugar and sodium hypochlorite (NaClO) at 20-60% concentrations were used to purify oocyst. It was found that about 96.99% oocysts (8609×g for 10 min) were recovered under these conditions without any effect on the viability of sporocysts. The recovery rate of oocysts using 50% NaClO (V/V) was significantly higher than 35% saturated salt flotation solution (P < 0.05). The optimal method for purification of oocysts based our experimentation was centrifugation at 8609×g for 3 min using 50% NaClO floatation solution, and the optimized centrifugation conditions for improved recovery of sporocysts (about 99.3%) were at 2152×g for 5 min. The present study provided a better method for the coccidian oocyst purification, which could be successfully adopted as a better alternative to existing techniques commonly used for investigations/research pertaining to coccidia.

Direct and sensitive detection of a microsporidian parasite of bumblebees using loop-mediated isothermal amplification (LAMP)

The reduction of bumblebee populations has been reported in the last decades, and the microsporidian parasite Nosema bombi is considered as one of the factors contributing to such reduction. Although the decline of bee populations affects both wild plants and human food supply, the effects of Nosema spp. infections are not known because it is difficult to obtain infective spores from wild bees due to their low prevalence. Microscopical observation of fecal samples or midgut homogenates and/or PCR are generally used for N. bombi detection. However, the germination rate of microsporidian spore declines if they are kept at 4 °C for a long time or frozen. It is therefore crucial to minimize the diagnosis and isolation time of infective spores from field-collected samples. Therefore, we performed a loop-mediated isothermal amplification (LAMP) assay for the direct detection of N. bombi in bumblebee midgut homogenates. Using this method, we could detect N. bombi from individuals from which it was visible under the microscope and directly from wild individuals.

Selection and characterization of a precocious line of Eimeria media

Coccidiosis, caused by the infection of Eimeria parasites, is one of the most common diseases in domestic rabbits. Live anticoccidial vaccine formulated with attenuated precocious lines of pathogenic eimerian parasites is expected to be valuable for the control of rabbit coccidiosis as a similar strategy to produce anticoccidial vaccines against chicken coccidiosis has being used for several decades. Eimeria media, moderate pathogenic, is widespread in China. Therefore, attenuated anticoccidial vaccines against rabbit coccidiosis should contain vaccine strain(s) of E. media. In this study, a precocious line of E. media (Empre) was selected by collecting and propagating the early excreted oocysts with 16 successive generations. The prepatent period of Empre reduced from 108 h of its parental strain (Emwt) to 70 h. The fecundity of Empre was about 1/10 to 1/3 lower than that of Emwt. Each sporocyst of Empre sporulated oocyst contained only one large refractile body instead of two smaller ones seen in the parental strain. When vaccinated with 1 × 10³ or 1 × 10⁴ precocious line oocysts, the rabbits were completely protected against homologous challenge with the parental strain 14 days post challenge by terms of body weight gain and oocyst output counting, indicating the efficacy of Empre. Meanwhile, all immunized rabbits showed no clinical sign post immunization, indicating the safety of Empre. For co-immunization, 1 × 10³Empre oocysts and 5 × 10² oocysts of a precocious line of E. intestinalis (EIP8) were inoculated to each rabbit in a trial. No diarrhea or mortality was found after vaccination, and the weight gains of the vaccinated group were similar to that of unvaccinated-unchallenged control (UUC) group, while the weight gains of the vaccinated group were similar to that of unvaccinated-unchallenged control (UUC) group (P > 0.05), but significantly higher than that of UCC group (P < 0.01) after challenge, indicating it is safe and effective when using co-immunization. These results together show that Empre, as a precocious line, is a good candidate of precocious line of E. media for anticoccidial vaccine development.

The effect of autophagy on the survival and invasive activity of Eimeria tenella sporozoites

Autophagy is a cellular process that is vital for the maintenance of homeostasis in eukaryotic cells. Currently, autophagy-related genes (atgs) in the Eimeria tenella genome database have been reported, but very little is known about the effects of autophagy on the survival and invasive activity of this protozoan. In this study, we investigated the autophagy in E. tenella sporozoites under starvation and autophagy-modulators treatments and evaluated the autophagy influence on cellular adenosine triphosphate (ATP) levels, the survival rate and the invasive activity of the sporozoites. The results showed that the autophagy could be induced in the sporozoites by starvation or inducer rapamycin (RP), but it could be inhibited by 3-methyladenine (3-MA) treatment. The sporozoites after starvation and RP-treatment displayed punctate signals of EtATG8 and formed autophagosomes. The survival rate of the sporozoites under starvation was significantly lower than that in the control group, whereas the ATP levels in sporozoite were far greater than those in the control. The quantitative real-time reverse transcriptase polymerase chain reaction (qRT-PCR) showed that the invasive activity of the sporozoites was up- and down-regulated by RP and 3-MA induction, respectively. Our results indicate that autophagy has effects on the survival and invasive activity of E. tenella sporozoites, which may provide new insights into anti-coccidial drugs.

Oocyst-Shedding Patterns of Three Eimeria Species in Chickens and Shedding Pattern Variation Depending on the Storage Period of Eimeria tenella Oocysts

Various species of Eimeria have different prepatent times and predilection sites, but their life cycles in infected poultry are similar. Practically speaking, chickens can be continuously exposed to various Eimeria species through environmental contamination. Furthermore, storage condition of the oocysts influences subsequent challenge infectivity, since coccidian oocysts contain a polysaccharide energy source known as amylopectin that is required for sporulation of oocysts and survival of the sporozoites. Here analysis of the oocyst-shedding patterns of 3 Eimeria species ( Eimeria acervulina, Eimeria maxima, and Eimeria tenella) and the effects of different oocyst storage time (64, 143, 225, and 332 days) on subsequent propagation patterns were evaluated. Based on the analysis of oocyst-shedding patterns and infectious lesions evaluated by oocyst counts and histopathology, respectively, the peak points of oocyst production and infectious lesion generation in animals infected with E. acervulina were observed to occur earlier in comparison to E. maxima- and E. tenella-infected animals. Prolonged storage of E. tenella oocysts decreased oocyst excretion (measured as oocysts per gram of feces [OPG]) and lengthened the peak period. Chickens infected with the freshest oocysts (Group A) had the highest fecal oocyst output, and animals in this group reached their peak at 7 days post-infection (dpi), which is similar to the normal pattern of oocyst output in fresh isolates. Infection with oocysts stored for longer periods showed a 1-day delay in the fecal oocyst peak count (8 dpi), and these infections also resulted in fewer OPG compared to Group A. Therefore, these results indicate that the storage period is important in affecting the peak point and pattern of oocyst shedding.