Phage Therapy Is Effective in a Mouse Model of Bacterial Equine Keratitis

Abstract

Bacterial keratitis of the horse is mainly caused by staphylococci, streptococci, and pseudomonads. Of these bacteria, Pseudomonas aeruginosa sometimes causes rapid corneal corruption and, in some cases, blindness. Antimicrobial resistance can make treatment very difficult. Therefore, new strategies to control bacterial infection are required. A bacteriophage (phage) is a virus that specifically infects and kills bacteria. Since phage often can lyse antibiotic-resistant bacteria because the killing mechanism is different, we examined the use of phage to treat horse bacterial keratitis. We isolated Myoviridae or Podoviridae phages, which together have a broad host range. They adsorb efficiently to host bacteria; more than 80% of the ⌽R18 phage were adsorbed to host cells after 30 s. In our keratitis mouse model, the administration of phage within 3 h also could kill bacteria and suppress keratitis. A phage multiplicity of infection of 100 times the host bacterial number could kill host bacteria effectively. A cocktail of two phages suppressed bacteria in the keratitis model mouse. These data demonstrated that the phages in this study could completely prevent the keratitis caused by P. aeruginosa in a keratitis mouse model. Furthermore, these results suggest that phage may be a more effective prophylaxis for horse keratitis than the current preventive use of antibiotics. Such treatment may reduce the use of antibiotics and therefore antibiotic resistance. Further studies are required to assess phage therapy as a candidate for treatment of horse keratitis. IMPORTANCEAntibiotic-resistant bacteria are emerging all over the world. Bacteriophages have great potential for resolution of this problem. A bacteriophage, or phage, is a virus that infects bacteria specifically. As a novel therapeutic strategy against racehorse keratitis caused by Pseudomonas aeruginosa, we propose the application of phages for treatment. Phages isolated in this work had in vitro effectiveness for a broad range of P. aeruginosa strains. Indeed, a great reduction of bacterial proliferation was shown in phage therapy for mouse models of P. aeruginosa keratitis. Therefore, to reduce antibiotic usage, phage therapy should be investigated and developed further.

Differential Effect of Newly Isolated Phages Belonging to PB1-Like, phiKZ-Like and LUZ24-Like Viruses against Multi-Drug Resistant Pseudomonas aeruginosa under Varying Growth Conditions

“…In a number of liquid infection studies, it has been shown that the initial phage-driven decline of P. aeruginosa was followed by regrowth of bacterial populations, indicative of the evolvement of phage resistance [ 28 , 42 , 43 , 44 , 45 , 47 , 51 , 52 ]. This observation differs from our study, as regrowth after decline of bacteria did not occur within the timeframe of the experiment (except for phage SL1 and strain MDR-PA4, Figure 5 ).…”

Predatory Bacteria Attenuate Klebsiella pneumoniae Burden in Rat Lungs

“…For these reasons, among others, it is crucial that we begin to develop new treatments to combat bacterial infection. Researchers have already begun investigating potential new antimicrobial strategies (22), such as the use of antimicrobial peptides (23, 24), phage therapy (25, 26), and gene-editing enzymes (27, 28). Here, we report another promising novel approach: the use of predatory bacteria to control Gram-negative human pathogens.…”

Bacteriophage ΦSA012 Has a Broad Host Range against Staphylococcus aureus and Effective Lytic Capacity in a Mouse Mastitis Model

“…The procedure was carried out, according to a previously reported method [ 28 , 29 ]. A 5-µL aliquot of phage suspension (10 10 plaque-forming units (PFU)/mL) was dropped onto a double-layer agar plate containing an S. aureus strain.…”

“…The pellet was resuspended and diluted in PBS to a density of 2 × 10 6 CFU/mL. Phage was isolated by large-scale culture using soft agar plate, and the phage suspension was purified by density gradient ultracentrifugation using CsCl, according to a previously reported method [ 29 ]. Mice were anesthetized 30 min before infection with a mixture of three types of anesthetic agents: 6 mg/kg midazolam (Dormicum; Astellas, Tokyo, Japan), 0.45 mg/kg medetomidine (Dorbene; Kyoritsu Seiyaku Corp., Tokyo, Japan), and 7.5 mg/kg butorphanol (Vetorpale; Meiji Seika Pharma Co., Ltd., Tokyo, Japan).…”