The predatory potential of Bdellovibrio bacteriovorus against clinically isolated pathogens with extensively drug-resistance (XDR)

Bdellovibrio-and-like organisms (BALOs) are a group of predatory bacteria which invade other Gram-negative bacterial cells for growth. The bacteriolytic nature of Bdellovibrios make them one of the promising alternatives for conventional antibiotics. In this study, the isolation and molecular identification of Bdellovibrio bacteriovorus strain SOIR-1 was described. The antibiotic resistance pattern of some clinically isolated Gram-negative pathogens was determined, and the predatory potency of SOIR-1 toward them was evaluated.

Double-layer agar technique, transmission electron microscopy, and PCR targeting the Bdellovibrios-specific hit locus were used for the isolation, morphological investigation, and molecular identification of SOIR-1, respectively. Following the antibiotic resistance profile determination of clinical isolates, the bacteriolytic activity of SOIR-1 against them was evaluated through the plaque formation assay and lysis analysis in the broth co-cultures.

SOIR-1 was identified as a strain of Bdellovibrios bacteriovorus through the transmission electron microscopy examination and specific PCR detection. All clinical isolates showed the properties of extensively drug-resistant (XDR) and typical Bdellovibrios plaques were developed on their lawns of cells. The SOIR-1 had the highest and lowest predation efficiency among the clinical isolates toward Acinetobacter baumannii (84.33%) and Pseudomonas aeruginosa-369 (55.16%), respectively.

This study highlights the great potential of SOIR-1 to prey and lyse XDR pathogens, regardless of their antimicrobial resistance state. So, B. bacteriovorus can be considered as a living antibiotic in the cases of infections caused by multidrug-resistant bacteria.