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Robert Shanks, Kevin To, Nicholas Stella, Kimberly Brothers, Regis Kowalski, Eric Romanowski, Daniel Kadouri; The use of predatory prokaryotes to control human ocular pathogens. Invest. Ophthalmol. Vis. Sci. 2013;54(15):4284. doi: https://doi.org/.
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Antibiotic resistant, disease-causing microorganisms are an increasing cause for concern in ocular infections. In an attempt to find innovative approaches to eradicate bacteria that cause ocular infections, we measured whether predatory bacteria could successfully kill clinical keratitis isolates of Pseudomonas aeruginosa and Serratia marcescens in vitro. The cytotoxic impact of predatory bacteria on a human corneal cell line was also assessed.
The predatory bacteria used in this study were Bdellovibrio bacteriovorus, strains HD100 and 109J, and Micavibrio aeruginosavorus ARL-13. These are non-pathogenic, soil-derived, Gram-negative, obligatory parasites that feed on other Gram-negative bacteria. 108 CFU of fluoroquinolone-resistant and susceptible ocular isolates of P. aeruginosa and multidrug resistant strains of S. marcescens were mixed with 108 CFU of predatory bacteria. After 24 and 48 hours, the numbers of surviving bacteria were enumerated. Human corneal limbal epithelial cells (HCLE) were challenged with ~108 CFU of predatory bacteria or 5 x107 CFU of P. aeruginosa; HCLE viability was measured at 4 and 24 hours using alamar blue.
B. bacteriovorus predatory bacteria reduced viable counts of the S. marcescens isolates examined (n=9) by 2-4 logs. B. bacteriovorus and M. aeruginosavorus predatory bacteria reduced fluoroquinolone-resistant P. aeruginosa isolates (n=9) viable counts by up to 5 logs, and had mixed results with fluoroquinolone-susceptible isolates, ranging from no effect to a 4-log reduction. Although predatory bacteria were lethal to ocular pathogens, little cytotoxic effect was observed when high doses of the predators were exposed to a human corneal cell line.
This work highlights the potential use of predatory bacteria as biological based agent for eradicating antibiotic-resistant ocular infections.
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