Prevalence of Salmonella sp. in African Catfish (Clarias gariepinus) obtained from farms and wet markets in Kelantan, Malaysia and their antibiotic resistance

The present study was conducted to determine the prevalence and antibiotic resistance of Salmonella sp. isolated from African catfish (Clarias gariepinus). A total of 30 catfish were harvested from four different farms and four different wet markets. A total of 60 samples (30 catfish skins and 30 catfish intestines) were used for Salmonella sp. isolation (pellet-method), its biochemical and serological test. Confirmation of Salmonella sp. were determined by polyvalent O antisera and polymerase chain reaction (PCR) using genus specific primers for invA genes (DNA amplification showed one distinct band with molecular weight of 389 bp) and the species of isolated Salmonella sp. were identified by serotyping. The result showed 6/30 (20%) of fish or 6/60 (10%) of organ samples were positive for Salmonella sp. Among those positive for Salmonella sp., 4/6 were from intestine samples and 2/6 were from skin samples. No significant difference was found in the prevalence of Salmonella sp. isolates between fish harvested from farms and wet markets (p-value= 0.406). The Salmonella serovars identified were Salmonella corvallis (n=3), Salmonella mbandaka (n=2) and Salmonella typhmurium (n=1). Salmonella sp. isolates were resistance to Penicillin (P 10, 100%), Clindamycin (DA 2, 100%), Tetracycline (TE 30, 100%) and Rifampicin (RD 5, 100%) and all of the isolates were susceptible or intermediate resistance to Ceftazidime (CAZ 30) and Trimethopin (W 5). Multiple antibiotic resistance (MAR) index of all Salmonella sp. isolates in current study was 0.67 indicating that fish sampled in the present study was under high risk of been exposed to the tested antibiotics

Toxicological efects and behavioural and biochemical responses of Oreochromis mossambicus gills and its cholinesterase to copper: a biomarker application

Gills are both morphologically and physiologically complex whereby they perform several functions such as gas exchange, ion and water exchange, acid base balance, nitrogenous waste excretion, and other metabolic transformations. They are one of the frst fsh organs to be exposed to heavy metals in the aquatic environment. The exposure of Oreochromis mossambicus to copper showed deleterious efects to normal fsh behaviours and varying degrees of gill damage when visualized under inverted light microscopy (stained with haematoxylin–eosin), scanning electron microscopy, and transmission electron microscopy. Abnormalities of the nucleus shape, swollen cells, lipid droplet deposition, and an increase in vacuolation on the afected gills were observed with the degree of damage associated with CuSO4 exposure concentration. CuSO4 exposure in O. mossambicus also gave various patterns of inhibitory efects on cholinesterase (ChE) depending on the concentration of exposure and the organs exposed. Copper exposure altered ChE activity extracted from the gills of O. mossambicus with 99.9% of inhibition at the highest exposure concentration of CuSO4 (20 mg/L). Hence, this study suggests the potential of this fsh to become a sentinel species that permits the detection of lower copper contamination levels

Detecting Aphanomyces Invadans in Pure Cultures and EUS-infected Fish Lesions by Applying PCR

Aphanomyces invadans is an oomycete fungus which causes Epizootic Ulcerative Syndrome (EUS) disease in wide range of fresh and brackish water fish worldwide imposing serious economic losses. A diagnostic procedure, based on a polymerase chain reaction method (PCR) was developed to detect infection of fish with the A.invadans.  A set of primers (1APM 1F and 1APM 6R) was used to specifically amplify A. invadans DNA. The PCR amplifies a 400 bp amplicon. A protocol for the extraction of A. invadans DNA from infected fish tissue and pure fungal cultures was developed. The method was tested on seven EUS-susceptible fish species (snakehead, snakeskin gourami, moonlight gourami, koi carp, catfish, gold fish, climbing perch) and one EUS-resistant fish (tilapia), artificially infected with A. invadans and pure cultures of Aphanomyces spp., Saprolegnia spp., Achlya spp., and Allomyces sp. Detection of A. invadans was possible at the early stage of sampling, which was 24 hours post injection in both EUS-susceptible and resistant fish. Resistant fish was found to be PCR-negative after 6 days of inoculation but in susceptible fish PCR-positive results obtained even after day 28 or in dead fish. Therefore PCR may be a useful method for detection EUS infection in fish from early stage of disease onset. &nbsp

Experimental infection of Aphanomyces invadans and susceptibility in seven species of tropical fish

Aim: Epizootic ulcerative syndrome (EUS) causes by aquatic oomycete fungus, Aphanomyces invadans is a dangerous fish disease of a wide range of fresh and brackish water, wild and farmed fish throughout the world. The objective of the present study was to determine the susceptibility of a number of tropical fish species to the EUS and compare the severity of infection between experimental groups. Materials and Methods: Snakehead, Channa striata (Bloch, 1793); snakeskin gourami, Trichopodus pectoralis (Regan, 1910); koi carp, Cyprinus carpio (Linnaeus, 1758); broadhead catfish, Clarias macrocephalus (Günther, 1864); goldfish, Carassius auratus (Linnaeus, 1758); climbing perch, Anabas testudineus (Bloch, 1792); and Nile tilapia, Oreochromis niloticus (Linnaeus, 1758) were challenged by intramuscular injection using zoospores of Aphanomyces invadans (NJM9701). The infected fish skins and muscles were examined for EUS histopathological characteristics, and the results on the severity of lesions and mortality were analyzed using SPSS program. Results: All zoospore-injected fish were shown to be susceptible to the EUS infection except Nile tilapia. Although, the general histopathological pattern was similar in the zoospore-injected group, but there were some variation in granulomatous reaction, that is the presence or absence of giant cells, and time of mortality were detected. The result of statistical analysis showed that there was a significant difference between species, (c2=145.11 and p<0.01). Conclusion: Gourami, koi carp, and catfish were demonstrated to be highly susceptible while goldfish and climbing perch were found to be moderately susceptible to the EUS infection. These findings suggested that the cellular response of fish to mycotic infection and granulomatous reaction varied in different fish species, which could not be an indicator of susceptibility or resistant to the EUS itself, although it was shown that the granulation rate and the level of maturity or solidification (consolidation of granulomas) were higher in resistant fish

Crude extracts of epidermal mucus and epidermis of climbing perch Anabas testudineus and its antibacterial and hemolytic activities

Epidermal mucus of fish contains a number of biologically active constituents including antimicrobial peptides that are continuously expressed and also engaged in provision of protection to the fish against injurious substances as well as potential pathogenic microbes. This study seeks to determine the hemolytic and antibacterial properties of crude extract from epidermal mucus of climbing perch. Epidermal mucus and epidermis were obtained from 15 climbing perches after hypothermic stress stimulation for extraction of crude by aqueous and acidic methods. Antibacterial activity by well diffusion agar was applied for both extracts against 11 strains belonging to 7 different bacterial species using well agar diffusion test assay. In addition, haemolytic activity was investigated using horse RBCs. Antibacterial activity was performed for acidified crude extract only and it was found to be significant (P < 0.05) against P. aeruginosa while the least reactivity was observed against Methicillin Resistant Staphylococcus aureus. Total soluble protein concentration was 1.2 mg/ml with 13 bands of proteins (245–11) kDa distinguished. There was absence of haemolytic activity of acidified crude extract using horse RBCs. The finding of this study indicates that proteins in bioactive crude extracted from climbing perch have potential therapeutic application. Keywords: Epidermal mucus, Anabas testudineus, Antibacterial peptides, Hemolytic activity, Innate immunity, Fis