Clearance of Gram-Negative Bacterial Pathogens from the Ocular Surface by Predatory Bacteria

Abstract

It was previously demonstrated that predatory bacteria are able to efficiently eliminate Gram-negative pathogens including antibiotic-resistant and biofilm-associated bacteria. In this proof-of-concept study we evaluated whether two species of predatory bacteria, Bdellovibrio bacteriovorus and Micavibrio aeruginosavorus, were able to alter the survival of Gram-negative pathogens on the ocular surface. Clinical keratitis isolates of Pseudomonas aeruginosa (strain PAC) and Serratia marcescens (strain K904) were applied to the ocular surface of NZW rabbits followed by application of predatory bacteria. At time intervals, surviving pathogenic bacteria were enumerated. In addition, B. bacteriovorus and S. marcescens were applied to porcine organ culture corneas under contact lenses, and the ocular surface was examined by scanning electron microscopy. The ocular surface epithelial layer of porcine corneas exposed to S. marcescens, but not B. bacteriovorus was damaged. Using this model, neither pathogen could survive on the rabbit ocular surface for longer than 24 h. M. aeruginosavorus correlated with a more rapid clearance of P. aeruginosa but not S. marcescens from rabbit eyes. This study supports previous evidence that predatory bacteria are well tolerated by the cornea, but suggest that predatory bacteria do not considerably change the ability of the ocular surface to clear the tested Gram-negative bacterial pathogens from the ocular surface.

Effects of Bdellovibrio bacteriovorus HD100 on experimental periodontitis in rats

“…However, this inflammatory response does not seem to cause any tissue damage. Despite the increase in the levels of proinflammatory cytokines, no damage was observed in the lung, intestinal, ocular, or periodontal tissues of rats after inoculation with Bdellovibrio (Cui et al., 2021; Findlay et al., 2019; Romanowski et al., 2021; Shatzkes et al., 2015; Shatzkes et al., 2016; Shatzkes, Singleton, et al., 2017; Shatzkes, Tang, et al., 2017; Silva et al., 2019). It has been proposed that B. bacteriovorus could be intrinsically nonpathogenic to mammalian cells due to its neutrally charged LPS, which could not induce an immunogenic response in cells (Schwudke et al., 2003).…”

Anti-Infective Treatment and Resistance Is Rarely Problematic with Eye Infections

“…Nanoparticles in an emulsion has been tested to treat bacterial keratitis with ciprofloxacin [ 51 ]. Shanks proposed the use of predatory bacteria to eliminate ocular pathogens as method to treat ocular infections [ 52 , 53 ]. Photoactivated chromophore for collagen cross-linking of the cornea [ 54 ] and rose Bengal photodynamic antimicrobial therapy [ 55 ] have been tested to treat severe, progressive infectious keratitis.…”

Bdellovibrio bacteriovorus: More than Just a Bacterial Hunter

“…Furthermore, in terms of cytotoxicity in animal models, B. riovorus is reported to show no cytotoxicity towards the ocular surface of mice [57]. However, its contribution is insubstantial in clearing the pathogens from the corneal epithelium [56].…”