Characterization of lactic acid bacteria isolated from street pickles of Dhaka, Bangladesh

Avijit Banik; Hasnain Anjum; Humayra Habib; Maruf Abony; Anowara Begum; Zakaria Ahmed

doi:10.1016/j.heliyon.2023.e17508

Characterization of lactic acid bacteria isolated from street pickles of Dhaka, Bangladesh

Heliyon. 2023 Jun 21;9(6):e17508. doi: 10.1016/j.heliyon.2023.e17508. eCollection 2023 Jun.

Authors

Avijit Banik¹, Hasnain Anjum¹, Humayra Habib¹, Maruf Abony¹, Anowara Begum², Zakaria Ahmed³

Affiliations

¹ Department of Microbiology, Primeasia University, Dhaka, Bangladesh.
² Department of Microbiology, Dhaka University, Bangladesh.
³ Bangladesh Jute Research Institute, Dhaka, Bangladesh.

Abstract

Traditionally fermented pickles are a popular street food in Bangladesh famous for their unique flavors and health benefits. Pickles are often prepared by fermentation using lactic acid bacteria (LAB) that can act as probiotics. The study was aimed to isolate and characterize lactic acid bacteria from pickle samples collected from streets of Dhaka city, as well as assess the microbial quality of pickles for food safety. A total of 30 pickle samples of different kinds were collected from streets of Dhaka city. Isolation and identification were conducted using conventional cultural and biochemical tests, followed by molecular confirmation of identity. Antibiotic susceptibility of isolates was investigated against 7 antibiotics of different groups. Antimicrobial activity of LAB isolates was analyzed by well-diffusion assay and phenotypic enterocin activity assay. Physiological characterizations of LAB were performed to determine their tolerance to temperature, salt, pH, bile, carbohydrate fermentation pattern, proteolytic activity and biofilm formation. Fifty isolates were obtained from pickle samples, of which 18% was identified as LAB, including Enterococcus faecalis (6) and Enterococcus faecium (3). The rest included S. aureus (18), E. coli (11), Klebsiella spp. (5), Salmonella (3), Shigella (3) and Pseudomonas aeruginosa (1). Antibiotic resistance pattern revealed higher occurrence of resistance against azithromycin among the non-LAB isolates, but none of the LAB isolates were found to resist any of the antibiotics used. Antimicrobial activity of LAB isolates was not observed against the foodborne isolates. All LAB isolates fermented a wide range of carbohydrates and showed adequate tolerance to salt, pH, temperature and bile. Out of 9 isolates, 5 displayed proteolytic activity, and 6 were found as strong biofilm producer. These results suggest that although the LAB isolates from street pickles collected from Dhaka does not have antimicrobial activities, they still have potential to be used as probiotics. It also shows high occurrence of antibiotic resistant foodborne pathogens in pickles, indicating that consumption of such street food can be serious health hazard.

Keywords: Enterococcus; Fermented pickles; Lactic acid bacteria.