The in vitro and in vivo antimicrobial effects of Lactobacillus plantarum and Lactobacillus acidophilus were
evaluated individually and synergistically against multidrug-resistant enteroaggregative Escherichia coli
(MDR-EAEC). In vitro evaluation of each probiotic strain when co-cultured with MDR-EAEC isolates revealed
a reduction in MDR-EAEC counts (eosin–methylene blue agar) in a dose- and time-dependent
manner: probiotics at a dose rate of 1010 CFU inhibited MDR-EAEC isolates at 72 h post-inoculation (PI),
whereas at lower concentrations (108 and 109 CFU) MDR-EAEC isolates were inhibited at 96 h PI. The synergistic
antimicrobial effect of both probiotic strains (each at 1010 CFU) was highly significant (P < 0.01)
and inhibited the growth of MDR-EAEC isolates at 24 h PI. For in vivo evaluation, weaned mice were fed
orally with 107 CFU of MDR-EAEC. At Day 3 post-infection, treated mice were fed orally with the probiotic
strains (each at 1010 CFU). Compared with the control, post-treatment a significant (P < 0.01) reduction
in MDR-EAEC counts was observed in faeces by Day 2 and in intestinal tissues of treated mice by Days 3
and 4 as evidenced by plate count (mean 2.71 log and 2.27 log, respectively) and real-time PCR (mean
1.62 log and 1.57 log, respectively) methods. Histopathologically, comparatively mild changes were observed
in the ileum and colon from Days 3 to 5 post-treatment with probiotics; however, from Day 6
the changes were regenerative or normal. These observations suggest that these probiotic strains can
serve as alternative therapeutics against MDR-EAEC-associated infections in humans and animals.