Predatory potentials of novel isolates against multidrug-resistant and extremely drug-resistant bacterial pathogens of animals and plants.

Unlabelled: and like organisms (BALOs) predate on Gram-negative bacteria selectively, which holds promise as an alternate to combat against multidrug-resistant bacterial pathogens. In this study, two strains designated MPR17 and MPR18 were isolated from water samples by double-layer agar technique using as prey and investigated for their predatory potentials against six pathogenic Gram-negative, MDR and XDR bacteria. Both the BALOs preyed on all the tested bacteria including , , , , , and with different killing rates. Against , sp. MPR18 produced a maximum of 2.11 × 10 PFU/ml, but MPR17 did not produce any detectable PFUs. TEM analysis of predator-prey interactions recorded different life stages including attachment, bdelloplast formation, prey lysis, and release. Morphologically, both the isolates MPR17 and MPR18 were small vibrioid in shape with a long single polar flagellum and measured of about < 500 nm diameter in size, suggesting that they are the smallest ever described . Predatory activity was further assessed in liquid co-cultures that evidenced time-dependent decrease in the prey cell density from 24 h with significant reduction at 72 h with different degrees of predation with respective prey bacteria. sp. MPR17 and MPR18 exhibited strong bacteriolytic activity in liquid cultures, which was equivalent to the bactericidal activities of standard antibiotics especially for (99%), (90%) and (90%). The findings of this study signify the potential of novel sp. MPR17 and MPR18 as a biocontrol agent with multiple host range to eradicate different MDR and XDR bacterial infections, which could contribute positively for resolving the crisis of antimicrobial resistance.

Supplementary Information: The online version contains supplementary material available at 10.1007/s13205-025-04230-8.