Comparative Antimicrobial Activity of Lactobacillus acidophilus and Lactobacillus rhamnosus on Clinically Isolated Escherichia coli: An In vitro Study

Aim: The aim of present study is to evaluate the comparative antimicrobial activity of Lactobacillus acidophilus and Lactobacillus rhamnosus on clinical isolates of Escherichia coli.

Study Design: Cross-sectional observational study.

Place and Duration of Study: This study was conducted in Department of Medical Microbiology, School of Medical Education between January 2023 to September 2023.

Methodology: A total of 100 E. coli isolates collected from various diagnostic laboratories were included in the sample population and the prevalence of XDR, MDR, and non MDR isolates among them were determined by Kirby-Bauer disk diffusion method. The inhibitory activity of untreated and treated (pH adjusted) suspension of standard strains of L. acidophilus and L. rhamnosus on E. coli were determined by agar overlay method and the data was statistically analysed using ANOVA single-factor.

Results: The antimicrobial activity was confirmed for untreated and treated suspension of Lactobacillus spp. by measuring the zone of inhibition surrounding E. coli strains spotted on MRS medium but treated suspension exerted greater inhibitory activity than untreated suspensions of both Lactobacillus spp. and among the treated suspension L. rhamnosus exhibit greater inhibitory activity. Statistical analysis of this data using ANOVA single-factor was found to be not significant (P >0.05), that is treated suspension of both L. acidophilus and L. rhamnosus has the independent activity against E. coli. While untreated suspensions of both L. acidophilus and L. rhamnosus was significant (P =0.03), that is untreated suspension of L. rhamnosus (mean inhibition of 12.19 mm) has greater inhibitory activity than untreated cell cultures of L. acidophilus (mean inhibition of 11.39 mm).

Conclusion: This result, disclosed that even if both Lactobacillus spp. exhibit antimicrobial activity against E. coli, L. rhamnosus showed greater inhibition than L. acidophilus. The study suggested the use probiotic Lactobacillus as a biotherapeutic in antibiotic resistant E. coli infection and should be further studied for their human health benefits.