Predatory Bacteria can ReducePseudomonas aeruginosaInduced Corneal Perforation and Proliferation in a Rabbit Keratitis Model

Abstract

Purpose: Pseudomonas aeruginosa keratitis is a severe ocular infection that can lead to perforation of the cornea. In this study we evaluated the role of bacterial quorum sensing in generating corneal perforation and bacterial proliferation and tested whether co-injection of the predatory bacteria Bdellovibrio bacteriovorus could alter the clinical outcome. P. aeruginosa with lasR mutations were observed among keratitis isolates from a study collecting samples from India, so an isogenic lasR mutant strain of P. aeruginosa was included. Methods: Rabbit corneas were intracorneally infected with P. aeruginosa strain PA14 or an isogenic ΔlasR mutant and co-injected with PBS or B. bacteriovorus. After 24 h, eyes were evaluated for clinical signs of infection. Samples were analyzed by scanning electron microscopy, optical coherence tomography, sectioned for histology, and corneas were homogenized for CFU enumeration and for inflammatory cytokines. Results: We observed that 54% of corneas infected by wild-type PA14 presented with a corneal perforation (n=24), whereas only 4% of PA14 infected corneas that were co-infected with B. bacteriovorus perforate (n=25). Wild-type P. aeruginosa proliferation was reduced 7-fold in the predatory bacteria treated eyes. The ΔlasR mutant was less able to proliferate compared to the wild-type, but was largely unaffected by B. bacteriovorus. Conclusion: These studies indicate a role for bacterial quorum sensing in the ability of P. aeruginosa to proliferate and cause perforation of the rabbit cornea. Additionally, this study suggests that predatory bacteria can reduce the virulence of P. aeruginosa in an ocular prophylaxis model.

Intra-ocular Predation of Fluoroquinolone-ResistantPseudomonas aeruginosaandSerratia marcescensby Predatory Bacteria

“…Unlike the tested pathogens, predatory bacteria failed to significantly induce intraocular cytokine levels above that of eyes injected with the PBS vehicle. This is in agreement with prior in vitro and in vivo studies [12,13,19,20,28,32,[40][41][42]] and, at least for B. bacteriovorus due to its unusual outer membrane composition and membranesheathed flagellum which reduce TLR4 and TLR5 activation [43,44], which are major mediators of inflammation in bacterial endophthalmitis [45,46].…”

“…Recent studies have evaluated the use of predatory bacteria for treatment of ocular surface infections [17][18][19]. These have demonstrated some efficacy against Escherichia coli [17] in a mouse model and Pseudomonas aeruginosa in rabbit models including the prevention of corneal perforations [19]. However freeze-dried B. bacteriovorus proved to be ineffective in treating Moraxella bovis in a large animal keratoconjunctivitis model [20].…”

“…Recent studies have evaluated the use of predatory bacteria for treatment of ocular surface infections [17-19]. These have demonstrated some efficacy against Escherichia coli [17] in a mouse model and Pseudomonas aeruginosa in rabbit models including the prevention of corneal perforations [19].…”

Predatory bacteria prevent the proliferation of intraocular Serratia marcescens and fluoroquinolone-resistant Pseudomonas aeruginosa

“…Unlike the tested pathogens, predatory bacteria failed to significantly induce intraocular cytokine levels above that of eyes injected with vehicle. This is in with prior in vitro and in vivo studies [12,13,19,20,28,32,[40][41][42] and, at least for B. bacteriovorus due to its unusual outer membrane composition and membrane-sheathed flagellum which reduce TLR4 and TLR5 activation [43,44], which are major mediators of inflammation in bacterial endophthalmitis [45,46].…”

“…Recent studies have evaluated the use of predatory bacteria for treatment of ocular surface infections [17][18][19]. These have demonstrated some efficacy against Escherichia coli [17] in a mouse model and Pseudomonas aeruginosa in rabbit models including the prevention of corneal perforations [19]. However freeze-dried B. bacteriovorus proved to be ineffective in treating Moraxella bovis in a large animal keratoconjunctivitis model [20].…”