Detection and description of a novel Psychrobacter glacincola infection in some Red Sea marine fishes, Hurghada, Egypt

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Abstract Background: Aquaculture is an important food-producing sector in Egypt, but several pathogenic microorganisms lead to high mortalities and significate economic losses, challenge this sector. The present study investigated the occurrence of Psychrobacter glacincola infection among 180 wild Snubnose emperor (Lethrinus borbonicus), Blackspot snapper (Lutjanus ehrenbergii), Marbled spinefoot (Siganus rivulatus), Haffara seabream (Rhabdosargus haffara), Blue-barred parrotfish (Scarus ghobban) and Broomtail wrasse (Cheilinus lunulatus) marine fishes collected from the Red sea at Hurghada, Egypt. The prevalence rate of disease was 6.7%. The recovered isolates were then subjected to bacteriological, biochemical, and molecular identification. The study also investigated pathogenicity and the antibiogram profile of the recovered isolates. Results: The clinical examination of the infected fish revealed various signs that included lethargy and sluggish movement, hemorrhages and ulcers on the body and the operculum, scale loss, fin congestion and rot, especially at the tail fin. In addition to, congestion of the liver, spleen, and kidney was observed during postmortem examination. Interestingly, 12 isolates were recovered and were homogenous bacteriologically and biochemically. Alongside the biochemical and bacteriological tests, the phylogenetic analysis based on 16S ribosomal RNA (16S rRNA) gene fragment confirmed that the MRB62 identified strain was closely related to members of the genus Psychrobacter and identified as P. glacincola. Furthermore, the recovered Ps. glacincola (MRB62) strain was pathogenic to Rhabdosargus haffara fish, causing 23.3% mortality combined with reporting a series of clinical signs similar to that found in naturally infected fishes. In addition, the recovered strain was sensitive to amikacin, streptomycin, ciprofloxacin, gentamycin, chloramphenicol, tobramycin, and ofloxacin. Conclusions: Our findings add to the body of knowledge about the occurrence of pathogenic P. glacincola infection in Egyptian marine fishes and its potential effects on fish. The study also suggests future large-scale surveys for exploring this bacterium among other freshwater and marine fishes in Egypt that would be helpful for the implementation of effective strategies for prevention and control of this infection.

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