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Legionella pneumophila is a virulent bacterial pathogen that can cause a severe and deadly form of pneumonia called Legionnaires’ disease. Documented cases of Legionnaires’ disease have been rising since 2000. Risk of infection increases when L. pneumophila are harbored inside free-living amoebae, which are resistant to traditional disinfection processes. The ability of amoebae to phagocytose L. pneumophila allows amoebae to act as ‘Trojan horses’ for pathogen transport. This project aims to extract an unintended benefit from low-intensity microwave (MW) radiation (already found in many homes across economic cross-sections) by employing nanomaterials (e.g., silver, copper oxide, and carbon nanotubes) that are capable of harnessing such radiation and localizing the otherwise dissipated energy. In this alternative technology, we hypothesize that amoebae will be lysed via localized interfacial heating, and the released L. pneumophila will be inactivated subsequently by heat, metal ions (from nanoparticle dissolution), and reactive oxygen species (ROS) produced in the process. Traditionally, inactivation of up to 3-logs of planktonic L. pneumophila with dissolved silver requires hours of contact time. This study reports rapid inactivation (in minutes) of 3-log or higher when the planktonic L. pneumophila is subjected to AgNPs (5 mg/L) and MW radiation (2,450 MHz; 70 W). Ensuing phases of this project will incorporate copper oxide nanoparticles – which are anticipated to increase toxicity akin to copper-silver ionization systems currently employed in hospitals for L. pneumophila control – and enhance inactivation potency with potentially lower microwave radiation input and/or a lower concentration of nanoparticles. Ultimately, the nanomaterials will be immobilized on a plaster of Paris or ceramic surface for flow-through applications for lysing amoebae and inactivating L. pneumophila.
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Legionella pneumophila inactivation potency of silver nanoparticles and ionic silver and copper enhanced with microwave radiation
Legionella pneumophila is a virulent bacterial pathogen that can cause a severe and deadly form of pneumonia called Legionnaires’ disease. Risk of infection increases when L. pneumophila are harbored inside free-living amoebae, which are resistant to traditional disinfection processes but lyse upon heat exposure. This project aims to develop a point-of-use technology based on microwave (MW) radiation and nanomaterial (e.g., silver, copper oxide, carbon nanotubes) exposure for L. pneumophila control. In this alternative technology, we hypothesize that amoebae will be lysed via localized interfacial heating, and the released L. pneumophila will be inactivated subsequently by heat, metal ions (from nanoparticle dissolution), and reactive oxygen species (ROS) produced in the process. The synergistic effect of microwaves and silver nanoparticles for enhanced, rapid inactivation has been demonstrated for Escherichia coli and planktonic L. pneumophila. Inactivation greater than 3-logs of each species has been achieved when subjected to silver nanoparticles (2-5 mg/L) and MW (2,450 MHz; 70 W) radiation. A mechanistic study using E. coli has determined the dominant interaction to be between released ions and MW radiation. Ultimately, the nanomaterials will be immobilized on a plaster of Paris or ceramic surface for flow through applications where both amoeba lysing and L. pneumophila inactivation will be achieved.
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- Award ID(s):
- 1805958
- PAR ID:
- 10174721
- Date Published:
- Journal Name:
- 8th Sustainable Nanotechnology Organization Conference
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Legionella pneumophila is an opportunistic human pathogen that can cause a severe and deadly form of pneumonia called Legionnaires’ disease. Over the past decade, the number of reported cases of Legionnaires’ disease has quadrupled in the U.S., with 8,000-18,000 hospitalizations per year at a yearly incidence rate of 1.7/100,000. Within the water sector, this public health risk is exacerbated by the proliferation of L. pneumophila in complex biological matrices such as biofilms and within free-living amoebae. Traditional disinfection technologies fail to effectively mitigate this emerging pathogen issue, necessitating development of point-of-use (POU) technologies with high inactivation efficacy. We aim to harness microwave (MW) radiation and take advantage of its synergy with ion-mediated toxicity to effectively inactivate L. pneumophila. In this study, planktonic L. pneumophila cells have been exposed to ionic and nano-particulate silver. While neither treatment alone is effective over a short exposure period, a combined treatment of silver with MW radiation successfully achieves 3-4 log removal within 6 min of irradiation, as shown in Figure 1. Enhanced toxicity was observed when L. pneumophila was pre-exposed to either treatment (i.e., MW heating or silver exposure) prior to exposure to the other; these results suggest that silver ion transport within the cells is facilitated by heat treatment. Data presented here serve as the proof-of-concept toward the development of a L pneumophila inactivation device that harnesses MW radiation and can potentially mitigate this public health risk, even if the cells are protected by amoebae or biofilms.more » « less
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