Bacterial Septicemia Research Articles

Penumbra Indigo® system to safely remove intracardiac thrombus in a 7-month-old infant with severe immunodeficiency disorder.

We report on a 7-month-old boy (4.2 kg/60 cm) with severe immunodeficiency disorder and bacterial septicaemia who was referred for an infected atrial thrombus secondary to a jugular central line. The echocardiogram showed a teardrop-shaped thrombus with a wide base adherent to the interatrial wall and a flimsy tail moving freely in the right atrium. Chest CT scan showed multiple lesions in both lungs consistent with infected micro-thrombi. The thrombus increased in size despite 2 weeks of antibiotics and anticoagulation. We applied the Indigo® Lightning® 7 aspiration system from Penumbra® (Alameda, USA) and removed percutaneously the thrombus under transoesophageal ultrasound and biplane fluoroscopic guidance. At 6 weeks of follow-up, the patient is alive, under enoxaparin with no procedure-related complication.

Opportunistic Infections among People Living with HIV in the Infectious Disease Department, the University Hospital of Fann in Dakar, Senegal

Aim: The aim of this study was to identify the main infections and opportunistic infections in hospitalized patients living with HIV and to determine the hospital lethality rate. Patients and Methods: This was a retrospective, descriptive study of patients hospitalized in the infectious diseases department of the University Hospital of Fann over a 02-year period from 1 January 2021 to 31 December 2022. Results: We recorded 308 cases, 296 of which were patients living with HIV, out of a total of 1208 patients admitted to the department, a hospital prevalence rate of 24.5%. The average age of the patients was 43.3 ± 13.3 years, with a sex ratio of 0.7. One hundred and thirty-one patients (44.26%) were married. 22.97% had no occupation and 35.5% of patients came from home. The average diagnostic period was 3.9 days ± 4.78 days. Two hundred and five patients (69.26%) were at WHO stage 4. Tuberculosis was the most common bacterial infection, with 114 cases (38.5%), followed by common bacterial pneumonia (7.77%) and septicemia (4.72%). With regard to viral infections, the prevalence of viral hepatitis B was 6.76%, followed by herpes (1.68%). Among parasitic infections, toxoplasmosis was noted in 6.41% and cryptosporidiosis in 2.02%. Candidiasis was the most common fungal opportunistic infection, affecting forty-three patients (14.52%), followed by pneumocystis (7.09%) and cryptococcosis (2.36%). More than a third of our patients (37.84%) had severe anaemia, with haemoglobin levels below 8g/dl. Nearly a quarter of patients (21.28%) had impaired kidney function. Conclusion: HIV infection occurs in young adults at a late stage. Mortality remains high due to opportunistic infection. It is essential to carry out early screening, but above all to make available diagnostic tools and certain molecules for treatment of opportunistic infections.

Endonuclease A in Streptococcus pneumoniae: escaping from neutrophil extracellular traps (NETs) and relationship in immunogenicity

Streptococcus pneumoniae (S. pneumoniae), which is a Gram-positive diplococcus, has emerged as a significant human pathogen. It is a primary cause of bacterial pneumonia, otitis media, meningitis, and septicemia, leading to a considerable impact on global morbidity and mortality. The investigation of S. pneumoniae and its virulence factors has resulted in the identification of surface endonuclease A (EndA). EndA functions in DNA uptake during natural transformation and plays a significant role in gene transfer. The ability of S. pneumoniae to degrade neutrophil extracellular traps (NETs) enhances its virulence and invasive potential in pneumococcal infections. NETosis occurs when neutrophils release chromatin into the extracellular space to form NETs, capturing and neutralizing pathogens. Currently, NETosis can be induced by several microbes, particulate matter, and sterile stimuli through distinct cellular mechanisms, and this includes the involvement of EndA in S. pneumoniae. Here, we reviewed the cellular functions of EndA, its role in S. pneumoniae as a virulence factor in relation to NETosis, its relationship to immunogenicity, and its involvement in several diseases. The discovery of this relationship would significantly impact therapeutic technology in reducing disease burden, especially pneumococcal infections.

Uncommon Organisms in Neonatal Meningitis: Two Case Reports

These case reports describe two neonates, born at term, diagnosed with bacterial meningitis and septicemia caused by uncommon organisms. The clinical presentation, diagnostic reasoning, national guidelines, hospital course, and follow-up are discussed. Meningitis is among the differential diagnoses when there is a concern for neonatal sepsis. Concern for sepsis can arise from a variety of antepartum, intrapartum, and postpartum risk factors and present with a variety of symptoms. Neonatal sepsis is a significant cause of mortality, with 750,000 infant deaths annually. Effective treatment of neonatal sepsis requires timely diagnosis and tailored antimicrobial therapy that targets the causative pathogens.

Adjuvant-dependent impacts on vaccine-induced humoral responses and protection in preclinical models of nasal and genital colonization by pathogenic Neisseria.

Neisseria gonorrhoeae, which causes the sexually transmitted infection gonorrhea and N. meningitidis, a leading cause of bacterial meningitis and septicemia, are closely related human-restricted pathogens that inhabit distinct primary mucosal niches. While successful vaccines against invasive meningococcal disease have been available for decades, the rapid rise in antibiotic resistance has led to an urgent need to develop an effective gonococcal vaccine. Several surface antigens are shared among these two pathogens, making cross-species protection an exciting prospect. However, the type of vaccine-mediated immune response required to achieve protection against respiratory versus genital infection remains ill defined. In this study, we utilize well established mouse models of female lower genital tract colonization by N. gonorrhoeae and upper respiratory tract colonization by N. meningitidis to examine the performance of transferrin binding protein B (TbpB) vaccines formulated with immunologically distinct vaccine adjuvants. We demonstrate that vaccine-mediated protection is influenced by the choice of adjuvant, with Th1/2-balanced adjuvants performing optimally against N. gonorrhoeae, and both Th1/2-balanced and Th2-skewing adjuvants leading to a significant reduction in N. meningitidis burden. We further establish a lack of correlation between protection status and the humoral response or bactericidal titre. Combined, this work provides supports the feasibility for a single vaccine formulation to achieve pan-neisserial coverage.

Evaluation of virulence of Aeromonas veronii strain GZ21-2 and development of a highly effective vaccine for grass carp with the potential for industrial application

Bacterial septicemia represents a significant disease affecting cultured grass carp culture, with the primary etiological agent identified as the Gram-negative bacterium Aeromonas veronii. In response to an outbreak of septicemia in Guangzhou, we developed a formaldehyde-inactivated vaccine against an A. veronii strain designated AV-GZ21-2. This strain exhibited high pathogenicity in experimental infections across at all developmental stages of grass carp. Mortality rates for grass carp weighing 15 ± 5 g ranged from 16 % to 92 % at exposure temperatures of 19 °C–34 °C, respectively. The median lethal dose (LD50) for grass carp groups weighing 15 ± 5 g, 60 ± 10 g, 150 ± 30 g and 500 ± 50 g were determined to be 1.43, 2.52, 4.65 and 7.12 × 107(CFU/mL), respectively. We investigated the inactivated vaccine in conbination with aluminum hydroxide gel (AV-AHG), Montanide ISA201VG (AV-201VG), and white oil (AV-WO) adjuvants. This study aimed to optimize inactivation conditions and identify the adjuvant that elicits the most robust immune response. The AV-GZ21-2 inactivated bacterial solution (AV),when combined with various adjuvants, was capable of inducing a strong specific immune response in grass carp. The relative percent survival (RPS) following a lethal challenge with AV-GZ21-2 were 94 % for AV-AHG, 88 % for AV-201VG, 84 % for AV-WO and 78 % for AV alone. The minimum immunization dose of the AV-AHG vaccine was determined to be 6.0 × 107 CFU per fish, providing immunity for a duration of six months with an immune protection level exceeding 75 %. Furthermore, the AV-AHG vaccine demonstrated significant protective efficacy against various epidemic isolates of A. veronii. Consequently, we developed an inactivated vaccine targeting a highly pathogenic strain of A. veronii, incorporating an aluminum hydroxide gel adjuvant, which resulted in high immune protection and a duration of immunity exceeding six months. These findings suggest that the AV-AHG vaccine holds substantial potential for industrial application.

PCR identification of Enterococcus Species as a Primary Pathogen in Neonatal Bloodstream Infections at Damascus University Paediatric Hospital

Bacterial septicaemia is one of the most common causes of death in newborns throughout the globe. Recently, gram positive bacteria have been detected as a main responsible of hospital acquired blood infection in developed country especially Enterococcus sp. and Staphylococcus sp. This preliminary study aimed to identify Enterococcus species and Staphylococcus species isolated form acquired blood infection in the department of premature and neonates at paediatric university hospital in Damascus, based on PCR technology. the antibiotic sensitivity these pathogens was also investigated against common antibiotics usually used to treat septicaemia in this hospital. Bacterial gDNA was extracted directly from blood samples of children with acquired Septicemia. The bacterial infection was confirmed in 50 samples based on the amplification of 16srDNA gene. Genus Enterococcus sp. and Staphylococcus species were identified as source of infection in samples using specific primers via PCR technique. The antibiotic sensitivity of isolated bacterial strains was studied using Kirby-Bauer disc method. Our study showed that 47 of the 50 samples of the infection were bacterial. The rate of blood infection caused by Enterococcus species was 24%, and 4% for Staphylococcus sp. the isolated bacteria showed a high sensitivity to Amikacin, medium sensitivity to Vancomycin, and less sensitivity to Ampicillin and Gentamycin. Enterococcus species Showed good sensitivity to Amikacin and Vancomycin and low sensitivity to Gentamycin, while was resistant to Ampicillin. Furthermore, the two isolated stains Enterococcus sp and Staphylococcus species showed a good sensitivity against chlorhexidine. This study confirmed the importance of molecular technologies in diagnosing the acquired septicaemia and identifying the specific infectious agent. The molecular test showed that Enterococcus sp. was an important cause of acquired blood infection in neonates respect to ampicillin resistant staphylococcus species.

Susceptibility and host immune response comparison between Siniperca chuatsi and Siniperca scherzeri infected by Aeromonas veronii

The bacterial hemorrhagic septicemia caused by Aeromonas veronii is a highly contagious disease leading to high mortality in various aquatic animals, which has become one of the most serious diseases in mandarin fish, Siniperca chuatsi and Siniperca scherzeri. The difference of susceptibility and host immune response between S. chuatsi and S. scherzeri to A. veronii has not been revealed. In this study, the calculated LD50 of A. veronii SJ4 to S. chuatsi and S. scherzeri was 3.8 × 105 CFU/ mL and 4.8 × 106 CFU/mL, respectively, indicating S. chuatsi displays more susceptible to A. veronii than S. scherzeri. The differences of immune response between S. chuatsi and S. scherzeri infected by A. veronii SJ4 was analyzed by transcriptome technology. A total of 6010 and 1676 differentially expressed genes (DEGs) of kidneys were detected in the S. scherzeri experimental group (S-S-E/C) and S. chuatsi experimental group (S-C-E/C) at the 12 hpi, respectively. GO and KEGG functional analysis of DEGs indicated that numerous enriched immune terms were mainly related to antigen processing and presentation, toll-like receptor signaling, and C-type lectin receptor signaling. 8 DEGs (CLE, HSP90, IL6, MHC I, MHC II, RAS, TLR5 and TLR9) were selected from these immune related pathways, and the spatiotemporal expression of these DEGs in S. chuatsi and S. scherzeri were evaluated and compared. The results showed that CLE, HSP90, IL6, MHC I, MHC II, RAS, TLR5 and TLR9 in S. scherzeri after A. veronii infection were significantly up-regulated than in S. chuatsi. Our results indicated that these immune-related genes may exert a pivotal role during the initial phase of infection, and the priming speed of these immune-related genes lead to the differences in host immunity. This study screened the potential genes and pathways which involved in the immune response of mandarin fish, which helps for further understanding on fish immune. By selecting immune-related genes and comparing the immune mechanisms of S. chuatsi and S. scherzeri at the transcriptome level, the research offers new insights for the genetic breeding of Siniperca species to enhance infection resistance.

Integrating Clinical and Neuroimaging Markers to Predict the Onset of Posthemorrhagic Ventricular Dilatation in Preterm Neonates

BackgroundPosthemorrhagic ventricular dilatation (PHVD) is a major complication of intraventricular hemorrhage (IVH); it is associated with high risks of cerebral palsy and cognitive deficits compared with infants without PHVD. This study aims to explore the early perinatal risk factors-associated with the risk of progressive PHVD. MethodsNeonates ≤29 weeks gestational age (GA) with Grade II-III IVH and periventricular hemorrhagic infarct (PVHI) between 2015 and 2021 were retrospectively reviewed. All cranial ultrasounds done within 14 days postnatal age (PNA) were assessed for grade of IVH, anterior horn width (AHW), ventricular index (VI), and thalamo-occipital index (TOD). The outcome was defined as death of any cause or VI and/or AHW and/or TOD ≥ moderate-risk zone based on an ultrasound done beyond two weeks PNA. ResultsA total of 146 infants with a mean GA of 26 ± 1.8 weeks, birth weight 900 ± 234 g were included, 46% were females. The primary outcome occurred in 56 (39%) infants; among them 17 (30%) and 11 (20%) needed ventricular reservoir and shunt insertion, respectively. The risk factors present within 14 days PNA that significantly increased the odds of developing PHVD were hemodynamically significant patent ductus arteriosus (odds ratio [OR] 6.1, 95% confidence interval [CI] 1.9 to 22), culture-proven sepsis (OR 5.4, 95% CI 1.8 to 18), Grade III IVH (OR 4.6, 95% CI 1.1 to 22), PVHI (OR 3.0, 95% CI 0.9 to 10), and VI (OR 2.1, 95% CI 1.6 to 2.9). ConclusionsClinical predictors such as significant ductus arteriosus and bacterial septicemia, along with risk levels of AHW and VI measured with early cranial ultrasounds, are potential predictors of subsequent onset of PHVD.

Oligodeoxynucleotides containing CpG motifs upregulate bactericidal activities of heterophils and enhance immunoprotection of neonatal broiler chickens against Salmonella Typhimurium septicemia

In the past, we demonstrated that oligodeoxynucleotides containing CpG motifs (CpG-ODN) mimicking bacterial DNA, stimulate the innate immune system of neonatal broiler chickens and protect them against Escherichia coli and Salmonella Typhimurium (S. Typhimurium) septicemia. The first line of innate immune defense mechanism is formed by heterophils and plays a critical protective role against bacterial septicemia in avian species. Therefore, the objectives of this study were 1) to explore the kinetics of CpG-ODN mediated antibacterial mechanisms of heterophils following single or twice administration of CpG-ODN in neonatal broiler chickens and 2) to investigate the kinetics of the immunoprotective efficacy of single versus twice administration of CpG-ODN against S. Typhimurium septicemia. In this study, we successfully developed and optimized flow cytometry-based assays to measure phagocytosis, oxidative burst, and degranulation activity of heterophils. Birds that received CpG-ODN had significantly increased (p < 0.05) phagocytosis, oxidative burst, and degranulation activity of heterophils as early as 24 h following CpG-ODN administration. Twice administration of CpG-ODN significantly increased the phagocytosis activity of heterophils. In addition, our newly developed CD107a based flow cytometry assay demonstrated a significantly higher degranulation activity of heterophils following twice than single administration of CpG-ODN. However, the oxidative burst activity of heterophils was not significantly different between birds that received CpG-ODN only once or twice. Furthermore, delivery of CpG-ODN twice increased immunoprotection against S. Typhimurium septicemia compared to once but the difference was not statistically significant. In conclusion, we demonstrated enhanced bactericidal activity of heterophils after administration of CpG-ODN to neonatal broiler chickens. Further investigations will be required to identify other activated innate immune cells and the specific molecular pathways associated with the CpG-ODN mediated activation of heterophils.

Bacterial septicemia and herpesvirus infection in Antarctic fur seals (Arctocephalus gazella) stranded in the São Paulo coast, Brazil

In August 2021, two juvenile male Antarctic fur seals (Arctocephalus gazella) stranded in the southeastern Brazilian coast and were referred to rehabilitation centers. The animals presented increased body temperature, prostration, respiratory distress and despite treatment died. A necropsy following a standardized protocol was performed, and formalin-fixed tissues were processed for microscopic examination. Samples were screened for morbillivirus, herpesvirus, and Brucella spp. by molecular analyses (PCR, RT-PCR). Bacteriological culture was performed in samples collected from the lungs, trachea, and lymph nodes of both cases. The main histopathologic findings were of infectious nature, including multifocal necrotizing and fibrinous mixed interstitial pneumonia, bronchiolitis, and bronchitis, with intralesional myriad bacteria associated with vascular fibrinoid necrosis. Pseudomonas aeruginosa was isolated from tracheal and lung swabs of Case 1, and Klebsiella oxytoca was found in nostril swabs, tracheobronchial lymph nodes, and lung of Case 2. Gammaherpesvirus infection was detected in both cases, and the sequences retrieved were classified into the genus Percavirus. All tested samples were PCR-negative for Brucella spp. and morbillivirus. We hypothesize that the deficient immunological status in association with starvation predisposed the reactivation of herpesvirus and secondary bacterial co-infections. To the authors’ knowledge, this is the first molecular detection of herpesvirus in an Antarctic pinniped. These findings reinforce that Otariid gammaherpesvirus circulating in the Southern Hemisphere are likely endemic in the Arctocephalus genus. This report contributes to the current knowledge of health aspects affecting wild pinnipeds, especially in the poorly studied Antarctic species.

Immunoprotective efficacy evaluation of OmpTS subunit vaccine against Aeromonas hydrophila infection in Megalobrama amblycephala

Bacterial septicemia in freshwater fish is mainly caused by Aeromonas hydrophila infection, which affects the development of aquaculture industry. In the context of sustainable aquaculture, subunit vaccines are of great values because they play positive roles in reducing the overuse of antibiotics and protecting aquatic animals against bacterial infection. In this study, the recombinant outer membrane protein OmpTS of A. hydrophila were used as subunit vaccine to immunize Megalobrama amblycephala, and its immunoprotective effect and host immune responses were evaluated. The survival rates of the vaccinated groups after bacterial infection were significantly higher than that of the control group, especially of the OmpTS high-dose vaccinated group. The better protective effects of vaccinated groups might be attributed to the increased levels of serum IgM-specific antibody titer, the reduced relative abundance of A. hydrophila in various tissues, the increased number of immune-positive cells with different epitopes, the up-regulated expression levels of immune-related genes, and the enhanced activities of antibacterial enzymes. In conclusion, OmpTS subunit vaccine could strongly induce host immune responses in M. amblycephala, thereby enhancing both cellular and humoral immunity, which exhibited excellent and effective immunoprotective efficacy.

Lactate to Albumin Ratio Is Not Predictive of Outcome in Septic Dogs: A Retrospective Case-Control Study.

The objective of this study was to investigate the value of the lactate to albumin ratio (L:A) as a prognostic marker for mortality in septic dogs. A single-center retrospective case-control study based on clinical record review was conducted at an academic teaching hospital. All records were extracted for diagnoses of bacterial sepsis, septic peritonitis, septic shock, or septicemia between February 2012 and October 2021. The study included 143 dogs. The most commonly identified sepsis diagnoses in dogs were septic peritonitis (55%; 78/143), unclassified sepsis (20%), and sepsis secondary to wounds or dermatological conditions (10%; 15/143). Median lactate and albumin for all dogs at presentation were 2.80 mmol/L and 2.6 g/dL, respectively; the median L:A ratio was 1.22. No clinically or statistically significant differences in lactate (P = 0.631), albumin (P = 0.695), or L:A (P = 0.908) were found between survivors and nonsurvivors.

Erysipelothrix amsterdamensis sp. nov., associated with mortalities among endangered seabirds.

Infectious diseases threaten endangered species, particularly in small isolated populations. Seabird populations on the remote Amsterdam Island in the Indian Ocean have been in decline for the past three decades, with avian cholera caused by Pasteurella multocida proposed as the primary driver. However, Erysipelothrix species have also been sporadically detected from albatrosses on Amsterdam Island and may be contributing to some of the observed mortality. In this study, we genomically characterized 16 Erysipelothrix species isolates obtained from three Indian yellow-nosed albatross (Thalassarche carteri) chick carcasses in 2019. Histological analyses suggest that they died of bacterial septicaemia. Two isolates were sequenced using both Illumina short-read and MinION long-read approaches, which - following hybrid assembly - resulted in closed circular genomes. Mapping of Illumina reads from the remaining isolates to one of these new reference genomes revealed that all 16 isolates were closely related, with a maximum of 13 nucleotide differences distinguishing any pair of isolates. The nucleotide diversity of isolates obtained from the same or different carcasses was similar, suggesting all three chicks were likely infected from a common source. These genomes were compared with a global collection of genomes from Erysipelothrix rhusiopathiae and other species from the same genus. The isolates from albatrosses were phylogenetically distinct, sharing a most recent common ancestor with E. rhusiopathiae. Based on phylogenomic analysis and standard thresholds for average nucleotide identity and digital DNA-DNA hybridization, these isolates represent a novel Erysipelothrix species, for which we propose the name Erysipelothrix amsterdamensis sp. nov. The type strain is A18Y020dT (=CIP 112216T=DSM 115297T). The implications of this bacterium for albatross conservation will require further study.

Pathology, microbiology, and genetic diversity associated with Erysipelothrix rhusiopathiae and novel Erysipelothrix spp. infections in southern sea otters (Enhydra lutris nereis).

Erysipelothrix spp., including E. rhusiopathiae, are zoonotic bacterial pathogens that can cause morbidity and mortality in mammals, fish, reptiles, birds, and humans. The southern sea otter (SSO; Enhydra lutris nereis) is a federally-listed threatened species for which infectious disease is a major cause of mortality. We estimated the frequency of detection of these opportunistic pathogens in dead SSOs, described pathology associated with Erysipelothrix infections in SSOs, characterized the genetic diversity and antimicrobial susceptibility of SSO isolates, and evaluated the virulence of two novel Erysipelothrix isolates from SSOs using an in vivo fish model. From 1998 to 2021 Erysipelothrix spp. were isolated from six of >500 necropsied SSOs. Erysipelothrix spp. were isolated in pure culture from three cases, while the other three were mixed cultures. Bacterial septicemia was a primary or contributing cause of death in five of the six cases. Other pathology observed included suppurative lymphadenopathy, fibrinosuppurative arteritis with thrombosis and infarction, bilateral uveitis and endophthalmitis, hypopyon, petechia and ecchymoses, mucosal infarction, and suppurative meningoencephalitis and ventriculitis. Short to long slender Gram-positive or Gram-variable bacterial rods were identified within lesions, alone or with other opportunistic bacteria. All six SSO isolates had the spaA genotype-four isolates clustered with spaA E. rhusiopathiae strains from various terrestrial and marine animal hosts. Two isolates did not cluster with any known Erysipelothrix spp.; whole genome sequencing revealed a novel Erysipelothrix species and a novel E. rhusiopathiae subspecies. We propose the names Erysipelothrix enhydrae sp. nov. and Erysipelothrix rhusiopathiae ohloneorum ssp. nov. respectively. The type strains are E. enhydrae UCD-4322-04 and E. rhusiopathiae ohloneorum UCD-4724-06, respectively. Experimental injection of tiger barbs (Puntigrus tetrazona) resulted in infection and mortality from the two novel Erysipelothrix spp. Antimicrobial susceptibility testing of Erysipelothrix isolates from SSOs shows similar susceptibility profiles to isolates from other terrestrial and aquatic animals. This is the first description of the pathology, microbial characteristics, and genetic diversity of Erysipelothrix isolates recovered from diseased SSOs. Methods presented here can facilitate case recognition, aid characterization of Erysipelothrix isolates, and illustrate assessment of virulence using fish models.

Borna disease in an adult free-ranging Eurasian beaver (Castor fiber albicus)

Borna disease (BD) associated with a peracute bacterial septicaemia with Escherichia coli was diagnosed in an adult female, naturally infected, free-ranging Eurasian beaver of the subspecies Castor fiber albicus, clinically characterized by weight loss, depression, weakness and gurgled peristaltic sounds. The beaver was euthanized humanely. Necropsy and light microscopy revealed a non-purulent meningoencephalitis with typical mononuclear perivascular cuffs and parenchymal infiltrates. The diagnosis of BD was confirmed by detection of viral antigen and RNA by immunohistochemistry and reverse transcription-polymerase chain reaction (RT-PCR). The PCR product was sequenced and cluster analysis revealed a close relationship between endemic clusters in Saxony-Anhalt. This is the first report of naturally occurring BD in a free-ranging Eurasian beaver.

Evaluation of the effectiveness of the use of a complex of antibacterial drugs for the treatment of bacterial hemorrhagic septicemia in fish

The aim of the study was to develop therapeutic measures to combat bacterial hemorrhagic septicemia of fish using a complex of antibacterial drugs “Levofloxacin” and “Chlortetracycline”.Methods used: experiments were carried out in aquarium conditions on juvenile carp and hybrids «Siberian sturgeon×Kaluga» (hereinafter hybrid SO×K) infected with a mixed culture of pathogens: highly pathogenic strains of Aeromonas sp., strains of R.R. Acinetobacter and Citrobacter. In the experiment, 2 variants of the use of antibiotics for a course of 7 days were tested. Bacteriological seeding of fish parenchymal organ samples was carried out on nutrient and differential diagnostic media.Novelty: it consists in working out the scheme of application for fish of a complex of new antibiotics for aquaculture.Results: the results of the evaluation of the therapeutic effect of antibiotics “Levofloxacin” + “Chlortetracycline” in the treatment of bacterial hemorrhagic septicemia are presented. The cessation of fish death was noted the next day after the start of therapy. Positive results were obtained in carp — with a combination of levofloxacin at a dosage of 1000 mg/kg of ichthyomass and chlortetracycline — 100 mg/kg of ichthyomass, in a hybrid of SO×K — 500 mg/kg of ichthyomass of levofloxacin + 200 mg/kg of ichthyomass of chlortetracycline. Evaluation of their combinations with different dosages did not show 100% effect. The difficulties of therapy have been identified, which are associated with the spread of strains of microorganisms resistant to antibacterial drugs.Practical significance: the developed method of therapy is effective, reduces the damage from the disease and can be recommended when developing measures to combat bacterial hemorrhagic septicemia in fish in aquaculture.

Thyroid neoplasia associated with nutritional deficiency in cultured jade perch in Hong Kong.

Non-neoplastic thyroid hyperplasia is common in terrestrial animals, secondary to nutritional imbalances or other goitrogenic compounds. Thyroid hyperplasia is relatively common in teleost fish; however, malignant thyroid neoplasia is rarely reported. We diagnosed cases of thyroid neoplasia in a population of jade perch (Scortum barcoo). The 3,000 affected fish had grossly apparent, bilateral pharyngeal swellings. Histologic examination confirmed proliferative thyroid lesions ranging from hyperplasia to well-differentiated follicular cell carcinoma. In addition, the younger population of animals on the farm also had bacterial septicemia and mild Dactylogyrus sp. gill infections. Feed analysis revealed a severe deficiency of iodine and vitamin C in the homemade fish diet used on the farm. The concentrations of other minerals, such as zinc, were also on the lower end of the recommended requirements for freshwater fish. The farm was using surface water in its recirculating aquaculture system. We recommended a switch to a commercial aquaculture diet, as well as to use well water rather than surface water to avoid any contaminants, and to treat the younger fish with an antibiotic for bacterial septicemia. Our case provides evidence of progression from nutritional-associated thyroid hyperplasia to neoplasia in farmed teleost fish.

Identification and characterisation of emerging fish pathogens Aeromonas veronii and Aeromonas hydrophila isolated from naturally infected Channa punctata.

Naturally infected Channa punctata exhibiting bacterial septicemic syndrome including ulcerations along with mortality records were collected from a fish farm in Assam during winter season (early November 2020 to early January 2021). The moribund fishes were subjected for bacterial isolation followed by identification of the bacteria. Two dominant emerging bacterial pathogens were identified as Aeromonas veronii (isolate ZooGURD-01) and Aeromonas hydrophila (isolate ZooGURD-05) by standard biochemical characterization and 16S rRNA and rpo B gene amplification. Re-infection experiments of both the bacterial isolates in healthy disease-free C. punctata showed similar symptoms to that of natural infection thus confirming their virulence. The LD50 calculated during challenge test for both the isolates ZooGURD-01 and ZooGURD-05 found to be pathogenic at 2.6 × 104 and 1.6 × 104CFU/fish respectively. Further PCR amplification of specific virulent genes (aerolysin, hemolysin and enterotoxin) confirmed pathogenicity for both isolates. Histopathological examinations of liver and kidney in re-infection experiments showed prominent changes supporting bacterial septicaemia. Antibiotic sensitivity pattern showed that the isolates ZooGURD-01 and ZooGURD-05 were sensitive to 22 and 19 out of 25 antimicrobials respectively. The present study was the first report on the mortality of farmed C. punctata associated with natural infection caused by A. veronii and A. hydrophila with no record of pathogenicity of A. veronii in C. punctata.

Deployment of in-silico analysis to reveal the antibacterial profiles of Allium sativum against Aeromonas hydrophila

The key challenges in aquaculture are the emergence of antimicrobial resistance in fish cultivation due to the frequent use of antibiotics. Over the past three decades, this led to a major threat in the persistence of multidrug-resistant bacteria. Aeromonas hydrophila is a Gram-negative bacterium, a common causative agent of motile bacterial septicemia in fisheries. Combining these two key factors of the presented narrative, the essential type II topoisomerase enzyme ‘DNA gyrase’ (encoded by the gyrA and gyrB genes) as a potential drug target in Aeromonas hydrophila was taken, retrieve its sequence from UniProtKB (Id-A0KKQ2), constructs the 3-D structure using SWISS-MODEL (in absence of the experimental structure), and performs an in-silico screening of selected drug-like compounds (25 antibacterial phytochemicals) most of which are bioactive compounds of A. sativum through molecular docking. Quercetin a derivative of A. sativum was observed as a more potent drug molecule than other studied molecules based on ligand binding energy as docking score −7.812, showed highly encouraging results, supported by a study using structural dynamics of the receptor-ligand complex for a duration of 100 ns by Molecular Dynamic Simulations and confirm binding stability with MM-GBSA calculations. This study also provides theoretical grounds for drug discovery against other pathogenic bacteria posing threats to the ecosystem. Switching to herbal products is the best way to combat the plurality of problems to avoid seen or unseen post-treatment side effects. Communicated by Ramaswamy H. Sarma