BACKGROUND: Recently chitosan nanoparticles have been applied as an immunostimulant and adjuvant in biomedical fields. OBJECTIVES: In this study the adjuvant effects of nanochitosan, derived from shrimp shell's chithin, on immunogenicity of Aeromonas hydrophila vaccine in common carp were evaluated. METHODS: Totally 300 juvenile common carp (51±5.6 g, Mean ±SD) were randomly divided into four groups each contained three subgroups with 25 fishes. Groups 1, 2 and 3 were immunized intraperitoneally with A. hydrophila vaccine. No adjuvant used in group 1, but nanochitosan and freund adjuvant were used with vaccine in groups 2 and 3 respectively. Group 4 (Control) injected with normal saline instead of vaccine. Fish were immunised at days zero and 14 and fishes were reared in the same situation for 6 weeks. Serum samples were taken every other weeks and immunological parameters including WBC, serum lysozyme and bactericidal activity, serum complement activity, NBT reduction activity, total protein and globulin levels and anti A.hydrophila antibody titer were compared among the groups. At the end of experiment all groups were challenged with LD50 concentration of A. hydrophila and mortality recorded for ten days. RESULTS: WBC, serum lysozyme and complement activity, NBT activity, globulin level and anti A.hydrophila antibody titer were increased in nanochitosan and freund groups compare to control group (P<0.05). Serum bactericidal activity and serum albumin level showed no significant change among the groups (P>0.05). Challenge mortality decreased in immunised groups compare to control. CONCLUSIONS: Nonochitosan posses proper adjuvant effects which is comparable with freund adjuvant and can be a good candidate as an alternative to current adjuvant in fish vaccines.

A study was conducted to investigate the pathogenicity and the median lethal dose (LD50) of Aeromonas hydrophila isolated from clinically diseased catfish against apparently healthy homologous fish to evaluate the lethality of extra-cellular products (ECPs) of the isolated strain in vivo. For pathogenicity experiment, five different concentrations of Aeromonas hydrophila strain BNS 01614 including 3× 108, 1.5 × 108, 1.5 × 107, 1.5 × 106 and 1.5 × 105 CFU/fish used via intra peritoneal. The results revealed that pathogenicity of BNS 01614 was confirmed by the mortality of 30 % to 100 % of all tested fish within 4 to 12 days with LD50 1.5 × 107 CFU/fish. The Concentrated extracellular products (ECPs) of the selected bacterium were prepared and confirmed to be toxic in Clarias garipineus with LC50 of 20µg.

Aeromonas hydrophila and Campylobacter jejuni are bacteria of emerging importance in public health. However, little has been published about fish contaminated by these pathogens. The present study aimed to verify the presence of Aeromonas hydrophila and Campylobacter jejuni in fresh tuna samples (Thunnus spp.) caught off the coast of Santa Catarina State and distributed in the wholesale market of São Paulo/SP. A total of 85 tuna fillet samples were collected and examined by PCR and bacteriological analyses. Aeromonas spp. was detected in 11/85 (13%) samples, with 10/11 (90.9 %) being confirmed as Aeromonas hydrophila by PCR. Campylobacter spp. was found in 10/85 (11.7%) samples, 10/10 (100%) identified as Campylobacter jejuni by PCR and conventional biochemical analyses. Both pathogens were found in 2/85 (2.3%) samples. This is the first report on the contamination of fresh tuna by Campylobacter jejuni and Aeromonas hydrophila in Brazil. In addition to show that tuna can be a vehicle for transmission of pathogens when consumed raw, it emphasizes the importance of further studies to support the control these pathogens in fish.

Introduction: Immune-potentiating functions of Lactobacillus plantarum strains in the common carp were evaluated. Material and Methods: Fourteen days of feeding fish dry diet supplemented with the bacteria provided parameters of nonspecific humoral immunity (lysozyme, ceruloplasmin, γ-globulin, total protein levels, and serum bactericidal activity) and cellular immunity (pinocytosis, respiratory burst activity, and potential killing activity of organ phagocytes), as well as the proliferative response of organ lymphocytes stimulated with mitogens. The resistance of fish to infection with Aeromonas hydrophila was also determined. Results: Dietary supplementation with L. plantarum had a substantial influence on the activity of organ phagocytes, especially the potential killing activity of head kidney cells. A significant increase in the proliferative activity of LPS-stimulated B lymphocytes and in the levels of γ-globulins and total protein was observed. The supplemented diet conveyed higher resistance than the control diet as the cumulative fish mortalities after infection with A. hydrophila were 65% and 85%, respectively. Conclusion: The results indicate that dietary supplementation with L. plantarum stimulates the antibacterial resistance of common carp and may reinforce defence against bacterial infections, but further studies need to be conducted.

Introduction: In the present study, some of the commercial fish farms located in the Black Sea region of Turkey, were screened for bacteria between 2012 and 2014.Material and Methods: The bacterial agents isolated from fish were identified by classical biochemical tests and the rapid diagnostic tests (API 20 E and API 20 Strep). All strains were further identified by sequencing of the 16S rRNA genes. The strains were also investigated for resistance to different antimicrobials by the disc diffusion method. Antibiotic resistance genes, including tetracycline (B), β-lactam (ampC, blaTEM, blaPSE), florfenicol (floR), erythromycine (ereA, ereB), sulphonamide (sulI, sulII), and trimethoprim (dhfr1) genes, were determined by the PCR method.Results:Vibrio anguillarum, Vibrio fluvialis, Photobacterium damselae subsp. piscicida, Pseudomonas luteola, Lactococcus garvieae, Streptococcus iniae, Aeromonas hydrophila, and Yersinia ruckeri were isolated from marine and freshwater cultured fish. According to the results of disc diffusion, all isolates were sensitive to florfenicol, trimethoprim+sulfamethoxazole, oxitetracycline, and enrofloxacin, and resistant to lincomycin, penicillin G, and amoxicillin. Also, sulI, sulII, and floR resistance genes were detected in the bacteria.Conclusion: The results of the study open up the opportunity to perform further investigations which could determine the possible role of ARGs in fish pathogens.

This study was undertaken for isolation, identification and determination of antibiogram profile of Aeromonas hydrophila in farm raised fresh water prawn (Macrobrachium rosenbergii) on five commercial ghers. Fresh water prawns (n=25) were collected from five ghers located at Satkhira, Bagerhat and Khulna districts of Bangladesh. Brain (n=25), muscle (n=25) and intestine (n=25) samples were collected aseptically from fresh water prawn and inoculated into alkaline peptone (APW) water for enrichment at 37℃ for 8 h. Enriched cultured was streaked into Thiosulfate Citrate Bile Salt Sucrose (TCBS) agar to isolate bacteria. Bacteria were identified by cultural, Gram staining, biochemical properties and polymerase chain reaction (PCR) assay. The antibiogram profiles of bacteria were investigated against 5 commonly used antibiotics (Gentamicin, Cefalexin, Ampicillin, Azithromycin and Ciprofloxacin) by disc diffusion method. Thirteen A. hydrophila isolates were identified and the prevalence of the A. hydrophila in fresh water prawn was 17.33%. All 13 (100%) isolates were sensitive to Ciprofloxacin, Gentamicin, Azithromycin and resistant to Ampicillin and Cefalexin. The results of this study indicate that farm raised fresh water prawn harbor multidrug resistant A. hydrophila which might causes public health problem if enter into human food chain.

Nile tilapia aquaculture is a fast-growing industrial sector in Egypt. However, the progress of this industry is hindered by many challenges as poor water quality and associated bacterial infections. Aeromonas hydrophila is an important zoonotic waterborne aquatic pathogen responsible for severe outbreaks in tilapia culture so the current study aimed to investigate the prevalence of Aeromonas hydrophila in tilapia fish and their aquaculture water, the fish and water samples were collected from three farms located in Assiut and Minia Governorates, Egypt. Aeromonas hydrophila was isolated from tilapia five organs including liver, kidney, intestine, spleen and gills with a percentage of 7.1%, 6.5%, 9.1%, 5.1%, 11.7%, receptively, and from water samples with 59.7%. The isolates were molecularly confirmed as Aeromonas hydrophila in 70.9% and 82.4% of the tested isolates using 16s RNA and gyr-β primers, respectively. Aeromonas hydrophila isolates revealed a marked resistance for the tested antibiotics; amoxicillin and novobiocin (100%), streptomycin (71.4 %), chloramphenicol (57%), doxycycline and trimethoprim/Sulphamethoxazole (50%), colistin (43%), ciprofloxacin and norfloxacin (14%). The isolates showed multiple antibiotic resistance indexes ranging from 0.3 to 1. The present study highlights the Aeromonas hydrophila resistance and virulence, tilapia aquaculture health hazard to the human population, so adequate control measures should be applied. Furthermore, there is an essential need to promote an alternative non-antibiotic control in farmed fish.

Fish is one of the most important foods because of its high nutritional value, high palatability, and easy digestion. At the same time, it acts as a vehicle for many types of pathogenic microorganisms especially Aeromonas species, which results in public health hazards. Therefore, the present study was conducted to evaluate the prevalence of Aeromonas species in fresh fish (catfish, mullet, lizardfish, and coralfish) marketed in Zagazig city, Sharkia Governorate, Egypt. In addition, multiplex PCR was performed to detect some virulence-associated genes in A. hydrophila isolates. Furthermore, antimicrobial susceptibility testing was carried out on A. hydrophila isolates using commonly used antimicrobials in Egypt through the disc diffusion method. The achieved results indicated contamination of fish with different species of Aeromonas such as A. veronii, A. sobria, A. caviae and A. hydrophila. The results revealed that Aeromonas species isolated with an overall percentage of 55% of all examined fish. Bacteriological examinations revealed 20% A. hydrophila, 20% A. sobria, 10% A. caviae and 5% A. veronii. Antibiotic sensitivity declared high resistance of the isolates to different antimicrobial agents used in Egypt, including penicillin (100%), Ampicillin (90.0%), Streptomycin (90.9%), Cephalothin (72.7%), Tetracycline (72.7%), Cefotaxime (63.6%), and Sulfamethoxazole (54.5%). Therefore, hygienic measures should be adopted to control microbial contamination either in the aquatic environment or in fish markets.

The purpose of the study was to verify the existence and pathogenicity of Aeromonas hydrophila (A. hydrophila) in fish by validating the bactericidal effects of microwave and Gamma radiation on infected fish fillets. A total of 100 frozen Basa fish fillet samples were collected randomly from different markets in Zagazig, Sharkia Governorate, Egypt, and subjected to microbiological examination. The results revealed a 14% prevalence rate of A. hydrophila in fish fillets, which were tested for the presence of seven virulence genes: aerA, act, ast, alt, hyl, ahhR, and ahh1. All isolates exhibited traits related to virulence. The most predominated gene was ast (64.2%), followed by aerA, act, hyl, and ahhR (57.14% for each). Then, an experimental protocol for several treatments showed that Gamma radiation at a dose of 1 kGy decreased the count of A. hydrophila in fish fillets by 4.4 log10 CFU/g whereas doses of 2 and 3 kGy eradicated the pathogen. The same positive effect was recorded towards the microwave after cooking for 1, 2, and 3 minutes. Therefore, using microwave cooking and Gamma-irradiation alone and in combination with other decontamination methods may be more efficient in lowering the pathogen counts in fish meat.

In the present study, Aeromonas (A.) hydrophila was isolated from a captive-bred adult freshwater stingray (Potamotrygon motoro) reared at a commercial aquarium in Korea. The stingray had bites on its fins, hemorrhages on the ventral part, and congested internal organs. A bacterium was isolated from kidney and subsequently identified as A. hydrophila. Based on phylogenetic analysis results, the isolate in the present study (SNUAh-LA1) was most closely related to A. hydrophila AH10 (China) and A. hydrophila AKR1 (Korea). It is most likely that the pathogen infection resulted from Potamotrygon motoro cohabiting with ricefish (Oryzias latipes).