In this article, the presence and physiological characteristics of lactic acid bacteria (LAB) isolated from traditionally made cheese from Southeastern Serbia were examined. Three samples, from different households, were obtained in spring. The screening of antagonistic potentials, using agar‐well diffusion method, was evaluated. Briefly, three different genera of LAB (Enterococcus [32%], Lactococcus [53%], and Lactobacillus [15%]) were identified. The members of the genus Enterococcus were Enterococcus faecium and Enterococcus faecalis. The member of genus Lactococcus was Lactococcus lactis subsp. lactis var. diacetylactis. The members of genus Lactobacillus were Lactobacillus fermentum, Lactobacillus plantarum, and Lactobacillus paracasei subsp. paracasei. The antagonism of LAB on the growth of Escherichia coli ATCC 25922, Proteus mirabilis ATCC 12453, Klebsiella oxytoca KGPMF1, Klebsiella ornithinolytica KGPMF8, and Aeromonas hydrophila was examined. All tested isolates inhibited the growth of at least one indicator strain with growth inhibition zone from 10 to 21 mm. Results indicated that LAB demonstrated the potential of food biopreservation. Practical applications Traditionally made cheeses represent excellent source of unexplored microflora, especially of autochthonous lactic acid bacteria (LAB). In cheese from Sokobanja, the isolated LAB genera were Lactobacillus sp., Lactococcus sp., and Enterococcus sp. Also, the physiological activity of LAB, as well as their interaction with enterobacteria, which also was isolated from the mentioned cheese, was investigated. The results of this study demonstrated potential of LAB to interact agonistically with the growth of enterobacteria, which was important due to the well‐known fact that enterobacteria could affect the organoleptic properties of cheese. LAB showed potential of food biopreservation. Further investigation should include antagonistic potential related to food‐borne bacteria and the mechanisms of action.

In this paper, the presence, biochemical and physiological characteristics of the members of genus Enterococcus, isolated from traditionally made Serbian cheese, were investigated. The members were identified as: Enterococcus faecium (8 isolates), E. faecalis (14 isolates), E. hirae (4 isolates) and E. durans (4 isolates), using the biochemical tests and MALDI-TOF mass spectrometry. All the tested isolates showed good acidification ability in pure and enriched milk. The antagonism of enterococci on the growth of Escherichia coli ATCC 25922, Proteus mirabilis ATCC 12453, Klebsiella oxytoca KGPMF1, Klebsiella ornithinolytica KGPMF8 and Aeromonas hydrophila, as well as their ability to form biofilms, were examined. The tested isolates showed moderate inhibitory activity (10-22 mm) on the growth of the indicator strains. Among all the isolates, only E. hirae KGPMF9 and E. faecium KGPMF14 showed the ability of biofilm formation. The results provide a basis for further research into the possible practical application of the isolated enterococci.

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.

ABSTRACT. In this study, the effects of environmental factors (different media, temperature, pH, salt and sugar concentrations) on the planktonic growth, biofilm formation and formed biofilm of Escherichia coli KGPMF 16 and Escherichia coli KGPMF 17 were investigated. Tested bacteria were isolated from traditionally made cheese produced in Southeastern Serbia (Sokobanja region). The influence on planktonic growth, biofilm formation and formed biofilm was determined using spectrophotometric method. The limiting factors for the planktonic growth and biofilm formation were temperature of 4 °C and all tested concentrations of salt. The growth of tested bacteria was higher in media enriched with lactose than in media containing glucose. TSB was more congenial media to the planktonic growth of bacteria than MHB broth. None of the tested bacteria demonstrated the ability to form biofilm at 4 °C and 44 °C. Only E. coli KGPMF 17 showed ability to form biofilm in TSB at 37 °C. Different concentrations of salt, glucose and lactose exhibited inhibitory effect on biofilm formation, but all tested concentrations of lactose showed stimulating effect on formed biofilm of E. coli KGPMF 17. These results contribute to better understanding of the effects of environmental factors on the development of E. coli in cheese.