Antimicrobial effect of selected probiotic strains on salmonella typhimurium and e. coli o157:h7 isolated in a commercial slaughterhouse in Windhoek, Namibia
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Date
2022
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Publisher
University of Namibia
Abstract
In recent years, Lactic Acid Bacteria (LAB) have gained popularity due to their preservative and antimicrobial activities. Therefore, there has been a growing interest in researching and developing new antimicrobial agents from various sources to control and eliminate pathogens such as Salmonella typhimurium and E. coli O157:H7 in food niches. The two pathogens are the major causative agents of foodborne diseases especially in meat products. Therefore, this study aimed to evaluate the antimicrobial activity of selected commercial probiotic strains of P. acidilactici and P. pentosaceus against S. typhimurium and E. coli O157:H7 isolated from beef samples using monoculture and co-cultures design. Beef samples were collected from Meatco Abattoir and antimicrobial activity of the probiotics strains was evaluated using pour plate methods over general and selective media such as Salmonella Shigella (SS) agar and MacConkey agar. The optical density (OD) was measured at 600 nm to study the growth kinetics of microbial mass for the probiotic and pathogenic strains in mono and co-cultures models. The co-cultures of S. typhimurium and P. acidilactici gave the significant reduction of 1.2 log cfu in S. typhimurium population, indicating that, it is more sensitive to the tested Pediococcus strains than E. coli O157:H7. Both LAB strains showed antagonistic activities against S. typhimurium and E. coli O157:H7, although none of the LAB showed a complete inhibition. However, P. acidilactici had a greater antimicrobial activity compared to P. pentosaceus. The OD value of S. typhimurium co-culture decreased with 2.24 log cfu when it was co-cultured with P. acidilactici and 2.28 log cfu when it was co-cultured with P. pentosaceus. Meanwhile, OD value of E. coli O157:H7 decreased significantly with 2.22 log cfu when it was co-cultured with P. pentosaceus and 2.33 log cfu with P. acidilactici showing their potential bio-preservation in meat products. However, further confirmatory tests are ii needed especially in their permitted concentration on the surface of cow carcasses and meat cuts during the storage.
Description
A thesis submitted in fulfilment of the requirements for the Degree of Master of Science (Microbiology)
Keywords
Antimicrobial effect, Lactic Acid Bacteria S. typhimurium, E. coli O157:H7, Meat