Friend or foe? A critical evaluation of compositional quality and antibiotic resistance profiles of probiotic dietary supplements in Türkiye

This study analyzed 10 commercial probiotic dietary supplements for the enumeration and identification of lactobacilli and bifidobacteria, as well as their antibiotic resistance profiles. The isolated strains were identified using molecular methods, and their resistance to 18 antibiotics was assessed using the disc diffusion method. Four of the tested products had a lower number of viable bacteria than stated on the label. A total of 13 presumptive lactobacilli and bifidobacteria strains were identified using molecular methods. The results showed discrepancies between the bacterial species listed on the labels of some products and the actual strains present. All of the Lactobacillus strains were resistant to methicillin, cefoxitin, and vancomycin. Furthermore, low levels of resistance to cefazolin, enrofloxacin, ciprofloxacin, norfloxacin, kanamycin, and trimethoprim was observed in Lactobacillus spp. All Bifidobacterium strains were resistant to methicillin and vancomycin. In addition, Bifidobacterium spp. strains that were resistant to cefazolin, cefoxiti, kanamycin, norfloxacin, ampicillin, clindamycin, enrofloxacin, trimethoprim, and ciprofloxacin were determined. Multidrug resistance was found in all Lactobacillus and Bifdobacterium strains. Finally, MDR rates were found to be 100% in both Bifidobacterium and Lactobacillus species. The MAR index indicated a high-risk source of contamination for most strains, with 11 out of 13 strains exceeding the threshold of 0.2. These findings emphasize the critical role of precise labeling in fostering consumer trust and enabling informed decision-making. Antibiotic resistance should be regarded a significant part of the safety assessment of probiotics. Novel approaches will be essential for addressing MDR bacteria. MAR index findings highlight the need for stricter quality control in probiotic product labeling and a closer examination of antibiotic resistance in probiotic strains, given their potential implications for health and safety.