Mortality of Clarias gariepinus caused by Aeromonas caviae and nitrite toxicity in a fish farm

In Nigeria, farming of freshwater fish, mainly that of Clarias gariepinus has gained prominence as means of improved protein supply and livelihood. Many farmers suffer untold losses in their bid to make a living from commercial fish production. Among the major causes of infectious disease outbreaks in fish farms are pathogenic bacteria of the genus Aeromonas. This is a case report of outbreak of Aeromonas caviae infection complicated by nitrite toxicity in Clarias gariepinus. Carcasses of 17 African catfish juveniles and two water samples were presented to the poultry and fish clinic of the Veterinary Teaching Hospital, University of Jos for investigation. The fishes had been on medication (Fish cure antibiotic +®) for over 5 days with cumulative mortality of 230 out of 2,500 fishes (9.2 %). Necropsy was conducted and samples were taken for microbial analysis and histopathology while water samples were subjected to chemical analysis. Gross lesions were broken barbels, cutaneous depigmentation, branchial pallor, ascites, renal and splenic congestion. Histologically, there was dissociation of hepatic cords, necrosis of hepatocytes with vacuolation and mononuclear cellular infiltrations. Also, there was renal tubular epithelial necrosis with mononuclear and heterophilic infiltration while micro abscesses were observed in the brain. Marked Zenker’s necrosis and edema were seen in the skeletal muscles. Organism isolated from livers and kidneys was identified as Aeromonas caviae and was susceptible to enrofloxacin, furaltadone and florfenicol. Nitrite in fish pond water was 1mg/L. Bath medication with enrofloxacin at 33mg/litre of water for 6 hours treatment per day was done to reduce the mortality. The farmer was advised to change the source of water for the fish pond immediately. It is recommended that to avoid losses in fish farming, farmers should check the quality of water intended for use on fish farms and ensure early health check on fingerlings purchased for rearing.

Effects of Probiotic Bacillus on Growth Performance, Immune Response and Disease Resistance in Aquaculture

Aquaculture is one of the fastest-growing animal food-producing agricultural industries in the world and proper performance of fish in morphological, physiological and immunological aspects is important for fish production and sustainable expansion of aquaculture. But several inhibitors like disease, pathogen, and adverse environment can overpower these performances. At present, antibiotics in preventing these inhibitors have been seen as becoming favorable to those inhibitors. So, Bacillus, an important group of probiotic bacteria can be an alternative to these antibiotics in aquaculture. Bacillus has been seen used in different experiments, mainly as a supplement in feed at various concentrations. Bacillus showed effective results like improved growth with minimum cost, improvement in reproduction, hematology, improved immune response and disease, and stress resistance as well as better proximate composition in different fish species. Application of Bacillus strains has proven efficient in improving water quality by reducing ammonia and nitrite toxicity, harmful algal blooms and utilization of H+ ion. Larger application of probiotic Bacillus instead of the hazardous synthetic chemicals would promote eco-friendly low-input sustainable aquaculture for food and nutritional security of the increasing world population. So many more experiments should be conducted in commercially important fishes for better growth and health of fishes which will certainly increase fish

Caenorhabditis elegans to Model the Capacity of Ascorbic Acid to Reduce Acute Nitrite Toxicity under Different Feed Conditions: Multivariate Analytics on Behavioral Imaging

Nitrocompounds are present in the environment and human diet and form part of vegetables and processed meat products as additives. These compounds are related to negative impacts on human and animal health. The protective effect of ascorbic acid has been demonstrated by some biological systems as regards several nitrocompounds. This work focused on studying the possibility of modeling this effect on nitrite toxicity with the model Caenorhabditis elegans. The three factors studied in this work were ascorbic acid concentration, nitrite exposure concentration, and presence/absence of food. The protective effect was evaluated by scoring lethality and its impact on behavior by means of multivariate statistical methods and imaging analytics. The effects of nitrite and the influence of food availability were evidenced. Apart from increasing lethality, nitrite had disruption effects on movements. All the observed symptoms reduced when ascorbic acid was administered, and it diminished lethality in all cases. Ascorbic acid maintained nematodes’ postural capacities. The results suggest that nitrites’ nonspecific toxicity in C. elegans can be mitigated by ascorbic acid, as previously evidenced in other biological systems. Thus, our results reveal the ability of C. elegans to reproduce the known protective effect of ascorbic acid against nitrite.

Severe methemoglobinemia secondary to isobutyl nitrite toxicity: the case of the ‘Gold Rush’

ABSTRACT Isobutyl nitrite is one of the popular recreational drugs with high abuse potential that is known to cause methemoglobinemia. While inhaling this recreational drug, often referred to as a ‘popper’, is the typical route of administration, oral ingestion can produce a more rapid and fulminant course of methemoglobinemia. We present the case of a 69-year-old male that presented to our emergency department in extreme, life-threatening methemoglobinemia due to the ingestion of isobutyl nitrite that he obtained from an adult novelty store. The patient had a methemoglobin level above our lab cut-off of 28% and was subsequently treated with two doses of intravenous methylene blue. His hospital course was unremarkable, and he was discharged on Day 2. Methemoglobinemia is a medical emergency that requires a high index of clinical suspicion, prompt recognition, and rapid treatment.

Determination of Median Lethal Concentration (LC50) and Nitrite Accumulation in the Blood and Tissue of Blood Cockle (Tegillarca granosa, Linnaeus 1758)

This study aimed to determine the nitrite toxicity of blood cockle Tegillarca granosa, with the objectives being to identify the median lethal concentration (LC50) and the accumulation level of nitrite in Tegillarca granosa, and to determine the relationship of nitrite accumulation with mortality percentage. The levels of LC50 and accumulation of nitrite were determined after 72 h of exposure to different nitrite concentrations (0, 0.5, 1.0, 1.5, and 2.0 mg/L). Nitrite accumulation was analysed using Method 8153 and a DR2800 spectrophotometer (HACH, Loveland, CO, USA). LC50 was identified at 1.53 mg/L, and nitrite accumulated in the ranges of 0.012 to 0.106 mg/L wet weight and 0.002 to 0.089 mg/L wet weight in the blood and soft tissue samples, respectively. Accumulation concentration in both tissue and blood cells increased proportionally with the exposure concentration, and had a strong positive relationship with the percentage of mortality. Our findings suggest that prolonged exposure of nitrite led to accumulation in the blood and tissues and caused cockle mortality.

The conserved 3′ UTR-derived small RNA NarS mediates mRNA crossregulation during nitrate respiration

Small noncoding RNAs (sRNAs) from mRNA 3′ UTRs seem to present a previously unrecognized layer of bacterial post-transcriptional control whereby mRNAs influence each other's expression, independently of transcriptional control. Studies in Escherichia coli and Salmonella enterica showed that such sRNAs are natural products of RNase E-mediated mRNA decay and associate with major RNA-binding proteins (RBPs) such as Hfq and ProQ. If so, there must be additional sRNAs from mRNAs that accumulate only under specific physiological conditions. We test this prediction by characterizing candidate NarS that represents the 3′ UTR of nitrate transporter NarK whose gene is silent during standard aerobic growth. We find that NarS acts by Hfq-dependent base pairing to repress the synthesis of the nitrite transporter, NirC, resulting in mRNA cross-regulation of nitrate and nitrite transporter genes. Interestingly, the NarS-mediated repression selectively targets the nirC cistron of the long nirBDC-cysG operon, an observation that we rationalize as a mechanism to protect the bacterial cytoplasm from excessive nitrite toxicity during anaerobic respiration with abundant nitrate. Our successful functional assignment of a 3′ UTR sRNA from a non-standard growth condition supports the notion that mRNA crossregulation is more pervasive than currently appreciated.

Manganese Oxide Biomineralization Provides Protection against Nitrite Toxicity in a Cell-Density-Dependent Manner

ABSTRACTManganese biomineralization is a widespread process among bacteria and fungi. To date, there is no conclusive experimental evidence for how and if this process impacts microbial fitness in the environment. Here, we show how a model organism for manganese oxidation is growth inhibited by nitrite, and that this inhibition is mitigated in the presence of manganese. We show that such manganese-mediated mitigation of nitrite inhibition is dependent on the culture inoculum size, and that manganese oxide (MnOX) forms granular precipitates in the culture, rather than sheaths around individual cells. We provide evidence that MnOXprotection involves both its ability to catalyze nitrite oxidation into (nontoxic) nitrate under physiological conditions and its potential role in influencing processes involving reactive oxygen species (ROS). Taken together, these results demonstrate improved microbial fitness through MnOXdeposition in an ecological setting, i.e., mitigation of nitrite toxicity, and point to a key role of MnOXin handling stresses arising from ROS.IMPORTANCEWe present here a direct fitness benefit (i.e., growth advantage) for manganese oxide biomineralization activity inRoseobactersp. strain AzwK-3b, a model organism used to study this process. We find that strain AzwK-3b in a laboratory culture experiment is growth inhibited by nitrite in manganese-free cultures, while the inhibition is considerably relieved by manganese supplementation and manganese oxide (MnOX) formation. We show that biogenic MnOXinteracts directly with nitrite and possibly with reactive oxygen species and find that its beneficial effects are established through formation of dispersed MnOXgranules in a manner dependent on the population size. These experiments raise the possibility that manganese biomineralization could confer protection against nitrite toxicity to a population of cells. They open up new avenues of interrogating this process in other species and provide possible routes to their biotechnological applications, including in metal recovery, biomaterials production, and synthetic community engineering.