Abstract
Background:
Bdellovibrio bacteriovorus has stood out since its initial discovery because of its exceptional capacity to feed on other Gram-negative bacteria. Since this specific “predatory bacterium” may be used as both a probiotic and an antibiotic, research on it has expanded in response to the growing issue of AMR. It is necessary to investigate the relationship between B. bacteriovorus and other Gram-negative bacteria, as well as the presence of Gram-positive bacteria, in the same environment to determine whether or not these factors have an impact on their ability as predators.

Aim:
This study aimed to assess the effectiveness of the combination of the predatory bacterium B. bacteriovorus with Pseudomonas fluorescens and Lactobacillus acidophilus as potential candidates for in vitro anticolibacillosis.

Methods:
The method employed Escherichia coli ATCC 15144 as the prey, while B. bacteriovorus 109 J ATCC 15143 was used as the predator, combined with P. fluorescens and L. acidophilus as the nutrient sources of the predator. In the challenge experiment, a ratio of the bacterial combination was used to optimize predation to E. coli of 107 PFU/105 CFU per ml.

Results:
The study showed that the combination of B. bacteriovorus with P. fluorescens and L. acidophilus after 24 hours of in vitro incubation at 37°C increased the predatory bacteria count by tenfold, effectively reducing the E. coli population. However, in the absence of Gram-negative bacteria as a nutrient source, the predator population gradually declined.

Conclusion:
The combination of B. bacteriovorus as a predatory bacterium with P. fluorescens and L. acidophilus is an effective candidate for in vitro anticolibacillosis.

Key words: B. bacteriovorus, P. fluorescens, L. acidophilus, Anticolibacillosis, in vitro