In Vitro Treatment of Different Isolates from Cattle Dung and Pig Slurry by Nisin

Lauková A . : In Vitro Treatment of Different Isolates from Cattle Dung and Pig Slurry by Nisin. Acta Vet. Brno 2000, 69: 147–151. The antimicrobial effect of nisin against selected environmental isolates (from cattle dung and pig slurry) was tested using two methods: well diffusion test and agar spot test. Following isolates were included in the tests: enterococci (33), staphylococci (11), Bacillus spp. (2), Providencia spp. (3), Citrobacter freundii (1), Morganella morganii (2) and Acinetobacter -like sp. (1). Using well diffusion test all indicator organisms were sensitive to nisin at a concentration of 1 mg ml-1, except of species Morganella morganii and Citrobacter freundii. Inhibition zones measured from 11 up to 26 mm (in diameter). The nisin activity towards indicators expressed in AU ml-1 ranged from 100 AU ml-1 up to 6400 AU ml-1. The most sensitive to nisin was found Enterococcus faecalis V24 strain and Bacillus pumilus BP17 strain (3200 – 6400 AU ml-1). Moreover, in our in vitro tests, the Gram-negative species of genera Providencia and Acinetobacter were sensitive to nisin (200, 400 AU ml-1); in spite of the predominat effect of nisin against Gram-positive bacteria. Animal excrements, antimicrobial substance, effect of treatment In today’s world, the contamination of the environment, in general is serious concern. Large volumes of pollutants are introduced into the ecosystem every day because of the production of agricultural waste and industrial chemicals. The excrements of farm animals, in the form of slurry or dung are accumulated in large quantities and forms organic manure which is a source of a diverse bacterial environment (Boopathy 1997). Thus, such excrements represent a potential health hazard mainly from the aspect of their using for land application (Paulsrud and Nedland 1997). Aerobic and/or anaerobic treatment in the thermophile and mesophile zones are used in dealing with a wide range of problems associated with slurry stabilization (Novák et al. 1994; Jepsen et al. 1997). However, these treatments e.g. in mesophile zone were found not sufficiently effective for complete decontamination (stabilization) of the excrements (Jepsen et al. 1997). Therefore, new ways are experimented and searched to reach higher effectiveness of stabilization processes. And, one of possible ways to solve this problem could be to utilize the ability of some bacteria to produce antimicrobial substances. Nisin is a bacteriocin (antimicrobial substance) of the lantibiotic type produced by certain strains of Lactococcus lactis subsp. lactis. It is composed of 34 amino acids. Nisin displays a bactericidal mode of activity and finds exclusive use as a biological food preservative to prevent Gram-positive but also Gram-negative spoilage bacteria (Blackburn et al.1990; De Vuyst and Vandamme 1994). Nisin showed inhibitory effect also against ruminal isolates (Lauková 1995). Because of its strongly bactericidal effect towards mastitis pathogens, it was also used for this type of treatment (Delves-Broughton et al. 1996). Moreover, the effect of other bacteriocins was reported for experimental treatment in slurry (Lauková et al. 1998a). Therefore, in this paper the antimicrobial effect of nisin against environmental isolates (from cattle dung and pig slurry) was tested. The aim of the ACTA VET. BRNO 2000, 69: 147–151 Address for correspondence: MVDr. Andrea Lauková, CSc. Institute of Animal Physiology, Slovak Academy of Sciences ·oltésovej 4-6, 04001 Ko‰ice, Slovakia Fax:+421 95 762 162 Phone: +1421 95 633 0283 email:[email protected]