No abstract

A Pseudomonas sp PS-102 recovered from Muttukkadu brackish water lagoon, situated south of Chennai, showed significant activity against a number of shrimp pathogenic vibrios. Out of the 112 isolates of bacterial pathogens comprising Vibrio harveyi, V. vulnificus, V. parahaemolyticus, V. alginolyticus, V. fluvialis, and Aeromonas spp, 73% were inhibited in vitro by the cell-free culture supernatant of Pseudomonas sp PS-102 isolate. The organism produced yellowish fluorescent pigment on King's B medium, hydrolysed starch and protein, and produced 36.4% siderophore units by CAS assay and 32 μM of catechol siderophores as estimated by Arnow's assay. The PS-102 isolate showed wide ranging environmental tolerance with, temperatures from 25 to 40°C, pH from 6 to 8, salinity from 0 to 36 ppt, while the antagonistic activity peaked in cultures grown at 30°C, pH 8.0 and at 5 ppt saline conditions. The antagonistic activity of the culture supernatant was evident even at 30% v / v dilution against V. harveyi. The preliminary studies on the nature of the antibacterial action indicated that the antagonistic principle as heat stable and resistant to proteolytic, lipolytic and amylolytic enzymes. Pseudomonas sp PS 102 was found to be safe to shrimp when PL-9 stage were challenged at 10 7 CFU ml − 1 and by intramuscular injection into of ∼5 g sub-adults shrimp at 10 5 to 10 8 CFU. Further, its safety in a mammalian system, tested by its pathogenicity to mice, was also determined and its LD 50 to BALB/c mice was found to be 10 9 CFU. The results of this study indicated that the organism Pseudomonas sp PS 102 could be employed as a potential probiont in shrimp and prawn aquaculture systems for management and control of bacterial infections.

Larvae (15 to 21 d post hatch, dph) of the Asian sea bass Lates calcarifer (Bloch) suffered heavy mortalities (60 to 90%) during the hatchery-rearing phase. Darkened and moribund larvae showed no evidence of bacterial or parasitic infections. Tissue sections of brain and spinal cord showed clear necrotic vacuolation. Electron microscopy revealed membrane-bound viral particles in the cytoplasm of the nerve cells. The viral particles measured 28 to 30 nm in diameter. Primer sets, designed for the amplification of the RNA2 segment of the piscine nodavirus coat protein gene, were used in the RT-PCR analysis of moribund larvae of 20 and 21 dph which produced the amplified product of 430 bp. The clinical manifestations, pathology and electron microscopy observations supported by the RT-PCR analysis suggest that the nerve necrosis was due to nodavirus infection in the larvae. This is the first report of piscine nodavirus infection from the Indian sub-continent. KEY WORDS: Nodavirus · Lates calcarifer · Larvae · RT-PCR · Histopathology · Nervous necrosis virus Resale or republication not permitted without written consent of the publisherDis Aquat Org 63: [113][114][115][116][117][118] 2005 geographical locations have been reported to be susceptible to the virus (Glazebrook et al. 1990, Yoshikoshi & Inoue 1990, Mori et al. 1992, Muroga 1995, Comps et al. 1996, Munday & Nakai 1997, Castric et al. 2001. The disease has also been reported in freshwater aquarium fish from Singapore (Hegde et al. 2003).Histology and RT-PCR are the common methods used for diagnosis of the virus in fish (Mori et al. 1991, Munday et al. 1992, Nishizawa et al. 1994, Grotmol et al. 1995, Lai et al. 2001, Johansen et al. 2002, Hegde et al. 2003. Diagnosis of piscine nodavirus using RT-PCR for the T4 region (427 bp) of SJNNV coat protein gene (RNA2) has been widely used and many workers have reported positive amplification for the presence of the nodavirus in fish species from different geographical locations (Nishizawa et al. 1994, Castric et al. 2001, Curtis et al. 2001, Lai et al. 2001. Primer sequences of Nishizawa et al. (1994) have been recommended for the diagnosis of the piscine nodaviruses (OIE 1997).A batch of Asian sea bass larvae produced in the fish hatchery facilities of the Central Institute of Brackishwater Aquaculture were observed to experience sudden and unexplained mortality after 15 d of larval rearing. Subsequent investigations revealed that the cause of the disease was piscine nodavirus. The present investigation represents the first report of VNN from the Indian sub-continent and extends the known range of this disease. MATERIALS AND METHODSFish. Broodstock procured from the coastal waters of Chennai (Madras), acclimatized and maintained in cement tanks are being used for the purposes of seed production. Since 1997 more than 15 batches of Asian sea bass larvae have been produced in the institute facility. Though the hatchlings were sampled from 0 d post hatch (dph) for routine histology, the larvae from 15 to 2...

We have demonstrated the ability of OmpC of E. coli to induce neurodegeneration in mice.