In Vitro evaluation of antimicrobial activity of native probiotic bacteria against some common aquatic pathogens

چکیده مقاله

Abstract: Probiotics are live microorganisms, which when administered in adequate amounts, confer a health benefit on the host. Probiotics typically produce a wide range of antimicrobial substances that inhibit and control microbial pathogens. This study was conducted to evaluate antimicrobial activity of our native probiotic bacteria isolated from Persian Gulf fish.

A total of 83 Gram-positive isolates have been cultured from intestine and rectum of shrimp, crab, sole fish, flounder fish, goby fish and eel fish. These strains were initially characterized by phenotypic methods and survey for probiotic activity according to Iran National standard No. 19459. Among all, only 33 isolates passed all criteria and introduced as probiotic candidates which characterized by 16S rRNA gene sequencing.

Antimicrobial activity of selected strains against fish pathogens include Lactococcus garvieae (IBRC-M 11508), Yersinia ruckeri (IBRC-M 11507) and Streptococcus iniae (IBRC-M 11513)was carried out according to well diffusion method on Muller-Hinton agar. At first, cell-free supernatant of strains (CFS) were obtained by centrifugation of liquid probiotic culture and filtered through cellulose nitrate filter of 0.45 µm. The CFS was then freeze-dried and used as source for antimicrobial compounds in the process.

As a result, two probiotic strains by the name of Dash I (5) and LP7 (18) demonstrated significant efficacy against pathogens which characterized as Levilactobacillus brevis and Pediococcus acidilactici, respectively. Studies to evaluate the effects of these selected strains in amelioration disease symptoms in fish farm is ongoing.