Analysis of Antibiotic Resistance of the Probiotic Bacteria Found in Commercial Food Products

*Corresponding author: R. M. Asela Priyadarshana* and Clarencia R. Daniel

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The Lactobacillus is an industrially-important group of probiotic organisms that plays an important role in human health by inhibiting harmful and pathogenic bacterial growth, boosting immune function, and increasing resistance to infection. The aim of this study was to identify the probiotic bacteria Lactobacillus based on their phenotypic features and genotypic features. This study also shows the importance of probiotic bacterium, and the effects of their antibiotic resistance to human.


Six different brands were cultured on man, rogosa and sharpe (MRS) agar. The identity of the culture was based on the characteristics of the strains of Lactobacillus spp. which was characterized using their phenotypic features (cell morphology, Gram’s staining tests which are specific for Lactobacillus genus). The bacterial deoxyribonucleic acid (DNA) was extracted by two different methods, boiled cell method and cetyl trimethylammonium bromide (CTAB) method. Furthermore, the extracted DNA yields were compared to determine which gives the best yield. The bacterial genus was detected with using genus specific primers, specific to the Lactobacillus. All the isolates were further subjected to antibiotic resistance test using disc diffusion method against a total of 4 antibiotics (Erythromycin, Tetracycline, Vancomycin and Ampicillin) and the antibiotic resistant genes of tet(M) & erm(B), were analyzed by polymerase chain reaction (PCR).


Five isolates out of six samples (A to E) were found to exhibit multiple resistance against some of the most commonly used antibiotics. The isolates showed resistance toward tetracycline, erythromycin & vancomycin. Besides that, the isolates displayed a low-level of resistance toward ampicillin.


This study proves that antibiotic resistance is present in different species of probiotic strains, which may pose a food safety concern.


Lactobacillus; Probiotics; Antibiotics; Tetracycline; Vancomycin; Erythromycin; Ampicillin; Antibiotic resistance.