Antibiotic Resistance In Probiotic Lactic Acid Bacteria: A Safety Concern
Thirty domestic dahi samples collected from the different parts of north Bengaluru. 40 lactic isolates were obtained from 30 domestic dahi samples. To determine the probiotic nature the lactic isolates were subjected for acid and bile tolerance test and antibacterial compounds. Out of 40 lactic isolates only 21 lactic isolates showed varied tolerance to acid and bile all the acid and bile tolerance and all the 13 lactobacilli isolates which were produced antibacterial compounds against the indicator bacteria such as E.coli, Salmonella and Stap. aureusand other 9 isolates did not produced antibacterial compounds. These 21 lactic isolateswere identified to species level phenotypically and further identity confirmed by 16S rRNA sequencing. The identity revealed that 2 lactococci isolates as L.lactis ssp. lactis and L.lactis ssp. lactisbvdiacetylactis 13 lactobacilli isolates as L.rhamnosus(5 nos), L.plantarum (3 nos), L.fermnetum (3 nos), Lab.delbreukii ssp. bulgaricus (2 No.s) Leuconostocmesentroides ssp. mesentroides (3 nos) and S.thermophilus (3 nos). Further, both acid and bile and antibacterial activity lactobacilli isolates selected for antibiotic screening. The lactic cultures do carry antibiotic genes, if the antibiotic genes are transferable is a safety issue. Hence, in this study a screening test was conducted to determine whether the isolates obtained are resistance or susceptible to the used antibitics and lesser the inhibitory zone more the resistance and more the inhibitory zone indicates their susceptible nature. All the lactobacilli cultures used in this study were screened for their antibiotic resistance or susceptibility against the seven commonly used antibiotics such as vancomycin,penicillin, gentamycin, tetracycline, bacitracin, streptomycin, kanamycin. All the 5 strains of L.rhamnosus strains were susceptible to all the 7 antibiotics tested as they showed more than 10 mm diameter inhibitory zone. Similarly, all the 3 strains ofL.plantarum, all the 3 strains of L.fermentum and 2 strains of L.delbruckiissp. bulgaricus were susceptible to all the antibiotics to varying degrees. These results clearly demonstrate the susceptible nature of the probiotic lactic isolates in this study towards commonly used antibiotics.
Key words- Probiotic, Antibiotic Resistance, Lactic Acid Bacteria