Antibacterial activity of two newly isolated Bdellovibrio bacteriovorus strains on Salmonella enterica serovars of food safety concern.

Abstract

Bdellovibrio are obligate predators and have been described as living antibiotics since their predatory lifestyle enables them to kill pathogenic bacteria, making Bdellovibrio a promising biological control agent. Bdellovibrio strains were isolated from sampling sites in an urban watershed and tested for their killing activity on Salmonella enterica strains associated with human infections. An enrichment technique was used to isolate Bdellovibrio from surface water samples from local tributaries to the Oconee River, employing Salmonella Infantis as the prey bait. The isolated Bdellovibrio strains were sequenced; their prey range activity was tested against a panel of clinically significant S. enterica serovars, while predation efficiency was tested on S. Infantis. The result demonstrated the ability of two newly isolated periplasmic Bdellovibrio bacteriovorus strains, B. bacteriovorus YOA24 and B. bacteriovorus YOA38, to kill 11 antibiotic-resistant S. enterica serovars and effectively reduce S. Infantis populations. The strains were identified as periplasmic Bdellovibrio and members of B. bacteriovorus based on phenotypic, microscopic, and genotypic characterization. B. bacteriovorus YOA 24 and YOA38 demonstrated the ability to reduce S. Infantis by 2 logs in 24 h. The killing activity of B. bacteriovorus YOA24 and YOA38 indicates their potential to manage Salmonella outbreaks. Therefore, B. bacteriovorus strains YOA24 and YOA38 can be considered for development as therapeutic agents or probiotics against Salmonella.

Importance: Bdellovibrio is the most studied obligate predatory bacteria. It has potential for use as biological control of gram-negative bacteria in health, agriculture, and the food industry. Most basic research and applications use the type strain Bdellovibrio bacteriovorus HD100 or a closely related strain 109J. Screening for other Bdellovibrio strains and their killing activity should be explored, knowing that prey range and efficiency could differ among Bdellovibrio strains. This study presents two newly isolated B. bacteriovorus strains, YOA24 and YOA38, with lytic activity on Salmonella enterica serovars. B. bacteriovorus YOA24 and YOA38 represent a biological control agent for foodborne S. enterica serovars due to their killing activity on the important Salmonella strains tested.