Characterization and Evaluation of the Probiotic Potential In Vitro and In Situ of Lacticaseibacillus paracasei Isolated from Tenate Cheese.

ABSTRACT: The objectives of this investigation were (i) to isolate bacteria from various foods (dairy products, fruits, and vegetables) and evaluate their probiotic potential and (ii) to select, identify, and characterize the bacterial strain(s) with the highest probiotic potential. From 14 food samples, 117 bacterial strains were isolated; however, only 42 (T1 to T42) had the correct characteristics (gram positive, coccoid, and bacilliform) and were catalase and oxidase negative to be considered presumptive lactic acid bacteria (LAB). The antagonistic activity of the 42 strains was evaluated against Escherichia coli (O157:H7E09), Listeria monocytogenes (ATCC 19115), Staphylococcus aureus (ATCC 25923), and Salmonella enterica serotype Typhimurium (ATCC 14028). The nine strains with the highest antagonistic activity were recovered from the following foods: pulque (T1), sprouted beans (T26), Ranchero cheese (T30, T31, T32, T33, T35, and T36), and Tenate cheese (T40). The inhibition zones on culture and sensitivity plates were 17.0 ± 1.2 to 19.3 ± 2.8 mm in diameter. Based on the antagonistic activity against pathogenic bacteria and resistance to low pH and bile salts, strain T40 had the highest probiotic potential. A 16S rRNA technique was used to identify strain T40 as Lacticaseibacillus paracasei (renamed from Lactobacillus paracasei in April 2020). This strain had no resistance to ampicillin, gentamicin, erythromycin, and tetracycline. The antagonistic activity was evaluated in situ (fresh cheese) against pathogenic bacteria, supporting the probiotic potential of L. paracasei. Isolates of this LAB recovered from Tenate cheese had characteristics of a probiotic microorganism with high potential for use in food technology.

Attachment of 13 Types of Foodborne Bacteria to Jalapeño and Serrano Peppers and Antibacterial Effect of Roselle Calyx Extracts, Sodium Hypochlorite, Colloidal Silver, and Acetic Acid against These Foodborne Bacteria on Peppers.

Chili peppers are a very important crop in Mexico. However, these peppers have been associated with Salmonella infection outbreaks in the United States, and Salmonella and diarrheagenic Escherichia coli pathotypes have been isolated from jalapeño and serrano peppers in Mexico. To decrease microbial contamination of fruits and vegetables, chemical agents are commonly used; however, chemical agents used to eliminate pathogenic bacteria on vegetables have a limited antimicrobial effect. Roselle ( Hibiscus sabdariffa ) calyces have been reported to have an antimicrobial effect on pathogenic bacteria. In the present study, the antibacterial effect of four roselle calyx extracts (water, methanol, acetone, and ethyl acetate), sodium hypochlorite, colloidal silver, and acetic acid against foodborne bacteria was evaluated on contaminated jalapeño and serrano peppers. The 13 types of foodborne bacteria evaluated were Listeria monocytogenes , Shigella flexneri , Salmonella Typhimurium, Salmonella Typhi, Salmonella Montevideo, Staphylococcus aureus , E. coli O157:H7, five E. coli pathotypes (Shiga toxin producing, enteropathogenic, enterotoxigenic, enteroinvasive, and enteroaggregative), and Vibrio cholerae O1. All 13 types attached to both pepper types, with no significant differences in attachment between jalapeño and serrano peppers. Roselle calyx extract treatment resulted in a greater reduction in levels of all foodborne bacteria than did treatment with sodium hypochlorite, colloidal silver, and acetic acid on both pepper types. Roselle calyx extracts may be a useful for disinfection of chili peppers in the field, processing plants, restaurants, and homes.