Lyophilized inserts for nasal administration harboring bacteriophage selective for Staphylococcus aureus: in vitro evaluation
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Munerah Alfadhel1, Utsana Puapermpoonsiri, Steven J Ford
1Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow G4 0RE, UK.
Abstract:
Nasal carriage of methicillin-resistant Staphylococcus aureus (MRSA) poses an infection risk and eradication during hospitalization is recommended. Bacteriophage therapy may be effective in this scenario but suitable nasal formulations have yet to be developed. Here we show that lyophilization of bacteriophages in 1ml of a viscous solution of 1-2% (w/v) hydroxypropyl methylcellulose (HPMC) with/without the addition of 1% (w/v) mannitol, contained in Eppendorf tubes, yields nasal inserts composed of a highly porous leaflet-like matrix. Fluorescently labeled bacteriophage were observed to be homogenously distributed throughout the wafers of the dried matrix. The bacteriophage titer fell 10-fold following lyophilization to 10(8)pfu per insert, then falling a further 100- to 1000-fold over 6 to 12months storage at 4°C. This compares well with a total dose of 6×10(5)pfu in 0.2ml liquid applied into the ear during a recent clinical trial in humans. The residual water content of the lyophilized inserts was reduced upon the addition of mannitol to HPMC, but this did not have any correlation to the lytic activity. Mannitol underwent a transition from its amorphous to crystalline state during exposure of the inserts to increasing relative humidities (as would be experienced in the nose), although this transition was suppressed by higher HPMC concentrations and the presence of buffer containing gelatin and bacteriophages. Our results therefore suggest that lyophilized inserts harboring bacteriophage selective for S. aureus may be a novel means for the eradication of MRSA resident in the nose.
Insights
New nasal inserts effectively deliver bacteriophages for methicillin-resistant Staphylococcus aureus (MRSA) eradication. This innovative formulation offers a promising approach to combatting MRSA nasal carriage and reducing infection risk.
Area of Science:
- Biotechnology
- Microbiology
- Pharmaceutical Sciences
Background:
- Nasal carriage of methicillin-resistant Staphylococcus aureus (MRSA) presents a significant infection risk, particularly in hospitalized patients.
- Current strategies for MRSA eradication are limited, and effective nasal formulations for bacteriophage therapy are lacking.
Purpose of the Study:
- To develop and characterize novel lyophilized nasal inserts for bacteriophage delivery.
- To assess the stability and efficacy of bacteriophages within these inserts for MRSA eradication.
Main Methods:
- Bacteriophages were lyophilized in hydroxypropyl methylcellulose (HPMC) with or without mannitol to create porous, leaflet-like nasal inserts.
- Homogeneous distribution of bacteriophages within the matrix was confirmed using fluorescent labeling.
- Bacteriophage titers and stability were assessed post-lyophilization and during storage at 4°C.
Main Results:
- Lyophilized inserts maintained a bacteriophage titer of 10^8 plaque-forming units (pfu) per insert, with a 100- to 1000-fold reduction over 6-12 months of storage.
- Mannitol addition reduced residual water content but did not correlate with lytic activity.
- Mannitol crystallization was observed under humid conditions, but suppressed by higher HPMC concentrations and buffer components.
Conclusions:
- Lyophilized bacteriophage inserts represent a novel and potentially effective strategy for eradicating nasal MRSA.
- The developed formulation demonstrates good bacteriophage stability and offers a promising alternative to current MRSA nasal carriage treatments.
