A summary of the publication on Antimicrobial Activity of Novel Lactococcus lactis Strains against Salmonella Typhimurium DT12, Escherichia coli O157:H7 VT_ and Klebsiella pneumoniae in Raw and Pasteurized Camel Milk” written by Achenef Melaku Beyene:
Dairy products, particularly fermented milks and yogurt, are major sources of Lactic acid bacteria (LAB). Currently, there are no cultures identified or optimized to inhibit pathogens in camel milk. In order to identify such cultures, the authors of this study tested four novel Lactococcus lactis strains against Salmonella Typhimurium DT12, Escherichia coli O157:H7 VT_ and Klebsiella pneumoniae in raw and pasteurized camel milk.
Camel milk is often consumed in arid and semi-arid areas of the Middle East, Asia, and Africa where availability of green vegetables and fruits is limited. As a result, it is sometimes labelled as the ‘white gold of the desert’. Camel milk contains relatively higher concentrations of antibacterial or antiviral substances than cow’s milk. It also has significant nutritional relevance and is believed to have many medicinal benefits. Presence of different lactic acid bacteria, including Lactococcus lactis, may play a role in the health benefits of the product.
Lactic acid bacteria (LAB) have been used to ferment foods for many decades. They are very important in adding favorable flavor, aroma, texture and nutritional value to fermented food. Further, they increase the shelf life of food items, inhibit the multiplication of pathogenic organisms by competition, reducing pH, and produce antibacterial peptides. There is also evidence that LAB help to control intestinal infections, some types of cancer, serum cholesterol levels and other health problems.
Lactococcus lactisis a lactic acid bacterium, which is used extensively in the production of buttermilk and cheese. It also prevents the growth of pathogens or spoilage bacteria by producing multiple antimicrobial substances such as bacteriocins, organic acids and other low molecular compounds.
Contamination of milk by pathogenic bacteria can occur at any point in the supply chain, from production to consumption. Contamination should be minimized to prevent sickness in consumers. Use of water with poor quality, poor sanitation during milking, poor personal and environmental hygiene, use of unclean containers, and uncooled preservation and transportation are the main factors promoting contamination of camel milk. Salmonella species, Escherichia coli, and Klebsiella pneumoniae are commonly encountered bacterial contaminants in camel milk.
The authors of this study incubated Salmonella Typhimurium DT12, Escherichia coli O157:H7 VT_ and Klebsiella pneumoniae with different strains of L. lactis and found that L. lactisMS22333 and MS22337 significantly reduced the pathogens in the milk. However, L. lactisMS22314 and MS22336 showed no antimicrobial activity. This indicated that the ability of LAB to inhibit pathogenic bacterial is generally a strain-dependent trait and varies considerably among strains within the same species. They also demonstrated that S. Typhimurium and K. pneumoniae can be eliminated in camel milk by L. lactis strains. Hence, L. lactis MS22333 and L. lactis MS22337 isolated from spontaneously fermented camel milk can be applied as a starter culture to promote food safety in Africa and other part of the world.
Reference: Bragason E, Berhe T, Dashe D, Ib Sorensen K, Guya ME, Hansen EB, 2020. Antimicrobial activity of novel Lactococcus lactis strains against Salmonella Typhimurium DT12, Escherichia coli O157:H7 VT_ and Klebsiella pneumoniae in raw and pasteurized camel milk. International Dairy Journal, 111: 104832.