Unraveling the spawning and reproductive patterns of tomato hind grouper, Cephalopholis sonnerati (Valenciennes, 1828) from south Kerala waters.

The objective of this study is to provide information on the reproductive biology of tomato hind grouper, Cephalopholis sonnerati (Valenciennes, 1828) for conservation and management purposes. Fish caught by artisanal fishermen from September 2019 to August 2021 were analysed. A total of 280 females, 31 males, and 4 transitional and 178 sex-undetermined fish were analysed. The female to male sex proportion was 9:1, and the fish reached a maximum total body length of 38.5 and 54.5 cm for females and males, respectively. The following microscopic stages were identified: immature, developing, ripe, running ripe/releasing, and spent in both males and females. Several asynchronous development patterns were observed in the studied gonads, including multiple oocyte stages and early and advanced stages of sexual transition. High gonadosomatic index (GSI) for both males and females was recorded in March, May, and November. Running ripe and releasing stages in females were identified in the months from March to June, which indicates the spawning season. The absolute and relative fecundity of the species ranged from 162,723 ± 207,267 and 239 ± 285, respectively. An exponential relationship was found between fecundity and total body length (TL), fecundity and total body weight (TW), and fecundity and gonad weight (GW).

Impact of sub-chronic polystyrene nanoplastics exposure on hematology, histology, and endoplasmic reticulum stress-related protein expression in Nile tilapia (Oreochromis niloticus).

Nanoplastics (NPs) are one of the most hazardous marine litters, having the potential to cause far-reaching impacts on the environment and humankind. The effect of NPs on fish health has been studied, but their impact on the subcellular organelles remains unexplored. The present investigation studied the possible implications of polystyrene-nanoplastics (PS-NPs) on the hematology, tissue organization, and endoplasmic reticulum (ER) stress-related proteins in Nile tilapia (Oreochromis niloticus). Fish were exposed to ∼100 nm PS-NPs at environmentally relevant (0.1 mg/L), and sublethal (1, 10 mg/L) concentrations for 14 days through water exposure. The growth performance and hematological parameters such as erythrocytes, hemoglobin, hematocrit, and leucocytes decreased, while thrombocytes increased with PS-NPs dose-dependently. The gills, liver, kidney, and heart tissues displayed increasing degrees of pathology with increased concentrations of PS-NPs. The gills showed severe epithelial hyperplasia and lamellar fusion. The liver had an abstruse cellular framework, membrane breakage, and vacuolation. While glomerular and tubular atrophy was the most prominent pathology in the kidney tissue, the heart displayed extensive myofibrillar loss and disorderly arranged cardiac cells. The ER-stress-related genes such as bip, atf6, ire1, xbp1, pkr, and apoptotic genes such as casp3a, and bax were over-expressed, while, the anti-apoptotic bcl2 was under-expressed with increasing concentrations of PS-NPs. Immunohistochemistry and blotting results of GRP78, CHOP, EIF2S, and ATF6 in gills, liver, kidney, and heart tissues affirmed the translation to ER stress proteins. The results revealed the sub-lethal adverse effects and the activation of the ER-stress pathway in fish with sub-chronic exposure to PS-NPs.

Prevalence of antimicrobial resistance, biofilm formation, efflux pump activity, and virulence capabilities in multi-drug-resistant Klebsiella pneumoniae isolated from freshwater fish farms.

The present study aimed to determine the antibiotic resistance, underlying mechanisms, antibiotic residues, and virulence genes involved in 32 multi-drug-resistant Klebsiella pneumoniae isolates from freshwater fishes in Andhra Pradesh, India. Antibiogram studies revealed that all isolates were multi-drug-resistant, harbored tetA (96.8%), tetC (59.3%), tetD (71.9%), nfsA (59.3%), nfsB (53.1%), sul2 (68.7%), qnrC (43.7%), qnrD (50%), blaSHV (75%), blaTEM (68.7%), and blaCTX-M (93.7%) genes. Multiple antibiotic resistance index was calculated as 0.54. Sixteen isolates were confirmed to be hyper-virulent and harbored magA and rmpA genes. In total, 46.9, 31.2, and 21.9% of the isolates were categorized as strong, moderate, or weak biofilm formers, respectively. All isolates possessed an active efflux pump and harbored acrA, acrB, acrAB, and tolC genes in 94% of the isolates, followed by mdtK (56.2%). Porins such as ompK35 and ompK36 were detected in 59.3 and 62.5% of the isolates, respectively. Virulence genes fimH-1, mrkD, and entB were present in 84.3, 81.2, 87.5% of the isolates, respectively. These findings imply a potential threat that multi-drug-resistant bacterial pathogens could transmit to surrounding environments and humans through contaminated water and the aquaculture food chain.

Implications of deltamethrin on hematology, cardiac pathology, and gene expression in Nile tilapia (Oreochromis niloticus) and its possible amelioration with Shatavari (Asparagus racemosus).

Deltamethrin (DM) is one of the extensively used pyrethroids for controlling ectoparasites. Unfortunately, DM is highly toxic to fish as it primarily targets the sodium channels of the plasma membrane thereby affecting their cardiac and nervous systems. The present study investigated the protective efficacy of Shatavari (Asparagus racemosus) against DM-induced cardiotoxicity in Nile tilapia (Oreochromis niloticus). The fish were segregated into nine groups having 36 fish/group maintained in triplicates exposed to DM (1 µg/L) and fed with a diet containing three different concentrations (10 g, 20 g, and 30 g/kg feed) of aqueous extract of A. racemosus (ARE) for 21 days. DM caused significant alterations in the blood and serum parameters, and expression of cardiac and apoptotic genes compared to the control group. The ARE cotreatment significantly reduced the increase in serum transaminases, creatine kinase, and lactate dehydrogenase levels induced by DM. ARE facilitated the regain of electrolyte (sodium, potassium, chloride) homeostasis and antioxidants such as catalase, superoxide dismutase, glutathione peroxidase, and glutathione in DM-exposed fish. The cardiac histology exhibited loose separation of the cardiomyocytes and myofibrillar loss in the DM group which was ameliorated in the DM-ARE cotreatment group. Significant modulations were observed in the expression of cardiac-specific genes (gata4, myh6, tnT, cox1) and apoptosis signaling genes and proteins (HSP70, bax, bcl-2, caspase3), in the cotreatment group compared to the DM-exposed group. The current study suggests that ARE possesses potential cardioprotective properties that are effective in mitigating the toxic effects induced by DM via ameliorating oxidative stress, electrolyte imbalance, and apoptosis in tilapia.

Correlation of Diabetic Status and Coronavirus Disease 2019 (COVID-19) in Patients With Mucormycosis: A Retrospective Clinical Study.

AIM: Coronavirus disease 2019 (COVID-19) and its association with diabetes might lead to mucormycosis, and studies have reported an association between them. This study aims to find the correlation between COVID-19 and diabetic status in patients with mucormycosis and its role in disease progression and prognosis. The objectives of the study are to analyze the clinical range of mucormycosis in those with diabetes and COVID-19 and to correlate the clinical and radiographic findings. MATERIALS AND METHODOLOGY: A retrospective cohort analysis was carried out at Saveetha Dental College and Hospitals in Chennai (approval number: IHEC/SDC/OMED-2204/23/218). The data collection was done from the institution's electronic database from April 2019 to April 2023 which included the patients' age and gender and COVID-19 and diabetic status and clinical and radiographic features of mucormycosis. RESULTS: From the data analyzed, 25 patients had a history of mucormycosis with diabetes and COVID-19 infections. The patients' average age was 47.76, out of which 22 were males and three were females. The chi-squared test showed no significant association between age (0.178), diabetes (0.465), and COVID-19 (0.583). Spearman's correlation was done showing an association between mucormycosis, diabetes, and COVID-19. Radiographically, 100% of the patients had involvement of the maxillary sinus, followed by the palate (32%), orbit (28%), nasal floor (24%), ethmoidal sinus (16%), sphenoidal sinus (12%), and frontal sinus (8%). CONCLUSION: The findings of this study point out the importance of considering the presence of systemic comorbidities like diabetes in COVID-19 patients. Early identification, surgical debridement, and antifungal medications are part of the treatment for increased survival.

Isolation and identification of antimicrobial susceptibility, biofilm formation, efflux pump activity, and virulence determinants in multi-drug resistant Pseudomonas aeruginosa isolated from freshwater fishes.

The present study was undertaken to evaluate the prevalence, underlying resistance mechanism, and virulence involved in Pseudomonas aeruginosa (n = 35) isolated from freshwater fishes in Andhra Pradesh, India. Antibiogram studies revealed that 68.5, 62.8, 37.1, 11.4, 8.5, 57.1, 54.2, and 48.5% of isolates had resistance to oxytetracycline, co-trimoxazole, doxycycline, enrofloxacin, ciprofloxacin, cefotaxime, ceftazidime, and ampicillin, respectively. The resistant isolates harboured the tetA (85.7%), tetD (71.4%), tetM (91.4%), sul1 (80%), blaCTX-M (57.1%), blaTEM (42.8%), and blaSHV (48.5%) genes. In total, 50% of the isolates were altered as multi-drug resistant, and the multiple antibiotic resistance index was calculated as 0.4. Furthermore, 37.3, 48.5, and 14.2% of isolates were categorized as strong, moderate, and weak biofilm formers, possessing pslA (91.5%) and pslD (88.6%) biofilm encoding genes. In total, 82.8% of the isolates exhibited efflux pump activity and harboured the mexA (74.2%), mexB (77.1%), and oprM (37.1%) genes. Virulent genes oprL, toxA, exoS, and phzM were detected in 68.5, 68.5, 100, and 17.1% of isolates, respectively. The data suggested that P. aeruginosa harbours multiple resistance mechanisms and virulence factors that may contribute to antibiotic resistance and pathogenicity, and their distribution in fish culture facilities highlights the public health hazards of the food chain.

Complete genome sequence analysis of multi-drug resistant Klebsiella pneumoniae THK strain isolated from aquaculture farm in Kerala, India.

The emergence of microorganisms with resistance toward antibiotics has been widely recognized as a growing hazard to public health. Here, we report the whole genome sequence of Klebsiella pneumoniae strain THK, which was isolated from an aquaculture farm in Kerala, India. Standard disc diffusion and strip methods were used for antibiotic susceptibility testing and minimum inhibitory concentration detection. The isolate showed high level of resistance against beta-lactam, aminoglycosides, fluoroquinolones, macrolides, tetracyclines, chloramphenicol, sulfonamides, and cephalosporin class of antibiotics, but were sensitive to carbapenem and polymyxins. The whole genome sequence analysis revealed that the final assembly of THK strain consisted of 30 contigs of 5, 199,186 bp including four plasmid sequences plasmid_690 (1 contig), plasmid_710 (9 contigs), plasmid_1222 (6 contigs), and plasmid_1528 (1 contig). Sequence analysis revealed that the isolate has a number of genes encoding for antibiotic resistance and virulence. The findings indicated that antibiotics present in aquatic environments at sub-inhibitory concentrations increase the selection pressure affecting the cell function of even normal aquatic microorganisms to change the genetic expression of virulence factors or acquire resistance genes through various transfer mechanisms. This strain would be of significant interest for thorough comparative genomic study, given the known vast diversity of pathogenic and antibiotic resistance potentials.

SUNLIGHT-INDUCED decontamination of water from emerging pharmaceutical pollutants using ZnO nanoparticles.

A new class of environmental pollutants that have become a significant concern for the entire world's population over the last few decades are pharmaceutical contaminants due to the potential risks they pose to the environment and human health. An investigation on the photocatalytic degradation of four different model pharmaceutical contaminants: Tetracycline (TCT), Sulfamethoxazole (SMX), Chloroquine (CLQ), and Diclofenac (DCF) has been carried out using ZnO nanoparticles as the photocatalyst, and sunlight as the source of energy in a batch photocatalytic reactor. This process resulted in the degradation of about 51% for TCT, 65% for SMX, 61% for CLQ, and 55% for DCF within 30 min of solar irradiation. Complete degradation and COD reduction were achieved after a prolonged irradiation. The slow decay is attributed to the evolution of the intermediate compounds, which were identified using the liquid chromatography quadrupole time-of-flight mass spectrometry (LC-Q-TOF-MS) method. The possible intermediates formed were identified for each molecule (i.e., TCT having 6 products, SMX, having 4 products, DCF having 8 products and CLQ having 8 products), and the mechanism for each pollutant is proposed. The effect on distinct operational parameters, like catalyst loading, and pH, environmentally relevant parameters such as ionic effect, and multiple contaminants system were investigated. It was found that the anions such as Cl-, SO42-, CO32-, HCO3-, NO3-, F-, Br-, and I-both individually as well as in combination had no effect on the degradation except for SMX. For multiple component systems, when two pollutants are mixed, each pollutant affects the degradation of the other and in the case of CLQ/TCT system, CLQ inhibits the degradation of TCT drastically. The study demonstrates that ZnO is an effective and convenient option for photocatalytic decontamination of water sources contaminated with a variety of pharmaceutical contaminants.

Sub-chronic exposure of Oreochromis niloticus to environmentally relevant concentrations of smaller microplastics: Accumulation and toxico-physiological responses.

This study assesses the accumulation and toxic effects of environmentally relevant concentrations (0.01, 0.1 and 1 mg/L) of polystyrene MPs (1 µm) in Oreochromis niloticus (Nile tilapia) for 14 days. The results showed that 1 µm PS-MPs accumulated in the intestine, gills, liver, spleen, muscle, gonad and brain. RBC, Hb and HCT showed a significant decline, while WBC and PLT showed a significant increase after the exposure. Glucose, total protein, A/G ratio, SGOT, SGPT and ALP showed significant increments in 0.1 and 1 mg/L of PS-MPs treated groups. The increase in cortisol level and upregulation of HSP70 gene expression in response to MPs exposure indicate MPs-mediated stress in tilapia. MPs-induced oxidative stress is evident from reduced SOD activity, increased MDA levels and upregulated P53 gene expression. The immune response was enhanced by inducing respiratory burst activity, MPO activity and serum TNF-α and IgM levels. MPs exposure also led to down-regulation of CYP1A gene and decreased AChE activity, GNRH and vitellogenin levels, indicating the toxicity of MPs on the cellular detoxification mechanism, nervous and reproductive systems. The present study highlights the tissue accumulation of PS-MP and its effects on hematological, biochemical, immunological and physiological responses in tilapia with low environmentally relevant concentrations.

Isolation and identification of Streptococcus agalactiae in cage-cultured green chromide Etroplus suratensis in Kerala, India.

Streptococcus agalactiae is one of the main aetiological agents in large-scale mortalities of tilapia, having caused major economic losses to the aquaculture industry in recent years. This study describes the isolation and identification of the bacteria from cage-cultured Etroplus suratensis that experienced moderate to severe mortalities in Kerala, India. Gram-positive, catalase-negative S. agalactiae was identified from brain, eye and liver of the fish by antigen grouping and 16S rDNA sequencing. Multiplex PCR confirmed that the isolate belonged to capsular serotype Ia. Antibiotic susceptibility tests showed that the isolate was resistant to methicillin, vancomycin, tetracycline, kanamycin, streptomycin, ampicillin, oxacillin and amikacin. Histological sections of the infected E. suratensis brain revealed infiltration of inflammatory cells, vacuolation and meningitis. This report is the first description of S. agalactiae as a primary pathogen causing mortalities in E. suratensis culture in Kerala.

Genetic diversity and prevalence of extended-spectrum beta-lactamase-producing Escherichia coli and Klebsiella pneumoniae in aquatic environments receiving untreated hospital effluents.

The spread of extended-spectrum beta-lactamase (ESBL)-producing bacteria in the environment has been recognized as a challenge to public health. The aim of the present study was to assess the occurrence of ESBL-producing Escherichia coli and Klebsiella pneumoniae from selected water bodies receiving hospital effluents in Kerala, India. Nearly 69.8% of Enterobacteriaceae isolates were multi-drug resistant by the Kirby-Bauer disc diffusion method. The double disc synergy test was used to detect the ESBL production and the genes responsible for imparting resistance were detected by PCR. Conjugation experiments confirmed the mechanism of plasmid-mediated transfer of resistance. The prevalence of ESBL production in E. coli and K. pneumoniae was 49.2 and 46.8%, respectively. Among the ESBL-encoding genes, blaCTX-M was the most prevalent group followed by blaTEM, blaOXA, blaCMY, and blaSHV. The results suggest that healthcare settings are one of the key contributors to the spread of ESBL-producing bacteria, not only through cross-transmission and ingestion of antibiotics but also through the discharge of waste without a proper treatment, leading to harmful effects on the aquatic environment. The high prevalence of ESBL-producing Enterobacteriaceae with resistance genes in public water bodies even post-treatment poses a serious threat.

Dietary coriander (Coriandrum sativum L) oil improves antioxidant and anti-inflammatory activity, innate immune responses and resistance to Aeromonas hydrophila in Nile tilapia (Oreochromis niloticus).

The use of essential oils (EOs) as a natural alternative to antibiotics for disease prevention strategies is gaining much interest in recent decade. Coriander (Coriandrum sativum L.) essential oil is rich in bioactive compounds like linalool and geranyl acetate which have antioxidant, anti-inflammatory and antimicrobial activities. The present work was proposed to evaluate the inclusion levels of coriander oil in tilapia feed to enhance tilapia health and resistance to bacterial infection. Five iso-nitrogenous and iso-lipidic feeds were prepared with graded levels of coriander oil (0, 0.5, 1, 1.5 and 2%). The fish were then fed with the five experimental diet twice daily for a period of 60 days in triplicate. Haemoglobin, mean corpuscular volume, mean cell haemoglobin increased significantly in the coriander oil treated groups. The thrombocyte count was more in 2% inclusion level. The superoxide dismutase activity increased significantly in all the treated groups. The feeds with 1.5 and 2% coriander oil showed increased respiratory burst and myeloperoxidase activities while lysozyme and antiprotease activities were significantly higher in 1, 1.5 and 2% dietary treatments compared to control. The survival increased in dose dependent manner post challenge with an intraperitoneal injection of Aeromonas hydrophila at a LD50 dose of 5 × 106 cfu mL-1. The feed containing 1, 1.5 and 2% of coriander oil showed 89, 100 and 100% survival respectively compared to 39% in control diet. The expression level of IgM and IL-8 increased significantly post challenge with A. hydrophila in coriander oil fed groups. The expressions of TNFα, IL-1ß, TGFß and HSP 70 genes, however, decreased significantly in the treated groups compared to control. Histopathological examination of spleen showed large melano-macrophage centers in control and 0.5% coriander fed group with signs of necrosis and vacuolation post A. hydrophila infection, whereas 1, 1.5 and 2% treated groups showed normal architecture of spleen. From the above observations it can be concluded that coriander oil with 1% incorporation in feed improves tilapia health and resistance to bacterial infection.

Occurrence of infestation with the isopod, Alitropus typus M. Edwards (Crustacea: Flabellifera: Aegidae) on commercially important freshwater fishes of Kerala, India.

Rapidly rising temperatures and increasing organic load in the inland and coastal waters has led to a significant increase in parasite population. The isopod Alitropus typus infestation on fish in these waters have become more frequent, causing mortalities in both wild and cultured fishes. The present study was aimed to investigate the infestation on different fish hosts, mean intensity, prevalence, environmental influences on the parasite abundance and the histopathological changes it causes in the host. A total of 219 isopod specimens were collected from 149 infested fishes in two districts of Kerala, India. Among the different fish hosts, Channa striata was found to be the most susceptible, followed by Catla catla, Cyprinus carpio, and Wallago attu, with 81%, 10%, 7%, and 2% occurrence, respectively. The prevalence and mean intensity of infestation were found to be 69.8%, 44.4%, 68.2%, 62.5% and 1.33, 4.25, 1.26, 1.80 in C. striata, W. attu, C. catla, and C. carpio, respectively. The parasite abundance was directly influenced by temperature. The histopathology of affected gill tissues showed epithelial lifting, rupture of secondary gill filaments, vacuole formation and hemocytic infiltration. The findings indicated that the isopod parasite, A. typus had a negative impact on fish health and appearance, causing economic losses to the small scale farmers/fishermen. This is the first reported record of the infestation of isopod parasite, A. typus on the Indian major carp C. catla and C. carpio from India.

ß-Defensin: An adroit saviour in teleosts.

ß-Defensin (BD) is an important first line innate defense molecule with potent antimicrobial and immunomodulatory activities in fish. The signatures of ß-defensins are the presence of a net cationic charge and three intramolecular disulfide bonds mediated by six conserved cysteines. It consists of three exons and two introns. The signal peptide is usually conserved and sequence divergence is mostly seen in mature peptide region. The diverse amino acid sequences of matured peptide contribute to a strong positive selection and broad-spectrum antimicrobial activity. It is constitutively expressed in both mucosal as well as systemic sites. Increased expression of ß-defensin was mostly reported in bacterial and viral infections in fish. Its role during parasitic and fungal infections is yet to be investigated. ß-Defensin isoforms such as BD-1, BD-2, BD-3, BD-4 and BD-5 can be witnessed even in early developmental days to different pathogenic exposure in fish. ß-Defensins possess adjuvant properties to enhance antigen-specific immunity promoting both cellular and humoral immune response. It significantly reduces/increases bacterial colonization or viral copy numbers when overexpressed/knockdown. Based on its chemotactic and activating potentials, it can contribute to both innate and adaptive immune responses. With mediated expression, it can also control inflammation. It is potent governing resistance in early developmental days as well. Its expression in pituitary and testis suggests its participation in reproduction and endocrine regulation in fish. Overall, ß-defensins is an important member of antimicrobial peptides (AMPs) with multifunctional role in general homeostasis and to pathogen exposure possessing tremendous therapeutic approaches.

Identification and characterization of vancomycin-resistant Staphylococcus aureus in hospital wastewaters: evidence of horizontal spread of antimicrobial resistance.

Antibiotic resistance has become a major threat to human health around the world, but its spread through the aquatic environment has been often overlooked. This study aimed to determine the occurrence of vancomycin-resistant Staphylococcus aureus in hospital wastewaters and their transmission into public water bodies in Kerala, India. A total of 113 S. aureus were isolated from three hospital effluents in Kerala, India. Standard disc diffusion and the strip method were used for antibiotic susceptibility testing and minimum inhibitory concentration detection. Plasmid-mediated vancomycin resistance was confirmed by plasmid curing and conjugation; resistant genes were detected by the polymerase chain reaction (PCR). Nearly 76% of S. aureus isolates were resistant to ß-lactams, chloramphenicol, macrolides, aminoglycosides, and glycopeptide class of antibiotics. Among the vancomycin-resistant Staphylococcus aureus (VRSA) isolates, the prevalence rates of vanA and vanB resistance-encoding genes were 46.5 and 59.3%, respectively. Through the broth mating method, vanA gene was successfully transferred from VRSA donor to vancomycin-sensitive S. aureus. The study strongly indicates the contamination of water bodies with antibiotic-resistant bacteria from hospital discharges, their dissemination and possible transfer to microbes in the aquatic environment, posing a serious threat for public health.

Changes in the proximate and elemental composition of Alitropus typus (Crustacea: Flabellifera: Aegidae) exposed to lethal dose of bacterial consortium.

Alitropus typus is a crustacean parasite, which is increasingly becoming a menace to aquafarmers. In our previous study, a novel microbial consortium comprising of three exoskeleton degrading bacterial strains (Stenotrophomonas maltophilia, Bacillus altitudinis and Klebsiella pneumoniae) had shown promising results as a biocontrol agent for A. typus. The present investigation reports the changes in proximate and elemental composition associated with the application of microbial consortium on the isopod A. typus. Proximate analysis showed an increased level of protein, lipid, and moisture in treated isopod at 48 h compared with untreated isopod. However, ash and chitin concentrations were lower in treated isopod. The elements in the mid-tergite of untreated isopod was compared with the treated isopod at 48 h using scanning electron microscopy and energy dispersive x-ray spectroscopy (SEM-EDAX). The following elements were analyzed in the mid-tergite segment of untreated isopod: C, O, Na, Mg, Al, Si, P, S, Cl, K, Ca and Fe. The results showed that the concentration of calcium had decreased significantly in the treated isopod at 48 h (4.28 ± 0.11%) when compared to the untreated isopod (10.01 ± 0.32%), indicating that the bound form of calcium carbonate in the exoskeleton had been precipitated by microbial action. The concentration of carbon and phosphorous was higher in the treated isopods at 48 h compared to the untreated ones. The data suggests that treatment with microbial consortium is not only an effective but also an environmentally safe alternative for the control of A. typus.

Outbreaks of epizootic ulcerative syndrome in Kerala, India following episodes of flooding.

Large-scale fish mortality was observed in flood-affected fish farms across several parts of Kerala following heavy rainfall in August 2018 and 2019-nearly 53% above the normal monsoon rain that the region receives. The affected fish had severe haemorrhages and ulcers, typical of the highly infectious disease epizootic ulcerative syndrome (EUS) caused by the water mould Aphanomyces invadans. In freshwater, snakeheads Channa spp. and in brackish water mullet (Mugilidae) and pearl spot (Etroplus suratensis) were severely affected. EUS was observed in 4 freshwater fishes for the first time: dotted sawfin barb Pethia punctata (Cyprinidae), Malabar leaffish Pristolepis malabarica (Pristolepididae), mahecola barb Puntius mahecola (Cyprinidae) and giant snakehead Channa pseudomarulius (Channidae). Histology and molecular diagnosis confirmed the cause of mortality to be EUS. Fungal hyphae were also observed in deeply ulcerated fish, revealed by lactophenol cotton blue staining. The severity of the EUS outbreak was linked to the sudden change in water quality associated with the flood, such as lower water temperature, and decreases in pH, total alkalinity and total hardness.

Nitrospira as versatile nitrifiers: Taxonomy, ecophysiology, genome characteristics, growth, and metabolic diversity.

The global nitrogen cycle is of paramount significance as it affects important processes like primary productivity and decomposition. Nitrification, the oxidation of ammonia to nitrate via nitrite, is a key process in the nitrogen cycle. The knowledge about nitrification has been challenged during the last few decades with inventions like anaerobic ammonia oxidation, ammonia-oxidizing archaea, and recently the complete ammonia oxidation (comammox). The discovery of comammox Nitrospira has made a paradigm shift in nitrification, before which it was considered as a two-step process, mediated by chemolithoautotrophic ammonia oxidizers and nitrite oxidizers. The genome of comammox Nitrospira equipped with molecular machineries for both ammonia and nitrite oxidation. The genus Nitrospira is ubiquitous, comes under phylum Nitrospirae, which comprises six sublineages consisting of canonical nitrite oxidizers and comammox. The single-step nitrification is energetically more feasible; furthermore, the existence of diverse metabolic pathways in Nitrospira is critical for its establishment in various habitats. The present review discusses the taxonomy, ecophysiology, isolation, identification, growth, and metabolic diversity of the genus Nitrospira; compares the genomes of canonical nitrite-oxidizing Nitrospira and comammox Nitrospira, and analyses the differences of Nitrospira with other nitrifying bacteria.

Formulation of an exoskeleton degrading bacterial consortium from seafood processing effluent for the biocontrol of crustacean parasite Alitropus typus.

Parasitic infestations on cultured fish due to the crustacean isopod Alitropus typus has been on the rise in recent years, causing large scale mortality, leading to significant economic loss to the farmer. Crustaceans are encased by an exoskeleton composed of chitin, protein and lipid microfibril frameworks, in which calcium carbonate is deposited. A strategy focused on the degradation of the exoskeletal framework utilizing nonpathogenic microorganisms that produce a wide variety of hydrolytic enzymes may be an environment-friendly and safe alternative to control these pests. The present study was aimed to formulate a microbial consortium having chitinase, protease, lipase and urease producing bacteria from seafood processing effluents that can potentially degrade the exoskeleton of A. typus. Based on the qualitative and quantitative assessment of the extracellular enzymes produced by the isolates, a novel consortium was prepared with three strains that were not antagonistic to each other and were nonpathogenic. The chitinase producing - Stenotrophomonas maltophilia and Bacillus altitudinis that produced protease and lipase as well; and non-chitinase producing Klebsiella pneumoniae were taken in the ratio of 1:1:2 respectively (109 CFU/mL). The result showed 100 % mortality of the isopods within five days when applied at a concentration of 2% (v/v) of 107 CFU/mL without any adverse effect on the fish host Oreochromis niloticus. Analysis of the ultrastructural alterations of the parasites by Environmental Scanning Electron microscopy (ESEM) showed noticeable exoskeletal damages. The microbial members of the consortium displayed remarkable chemotactic properties towards A. typus. The results suggest that the microbial consortium acts as a potential parasiticide that can be used for the control of A. typus infestation in aquaculture ponds., thus benefitting the aquaculture industry especially the small-scale farmers.

Investigating the impact of hospital antibiotic usage on aquatic environment and aquaculture systems: A molecular study of quinolone resistance in Escherichia coli.

Quinolones are one of the most important classes of antibacterials available for the treatment of infectious diseases in humans. However, there is a growing concern about bacterial resistance to antimicrobials including quinolones. The spread of antibiotic-resistant bacteria in the aquatic environment has been recognized as a growing threat to public health and hospitals appear to be a major contributor to this. The objective of this study was to investigate the prevalence of quinolone resistance in Escherichia coli from selected water bodies receiving direct hospital effluents in Kerala, India. Standard disc diffusion and E-test were used for antibiotic susceptibility testing. As antibiotic resistance can develop in bacterial isolates by different means, EtBr Agar Cartwheel method was used to detect the efflux pump activity and presence of resistant genes was detected by PCR. The mechanism of transfer of plasmid mediated resistance was confirmed by conjugation experiments. A total of 209 multidrug-resistant Escherichia coli were isolated from different hospital effluent discharge sites and aquaculture farms located in their vicinity. Among them, qnrB was found to be most prevalent followed by qnrS, OqxAB, qnrA and aac (6')-Ib-cr. The results suggested that the antibiotics present at sub-inhibitory concentrations in direct hospital effluents increases the selection pressure impacting the cell function of even normal microorganisms in the aquatic environment to change the genetic expression of virulence factors or acquire resistance genes by different transfer mechanisms, posing a serious threat to public health.