Characterization of Micrococcus luteus and Bacillus marisflavi Recovered from Common Dentex (Dentex dentex) Larviculture System

In this manuscript, thirty yellow-pigmented Gram-positive bacteria were isolated from natural intestine microflora and from sea water around the marine cage of a rearing tank of common dentex (Dentex dentex), in the Aegean Sea on the Turkish coast and were characterized. Eighteen isolates were assigned to the species Micrococcus luteus, the other twelve to the species Bacillus marisflavi. Eight representative strains, six from B. marisflavi and two from M. luteus, were chosen for further 16S rDNA analyses. A pathogenicity assay for the isolated bacterial strains was carried out in rainbow trout and it evidenced absence of pathogenicity in the tested strains. The isolated strains were tested for in vitro antagonistic activity against Listonella anguillarum, a pathogen bacterium diffused in Mediterranean aquaculture and affecting various fish species. The isolated bacterial strains showed antagonistic activity against the pathogenic bacterium, suggesting a possible role of isolates as probiotics. In this study, for the first time, bacterial strains of the species B. marisflavi, known as an environmental species, were recovered in the gut microbiota of a healthy fish. The use of the isolates characterized in this study, mainly the yellow-pigmented bacterium, is suggested as possible probiotics to improve fish health, along with alternative methods of maintaining a healthy environment

Systemic Mycobacteriosis Caused by Mycobacterium marinum in Farmed Meagre (Argyrosomus regius), in Turkey

This paper describes systemic mycobacteriosis caused by Mycobacterium marinum, in farmed meager (Argyrosomus regius), in Turkey. Infected two year old fish showed signs of stunted growth, emaciation, slight ascites and exophtalmia, pale gills and significant mortalities. Only one fish sample showed hemorrhagic ulcerative skin lesions at the base of the caudal fin. Internal multifocal white colored granulomas in the spleen, kidney, and liver were observed. Ziehl-Neelsen (ZN) and Gram stained fresh squash mounts of the granulomas revealed Gram and ZN positive rods. Inoculation of sterile homogenates of the visceral organ granulomas on Lowenstein-Jensen slants produced slow-growing (3-4 weeks), yellow to orange colored, photochromogenic acid fast colonies. ZN positive bacterial isolates were identified using commercially available line probe assays (Genotype Mycobacterium CM/AS assay) and hsp65 gene sequencing analyses. According to molecular analysis results, the isolates were identified as Mycobacterium marinum. Epithelioid cell granulomas were microscopically observed in the visceral organs and gills. ZN stained tissue sections exhibited heavy acid-fast rods within the granulomas

Effect of different light intensities on prolactin and cortisol plasma concentration in farming African catfish (Clarias gariepinus) in RAS with low-water exchange

In the Bulgarian aquaculture sector, focusing research efforts on the technical specifications of the cultivation of African catfish (Clarias gariepinus) is important due to the need for more information. We aimed to assess the impact of light intensities on prolactin and cortisol levels as stress markers in African catfish. Fish were acclimated over an appropriate period to the short photoperiod (16D and 8L) and then distributed randomly to three groups, each separated by sex. Fish exposed to different light intensities (63, 51, and 40 lux, respectively) were followed for 45 days by lux meter. Blood samples were collected from the caudal vein using a 2 ml K2EDTA-coated syringe. A laser fluorescence reader assayed plasma prolactin and cortisol. The pituitary was removed from anesthetized fish and fixed for histological examinations. The results of our study suggest that increasing light intensity increases prolactin and cortisol levels in African catfish

A Study on Probiotic Bacteria Isolated from Common Dentex (Dentex dentex) Larvae and their antagonistic effect on Photobacterium damselae subsp. Damselae

Bacterial species that can be considered as probiotic are gradually gaining attention and contributing to the success of aquaculture. The aim of this study was to determine the indigenous dominant probiotic bacterial species of common dentex (Dentex dentex) larvae and their effectivness against the putative fish pathogen Photobacterium damselae subsp. damselae at different feeding stages. In 2009-2010 samples of larvae and tank water were collected at 5 different occasions. After inoculations of samples, bacterial isolates were identified with standard biochemical methods. The antagonistic effects of the identified probiotic bacteria against P. damselae subsp. damselae isolated from different mariculture fishes were determined by using disc diffusion method. Bacillus cereus, B. macquariensis, and other Bacillus sp., Micrococcus luteus, Flavobacterium flevense and Flavobacterium sp. were identified as candidate probiotic species and their antagonistic effect against different P. damselae isolates was identified. The results of this study showed that B. cereus and M. luteus are more effective against Photobacterium damselae subsp. damselae. As a result, the identification of the candidate probiotic species and the widespread use of probiotics may improve the success of common dentex culture in the future

A comparative study of detection methods for Lactococcus garvieae in experimentally infected rainbow trout (Oncorhynchus mykiss, W.)

This study was carried out to detect Lactococcus garvieae from experimentally infected rainbow trout (Oncorhynchus mykiss, W.) using bacteriological, serological, and histopathological techniques. Rainbow trout were experimentally infected with two Lactococcus garvieae strains (L1 and L2) by intraperitonal injection. These strains caused bilateral exophthalmia with periocular hemorrhage, corneal opacification, darkening of the skin, strong internal congestion in the visceral organs, and enlargement of the spleen in the infected rainbow trout. The two L. garvieae strains were re-isolated from experimentally infected fish groups and identified with standard biochemical methods and API 20 STREP system. The presence of L. garvieae in the tissue of experimentally infected fish was confirmed by Indirect Fluorescent Antibody Technique (IFAT). The humoral antibody response of the infected fish was confirmed by slide agglutination, IFAT, and Enzyme Linked Immunosorbent Assay (ELISA). Histopathologically, liquefactive necrosis in the liver, spleen, and kidney, epithelial cells hyperplasia, hemorrhages and telangiectasia of the gill filaments, and sub-retinal hemorrhages in the eyes were observed

Formation of Pinocytic Activity in Cultured Common Dentex (Dentex dentex) Larvae Intestine

Larval fish have a relatively poorly developed immune system and hence they primarily rely on non-specific immune responses produced in the skin and gut. This study aims to illustrate the fine structure of gut development in common dentex (Dentex dentex) larvae and determine the initiation of pinocytic activity, which is an important early non-specific immune response in fish intestines, during various live-food feeding stages (yeast enriched rotifer, Artemia nauplii and metanauplii) from hatching (D0) to 25 days after hatching (D25) by using transmission electron microscopy (TEM). A total of 54 larvae were sampled and examined with electron microscopy. The results show that hind-gut intestine enterocytes have morphological features which suggest they play a role in absorption and intracellular digestion of nutrients in fish. The presence of vigorous pinocytic activity in the Artemia feeding stage between 17-25 days after hatching is evidence for the development of a non-specific immune system. In the present study, the ultrastructural gut development of cultured common dentex was investigated for the first time and the data reported in this study may provide additional fundamental knowledge for improving larval rearing success in common dentex culture

Hasta Kültür Gökkuşağı Alabalıklarından (Oncorhynchus mykiss) İzole Edilen Gram-pozitif Bakterilerin Antibiyotik Duyarlılığının Tespiti

Akuakültürde bakteriyel hastalıklara karşı bilinçsiz antibiyotik kullanımı sonucunda, bakterilerde antibiyotiklere karşı direnç oluşumu gelişebilmekte ve bu nedenle de hastalıkların kontrolü ve tedavisi daha da zorlaşabilmektedir. Bu çalışma ile yurdumuzun farklı bölgelerinde kültürü yapılan gökkuşağı alabalıklarında (Oncorhynchus mykiss) hastalığa neden olan Gram-pozitif patojen bakterilerin tespiti ve bu bakterilerin antibiyotiklere karşı duyarlılık derecelerinin belirlenmesi amaçlanmıştır. Bu amaçla Akdeniz ve Marmara Bölgelerindeki farklı işletmelere gidilmiş, 18 adet hasta balığın iç organlarından besiyerlerine ekimler yapılmıştır. Bakteriyolojik örnekleme çalışmaları sonucu izole edilen Gram-pozitif bakterilerin morfolojik, fizyolojik ve biyokimyasal özellikleri incelendiğinde bu bakterilerin Lactococcus ve Staphylococcus genusuna ait oldukları tespit edilmiştir. İzole edilen bakterilerin antibiyogram duyarlılığını belirlemek için disk difüzyon yönteminde ticari olarak satılan farklı antibiyotikler kullanılmıştır. İnkübasyon sonrasında elde edilen sonuçlar zon çaplarına göre dirençli ve duyarlı olarak değerlendirilmiştir. Sonuç olarak hasta alabalıklardan izole ve identifiye edilen Gram-pozitif bakterilerin antibiyogram duyarlılıklarının türler arasında farklı olduğu tespit edilirken, Lactococcus garvieae’ nin siprofloksasin’e, Staphylococcus epidermidis’in ise florfenicol’ e daha duyarlı olduğu tespit edilmiştir

Histopathology and Antibiotic Susceptibility of Aeromonas hydrophila Isolated from Diseased Guppy (Poecilia reticulata)

This study was carried out to determine the reason of mortality in guppy (Poecilia reticulata) kept in an aquarium fish-rearing farm in Istanbul province and confirm damage caused in tissues and antibiotic susceptibility of isolated pathogen bacteria. Externally diseased guppies (n=15) showed sloughing scales, ulcerative skin lesions on the body surface and abdominal distension; internally pale liver and accumulation of a liquid in the abdominal cavity were observed. Bacteriological inoculation from internal organs such as liver, spleen and kidney of guppies (n=15) were made onto Tryptic Soy Agar (TSA) and Brain Heart Infusion Agar (BHIA). After incubation, all isolated bacteria were identified as Aeromonas hydrophila according to their psychological, morphological, biochemical characteristic, and API 20E profile. Also, these isolates (n=15) were determined to be sensitive to chloramphenicol and florfenicol. Histopathologically, multifocal liquefactive necrosis in the spleen, liver, kidney and heart, degeneration of tubular epithelium and necrosis in the kidney, desquamation of mucosa epithelium and necrotic gastric glands in the stomach, discharge of the white pulp in the spleen, desquamation of the lamina propria and mucosa epithelium in the intestine, and sloughed off the necrotic gill epithelium cells were observed