Septicemia Disease Research Articles

Production techniques and environmental management in frog farming in Dong Thap province

This study surveyed 40 farmers on their production techniques and environmental management in frog farming in Cao Lanh and Thap Muoi district, Dong Thap province, and the results showed that frogs were cultured in tarpaulin tanks (82.5%), hapas in an earth pond (35%), and earth ponds (2.5%). Most of the farmers (82.5%) had a combination of breeding frogs and production frogs to be self-sufficient froglet. Stocking density is high with 146.3±92.3 individuals/m2 for production frogs and 51.6±35.7 individuals/m2 for breeding frogs. The culture duration of froglet was an average of 33.6±8.8 days/crop (9.3±2.4 crops/year) and production frogs was 64.7±9.7 days/crop (5.1±0.6 crops/year). Frogs were raised with a commercial pellet feed of many brands. The diseases occurred in tadpole and froglet phase (2-30 days), including septicemia diseases (57.5%), red thighs (45%), white bodies (35%), blindness (35%), digestive disorders (20%), and flatulence (15%). The disease causes were mainly due to poor water quality, weather change, feed, and high stocking density. However, few farmers had treated farming system (37.5%), supplemental water (27.5%), and monitored and controlled water quality. There were 60% of households to discharge wastewater directly into rivers and canals. Some farmers have used nutrient for wastewater from frogs with combining frog with fish (27.5%), or discharging wastewater into ditches gardens, fields (7.5%), settling pond (5%), which have helped to increase income and protect the environment. Therefore, farmers need to be supported with knowledge of farming technique and environmental management from the local government.

Innate Immune Response Assessment in Cyprinus carpio L. upon Experimental Administration with Artemia salina Bio-Encapsulated Aeromonas hydrophila Bacterin.

The present study aimed to analyze the enhancement of innate immune responses in juvenile-stage common carp (Cyprinus carpio L.), upon the administration of heat-killed Aeromonas hydrophila at a dosage of 1 × 107 CFU ml-1 through bio-encapsulation in the aquatic crustacean, Artemia salina. This work emphasizes the modulation of innate immune response when administered with the bio-encapsulated heat-killed antigen that acts as an inactivated vaccine against Motile Aeromonas Septicemia disease. Bio-encapsulated oral administration of antigens promotes innate immunity in juvenile-stage fishes. The optimization of effective bio-encapsulation of bacterin in Artemia salina nauplii was carried out and the best optimal conditions were chosen for immunization. The functional immune parameters such as myeloperoxidase, lysozyme, alkaline phosphatase, antiprotease and respiratory burst activity in serum, blood and intestinal tissue samples were analyzed along with blood differential leukocyte count and tissue histopathology studies. Both humoral and cellular immune responses analyzed were substantially induced or enhanced in the treatment groups in comparison with the control group. The results showed a significant variation in the bio-encapsulation group than the control group and also were comparable to the protection conferred with immersion route immunization under similar conditions. Thus, most of the innate non-specific immune responses are inducible, despite being constitutive of the fish immune system, to exhibit a basal level of protection and a road to better vaccination strategy in Cyprinus carpio L. aquaculture worldwide.

Structure and gene cluster annotation of the O-antigen of Aeromonas sobria strain K928 isolated from common carp and classified into the new Aeromonas PGO1 serogroup

Aeromonas sobria strain K928 was isolated from a common carp during a Motile Aeromonas Infection/Motile Aeromonas Septicaemia disease outbreak on a Polish fish farm and classified into the new provisional PGO1 serogroup. The lipopolysaccharide of A. sobria K928 was subjected to mild acid hydrolysis, and the O-specific polysaccharide, which was isolated by gel-permeation chromatography, was studied using sugar and methylation analyses and 1H and 13C NMR spectroscopy. The following structure of the branched O-specific polysaccharide repeating unit of A. sobria K928 was established.→2)[α-D-Fucp3NRHb-(1→3)]-α-L-Rhap-(1→3)-β-L-Rhap-(1→4)-α-L-Rhap-(1→3)-β-D-FucpNAc-(1→The O-antigen gene cluster was identified and characterized in the genome of the A. sobria K928 strain after comparison with sequences in the available databases. The composition of the O-antigen genetic region was found to be consistent with the O-polysaccharide structure, and its organization was proposed.

In Vitro Characterization of Probiotic Potential of Limosilactobacillus fermentum against Salmonella Gallinarum Causing Fowl Typhoid.

Fowl typhoid, a septicaemic disease of poultry, is caused by Salmonella Gallinarum and leads to severe economic losses. The aim of the present study was to isolate, select and characterize indigenous probiotic lactobacilli with anti-Salmonella Gallinarum activity. A total 55 lactobacilli were isolated from the caeca and ileum parts of healthy chickens and identified to species level by 16S rDNA sequencing. All the isolates were initially screened for antimicrobial activity and selected isolates were further subjected to in vitro evaluation of probiotic properties. Lactobacilli isolates (n = 21) showed varying levels of activity (08-18 mm) against Salmonella Gallinarum. These selected isolates also showed tolerance to acidic conditions (pH 3 and 4). Out of these 21 isolates, 13 showed growth (>0.5 OD at 600 nm) 0.3% bile salts. Moreover, these isolates also had the ability of auto-aggregation (20.05 ± 0.62%-50.70 ± 1.40%), and co-aggregation with Salmonella Gallinarum (5.22 ± 0.21%-42.07 ± 0.70%). Results revealed that lactobacilli had a higher level of resistance to vancomycin (100%), streptomycin (100%), ciprofloxacin (95%), gentamicin (90%), doxycycline (90%), oxytetracycline (85%), and bacitracin (80%), and a lower level of resistance to penicillin (33%), erythromycin (28%), chloramphenicol (23%), fusidic acid (23%) and amoxicillin (4%). The Limosilactobacillus fermentum PC-10 and PC-76 were sensitive to most of the antibiotics. The overall results revealed that two Limosilactobacillus fermentum strains (PC-10 and PC-76) fulfill the in vitro selection criteria of probiotics, i.e, tolerance to low pH, resistance to bile salts, auto-aggregation, co-aggregation with Salmonella Gallinarum, and absence of acquired antibiotic resistance. The Limosilactobacillus fermentum PC-10 and PC-76 also inhibited the (>5 log10) growth of Salmonella Gallinarum in co-culture assay. It is concluded that Limosilactobacillus fermentum PC-10 and PC-76 may be further investigated and developed as anti-Salmonella Gallinarum probiotics for poultry.

Effects of β-1,3/1,6 glucan dietary supplements on some immunological and hematological health markersin Siberian sturgeon (Acipenser baerii) infected with Aeromonas hydrophila.

This experimental study aimed to investigate some hematological and immunological changes as a result of Aeromanas hydrophila infection in Siberian sturgeon (Acipenser baerii Brandt, 1869). Their feeds were supplemented with β-1,3/1,6 glucan at different ratios, 250 mg/kg (βG250); 500 mg/kg (βG500) and 750 mg/kg (βG750). To create an experimental infection, 4×106 cfu/ml Aeromonas hydrophila inoculum was intraperitoneally injected to fish. 0.1 ml intraperitoneal bacteria injection was given to the fish in 12 of 15 tanks, each consisting of 10 fish (the fish in the control group were not given bacteria). Considering the βG500 and βG750 group fish as positive (C+) and negative control (C-) groups in terms of hematological parameters, it was found that RBC (erythrocyte) and Hb (hemoglobin) values, as well as RBC indices (MCV, MCHC, MCH) significantly increased. The immunological parameters, including WBC (leukocyte), leukocyte cell percentages (lymphocyte, monocyte, neutrophil, eosinophil), as well as cytokines, including IL-1β, IL-6, IL-8, and TNF-α values showed similar increases in the βG500 and βG750 groups. It was found that the addition of 500 and 750 mg/kg doses of β-1,3/1,6 glucan to the feed stimulated non-specific immunity of fish against bacterial agents and/or septicemic diseases and beta glucan at this dosage range was determined to be ideal for fish health and that it may be a herbal immunostimulant that can be an alternative to many medicaments.

Re-engineering of bicistronic plasmid pGPD/IFN to construct fusion gene co-expressing Glyceraldehyde 3-phosphate dehydrogenase gene (GAPDH) of Edwardsiella tarda and Interferon-gamma (IFN-γ) gene of Labeo rohita (Hamilton) and its in vitro functional analysis

Edwardsiella septicemia disease in the cultured Indian major carps is caused by the fish pathogen Edwardsiella tarda and it is preventable by DNA vaccination. Here, we tried to develop a bicistronic DNA vaccine pGPD/IFN expressing the Glyceraldehyde 3-phosphate dehydrogenase (GAPDH) gene of Edwardsiella tarda and Interferon-gamma (IFN-γ) gene of Labeo rohita. The vaccine showed high protective efficiency in our previous studies; however as a limitation of bicistronic construct the expression of gene cloned in second frame (B) is poor. To overcome this limitation we re-engineered the construct and designed a fusion gene co-expressing the GAPDH and IFN-γ genes as one frame with an aim to get the optimum expression of both the genes. For this purpose, a fusion insert comprising GAPDH and IFN-γ coding sequences was cloned in to pcDNA3.1(+) plasmid vector. The fusion genes' in vitro expression was confirmed in the striped snakehead fish cell line (SSN-1). Successful expression of the re-engineered fusion gene DNA vaccine in the cell line was achieved at 48h post-transfection, which was confirmed by amplifying the expression transcripts of GAPDH and IFN-γ genes. Thus, the study concludes that the re-engineered fusion vaccine pcGPD/IFN (pcDNA3.1(+) plasmid having fusion GPD/IFN) is functional and can be effectively utilized to vaccinate rohu (Labeo rohita) as it contains the species-specific immune gene (IFN-γ) as an adjuvant.

Riemerella anatipestifer Endonuclease I displays enzymatic activity and is associated with bacterial virulence

Riemerella anatipestifer is an important pathogen of waterfowl, causing septicemic and exudative diseases. We previously reported that the R. anatipestifer AS87_RS02625 is a secretory protein of the type IX secretion system (T9SS). In this study, R. anatipestifer T9SS protein AS87_RS02625 was determined to be a functional Endonuclease I (EndoI), which has DNase and RNase activities. Optimal temperature and pH of the recombinant R. anatipestifer EndoI (rEndoI) to cleave λDNA were determined as 55–60 °C and 7.5 respectively. The DNase activity of the rEndoI was dependent on the presence of divalent metal ions. Presence of Mg2+ at a concentration range of 7.5–15 mM in the rEndoI reaction buffer displayed the highest DNase activity. In addition, the rEndoI displayed RNase activity to cleave MS2-RNA (ssRNA), either in the absence or presence of divalent cations Mg2+, Mn2+, Ca2+, Zn2+ and Cu2+. The DNase activity of the rEndoI was significantly enhanced by Mg2+, Mn2+ and Ca2+ but not Zn2+ and Cu2+. Moreover, we indicated that R. anatipestifer EndoI functioned on the bacterial adherence, invasion, in vivo survival and inducing inflammatory cytokines. These results indicate that the R. anatipestifer T9SS protein AS87_RS02625 is a novel EndoI, displays endonuclease activity and plays an important role in bacterial virulence.

Development and Evaluation of a Blocking Lateral Flow Assay Strip for Detection of Newcastle Disease Virus Antibodies.

Newcastle disease (ND) is an acute septicemic infectious disease caused by Newcastle disease virus (NDV). Considering that vaccination is currently the main modality for the prevention of ND, it is essential to assess the effectiveness of clinical immunization. In this study, we have developed a blocking lateral flow assay (bLFA) strip for the rapid detection of NDV antibodies using the monoclonal antibody 9C1 against haemagglutinin-neuraminidase (HN), which allows for the determination of an NDV-specific antibody titer within 10 min at room temperature. In addition, the bLFA strip has no cross-reactivity with the positive serum of other avian pathogens including avian influenza subtypes H5, H7, and H9, MD, IBD, IB, EDS, and avian adenovirus. The ability of the bLFA strip for detecting a neutralizing antibody was also estimated. The results showed that the chicken NDV hyperimmunized serum had a complete blocking (100%) titer of 11 log 2, and half-blocking titer of 13 log 2, which are 4 times less than and the same as that of the HI test (13 log 2), and 8 and 2 times less than that of the VN test (14 log 2), respectively. A total of 510 clinical samples were tested for NDV antibodies. The coincidence rate between the results of the bLFA strip and HI test was 97.65%. Therefore, it is an ideal alternative method for assessing the clinical immunity of ND vaccines in the field in real-time.

JMM Profile: Salmonella enterica serovar Gallinarum, biovars Pullorum and Gallinarum.

Salmonella serovar Gallinarum has two distinct biovars, Pullorum and Gallinarum. They are host-adapted avian pathogens that infect a number of wild and domesticated species but they pose a particular threat to farmed and backyard chickens and turkeys. Both biovars cause invasive and septicaemic disease, often resulting in high mortality. Pullorum is transmitted in eggs and typically affects birds soon after hatch. Gallinarum may cause disease in any age of bird, which often progresses through mature flocks. The establishment of clean breeding stock has resulted in freedom from the pathogens in many countries although even in these territories sporadic incursions still occur.

Forewarning the outbreak of Haemorrhagic Septicaemia disease by using suitable statistical models

Haemorrhagic Septicaemia was considered as one of the lethal diseases for the bovines. Ingestion or inhalation were considered as the major sources of natural infection of the disease, but the mortality rate was high when casual agent introduced to non-endemic regions. This disease was observed as most deadly bacterial disease which was responsible for highest number of annual deaths of bovines. Three generalized linear models such as poisson regression, zero inflated poisson and zero inflated negative binomial models were fitted, among these models zero inflated models were found to be best fit and the risk factors viz., land surface temperature, air temperature, potential evapotranspiration, rainfall and soil temperature were found to have significant effect in the outbreak of Haemorrhagic Septicaemia disease.

Genomic characteristics, pathogenicity and viral shedding of a novel DVEV variant derived from goose

Duck virus enteritis (DVE), caused by the DVE virus (DVEV), is an acute, septicemic, and contagious disease affecting ducks of different breeds, ages, and sexes. In late spring and summer 2019, several outbreaks of DVE were reported in areas with large waterfowl industries in central and southern China. A goose farm located in Jining County, Shandong Province, was impacted by an acute DVE outbreak in July 2019. The causative DVEV field strain (Goose/DVEV/SDJN/China/2019) was subsequently isolated from the liver specimens collected from acute cases of dead geese, which showed severe hemorrhagic lesions on the esophageal mucosal membranes of specimens collected from all the postmortem cases. Comparison of the genome sequence of this newly isolated field strain (Goose/DVEV/SDJN/China/2019) with the common DVEV strains revealed insertions or mutations in the gB and gC genes, which possibly caused the observed high morbidity and mortality in this acute outbreak. We conducted a trial among geese to evaluate the pathogenicity of this strain. Healthy experimental goslings aged 15 d old were inoculated with 10-5.53 ELD50/0.2 mL doses orally or through intramuscular injection. Clinical signs and esophageal erosion appeared in infected geese. Necropsy revealed hemorrhage and necrosis of the cloacal mucosa and liver. Detection of the virus using real-time PCR in the liver, brain, and spleen indicated that they were the hotspots of DVEV infections. One day after the DVEV infection, virus release and seroconvert were observed in infected geese. Thus, our studies demonstrate that DVEV is highly pathogenic and contagious in geese. To the best of our knowledge, this is the first study on the pathogenicity of mutant duck viral enteritis virus in goslings. This study serves as a foundation for further investigations into the pathophysiology of the recently identified variant DVEV strains.

Improved methodology of in vivo mass multiplication of entomopathogenic nematodes: A remarkable bio agent for soil arthropod pests management

In the process of in vivo multiplication of EPN, the Infective Juvenile (IJs) enters into the body of host insect; Galleria mellonella (wax moth) larvae through natural openings and cuticle. They release symbiotic bacteria Photorhabdus luminescens in insect body. The bacteria multiply in hemocoel, cause septicemia disease and kills insect within 48 hours, multiplies and complete 2-3 generations inside host insect body. With the proven effectiveness demonstrated in recent years, the demand of EPNs is increasing day by day. The production of EPNs has been mainly restricted up to laboratory level only due to the low recovery rats of IJs in the existing method. Recovery of EPN by the existing method is labor intensive, time consuming and inconvenient for mass multiplication of EPN at large scale. The standardizations of technology with equipment modifications have been optimized for multiplication of EPN at small scale entrepreneurs. The higher recoveries 241424 IJs/GC in it as compared to existing white trap methodology 197445 IJs/GC. This is the first scalable system in India for mass production entomopathogenic nematode; In vivo methodology based on LOTEK. In present study we describe an improved version of it in which bulk conditioning, harvesting, separations are automated to reduce labor costs.

Actinobacillus suis isolated from diseased pigs are phylogenetically related but harbour different number of toxin gene copies in their genomes.

ObjectiveThe Gram‐negative bacterium Actinobacillus suis is an agent of global importance to the swine industry and the cause of lethal respiratory or septicaemic disease in pigs of different ages. Between 2018 and 2019, seven commercial farms in western Canada experienced episodes of increased mortality due to A. suis infection in grower pigs. The goal of this work was to profile, with molecular methods, A. suis isolated from diseased pigs and to compare them to other isolates.DesignThis inferential observational study used nine western Canadian strains obtained from diseased lungs (n = 6), heart (n = 2) and brain (n = 1) and whole genome sequencing was performed. Comparative genomic analyses were performed to characterise the genetic variability, antimicrobial resistance and the virulence genes present.ResultsCompared to the reference strain (ATCC 33415), an increased number of RTX (repeats in the structural toxin) gene copies were identified in strains isolated from organs without a mucosal surface, thus theoretically harder to invade. Western Canadian strains did not harbour genes associated with resistance to antimicrobial agents used in swine production. Novel regions were also identified in the genomes of five of nine strains demonstrating recombination and emergence of novel strains.ConclusionsThe results obtained in this study were associated with the emergence of new lineages. An increased number of RTX toxin gene copies is suggested to be associated with increased virulence. This study will contribute to improve our understanding regarding A. suis and may help guide vaccine development and agent control measures.

The Application of Different Probiotics for Prevention of Motile Aeromonas Septicemia Disease on African Catfish (Clarias gariepinus)

Motile Aeromonas Septicemia has become a problem in aquaculture. This study set out to investigate the usefulness of the probiotic Lactobacillus acidophilus and Staphylococcus lentus on survival rate, growth, and feed conversion efficiency of African Catfish (Clarias gariepinus). In vitro test was carried out to evaluate the effectiveness of probiotic against A. hydrophila and followed by in vivo test. In earlier treatment, Aeromonas hydrophila (final concentration 104 CFU mL−1), L. acidophilus, and S. lentus at a final concentration of 104 CFU mL−1 were added in aquaria every 2 days. there are four of the aquaria with three replicates, one control (without probiotic). In vitro test exposed the inhibition zone of L. acidophilus, S. lentus, and the combination of both bacteria was 11.72±0.55, 13.03±2.99, and 14.66±1.50 mm, respectively. After 21 days of treatment, the addition of the probiotic significantly increased the survival rate (P<0.05) for all conducts compared with controls. In vivo test showed that the application of probiotics in media of cultivation could reduce the number of A. hydrophila, improve the specific growth rate (SGR 6.00 ± 0.05%), and also increase the survival of catfish compared to the positive control. The results indicated that the combination of probiotics L. acidophilus and S. lentus appearances the highest survival (91.11 ± 1.53 %) of all treatments and the ratio of feed conversion was found to be decreased (0.23). This study highlights the combination of L. acidophilus and S. Lentus that could prevent MAS disease on Catfish.

Review on Listeriosis in small ruminants and public health significance in Ethiopia

Listeria monocytogenes is a bacterium mostly transmitted to man through food and it can cause mild gastroenteritis or severe infections of the bloodstream and/or the central nervous system, or abortion, depending on host susceptibility. Listeriosis is a serious illness caused by eating food contaminated with the bacterium Listeria, which is a Gram-positive psychotropic, facultatively anaerobic, none sporulating, motile, small rod. It displays characteristic tumbling motility that is facilitated by the presence of peritrichous flagella. Motility is temperature-dependent, showing high motility at 20-30°C when the flagellar expression is maximum. L. monocytogenes is ubiquitous in the environment and can be found in soil, water, feces, silage, effluent foods, and sewage. It has the ability to form biofilms which can contribute to its ability to colonize food processing facilities. The primary mode of transmission for Listeria is through soil contamination and ingestion of contaminated feed. Calves that develop the septicemic disease may acquire infection from contamination of the cow teat from the ingestion of milk containing the organism or from a cow with subclinical bacteremia, through the navel from the environment and also as congenital infection. Infection with Listeria. monocytogenes usually follow ingestion of contaminated feed and may result in septicemia, encephalitis, and abortion. There are few clinical features that are unique to listeriosis. Therefore, clinicians must consider a variety of potential causes of infection, including viral infections (influenza) and other bacterial infections that may cause sepsis or meningitis. Cook thoroughly raw food from animal sources, such as beef, pork, or poultry. Wash raw vegetables thoroughly before eating. Keep uncooked meats separate from vegetables and from cooked foods and ready-to-eat foods. Avoid raw (unpasteurized) milk or foods made from raw milk. Wash hands, knives, and cutting board and can contact with before and after handling cooked foods.

PENGGUNAAN TEPUNG JAHE (Zingiber officinale var. Amarum) PADA PAKAN IKAN PATIN (Pangasius Sp) UNTUK MENGOBATI INFEKSI Aeromonas hydrophila

Ginger is one type of traditional plant that can be used to control Motile Aeromonas Septicemia (MAS) disease which attacks catfish (Pangasius sp) cultivation. This study aims to determine the effect of ginger powder added to feed to treat A. hydrophila infection in catfish. The research was conducted at the Aquaculture Laboratory, Study Program of Aquaculture, Faculty of Agriculture, Sriwijaya University in October 2020. This study used a completely randomized design (CRD) consisting of 6 treatments (T) with 3 replications, namely (T0) without the addition of ginger flour, ( T1) adding 10 g.kg-1 ginger flour, (T2) adding ginger flour 12.5 g.kg-1, (T3) adding ginger flour 15 g.kg-1, (T4) adding ginger flour 17.5 g.kg-1 and (T5) adding ginger flour 20 g.kg-1. The parameters observed were length and weight growth, total erythrocytes, total leukocytes, larvae survival, water physics and chemistry (temperature, pH, DO and ammonia). The results of this study indicate that the best treatment is found at (T5) with an absolute weight growth of 6.25 grams, an absolute length growth of 1.09 cm, 90.00% survival. During maintenance the water quality is at conditions 27-29 0C for temperature, water pH 6-7, dissolved oxygen 5.00 mg.L-1, and ammonia 0.005-0.040 mg.L-1.Key words : Aeromonas hydrophila, Catfish, Ginger, Essential oil

Genome-Wide Analysis and Characterization of the Riemerella anatipestifer Putative T9SS Secretory Proteins with a Conserved C-Terminal Domain.

Riemerella anatipestifer is a major pathogenic agent of duck septicemic and exudative diseases. Recent studies have shown that the R. anatipestifer type IX secretion system (T9SS) acts as a crucial virulence factor. We previously identified two T9SS component proteins, GldK and GldM, and one T9SS effector metallophosphoesterase, which play important roles in bacterial virulence. In this study, 19 T9SS-secreted proteins that contained a conserved T9SS C-terminal domain (CTD) were predicted in R. anatipestifer strain Yb2 by searching for CTD-encoding sequences in the whole genome. The proteins were confirmed with a liquid chromatography-tandem mass spectrometry analysis of the bacterial culture supernatant. Nine of them were reported in our previous study. We generated recombinant proteins and mouse antisera for the 19 predicted proteins to confirm their expression in the bacterial culture supernatant and in bacterial cells. Western blotting indicated that the levels of 14 proteins were significantly reduced in the T9SS mutant Yb2ΔgldM culture medium but were increased in the bacterial cells. RT-qPCR indicated that the expression of these genes did not differ between the wild-type strain Yb2 and the T9SS mutant Yb2ΔgldM. Nineteen mutant strains were successfully constructed to determine their virulence and proteolytic activity, which indicated that seven proteins are associated with bacterial virulence, and two proteins, AS87_RS04190 and AS87_RS07295, are protease-activity-associated virulence factors. In summary, we have identified at least 19 genes encoding T9SS-secreted proteins in the R. anatipestifer strain Yb2 genome, which encode multiple functions associated with the bacterium's virulence and proteolytic activity. IMPORTANCE Riemerella anatipestifer T9SS plays an important role in bacterial virulence. We have previously reported nine R. anatipestifer T9SS-secreted proteins and clarified the function of the metallophosphoesterase. In this study, we identified 10 more secreted proteins associated with the R. anatipestifer T9SS, in addition to the nine previously reported. Of these, 14 proteins showed significantly reduced secretion into the bacterial culture medium but increased expression in the bacterial cells of the T9SS mutant Yb2ΔgldM; seven proteins were shown to be associated with bacterial virulence; and two proteins, AS87_RS04190 and AS87_RS07295, were shown to be protease-activity-associated virulence factors. Thus, we have demonstrated that multiple R. anatipestifer T9SS-secreted proteins function in virulence and proteolytic activity.

Effectiveness of Bacillus subtilis on survival rate of Nile tilapia (Oreochromis niloticus) infected with Pseudomonas fluorescens

A bacterial disease that infects freshwater fish, especially tilapia (Oreochromis niloticus), is a septicemia disease caused by Pseudomonas fluorescens infection. The purpose of this study was to determine the effectiveness of Bacillus subtilis on the survival of tilapia infected with P. fluorescens in vivo. The doses of B. subtilis used were different for each treatment, namely A (104 CFU/ml), B (106 CFU/ml), and C (108 CFU/ml). Fish were kept for 7 days to calculate their survival rate. Dosage of B. subtilis bacteria had a significant effect (α &gt; 0,05) on the survival of tilapia infected with P. fluorescens bacteria. The best dose of B. subtilis in treatment A (104 CFU/ml) could increase the survival rate of tilapia infected with P. fluorescens with a survival rate of 93.33 ± 11.55%. The average ranges of water quality during the maintenance period are 25°-30°C, pH 7.2-9, and dissolved oxygen 5.50-7.00 ppm.

Immune Status of Bighead Catfish (Clarias macrocephalus Günther, 1864) Crossbreeds Between Wild and Domesticated Strains and Their Response to Challenge With Aeromonas hydrophila

Aeromonas hydrophila is a major pathogen causing septicemic disease and high mortality in cultured bighead catfish, Clarias macrocephalus Günther, 1864. Crossbreeding for enhanced disease resistance may help alleviate the infection. This study aimed to evaluate the crossbreeding effects of bighead catfish from three broodstock sources, including one domesticated strain (Can Tho - CT) and two wild strains (Ca Mau - CM and Hau Giang - HG), on the innate immune response. Eight diallel crosses (excluding HG × CT) were reared in tanks for 100 days to the juvenile stage for use in this study. Forty-five bighead catfish juveniles of similar sizes, 4.5–6.1 g, were sampled from each cross to evaluate the immune response and stress indicators. Thirty fish from each cross were challenged with A. hydrophila. The results showed that innate immune responses of domesticated CT strains were higher than wild strains (HG and CM). Higher values of white blood cells, phagocytic activity, and lysozyme activity were observed in CT × CT and CT × CM crosses. These crosses had significantly lower cortisol levels and lower mortality rates of 40 % (CT × CT) and 43.3 % (CT × CM) after being challenged with A. hydrophila compared to the other crosses. The results demonstrate that domesticated CT strain and crossbreeding between CT and CM wild strains could improve the innate immune system and resistance to A. hydrophila. The innate immune responses of the domesticated CT strain were higher than wild strains (HG and CM).

Complete Lipopolysaccharide of Piscirickettsia salmonis Is Required for Full Virulence in the Intraperitoneally Challenged Atlantic Salmon, Salmo salar, Model.

Bacterial cell envelopes play a critical role in host-pathogen interactions. Macromolecular components of these structures have been closely linked to the virulence of pathogens. Piscirickettsia salmonis is a relevant salmonid pathogen with a worldwide distribution. This bacterium is the etiological agent of piscirickettsiosis, a septicemic disease that causes a high economic burden, especially for the Chilean salmon farming industry. Although P. salmonis has been discovered long ago, its pathogenicity and virulence mechanisms are not completely understood. In this work, we present a genetic approach for producing in-frame deletion mutants on genes related to the biosynthesis of membrane-associated polysaccharides. We provide a detailed in vitro phenotype description of knock-out mutants on wzx and wcaJ genes, which encode predicted lipopolysaccharide (LPS) flippase and undecaprenyl-phosphate glucose phosphotransferase enzymes, respectively. We exhibit evidence that the wzx mutant strain carries a defect in the probably most external LPS moiety, while the wcaJ mutant proved to be highly susceptible to the bactericidal action of serum but retained the ability of biofilm production. Beyond that, we demonstrate that the deletion of wzx, but not wcaJ, impairs the virulence of P. salmonis in an intraperitoneally infected Atlantic salmon, Salmo salar, model of piscirickettsiosis. Our findings support a role for LPS in the virulence of P. salmonis during the onset of piscirickettsiosis.