Characterization and molecular identification of lactic acid bacteria isolated from kefir and evaluation of their antibacterial activity against food-borne pathogens in Saudi Arabia.

OBJECTIVE: Pathogenic bacteria are usually present in raw milk. In order to prevent pathogens from growing, milk should be fermented. The present research work aimed to isolate lactic acid bacteria (LAB) from kefir, a fermented milk beverage, and assess their antibacterial activity against chosen pathogenic strains of bacteria. MATERIALS AND METHODS: An experimental investigation was carried out in the laboratory. Samples of kefir were collected from a local organic food store in Jeddah City, Saudi Arabia. LAB isolates were identified phenotypically and biochemically. The agar well diffusion technique evaluated the antimicrobial activities (AMAs) of LAB isolates against Escherichia coli, Listeria monocytogenes, and Salmonella Typhimurium. The isolates were molecularly identified through polymerase chain reaction PCR amplification of the 16S rRNA gene. RESULTS: Six LAB isolates were identified and given the following numbers: SK9, SK17, SK23, SK24, SK28, and SK33. The isolates belong to Enterococcus durans and Leuconostoc mesenteroides. After screening for antibacterial activity against food-borne bacteria, SK28 showed the strongest AMA against E. coli and S. Typhimurium. SK23 showed the highest AMA against L. monocytogenes, while SK33 showed no AMA against L. monocytogenes. CONCLUSIONS: LAB isolates exhibited AMA against the selected strains of bacteria. Enterococcus isolates showed the highest antibacterial activities against the tested bacterial strains. Therefore, in the era of antimicrobial resistance, they might serve as antibiotic alternatives. L. monocytogenes was the least sensitive to the antimicrobial activities of LAB isolates. Further experiments are required to isolate and identify the molecules responsible for the antimicrobial activities.

Antibacterial activity of chloroxylenol and thymol against pathogenic bacteria isolated from under long nails.

OBJECTIVE: Fingernails are a perfect area for harboring bacteria such as Staphylococcus aureus, Salmonella sp., Shigella sp., and Escherichia coli. These bacteria under the long nails may cause diseases due to the contact of nails with food or while biting the nails. Our study aimed to compare the antibacterial activity of chloroxylenol and thymol, two different detergent ingredients, on microorganisms isolated from long fingernails. This study was performed to raise awareness of the dangers of long nails and the importance of good nail hygiene. PATIENTS AND METHODS: The present study was performed on female students at the Faculty of Science, King Abdelaziz University. Bacteria were isolated from under one finger nails and cultured on both McConkey agar and mannitol salt agar. After incubation, we isolated bacteria on nutrient agar. After that, we conducted several tests to determine the isolate type. Finally, we prepared three different concentrations of chloroxylenol and thymol to compare their effect on the isolated bacteria using antibacterial activity on Mueller-Hinton agar. RESULTS: Two types of bacteria were isolated, pathogenic bacteria called Staphylococcus aureus and non-pathogenic bacteria called Staphylococcus epidermidis. Staphylococci have more sensitivity to chloroxylenol than thymol. In addition, chloroxylenol, at high concentrations had a more powerful antibacterial effect. CONCLUSIONS: The results emphasized that fingernails could harbor pathogenic bacteria which are difficult to remove. Perfect hand hygiene is essential to prevent the spread of diseases.