Diagnosis and management of nitrobenzene poisoning in a low-resource setting: A case report

Background

and Importance: Nitrobenzenes are aromatic oxidizing nitrate compounds, acute ingestion of which can cause methemoglobinemia (metHb) that impairs oxygen transport. Clinical presentation ranges from cyanosis to asphyxia depending on the level of methemoglobin in the blood. Lack of improvement of hypoxia despite administration of oxygen can also be a clue to the diagnosis.

Case presentation

A 23-year-old male with accidental ingestion of nitrobenzene presented with multiple episodes of vomiting, headache, and dyspnea. His venous blood was dark brown in color and oxygen saturation was not improving despite high-flow oxygen. He was managed with methylene blue and Vitamin C on this background with an appropriate history of nitrobenzene ingestion.

Discussion

Acute nitrobenzene poisoning results in methemoglobinemia which is diagnosed by Co-oximeter but in resource-limited settings, clinical findings such as no improvement in SpO₂ despite supplemental oxygen and chocolate brown appearance of blood aid in the diagnosis. Prompt treatment of methemoglobinemia with methylene blue along with Vitamin C has shown successful and effective outcomes.

Conclusion

Diagnosis of acute nitrobenzene poisoning can be made with proper history, physical and bedside examinations in resource-limited settings even without the aid of a co-oximeter.

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Methemoglobinemia can cause refractory hypoxia in nitrobenzene poisoning.

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Proper history and thorough physical examination can help reach a diagnosis in resource-limited settings.

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Methylene Blue along with Vitamin C can be used safely in suspected cases.

Effects of hot water spray and sub-zero saline chilling on bacterial decontamination of broiler carcasses

Reduction of Salmonella on poultry carcasses is one way to prevent salmonellosis. The purpose of this research was to evaluate the effects of subzero saline chilling (SSC) with/without hot water spray (HWS) on broiler carcasses prior to chilling for bacterial reduction. Eviscerated broiler carcasses were subjected to water immersion chilling (WIC, 0% NaCl/0.5°C) or SSC (4% NaCl/-2.41°C) with/without prior HWS at 71°C for 1 min. Broiler carcasses in SSC were chilled faster than those in WIC, regardless of HWS. The combination of HWS and SSC resulted in the best reduction of mesophilic aerobic bacteria, Escherichia coli, and total coliforms on the carcasses over the WIC, SSC, and HWS/WIC. No Salmonella was detected on the carcasses in SSC and HWS/SSC while Salmonella positive was observed on the carcasses chilled in WIC and HWS/WIC. A trace of Gram-negative genus was detected on carcasses in HWS/SSC while many other microbiomes were observed on those in WIC, SSC, and HWS/WIC when quantitative microbiota profiles of 16S rRNA gene sequences were evaluated. Based on these results, chilling of broiler carcasses in 4% NaCl/-2.41°C after HWS at 71°C for 1 min significantly reduced carcass chilling time and bacterial contamination over the control chilling.

Effectiveness of low-dose radiation therapy in COVID-19 patients globally: A systematic review

Background: Novel Corona Virus Disease 2019 (COVID-19) can affect multiple organs, including the lungs, resulting in pneumonia. Apart from steroids, other anti-COVID drugs that have been studied appear to have little or no effect on COVID-19 pneumonia. There is a well-known history of inflammatory disease, including pneumonia, treated with low-dose radiation therapy (LDRT). It reduces the production of proinflammatory cytokines, Interleukin-1a (IL-1a), and leukocyte recruitment.   Methods: A comprehensive literature search was conducted using PubMed, Scopus, Embase, CINAHL, and Google Scholar, with keywords such as "radiotherapy," "low-dose radiation therapy," "low-dose irradiation," "covid-19 pneumonia," "SARS-CoV-2 pneumonia," and "covid pneumonia." with additional filters for human studies and customized articles in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses. We reviewed randomized controlled trials, quasi-experimental studies, cohort, case-control, and cross-sectional studies with a clearly defined intervention, including low-dose radiotherapy alone or in combination with any therapy to treat COVID-19 pneumonia from December 2019 to May 2021. Patients receiving standard or high-dose radiotherapy, including for other diseases, were excluded. Zotero software was used to collect and organize research from various databases, remove duplicates, extract relevant data, and record decisions. Participants' demographics and baseline status were obtained from the full-text articles along with the intervention's outcome/effect on patient status.  Results: Four studies with 61 participants that met the inclusion criteria were included. One was a double-blind randomized controlled trial, one a non-randomized trial, while the other two were single-arm clinical trials. Low-dose radiation therapy did not show any significant improvement in COVID-19 patients.  Conclusion: Only two studies included in this review demonstrated an improvement in inflammatory markers; however, patients were also given steroids or other drugs. Therefore, the confounding effects must be considered before drawing conclusions. This systematic review does not support mortality benefit, clinical course improvement, or imaging changes with LDRT.

Awareness and Knowledge of Glaucoma and their Associated Factors among People Visiting a Tertiary Level Hospital in Central Nepal

Background Glaucoma is one of the major causes of irreversible blindness globally. Almost 60 million people globally are affected by glaucoma making it the second leading cause of blindness worldwide. Diagnosis of glaucoma early on is vital for timely management and prevention of blindness. However, it is challenging to diagnose it early because it is asymptomatic in the initial stage, and there is also the dearth of appropriate screening tools. Awareness, knowledge, and beliefs are believed to influence the treatment-seeking behavior of people as well as their uptake of services. Objective To assess the awareness and knowledge about glaucoma among general patients and patient attendants visiting Dhulikhel Hospital. Method We conducted a cross sectional quantitative study among general patients visiting Dhulikhel Hospital. We collected data using face-to-face interviews with semistructured questionnaires. We analyzed data in R version 4.0.3 (2020-10-10). We presented numerical variables as mean and standard deviation whereas categorical variables as frequency and percentage. We determined factors associated with awareness and knowledge of glaucoma using logistic regression analysis and estimated adjusted odds ratio (AOR) with 95% confidence interval. Result Of 379 participants, a total of 214 (56.5%) participants had heard about glaucoma. Out of the participants who heard about glaucoma, the mean knowledge score was 48.3±21.7 and 53.3% had good knowledge on glaucoma. The odds of having heard about glaucoma were two percent lower (AOR=0.98; 95%CI: 0.97-0.99; p-value 0.036) in the older participants compared to one year younger participant, 1.98 (95%CI:1.01-3.86; p-value 0.046) times higher among literates and 2.79 (95%CI: 1.76- 4.41; p-value < 0.001) times among participants with previous ocular examination. The odds of having good knowledge was 1.94 (95%CI: 1.10-3.42; p value 0.021) times among participants with previous ocular examinations. Conclusion The knowledge and awareness regarding glaucoma in a hospital-visiting population in central Nepal was low. Half of the participants were unaware of the disease glaucoma and half of the participants who heard of the glaucoma had poor knowledge on glaucoma.

Study on prevalence of suicidal ideation and risk factors of suicide among patients visiting psychiatric OPD at Shree Birendra Hospital, Kathmandu Nepal

INTRODUCTION

Suicide is a global public health issue. Several environmental, psychosocial, behavioral factors along with physical, sexual, and emotional abuse have been associated with suicidal ideation and attempts. Childhood physical, sexual abuse, and health risk behaviors are also associated with suicidal attempts. The suicidal ideation prevalence varied from 1 to 20% and it varied with study population, geography, age group, gender, and other factors. The Beck suicidal ideation scale is an effective tool for assessing the major suicidal ideation with a six cut-off score.

MATERIALS AND METHOD

160 patients who met the inclusion criteria were enrolled into this cross-sectional study after random sampling among the patients visiting the Psychiatric OPD of Shree Birendra Hospital, Kathmandu, Nepal. The Semi-Structured Interview Schedule (SSIS), Beck Scale for Suicide Ideation (BSS), and Kuppuswamy's Scale were used to collect the data from the patients enrolled in the study. The Chi-square test and binary logistic regression analyses were used to identify and differentiate the factors associated with high suicidal risk.

RESULTS

Out of total 160 patients, 65% (n = 104) were female, 92.5% (n = 148) were married, 61.9% (n = 99) were residing in urban area, 93.1% (n = 148) were Hindus, 74.4% (n = 119) patients were living in the nuclear family, 5% (n = 8) patients had family history of psychiatric illness and 10.6% (n = 17) patients were using the substance of abuse. In the Beck scale for suicidal ideation questionnaire, 87.5% (n = 140) patients had moderate to strong wish to live, 89.4% (n = 143) patients responded as they would take precautions to save a life, 88.8% (n = 142) patients had such ideation/wish for brief, 96.3% (n = 154) had not considered for specificity/planning of contemplated suicidal attempt, 91.9% (n = 147) patients stated that they would not attempt active suicide because of a deterrent example from family, religion, irreversibility of the act and 98.1% (n = 157) patients had revealed ideas of deception/concealment of contemplated suicide openly. 16.9% (n = 27) of participants were categorized as high risk for suicide while 83.1% (n = 133) patients were as a low-risk category for suicide based on the Beck scale for suicidal ideation scoring.

CONCLUSION

In conclusion, this study found that most of the suicidal attempts were done as an act of impulse and it is higher among female and married individuals residing in the urban areas. This study did not establish any statistically significant association or differences among independent variables with the higher risk scoring in the Beck suicidal ideation scale.

Comparison between Simple and Classical Techniques to Create Closed Pneumoperitoneum

Background Closed method of pneumoperitoneum using Veress needle is an established technique. Classical closed technique is popular. Simple technique is a modified closed technique. Objective To compare the classical and simple techniques of closed pneumoperitoneum. Method This study was conducted in the department of urology, Bir hospital from August 1st 2019 to March 30th 2021. Total 114 patients were randomized into simple and classical technique of creating closed pneumoperitoneum. Time taken for creation of pneumoperitoneum, complications and failure of creating pneumoperitoneum in each group noted and analyzed. Chi square test, Fischer exact test and student t test were used and p < 0.05 considered significant. Result Among 114 patients, 61 in simple and 53 in classical technique allocated. In simple technique, mean age was 42.98±18.21 years, BMI was 21.84±2.57 kg/m2 , mean time for pneumoperitoneum creation was 108.07±21.14 seconds. In classical technique, mean age was 40.15±17.58 years, BMI was 21.94±2.54 (kg/m2 ), mean time for pneumoperitoneum creation was 189.70±32.21 seconds. Mean time was less in simple technique than classical technique (p < 0.001). Complication rate observed was 6% in each technique (p=0.797) with cumulative rate of 10%. Omental injury was seen in 3.2% in simple technique and 5.6% in classical technique (p=0.662). Retroperitoneal insufflation was seen in 6.5% in simple technique and 5.6% in classical technique (p=0.842). No failed pneumoperitoneum was observed in both groups. Conclusion Simple technique is as effective, reproducible and safe method as classical technique of creating closed pneumoperitoneum.

Evaluation of in ovo Bacillus spp. based probiotic administration on horizontal transmission of virulent Escherichia coli in neonatal broiler chickens

This study evaluated the effect of in ovo Bacillus spp. base probiotic (BBP) administration on hatchability, Gram-negative bacteria (GNB) recovery, performance, and microbiota composition in 2 independent trials using a virulent E. coli seeder challenge model. In each trial, one hundred and eighty 18-day-old embryos were allocated into 1 of 2 groups: Control and treated group (inoculated with 107 BBP). On day 19 of embryogenesis, seeder embryos (n = 18) were inoculated with 4.5 × 104E. coli/mL+272 μg/mL tetracycline and segregated into mesh hatching bags. Twelve chicks per group were euthanized at hatch and at day 7 to evaluate the gastrointestinal composition of total GNB or total aerobic pasteurized bacteria. Also, in trial 2, ceca content from five chickens at day 7 were collected to evaluate microbiota composition. Embryos inoculated with BBP showed a significant (P < 0.05) reduction in the total number of GNB at day-of-hatch (DOH) and day 7. Probiotic treatment increased BW at DOH and day 7, and BW gain (days 0 to 7) when compared with Control chickens. Proteobacteria phylum was significantly reduced, while the Firmicutes was significantly increased by the BBP as compared to the Control (P < 0.05). At family level, Enterobacteriaceae was significantly decreased, while the Lachnospiraceae was significantly elevated in the BBP as compared to the Control group (P < 0.05). The genus Oscillospira was significantly enriched in the BBP group, whereas the unidentified genus of family Enterobacteriaceae in the Control group (P < 0.05). The BBP group increased the bacterial species richness, although there was no significant difference between treatments (P > 0.05). Interestingly, beta diversity showed a significant difference in bacterial community structure between Control and BBP groups (P < 0.05). The results of the present study suggest that in ovo administration of a BBP can reduce the severity of virulent E. coli horizontal transmission and infection of broiler chickens during hatch. The reduction in the severity of the transmission and infection by the BPP might be achieved through alterations of microbiota composition and its community structure.

Analysis of Factors Associated with Thyroid Dysfunction: A Hospital Based Study

Background Thyroid dysfunction (TD) is one of the major public health concerns in Nepal. This study intends to identify factors in association with thyroid dysfunction and its hospital based prevalence. Objective To determine hospital-based prevalence of thyroid dysfunction and to identify and analyze factors in association with thyroid dysfunction. Method A retroprospective cross-sectional study was conducted among patients attending Dhulikhel Hospital-Kathmandu University Hospital (DH,KUH) from January to December, 2015 with prospective part carried out from July to December 2015 in the patients visiting Dhulikhel hospital for health check-up and requested for Thyroid Function Tests (TFTs). Thyroid Function Tests of 1530 subjects were performed in the biochemistry laboratory and semi-structured questionnaire were introduced to 312 participants with convenient sampling method and their anthropometric measurements were taken. Chi-square test, Pearson's correlation and student-t test were used as a measure to analyze factors. Result Out of total 1530 subjects, 35.3% were having thyroid dysfunction with the prevalence of overt hyperthyroidism, subclinical hyperthyroidism, overt hypothyroidism and subclinical hypothyroidism to be 2.5%, 2.4%, 5.6% and 24.8% respectively. The distribution of thyroid dysfunction was preponderant among females and among older age. The prevalence of thyroid dysfunction was highest among Terai/Madhesi (40.0%) and lowest among Newars (28.5%) with higher fraction of hypothyroidism in each ethnic group. There were significant correlation between Thyroid Stimulating Hormone (TSH) with waist-hip ratio (p<0.05) and weight (kg) with free thyroxine (fT4) (p<0.05). Direct pesticide exposure (p<0.05) was significantly associated with hypothyroidism. The serum fT4 was significantly different (p<0.05) among vegetarian and non-vegetarian whereas TSH and free triiodothyronine (fT3) were not significantly different. Smoking, alcoholism, dietary food habits, diabetes and hypertension were not significantly associated with thyroid dysfunction. Conclusion Thyroid dysfunction was highly prevalent among participants with higher proportion of subclinical hypothyroidism. Besides, direct pesticide exposure found to be factor in association with hypothyroidism, this study could not find significance relation with other established risk factors.

Knowledge, Attitude and Practice on Hypertension Among Antihypertensive Medication Users

INTRODUCTION

Hypertension is growing among the population of Nepal. We aimed to determine the current knowledge, attitude and practice of hypertension among hypertensive patients taking antihypertensive medication in the community of Central Nepal.

METHODS

A cross-sectional study was conducted among the hypertensive patients in Bharatpur, Chitwan, Nepal from July 2015 to September 2015 using clustered sampling technique. Suitably designed and validated questionnaire of knowledge, attitude and practice on hypertension consisting of 27 questions were used to determine the KAP scores. The difference in the median KAP scores between sex, level of education and duration of hypertension were assessed using Mann-Whitney U test.

RESULTS

A total of 200 patients met the inclusion criteria and majority of them were male (60%), had received primary education (36%) and had hypertension for ≥5 years (46.5%). The blood pressure ranged from 100-180/60-110 mmHg. The median K, A and P scores were 8 (6), 5 (1) and 6 (3) respectively. K and A were statistically associated with sex both at p<0.001 and level of education (K at p<0.001 and A at p=0.016).

CONCLUSIONS

The current knowledge, attitude and practice among hypertensive patients using antihypertensive medication can be improved.

Production of succinic acid from sugarcane molasses supplemented with a mixture of corn steep liquor powder and peanut meal as nitrogen sources by Actinobacillus succinogenes

The potential of using corn steep liquor powder (CSLP), peanut meal (PM), soybean meal (SM), cotton meal (CM) and urea as the substitute of yeast extract (YE) as the nitrogen source was investigated for producing succinic acid (SA). Actinobacillus succinogenes GXAS137 was used as the fermenting bacterium and sugarcane molasses was used as the main substrate. None of these materials were able to produce SA as high as YE did. The CSLP could still be considered as a feasible and inexpensive alternate for YE as the yield of SA produced using CSLP was second only to the yield of SA obtained by YE. The use of CSLP-PM mixed formulation (CSLP to PM ratio = 2·6) as nitrogen source produced SA up to 59·2 g l(-1) with a productivity of 1·2 g l(-1) h(-1). A batch fermentation using a stirred bioreactor produced up to 60·7 g l(-1) of SA at the same formulation. Fed-batch fermentation that minimized the substrate inhibition produced 64·7 g l(-1) SA. These results suggest that sugarcane molasses supplemented with a mixture of CSLP and PM as the nitrogen source could be used to produce SA more economically using A. succinogenes. Significance and impact of the study: Succinic acid (SA) is commonly used as a platform chemical to produce a number of high value derivatives. Yeast extract (YE) is used as a nitrogen source to produce SA. The high cost of YE is currently the limiting factor for industrial production of SA. This study reports the use of a mixture of corn steep liquor powder (CSLP) and peanut meal (PM) as an inexpensive nitrogen source to substitute YE. The results showed that this CSLP-PM mixed formulation can be used as an effective and economic nitrogen source for the production of SA.

Association of Previous Smoking Habit and Perceived Social Discrimination with the Risk of Multi-Drug Resistant Tuberculosis in Central Nepal

BACKGROUND

Multidrug-resistant tuberculosis (MDR TB) caused by Mycobacterium tuberculosis resistant to both Isoniazid and Rifampicin with or without resistant to other drug, is among the most alarming pandemic problem. The objectives of this study was to assess the risk factors of MDR TB in Central Nepal.

METHODS

A matched case control study was conducted among 186 cases of MDR TB and 372 non-MDR TB controls from central region of Nepal. Pretested questionnaires containing socio-economic, cultural & behavioral; environmental, biological and health service factors were used. Variables significant in bivariate analysis were entered in multiple regression models for further analysis.

RESULTS

After adjusting for confounders, previous smoking habit (aOR= 4.5,(95%CI(1.24-16.2)) (p=0.04), and perceived social discrimination (aOR=5.83,95%CI (1.77-19.71)) (P=0.021) independently predicted greater MDR TB risk.

CONCLUSIONS

Encouraging MDR TB cases for smoking cessation through awareness activities should be a priority. Stigma reduction programs should include the empowerment of patients and communities while promoting TBrelated research for further exploration into the risk factors of TB and associated stigma.

A study of assessment of partial edentulous patients based on Kennedy's classification at Dhulikhel Hospital Kathmandu University Hospital

BACKGROUND

Oral health contributes significantly towards quality of life(QOL). Edentulousness falls in a special category among the various conditions of dental origin. Dietary intake and nutritional status is affected by poor oral health and loss of teeth. This will ultimately compromise general health.

OBJECTIVE

To identify the frequency of Kennedy's classification among partial edentulous patients and to compare occurrence among gender and between upper and lower arches and also to compare edentulousness among employed and unemployed population.

METHODS

This study was carried out at Dhulikhel Hospital Dental Department. The study was conducted randomly among 194 patients in dental OPD who were partially edentulous. A structured pro forma was used to find out the edentulousness based on Kennedy,s classification.

RESULTS

Among the Kennedy's classification ClassIII was found to be most common. Among them females and unemployed group were found to have more edentulousness and upper arch was more common. It was also found that females were more conscious and get the replacement of missing teeth among which those having Class IV missing were replaced most often.

CONCLUSION

The Kennedy Class III partial edentulousness type is most commonly found in this study.

Depression among undergraduate medical students

BACKGROUND

Psychological stress is common in medical school and associated with depression. Medical education is grooming in Nepal, but only few studies are done concerning mental health of medical students.

OBJECTIVE

To assess the prevalence of depression among medical students at different levels of education and find about their stressors.

METHODS

A cross sectional, questionnaire-based survey was carried out among the undergraduate medical students of B.P.Koirala Institute of Health Sciences, Nepal. 50 students each from Bachelor of Medicine and Bachelor of Surgery (MBBS) first and third year were enrolled in the study conducted between November 2008 to January 2009. The depression levels were assessed using Zung depression scale. Students were asked to complete the questionnaire and then the depression levels calculated .The stress inducing factors during their course of medical education were also assessed.

RESULTS

The overall prevalence of depression among the students was 29.78 percent. The prevalence of depression in first and third year was 36.74and 22.22 percent respectively. The prevalence of depression was 32.43 percent among female students versus 28.07 percent in male students. Both first and third year students gave high ratings to academic stress and hectic lifestyle as the main stress inducing factors.

CONCLUSION

The prevalence of depression is seen especially in the first year medical students. So, attempts should be made to alleviate the stressors right from the time they join medical school. Since academic stress proved to be one of the major factors, measures to make the academic curriculum more student-friendly are suggested.

Community attitudes towards leprosy affected persons in Pokhara municipality of western Nepal

BACKGROUND

Stigma is a social process of interpretation of an attribute. Leprosy has been seen as the epitome of stigmatization. The psychosocial impact a person has to bear in a society after the diagnosis weighs heavier than the physical afflictions it causes, which does not get cured with the mere medical treatment. There are various factors which construct the perception of stigma in both leprosy affected persons and unaffected persons. The main purpose of this study was to determine the level of perceived stigma and the risk factors contributing to it among community people living in ward 15, Pokhara municipality.

METHODS

Cross-sectional descriptive study among 281 community people above the age of 18 years was conducted. Two sets of questionnaire form with additional Explanatory Model Interview Catalogue (EMIC) for each individual were used.

RESULTS

Among 281 community people, the median score of perceived stigma was 12 while it ranged from 0-30. Ethnic groups, Brahmins, Dalits and minorities had highest perceived stigma score of 15 and above compared to the rest (p=0.001), community people living at the distance more than 2 km had highest perceived stigma score of 15 compared to those living closer to the hospital (p=0.019) and nuclear family had highest perceived stigma score of 15 compared to the joint family (p=0.014). People who lacked information on leprosy had higher score of perceived stigma compared to those who had information on leprosy (p=0.002).Similarly, those who perceived leprosy to be difficult to treat (p<0.001) and a severe disease (p<0.001) had highest score of perceived stigma.

CONCLUSIONS

Stigma in leprosy was found highly associated with the lack of information about leprosy and their perception in treatment and disease severity. Stigma reduction strategies should focus on health education, targeting to alleviate their perception about the disease with their active participation.

The inactivation kinetics of polyphenol oxidase in mushroom (Agaricus bisporus) during thermal and thermosonic treatments

The effect of thermal and thermosonic treatments on the inactivation kinetics of polyphenol oxidase (PPO) in mushroom (Agaricus bisporus) was studied in 55-75°C temperature range. In both the processes, the inactivation kinetics of PPO followed a first-order kinetics (R(2)=0.941-0.989). The D values during thermal inactivation varied from 112±8.4min to 1.2±0.07min while they varied from 57.8±6.1min to 0.88±0.05min during thermosonic inactivation at the same temperature range. The activation energy during thermal inactivation was found to be 214±17kJ/mol, while it was 183±32kJ/mol during thermosonic inactivation. The inactivating effect of combined ultrasound and heat was found to synergistically enhance the inactivation kinetics of PPO. The D values of PPO decreased by 1.3-3 times during thermosonic inactivation compared to the D values of PPO during thermal inactivation at the temperature range. Therefore, thermosonication can be further developed as an alternative to "hot break" process of mushroom.

Physicochemical and functional characteristics of lentil starch

The physicochemical properties of lentil starch were measured and linked up with its functional properties and compared with those of corn and potato starches. The amylose content of lentil starch was the highest among these starches. The crystallinity and gelatinization enthalpy of lentil starch were the lowest among these starches. The high amylose: amylopectin ratio in lentil starch resulted into low crystallinity and gelatinization enthalpy. Gelatinization and pasting temperatures of lentil starch were in between those of corn and potato starches. Lentil starch gels showed the highest storage modulus, gel strength and pasting viscosity than corn and potato starch gels. Peleg's model was able to predict the stress relaxation data of these starches well (R(2)>0.98). The elastic modulus of lentil starch gel was less frequency dependent and higher in magnitude at high temperature (60 °C) than at lower temperature (10 °C). Lentil starch is suitable where higher gel strengthened pasting viscosity are desired.

Composition analysis and material characterization of an emulsifying extracellular polysaccharide (EPS) produced by Bacillus megaterium RB-05: a hydrodynamic sediment-attached isolate of freshwater origin

AIMS

This work was aimed to isolate, purify and characterize an extracellular polysaccharide (EPS) produced by a freshwater dynamic sediment-attached micro-organism, Bacillus megaterium RB-05, and study its emulsifying potential in different hydrocarbon media.

METHODS AND RESULTS

Bacillus megaterium RB-05 was found to produce EPSs in glucose mineral salts medium, and maximum yield (0.864 g l(-1) ) was achieved after 24-h incubation. The recovery rates of the polysaccharide material by ion-exchange and gel filtration chromatography were around 67 and 93%, respectively. As evident from HPLC and FT-IR analyses, the polysaccharide was found to be a heteropolymer-containing glucose, galactose, mannose, arabinose, fucose and N-acetyl glucosamine. Different oligosaccharide combinations namely hexose(3), hexose(4), hexose(5) deoxyhexose(1) and hexose(5) deoxyhexose(1) pentose(3) were obtained after partial hydrolysis of the polymer using MALDI-ToF-MS. The polysaccharide with an average molecular weight of 170 kDa and thermal stability up to 180°C showed pseudoplastic rheology and significant emulsifying activity in hydrocarbon media.

CONCLUSIONS

Isolated polysaccharide was found to be of high molecular weight and thermally stable. The purified EPS fraction was composed of hexose, pentose and deoxyhexose sugar residues, which is a rare combination for bacterial polysaccharides. Emulsifying property was either better or comparable to that of other commercially available natural gums and polysaccharides.

SIGNIFICANCE AND IMPACT OF THE STUDY

This is probably one of the few reports about characterizing an emulsifying EPS produced by a freshwater sediment-attached bacterium. The results of this study contribute to understand the influence of chemical composition and material properties of a new microbial polysaccharide on its application in industrial biotechnology. Furthermore, this work reconfirms freshwater dynamic sediment as a potential habitat for bioprospecting extracellular polymer-producing bacteria. This study will improve our knowledge on the exploitation of a nonconventional renewable resource, which also seems to be ecologically significant.

Arsenate exposure affects amino acids, mineral nutrient status and antioxidants in rice (Oryza sativa L.) genotypes

Simulated pot experiments were conducted on four rice (Oryza sativa L.) genotypes (Triguna, IR-36, PNR-519, and IET-4786) to examine the effects of As(V) on amino acids and mineral nutrient status in grain along with antioxidant response to arsenic exposure. Rice genotypes responded differentially to As(V) exposure in terms of amino acids and antioxidant profiles. Total amino acid content in grains of all rice genotypes was positively correlated with arsenic accumulation. While, most of the essential amino acids increased in all cultivars except IR-36, glutamic acid and glycine increased in IET-4786 and PNR-519. The level of nonprotein thiols (NPTs) and the activities of superoxide dismutase (SOD; EC 1.15.1.1), glutathione reductase (GR; EC 1.6.4.2) and ascorbate peroxidase (APX; EC 1.11.1.11) increased in all rice cultivars except IET-4786. A significant genotypic variation was also observed in specific arsenic uptake (SAU; mg kg(-1)dw), which was in the order of Triguna (134) > IR-36 (71) > PNR-519 (53) > IET-4786 (29). Further, application of As(V) at lower doses (4 and 8 mg L(-1) As) enhanced the accumulation of selenium (Se) and other nutrients (Fe, P, Zn, and S), however, higher dose (12 mg L(-1) As) limits the nutrient uptake in rice. In conclusion, low As accumulating genotype, IET-4786, which also had significantly induced level of essential amino acids, seems suitable for cultivation in moderately As contaminated soil and would be safe for human consumption.

Arsenic affects mineral nutrients in grains of various Indian rice (Oryza sativa L.) genotypes grown on arsenic-contaminated soils of West Bengal

The exposure of paddy fields to arsenic (As) through groundwater irrigation is a serious concern that may not only lead to As accumulation to unacceptable levels but also interfere with mineral nutrients in rice grains. In the present field study, profiling of the mineral nutrients (iron (Fe), phosphorous, zinc, and selenium (Se)) was done in various rice genotypes with respect to As accumulation. A significant genotypic variation was observed in elemental retention on root Fe plaque and their accumulation in various plant parts including grains, specific As uptake (29-167 mg kg(-1) dw), as well as As transfer factor (4-45%). Grains retained the least level of As (0.7-3%) with inorganic As species being the dominant forms, while organic As species, viz., dimethylarsinic acid and monomethylarsonic acid, were non-detectable. In all tested varieties, the level of Se was low (0.05-0.12 mg kg(-1) dw), whereas that of As was high (0.4-1.68 mg kg(-1) dw), considering their safe/recommended daily intake limits, which may not warrant their human consumption. Hence, their utilization may increase the risk of arsenicosis, when grown in As-contaminated areas.

Fair and sustainable irrigation water management in the Babai basin, Nepal

This paper attempts to find a strategy to provide year-round irrigation for cultivating three crops per year in the southern plains of the country taking a case study of the Babai basin. Despite having enough flows during the summer for growing rice in total 27,000 ha area, the dry season flows of the Babai river can irrigate only 6,300 ha in winter and 4,000 ha in spring limiting the cropping intensity to 138.50%. It is proposed to irrigate the 7,500 ha southern dry area at the right bank bringing water from a large snow-fed river: the Karnali. Water balance study of the three irrigation regions to be irrigated from the Babai source preserving their existing water rights showed that the year-round irrigation at the west with the proposed arrangement will fall short of only 13.9 million m(3) water volume. At the east side, the head reach area and the tail portion will fall short of 19.4 and 66.4 million m(3) of water to insure a cropping intensity of 250%. The deficits can be fulfilled by means of capturing the excess river water of rainy season in local reservoirs and by making conjunctive use of groundwater. The proposed solution is financially, environmentally and socially viable being a cost effective, user friendly and should be the linchpin towards attaining a sustainable year-round irrigation in the region.

Appropriate rehabilitation strategy for a traditional irrigation supply system: a case from the Babai area in Nepal

This paper studies primary canals of three traditional irrigation systems in the southern plains of Nepal. It offers a scientific interpretation of the indigenous technology applied to the systems, which facilitates to use the same channel network for irrigation, drainage and flood management. The flood management technology of the farmers by diverting as much discharge as possible to the field channels results in the reduction of discharge towards the downstream part of the main channel. It is depicted in the simulation study that uses the river analysis program HEC-RAS 4.0. A cascade of weirs is found to be the most cost effective and user-friendly option to upgrade these systems preserving the existing irrigation, drainage as well as flood management functions. This study suggests that the conventional irrigation design principles should be applied very cautiously with full knowledge of the existing socio-institutional setting, hydro-ecological regime and indigenous technology for upgrading any traditional irrigation system successfully. The indigenous flood management technology strengthens the emerging concept that the floods in the Ganges plain are to be managed, not controlled.

Prevalence and clonal diversity of Campylobacter jejuni from dairy farms and urban sources

AIM

To investigate the role of free-living animals such as sparrows, rodents and flies as potential reservoirs of Campylobacter spp on a dairy farm, and to assess the genetic diversity among Campylobacter isolates from the farm and an urban source.

METHODS

A total of 290 samples (bovine, passerine and rodent faeces, and whole flies) were collected from a large commercial dairy farm in the Manawatu district in New Zealand, and from faeces from urban sparrows in a nearby city. Other samples collected from the dairy farm included five from silage, two from aprons worn by workers during milking, two from workers' boots and two from water in troughs in a paddock. Isolates of thermophilic Campylobacter spp were identified morphologically and phenotypically and further characterised molecularly using pulsed-field gel electrophoresis (PFGE) and the restriction enzyme SmaI.

RESULTS

Campylobacter jejuni was the only Campylobacter species isolated from all samples. The highest prevalence was found in faeces from dairy cows (54%), followed by faeces from sparrows from the urban area (40%) and the farm (38%), and from rodents (11%) and whole flies (9%). Other samples from the farm environment such as silage, trough water, and workers' aprons and boots were also positive for C. jejuni. Of the 22 restriction patterns obtained, seven were common to more than one source.

CONCLUSIONS

Cattle, sparrows, rodents and flies are potential reservoirs of C. jejuni on dairy farms. Identical clones of C. jejuni carried by cattle, sparrows, flies and rodents probably indicate a common source of infection. The high level of asymptomatic carriage of C. jejuni by healthy dairy cows could be sufficient to maintain infections within the dairy farm surroundings via environmental contamination.

Independent mobility of catalytic and regulatory domains of myosin heads

The recent determination of the myosin head atomic structure has led to a new model of muscle contraction, according to which mechanical torque is generated in the catalytic domain and amplified by the lever arm made of the regulatory domain [Fisher, A. J., Smith, C. A., Thoden, J., Smith, R., Sutoh, K., Holden, H. M. & Rayment, I. (1995) Biochemistry 34, 8960-8972]. A crucial aspect of this model is the ability of the regulatory domain to move independently of the catalytic domain. Saturation transfer-EPR measurements of mobility of these two domains in myosin filaments give strong support for this notion. The catalytic domain of the myosin head was labeled at Cys-707 with indane dione spin label; the regulatory domain was labeled at the single cysteine residue of the essential light chain and exchanged into myosin. The mobility of the regulatory domain in myosin filaments was characterized by an effective rotational correlation time (tauR) between 24 and 48 micros. In contrast, the mobility of the catalytic domain was found to be tauR = 5-9 micros. This difference in mobility between the two domains existed only in the filament form of myosin. In the monomeric form, or when bound to actin, the mobility of the two domains in myosin was indistinguishable, with tauR = 1-4 micros and >1,000 micros, respectively. Therefore, the observed difference in filaments cannot be ascribed to differences in local conformations of the spin-labeled sites. The most straightforward interpretation suggests a flexible hinge between the two domains, which would have to stiffen before force could be generated.