Abstract
Viable heterotrophic bacteria VHB -cultivated on ZoBell media and TCBS media TCBSBŽ . Ž . were enumerated from cysts that were hatched under laboratory sterile conditions as well as in a commercial hatchery without sterile conditions. Since the focus of this work was to study the TCBSB, 10 to 30 colonies growing on TCBS were isolated randomly from each sample. Results from 26 samples of different commercial brands and lots show that VHB concentration is comprised between 106 to 108 colony forming unites ŽCFU. per milliliter of Artemia nauplii homogenate. The TCBSB population has show an inverse correlation ŽR2s0.5795, as0.05. with cysts age, with values comprised between -101 to 107 CFUrml. Qualitatively, from 617 isolates, 94% were Gram-positive and only 6% were Gram-negative but oxidase-negative. These basic tests indicate that bacteria of the TCBSB population isolated from Artemia nauplii, do not correspond to Vibrio spp. When cysts of the same brand and same stock where hatched under sterile Žlaboratory. and nonsterile Žcommercial hatchery. conditions, Gram-positive bacteria constitute 95% of the bacterial population under sterile manipulation, instant of nonsterile conditions, where Gram-negative bacteria constitute 100% of the bacterial community that was isolated on TCBS medium and that taxonomical studies identified mainly as Vibrio alginolyticus. Those results indicate that Gram-negative heterotrophic bacteria growing on TCBS, normally reported as introduced by Artemia nauplii, are not associated with Artemia cysts but introduced by commercial hatchery operations. q2001 Elsevier Science B.V. All rights reserved.
บทคัดย่อViable heterotrophic bacteria VHB -cultivated on ZoBell media and TCBS media TCBSBŽ . Ž . were enumerated from cysts that were hatched under laboratory sterile conditions as well as in a commercial hatchery without sterile conditions. Since the focus of this work was to study the TCBSB, 10 to 30 colonies growing on TCBS were isolated randomly from each sample. Results from 26 samples of different commercial brands and lots show that VHB concentration is comprised between 106 to 108 colony forming unites ŽCFU. per milliliter of Artemia nauplii homogenate. The TCBSB population has show an inverse correlation ŽR2s0.5795, as0.05. with cysts age, with values comprised between -101 to 107 CFUrml. Qualitatively, from 617 isolates, 94% were Gram-positive and only 6% were Gram-negative but oxidase-negative. These basic tests indicate that bacteria of the TCBSB population isolated from Artemia nauplii, do not correspond to Vibrio spp. When cysts of the same brand and same stock where hatched under sterile Žlaboratory. and nonsterile Žcommercial hatchery. conditions, Gram-positive bacteria constitute 95% of the bacterial population under sterile manipulation, instant of nonsterile conditions, where Gram-negative bacteria constitute 100% of the bacterial community that was isolated on TCBS medium and that taxonomical studies identified mainly as Vibrio alginolyticus. Those results indicate that Gram-negative heterotrophic bacteria growing on TCBS, normally reported as introduced by Artemia nauplii, are not associated with Artemia cysts but introduced by commercial hatchery operations. q2001 Elsevier Science B.V. All rights reserved.
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