Evaluation of Soil Streptomyces Isolates from North-Western Ethiopia as Potential Inhibitors against Spoilage and Foodborne Bacterial Pathogens

Abstract

The outbreak and spread of foodborne diseases is a serious concern for global healthcare and security. Finding novel antimicrobial agents with diverse mechanisms of action against the current spoilage and foodborne bacterial pathogens is a central strategy to overcome the problems of antibiotic resistance. Soil actinomycetes are the major antimicrobial producers with great biopreservative and medical value. This study was aimed at isolating Streptomyces from soil samples of northwestern Ethiopia against spoilage and foodborne bacterial pathogens. Thirty-six soil samples were collected at a depth of 5–10 cm in the rhizosphere and agricultural soils of soybean. A total of 118 actinomycete strains were isolated and screened primarily using the perpendicular streak plate method against 3 Gram-positive and 3 Gram-negative bacterial strains. Out of 118 isolates, 36/118 (30.50%) were active against at least two of the tested bacteria, of which 8 isolates were selected for their wide-spectrum antibacterial activities. During the disc diffusion assay, the eight in vitro ethyl acetate extract antibacterial activities range from 7 to 24 mm. The minimum inhibitory concentration and minimum bactericidal concentration values range from 0.10 to 0.25 μg/mL and 0.15 to 0.40 μg/mL, respectively. Following the morphological, physiological, biochemical, and molecular characteristics, eight potent isolates were identified as follows: Streptomyces fasciculus, Streptomyces roseochromogenes, Streptomyces ruber, Streptomyces glaucus, Streptomyces griseus, Streptomyces cellulosae, Streptomyces griseoflavus, and Streptomyces xanthophaeus. After the treatment of potent Streptomyces cell-free culture supernatant with proteinase K, papain, α-amylase, and lysozyme enzymes, their antagonistic effects were also observed. Most Streptomyces cell-free culture supernatant antibacterial activity was highly resistant to heat, acidity, organic solvents, and additives. Thus, the results of this investigation revealed that soil actinomycetes could be a valuable source for novel antibacterial agents applicable in food biopreservation and the treatment of spoilage and foodborne bacterial pathogens.

The Probiotic Potential and Metabolite Characterization of Bioprotective Bacillus and Streptomyces for Applications in Animal Production

“…In vitro research has reported inhibition zones ranging from 3.3 ± 1.0 to 13.0 ± 1.4 mm when various Bacillus strains were used against S. Typhimurium [40]. Although similar studies with S. griseus against Salmonella were not found, scientific records suggest the antimicrobial efficacy of this bacterium [41,42].…”

Prevalence of Salmonella spp., Shigella spp., and intestinal parasites among food handlers working in University of Gondar student’s cafeteria, Northwest Ethiopia

“…Food-borne diseases (FBD) refer to illnesses caused by consuming pathogenic microorganisms, such as bacteria, fungus, viruses, and parasites, or their toxins in the case of bacteria and fungi (1)(2)(3). Additionally, FBD is caused by unprotected food handling and processing, and poor Sanitary conditions (4).…”

Antibacterial Activity and Mechanisms of Action of Inorganic Nanoparticles against Foodborne Bacterial Pathogens: A Systematic Review

“…Pathogenic and spoilage-causing agents must be controlled in a variety of foods to ensure food quality and safety [1][2][3][4]. The sporadic prevalence of microbial pathogens in food and the increased incidence of antibiotic-resistant strains and their genes have posed serious concerns for public health.…”