Antagonistic activity of probiotic Bacillus strains on planktonic forms of biofilm-forming bacteria and fungi

Abstract

The presence of microbial biofilms of pathogenic fungi and bacterial contaminants in animal feed can lead to disruption of the intestinal microflora and the development of infectious diseases. A promising field of study is the examination of the antagonistic effect of bacteria from the genus Bacillus on microbial biofilms and planktonic forms of pathogenic microorganisms in feed. The objective of this research is to investigate the antimicrobial and antifungal activity of the probiotic complex of bacteria from the genus Bacillus against planktonic forms of biofilm-forming pathogenic fungi and microorganisms isolated from pig feed. The antagonistic activity of five probiotic strains against the test cultures Pasteurella multocida type D No. 07, Neisseria meningitidis No. 18, Streptococcus haemolyticus No. 14, Escherichia coli No. 21, Actinobacillus pleuropneumoniae No. 12 was studied by the method of delayed inoculation (perpendicular strokes) in three replicates. The antifungal activity against the test fungi Aspergillus niger No. 1 and Aspergillus candidus No. 2 was evaluated by the injection method. According to the results of the study, it was determined that the strain B. licheniformis UNCSM-033 showed a pronounced antagonistic effect on the bacteria N. meningitidis No. 18 with an inhibition level of 26.7 ± 1.2 mm. Inhibition of growth and reproduction of S. haemolyticus No. 14 at a high level of intensity was determined in four probiotic strains with diameters of growth inhibition from 28.7 ± 1.2 mm to 34.0 ± 1.2 mm. A sufficiently high level of antagonism against the test culture E. coli No. 21 was shown by five experimental probiotic strains in the range of 24.7 ± 1.2 mm to 30.7 ± 2.3 mm, respectively. A very high level of antagonistic properties of the probiotic complex of bacteria of the genus Bacillus from five experimental strains against five types of pathogenic microorganisms from 38.3 ± 0.9 mm was shown in A. pleuropneumoniae No. 12 and up to 47.3 ± 0.9 mm in P. multocida type D No. 07. The highest degree of antagonistic activity against five test cultures of biofilm-forming microorganisms and antifungal effect against two test strains of pathogenic fungi, A. niger No. 1 and A. candidus No. 2, was demonstrated by the probiotic complex of bacteria belonging to the genus Bacillus (five strains). The pronounced antimicrobial properties of the five strains of the probiotic complex of bacteria of the genus Bacillus allow for the potential development of drugs based on them as an alternative to antibiotics