ANTIMICROBIAL ACTIVITY AND ENZYMES ON SKIN MUCUS FROM MALE AND FEMALE CASPIAN KUTUM (Rutilus frisii kutum Kamensky, 1901) SPECIMENS

The mucus layer covering the surface of fish contain a high number of antimicrobial compounds that provide a first line of defense against aquatic pathogens. In the present study, bactericidal activity present on skin mucus of Caspian kutum (Rutilus frisii kutum) broodstock was tested against six pathogenic bacterial strains (Streptococcus iniae, Yersinia ruckeri, Staphylococcus aureus, Listeria monocytogenes, Pseudomonas aeruginosa and Escherichia coli). Furthermore, fungicidal activity was assessed against four pathogenic fungi (Saprolegnia sp., Fusarium solani, Candida albicans and Aspergillus flavus). Maximum and minimum antibacterial activity was observed against Y. ruckeri and S. iniae, respectively, while maximum and minimun fungicidal activty was detected against F. solani and C. albicans, respectively. Curiously, antimicrobial activity was higher in the fish mucus of female than male against most tested strains. In addition, minimum inhibitory concentration test showed that minimum concentrations of mucus ranged between 125 to 500 μg/L were able to inhibit the growth of the selected bacterial and fungal pathogens. Alkaline phosphatase, lysozyme, protease and esterase activities were also studied on mucus samples being the observed activities very similar between both sexes, although higher lysozyme activity was detected in the mucus of female fish in comparison to the values recorded on male samples. Skin mucus of this fish species (especially females) could be a potential source of newer and more effective antibacterial components.Key words: Rutilus frisii kutum; skin mucus; bactericidal activity; antifungal activity; fish PROTIBAKTERIJSKA AKTIVNOST IN ENCIMI V VZORCIH SLUZI KOŽE SAMCEV IN SAMIC KASPIJSKEGA KUTUMA (Rutilus frisii kutum Kamensky, 1901)Povzetek: Sloj sluzi, ki pokriva površino rib, vsebuje veliko količino protimikrobnih spojin, ki zagotavljajo prvo obrambo pred škodljivimi mikroorganizmi v vodi. V študiji je bila testirana baktericidna aktivnost sluzi s površine kože kaspijskega kutuma (Rutilus frisii kutum) na šestih patogenih bakterijskih sevih (Streptococcus iniae, Yersinia ruckeri, Staphylococcus aureus, Listeria monocytogenes, Pseudomonas aeruginosa in Escherichia coli). Ocenjena je bila tudi fungicidna aktivnost proti štirim patogenem vrstam gliv (Saprolegnia sp., Fusarium solani, Candida albicans in Aspergillus flavus). Največja in najmanjša protibakterijska aktivnost je bila opažena proti Y. ruckeri in S. iniae, medtem ko je bila pri F. solani in C. albicans odkrita največja in najmanjša fungicidna aktivnost. Zanimivo je, da je bila protimikrobna aktivnost višja pri sluzi samic kot pri sluzi samcev. Minimalni zaviralni preizkus koncentracije je pokazal, da so najmanjše koncentracije sluzi, ki so zavirale rast izbranih bakterijskih in glivičnih patogenov med 125 do 500 μg/L. V vzorcih sluzi so bili proučevani tudi aktivnosti alkalne fosfataze, lizocima, proteaz in esteraz. Pri večini meritev ni bilo razlik med spoloma, le pri aktivnosti lizocima je bila ta aktivnost višja v sluzi samic v primerjavi z vrednostmi, izmerjenimi v vzorcih samcev. Kožna sluznica te vrste rib (zlasti samic) bi lahko bil potencialni vir novih in učinkovitejših antibakterijskih sredstev.Ključne besede: Rutilus frisii kutum; kožna sluznica; baktericidna aktivnost; proti glivično delovanje; ribe