Abstract
Sessile bacteria growing on surfaces are more resistant to standard antibiotics than their planktonic counterpart. Due to their antimicrobial properties, bacteriophages have re-emerged as a promising approach to treat bacterial biofilm-associated infections. Here, we evaluated the ability of two commercially available phage formulations, Staphylococcal bacteriophage (containing the monophage Sb-1) and PYO bacteriophage (a polyphage), in preventing and eradicating an in vitro biofilm of methicillin-resistant Staphylococcus aureus (MRSA) by isothermal microcalorimetry and high-resolution confocal laser scanning microscopy (CLSM). Moreover, to assess the potential in vivo efficacy of both phage preparations, a Galleria mellonella model of MRSA systemic infection was used. Microcalorimetry measurement showed that 107 PFU/ml (the highest tested titer) of both phage formulations were able to inhibit planktonic growth in a concentration-dependent manner. However, MRSA biofilm was eradicated only by co-incubation of 5–7 days with the highest phage titers, respectively. In the experiments of biofilm prevention, isothermal microcalorimetry revealed that the heat production was completely abolished in the presence of sub-inhibitory titers (104 PFU/ml) of phages. These data were also confirmed by confocal laser scanning microscopy. Both phage formulations increased the survival of G. mellonella larvae preventing or treating MRSA infection compared to untreated control. In conclusion, tested phage formulations are promising for preventing device colonization and killing biofilm bacteria attached on a surface. Novel strategies for direct coating and release of phages from material should be investigated.
Highlights
Staphylococcus aureus is causing a variety of communityacquired and healthcare-associated infections (Magill et al, 2014; Tong et al, 2015)
The emergence of spreading of staphylococcal strains resistant to different antimicrobial agents, including methicillin, vancomycin, daptomycin and/ or rifampicin (O’Neill et al, 2006; Kos et al, 2012; Hassoun et al, 2017; Ma et al, 2018) represents a serious threat to global health (Sugden et al, 2016; Monaco et al, 2017). This scenario is further complicated by the fact that production pipelines for the development of novel antibiotics has been running dry over the past few decades, resulting in an crucial requirement to identify novel therapeutic strategies to control bacterial infections mainly due to multi-drug resistant bacteria embedded in a biofilm (Ribeiro et al, 2016)
Bacteria viability and biofilm thickness after phage co-incubation/treatment was determined by CLSM after staining cells with Syto9 (488 nm/500–540 nm) and propidium iodide (PI) (561 nm/600–650 nm) as recommended by the manufacturer
Summary
Staphylococcus aureus is causing a variety of communityacquired and healthcare-associated infections (Magill et al, 2014; Tong et al, 2015). The emergence of spreading of staphylococcal strains resistant to different antimicrobial agents, including methicillin, vancomycin, daptomycin and/ or rifampicin (O’Neill et al, 2006; Kos et al, 2012; Hassoun et al, 2017; Ma et al, 2018) represents a serious threat to global health (Sugden et al, 2016; Monaco et al, 2017) This scenario is further complicated by the fact that production pipelines for the development of novel antibiotics has been running dry over the past few decades, resulting in an crucial requirement to identify novel therapeutic strategies to control bacterial infections mainly due to multi-drug resistant bacteria embedded in a biofilm (Ribeiro et al, 2016)
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