SEAFDEC/AQD-Asian Fisheries Society

Studies on the efficacy of Sarafin® (sarafloxacin hydrochloride) on vibrios associated with vibriosis in black tiger shrimp (Penaeus monodon)

2023-04-12T06:11:31Z

Studies on the efficacy of Sarafin® (sarafloxacin hydrochloride) on vibrios associated with vibriosis in black tiger shrimp (Penaeus monodon) Pakingking, Rolando V., Jr.; Lacierda, Erlinda; Torres, James L. Lavilla-Pitogo, Celia R.; Cruz-Lacierda, Erlinda R. In vitro activity of Sarafin® (sarafloxacin hydrochloride) was determined against 7 luminous Vibrio harveyi isolates and 3 non-luminous Vibrio species (V. parahaemolyticus, V. alginolyticus and Vibrio species) isolated from diseased shrimp (Penaeus monodon) and rearing water, a strain of V. anguillarum from diseased marine fish, 1 strain each of V. alginolyticus, V. vulnificus, and V. mimicus from diseased grouper (Epinephelus coioides), and V. alginolyticus from diseased seabass (Lates calcarifer). Bacterial susceptibility was expressed as minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). The MIC and MBC values obtained for all V. harveyi isolates ranged from <0.3 to 1.25 µg/ml. For the non-luminous Vibrio species, MIC and MBC values ranged from <0.08 to 1.25 µg/ml. In vivo tolerance levels (24 h static bioassay) of larval and postlarval stages of P. monodon for Sarafin® were <10 µg/ml for nauplii, mysis, and postlarvae and ≤1 µg/ml for zoeae. Morphological deformities in the carapace, rostrum, and setae were noted among larvae exposed to >50 µg/ml Sarafin®. These results indicate that Sarafin® is a potential candidate as a chemotherapeutic agent against luminous vibriosis in P. monodon.

Swollen hindgut syndrome (SHG) in hatchery-reared Penaeus monodon postlarvae

2022-01-22T02:34:43Z

Swollen hindgut syndrome (SHG) in hatchery-reared Penaeus monodon postlarvae Lavilla-Pitogo, Celia R.; Paner, Milagros G.; Traviña, Remia D. Lavilla-Pitogo, Celia R.; Cruz-Lacierda, Erlinda R. In the course of routine microscopic analysis of hatchery-reared Penaeus monodon postlarvae, several batches were found with hindgut abnormalities not previously described in shrimp postlarvae. The abnormality was named swollen hindgut syndrome (SHG) because it affected mainly the hindgut. Postlarvae with SHG showed enlargement and distention of the hindgut folds and its junction with the midgut, although in some cases swelling also occurred in the midgut of the sixth abdominal segment. Over a five-year period, the yearly prevalence of SHG ranged from 6 to 13% of all batches examined. No seasonal pattern was observed as SHG occurred year-round. Despite the numerous samples obtained, SHG has not been associated with specific predisposing factors in the hatchery. The abnormality caused cessation of the rhythmic movements of the hindgut-midgut junction resulting to failure of affected postlarvae to excrete fecal pellets. Swollen hindgut syndrome, although reversible to some extent, caused mortality and significant size variation within batches of postlarvae resulting in their unsuitability for stocking in grow-out farms.

Quorum sensing and its potential application to vibriosis

2022-01-22T02:34:44Z

Quorum sensing and its potential application to vibriosis Dunlap, Paul V. Lavilla-Pitogo, Celia R.; Cruz-Lacierda, Erlinda R. Quorum sensing is a gene regulatory mechanism by which certain pathogenic and symbiotic bacteria respond to population density and host association. By mediating the ability of bacteria such as Vibrio harveyi to infect larval shrimp, quorum sensing could have application to the problem of vibriosis in shrimp mariculture. Knowledge of quorum sensing developed from studies of luminescence in the marine bacteria Vibrio fischeri and V. harveyi. In both species, luminescence is controlled by a quorum-sensing mechanism involving two signal molecules and several genetically defined and physiological factors. In V. fischeri, luminescence is regulated by LuxR protein and the Luxl-dependent 3-oxo-hexanoyl-homoserine lactone (3- oxo-C6-HSL), which together activate transcription of luxICDABEG (the lux operon, genes for LuxI and the luminescence enzymes). A second acyl-HSL, octanoyl-HSL, product of AinS, blocks premature lux operon induction by interfering with 3-oxo-C6-HSL binding to LuxR. In V. harveyi, quorumsensing control of luminescence involves the luxLM-dependent 3-hydroxy- butyryl-HSL and an unidentified luxS-dependent signal molecule. These signals, through independent branches of a phosphorylation cascade, control the phosphorylation state of LuxO. In the absence of the signals, LuxO, in phosphorylated form, represses lux operon (luxCDABEGH) expression. The presence of the signals operates to dephosphorylate LuxO, relieving the repression. A LuxR protein then activates lux operon transcription. Targets for blocking the quorum-sensing mechanism in these bacteria and potentially blocking vibriosis include the activity, production and persistence of the signals, the production and activity of the response proteins, and the activity of specific downstream quorum-sensing controlled proteins involved in host infection.

Identification and characterization of Vibrio bacteria isolated from fish and shellfish in Vietnam

2021-10-15T08:21:26Z

Identification and characterization of Vibrio bacteria isolated from fish and shellfish in Vietnam Oanh, Dang Thi Hoang; Pedersen, Karl; Larsen, Jens Laurits Lavilla-Pitogo, Celia R.; Cruz-Lacierda, Erlinda R. A taxonomic relationship of thirty one Vietnamese bacterial isolates from different fish and shellfish together with twenty two reference strains was investigated by Euclidean distance with unweighted average linkage clustering. Comparison based on fourty seven phenotypic characters showed that these isolates mainly clustered in six groups of which four were equated with the well known Vibrio species, V. alginolyticus, V. harveyi, V. cholerae and V. mimicus. For the remaining two groups comprising twelve isolates, it was more difficult to establish any relationship with known species when compared with reference strains. Strains were also subjected to rRNA gene restriction pattern analysis (ribotyping), using Mlu I as restriction enzyme. Eleven ribotypes were detected among the Vietnamese isolates. Similarity of ribotyping patterns between strains supported the phenotypic identification. Twenty-eight strains were found to carry at least one plasmid and 12 different sized plasmids were detected ranging from less than 2 to 140 kb. The two Vibrio spp. groups performed high phenotypic and genotypic similarity within each group but were only remotely related with the reference strains. The evidence suggest that these strains may represent new Vibrio species.