Abstract:

Objective: To examine the effect of synergistic purification with ultrasonic and running water on bacterial
quantity and community composition in live crawfish (Procambarus clarkii). Methods: The bacterial colony numbers in
the unshelled meat, grills and intestinal parts of crawfish were determined during the purification process and changes in
bacterial community composition were analyzed using random amplified polymorphic DNA (RAPD) fingerprint technique
combined with 16S rDNA sequencing identification. Results: The purification procedure by ultrasonic combined with
running water significantly reduced the bacterial loads in the unshelled meat, grills and intestine of crawfish to 2.18, 2.23
and 1.01 (lg (CFU/g)), respectively. A total of 218 single colonies were collected from bacterial counting plates, fingerprint
patterns of 21 colonies of which were obtained through RAPD analysis. The 16S rDNA sequencing identification showed
that the isolates with different fingerprint patterns belonged to 9 bacterial genera including 18 species, among which
Aeromonas sp., Flavobacterium sp., Pseudomonas sp., Shewanella sp. and Enterobacter sp. were the predominant bacterial
groups for crawfish shell, meat and gills. After being purified with ultrasonic and running water, the remaining bacterial
groups were reduced to 9 species from 6 genera, among which, Aeromonas sobria, Enterobacter cloacae, Flavobacterium
granuli and Shewanella putrefaciens were the major residual bacteria species. Conclusion: The synergistic purification with
ultrasonic and running water is highly effective in reducing bacterial level and species in live crawfish.

Key words: Procambarus clarkii, purification, ultrasonic, microflora