In vitro evaluation of the antimicrobial potential of streptococcus uberis isolated from a local cheese from southeastern Serbia

Abstract

© 2018, University of Zagreb, Facultty of Veterinary Medicine. All rights reserved. Streptococcus uberis is an environmental bacterium responsible for bovine mastitis. It is occasionally described as a human pathogen. In our study, the isolation was undertaken of lactic acid bacteria from a local cheese from Southeastern Serbia, produced in a traditional way. S. uberis (7 isolates) and S. agalactiae (1 isolate) were isolated from the cheese samples taken in the summer. The biochemical and physiological characteristics of the isolates were examined. Using tetracycline, chloramphenicol, novobiocin and rifampicin, the antibiotic susceptibility of the isolates was evaluated. The results demonstrated that all the isolates were susceptible to all the tested antibiotics, with a growth inhibition zone from 36-48 mm. Also, the antagonism was examined of S. uberis KGPMF1-7 and S. agalactiae KFPMF8 isolates on the growth of Escherichia coli ATCC 25922, Proteus mirabilis ATCC 12453, Klebsiella oxytoca KGPMF1, Klebsiella ornithinolytica KGPMF8 and Aeromonas hydrophila, as indicator stains. The results were compared with the activities of chloramphenicol, streptomycin and tetracycline on the tested indicator stains. The strongest antagonism was demonstrated by all Streptococcus isolates on the growth of K. oxytoca KGPMF1 (growth inhibition zone from 12-20 mm) and the A. hydrophila (growth inhibition zone from 13-20 mm). When these results were compared with the results of the sensitivity of tested indicator stains to antibiotics, S. uberis KGPMF1-7 and S. agalactiae KGPMF8 isolates showed a moderate antagonistic effect. Due to the specific way cheese is made in from Sokobanja, these isolates probably originate from cows’ udders.