Assessing phage therapy against Pseudomonas aeruginosa using a Galleria mellonella infection model

Abstract

The Galleria mellonella infection model was used to assess the in vivo efficacy of phage therapy against laboratory and clinical strains of Pseudomonas aeruginosa. In a first series of experiments, Galleria were infected with the laboratory strain P. aeruginosa PAO1 and were treated with varying multiplicity of infection (MOI) of phages either 2h post-infection (treatment) or 2h pre-infection (prevention) via injection into the haemolymph. To address the kinetics of infection, larvae were bled over a period of 24h for quantification of bacteria and phages. Survival rates at 24h when infected with 10 cells/larvae were greater in the prevention versus treatment model (47% vs. 40%, MOI=10; 47% vs. 20%, MOI=1; and 33% vs. 7%, MOI=0.1). This pattern held true when 100 cells/larvae were used (87% vs. 20%, MOI=10; 53% vs. 13%, MOI=1; 67% vs. 7%, MOI=0.1). By 24h post-infection, phages kept bacterial cell numbers in the haemolymph 1000-fold lower than in the non-treated group. In a second series of experiments using clinical strains to further validate the prevention model, phages protected Galleria when infected with both a bacteraemia (0% vs. 85%) and a cystic fibrosis (80% vs. 100%) isolate. Therefore, this study validates the use of G. mellonella as a simple, robust and cost-effective model for initial in vivo examination of P. aeruginosa-targeted phage therapy, which may be applied to other pathogens with similarly low infective doses.

‘Get in Early’; Biofilm and Wax Moth (Galleria mellonella) Models Reveal New Insights into the Therapeutic Potential of Clostridium difficile Bacteriophages

“…Although previous work reported the inoculation of bacteria/phages by intrahaemocoelic injection (Abbasifar et al, 2014; Beeton et al, 2015), we found ingestion via the oral route more efficient at inducing colonization and producing reproducible therapy results. The observed higher efficacy of the phages when used prophylactically rather than with remedial treatment is consistent with a previous report (Beeton et al, 2015). Interestingly, the best treatment was observed when vancomycin was given prophylactically followed by phage application.…”

“…Although the insect is used as an infection model for various pathogens (Mukherjee et al, 2010; Ramarao et al, 2012; Hill et al, 2014; Beeton et al, 2015) and antimicrobial testing (Seed and Dennis, 2009; Abbasifar et al, 2014; Beeton et al, 2015; Olszak et al, 2015), to our knowledge this report is the first published data to describe its use to study C. difficile colonization and phage treatment. We established that 10 5 C. difficile cells were sufficient for colonization to occur in the larvae and to cause the first and total mortality at 24 and 60 h respectively post-infection.…”

“…This is significant as it could potentially serve as an intervention therapy to supplement vancomycin and prevent disease relapse. Similarly, the effectiveness of increased window time of having phages prior to bacterial infection could also be attributed to the ability of the phages to be distributed throughout the gut and acclimatize to the incubation temperature (Jończyk et al, 2011; Beeton et al, 2015) for effective bacteriolysis. The increased survival rates and corresponding decreased bacterial counts observed with the multiple phage dose regimens could be attributed to increased number of phages consequently leading to increased MOI and activity.…”

“…The model has also been used to study pathogenesis of bacteria such as Pseudomonas aeruginosa , Listeria monocytogenes, Bacillus cereus , and Francisella tularensis (Miyata et al, 2003; Aperis et al, 2007; Fedhila et al, 2010; Mukherjee et al, 2010) and phage therapy for Burkholderia cepacia and P. aeruginosa (Seed and Dennis, 2009; Beeton et al, 2015). However, no studies have been published to date to examine how useful Galleria would be as a model for CDI colonization, or subsequent phage therapeutic studies.…”

Characterization of the first double-stranded RNA bacteriophage infecting Pseudomonas aeruginosa

“…Given that P. aeruginosa is becoming resistant to most antibiotics, a common infection may be fatal. Therefore, the feasibility of treating bacterial infections with bacteriophages has been extensively studied2728293031. Several studies have reported the efficacy of phage therapy against P. aeruginosa .…”