Microbiology in relation to nuclear waste repository safety

V současnosti je všeobecně přijímaná strategie managementu a ukládání radioaktivního odpadu v úložišti hluboko v geologickém masivu. Zatímco fyzikálně-chemické aspekty úložiště jsou již desetiletí pečlivě studované s cílem zajistit jeho dlouhodobou bezpečnost, vliv mikroorganizmů byl ještě nedávno podceňovaný, i když je známo, že mikroorganizmy dokáží přežít a rozmnožovat se i v podmínkách úložiště. Metabolicky různorodé anaerobní mikroorganizmy, které jsou přítomné v podzemní vodě i bentonitech, mohou negativně ovlivňovat dlouhodobou bezpečnost úložiště. Tato disertace je proto zaměřená na studium vlivu mikrobiálních procesů v úložišti radioaktivních odpadů. Konkrétně je zaměřená na mikrobiální aktivitu a životaschopnost v simulovaných podmínkám, které mohou nastat v úložišti. Byl studován vliv různých dávek radioaktivního záření, vývoj mikrobiálního společenstva při různých koncentracích živin a interakce mikroorganizmů s bentonitem a betonem. Dále byla studovaná mikrobiálně ovlivněná koroze uhlíkové oceli v anaerobních podmínkách. Všechny experimenty, s výjimkou ozařovacího, byly provedené v anaerobním boxu s koncentrací plynného kyslíku do 1 ppm. Výsledky byly získány pomocí multidisciplinárního přístupu kombinujícího elektronovou mikroskopii, elektrochemickou impedanční spektroskopii s molekulárně biologickými metodami NGS sekvenování a kvantitativní PCR. Chemické analýzy byly provedené pomocí iontové chromatografie a spektroskopie. Nejčastěji byly detekovány anaerobní mikroorganizmy zahrnující sírany, železo a dusičnany redukující bakterie. Gama záření o celkové dávce 19656 Gy a konstantním dávkovém příkonu 13 Gy/h, nedokázalo úplně zničit bakterie v bentonitu. Bakterie také značně ovlivnily rychlost koroze uhlíkové oceli v porovnání se vzorky, které byly inkubované ve sterilních podmínkách. Například hustota populace bakterie rodu Methyloversatilis pozitivně korelovala s rychlostí koroze. Byla také potvrzena přítomnost mackinawitu, pravděpodobného produktu koroze indukované síran redukujícími bakteriemi. Dále bylo ukázáno, že přítomnost betonu, ačkoli obsahuje bohatou přirozenou mikroflóru, významným způsobem snižovala celkové početnosti přirozených bentonitových bakterií ve studovaných vzorcích a obzvláště potlačovala růst síran redukujících bakterií. Všechny tyto jevy mohou mít negativní efekt na bezpečnost úložiště a měly by proto být dále studovány in-situ v podzemních výzkumných laboratořích.The globally accepted strategy for the management and treatment of high level and long-lived radioactive waste is to dispose the waste in a deep and stable geological formation. The physicochemical aspects have been carefully studied to ensure the long-term safety of the repository, while the influence of microorganisms was until recently rather underestimated, although it is well known that microorganisms can survive and propagate under environmental conditions expected in nuclear waste repositories. Anaerobic microorganisms with diverse types of metabolism present in the groundwater or buffer material may influence and compromise the long-term safety performance of the repository. This thesis, therefore, intends to improve the knowledge about the influence of microbial processes on radioactive waste disposal. Particularly microbial activity and survivability under different repository relevant conditions were studied with a focus on the effect of variable doses of irradiation on the microorganisms, the evolution of anaerobic microbial ecosystem with and without added nutrients, and microbial interactions with cementitious material. Moreover, microbially influenced corrosion of carbon steel was studied under anaerobic conditions. All the experiments except the radiation one were carried out under a strictly anaerobic atmosphere in an argon-purged glove box with gaseous oxygen concentration lower than 1 ppm. The results were obtained employing a multidisciplinary approach combining advanced microscopy methods such as electron microscopy or electrochemical impedance spectroscopy analysis with molecular biology-based methods such as NGS and qPCR. Chemical analyses were performed using ion-chromatography or spectroscopy methods. Anaerobic microorganisms including sulfate, iron, and nitrate-reducing bacteria were mostly detected in the samples. Application of 19,656 Gy total absorbed dose of Gama radiation at the constant dose rate of 13 Gy/hr did not completely eradicate bacteria present in bentonite. Bacteria also strongly influenced the corrosion rate of carbon steel comparing to samples in sterile conditions. Particularly, abundance of Methyloversatilis population positively correlated with corrosion rates. The presence of mackinawite, a corrosion product usually attributed to the activity of sulfate-reducing bacteria, was confirmed by Raman spectroscopy. Furthermore, the presence of concrete, although rich in specific indigenous microflora, strongly reduced the relative abundance of bentonite bacteria in studied samples and especially the growth of SRB was limited in the concrete environment. All these effects might have a negative impact on repository safety and should be further studied in following laboratory experiments and in-situ conditions in underground research laboratories

Prevalence of dengue and diversity of cultivable bacteria in vector Aedes aegypti (L.) from two dengue endemic districts, Kanchanpur and Parsa of Nepal

Background: Dengue fever, an endemic arboviral disease, represents one of the major public health concerns in Nepal. It is transmitted by bites of infected Aedes aegypti and Aedes albopictus , the former being primary vector. The bacterial community plays a significant role in biology of mosquitoes; however, the bacterial communities of primary vector A. aegypti remain unstudied in Nepal. The study was designed to determine the rate of dengue seropositivity and to explore the bacterial diversity of A. aegypti from dengue endemic districts, Kanchanpur and Parsa of Nepal. Methods: A cross-sectional study was conducted between June 2013 and November 2013 at two hospitals of Kanchanpur and Parsa. A total of 221 serum samples were collected from patients (inpatients and outpatients) suspected of suffering from dengue fever and attending Mahakali Zonal Hospital, Mahendranagar, Kanchanpur, and Narayani Zonal Hospital, Birgunj, Parsa. Detection of anti-dengue IgM was performed by using human dengue IgM capture ELISA. The larvae and pupae of mosquitoes (A. aegypti) were collected, reared, and emerged. Then, the bacteria were isolated and identified from the gut of identified mosquitoes by using standard methods. Results: Out of total 221 serum samples collected from patients suspected of suffering from dengue fever, 34 (15.38%) were positive for anti-dengue IgM. Gram-negative bacteria were isolated in largest proportion (63%) followed by gram-positive cocci (23.27%) and gram-positive rods (13.73%). The most common cultivable bacteria isolated were Staphylococcus spp., Pseudomonas spp., and Acinetobacter spp. The average bacterial load in the vectors was 3.91 7 104 cfu/ml. Conclusions: High rate of anti-dengue IgM seropositivity was reported in our study. The environmental bacteria were predominantly isolated and identified in A. aegypti. The paratransgenic approach to control vector might be possible by spreading the genetically modified bacteria in larval habitat or shelter of adult mosquitoes

Challenges and opportunities for nurses during COVID-19 pandemic

Background: Pandemic of COVID-19 coincided with the year of Nurses and Midwives 2020. In war against invisible that has been ongoing during this pandemic, nurses play crucial role. As of June 2020, more than 600 nurses have lost their lives due to COVID-19. Nursing practice takes patients’ safety at paramount through continuum of testing, quarantine and isolation. Thus, there is need to review challenges that pandemic has posed as well as the avenues of opportunities that it has opened for nurses. Method: Review of existing literature on nurses, their challenges and opportunities during COVID-19 was done using electronic database. Freely accessible literatures in English language that clearly mentioned on challenges and opportunities of nurses during COVID-19 were included in the study. Result: One of thechallenges that nurses face during COVID-19 is workforce shortage. With increasing number of people infected with COVID-19, it outstretches the existing nursing health workforce, and disproportionately in the low and middle incomes countries. They are at risk of infection and have high job demand. The incidents of suicide among nurses are representation of physical distress and psychological trauma. Role of nurses in patients care during COVID-19 can be under-rated and stigmatized. Internationally trained nurses and minorities nurses are at increased risk of discrimination. Despite these challenges, COVID-19 puts forward opportunities for nurses on implementing humanistic theory in practice, self-esteem and sharing of real time stories, contingency management and creativity. It opens platform for leading infection prevention measures and advocacy of profession. Conclusion: Being the pertinent stakeholders in patient care, nurses’ faces different challenges as well as some opportunities. COVID-19 has opened avenues for advocacy of nursing profession to get acknowledged for their dedication, perseverance, high morale and contribution during the pandemic management

A smartphone microscopic method for simultaneous detection of (oo)cysts of Cryptosporidium and Giardia.

BackgroundFood and water-borne illness caused by ingestion of (oo)cysts of Cryptosporidium and Giardia is one of the major health problems globally. Several methods are available to detect Giardia cyst and Cryptosporidium oocyst in food and water. Most of the available methods require a good laboratory facility and well-trained manpower and are therefore costly. There is a need of affordable and reliable method that can be easily implemented in resource limited settings.Methodology/principle findingsWe developed a smartphone based microscopic assay method to screen (oo)cysts of Cryptosporidium and Giardia contamination of vegetable and water samples. The method consisting of a ball lens of 1 mm diameter, white LED as illumination source and Lugols's iodine staining provided magnification and contrast capable of distinguishing (oo)cysts of Cryptosporidium and Giardia. The analytical performance of the method was tested by spike recovery experiments. The spike recovery experiments performed on cabbage, carrot, cucumber, radish, tomatoes, and water resulted in 26.8±10.3, 40.1±8.5, 44.4±7.3, 47.6±11.3, 49.2 ±10.9, and 30.2±7.9% recovery for Cryptosporidium, respectively and 10.2±4.0, 14.1±7.3, 24.2±12.1, 23.2±13.7, 17.1±13.9, and 37.6±2.4% recovery for Giardia, respectively. The spike recovery results are comparable with data obtained using commercial brightfield and fluorescence microscope methods. Finally, we tested the smartphone microscope system for detecting (oo)cysts on 7 types of vegetable (n = 196) and river water (n = 18) samples. Forty-two percent vegetable and thirty-nine percent water samples were found to be contaminated with Cryptosporidium oocyst. Similarly, thirty-one percent vegetable and thirty-three percent water samples were contaminated with Giardia cyst.ConclusionsThe newly developed smartphone microscopic method showed comparable performance to commercial microscopic methods. The new method can be a low-cost and easy to implement alternative method for simultaneous detection of (oo)cysts in vegetable and water samples in resource limited settings