The transition metal gallium disrupts Pseudomonas aeruginosa iron metabolism and has antimicrobial and antibiofilm activity
Yukihiro Kaneko, … , Bradley E. Britigan, Pradeep K. Singh
Yukihiro Kaneko, … , Bradley E. Britigan, Pradeep K. Singh
Published April 2, 2007
Citation Information: J Clin Invest. 2007;117(4):877-888. https://doi.org/10.1172/JCI30783.
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Research Article Infectious disease

The transition metal gallium disrupts Pseudomonas aeruginosa iron metabolism and has antimicrobial and antibiofilm activity

Abstract

A novel antiinfective approach is to exploit stresses already imposed on invading organisms by the in vivo environment. Fe metabolism is a key vulnerability of infecting bacteria because organisms require Fe for growth, and it is critical in the pathogenesis of infections. Furthermore, humans have evolved potent Fe-withholding mechanisms that can block acute infection, prevent biofilm formation leading to chronic infection, and starve bacteria that succeed in infecting the host. Here we investigate a “Trojan horse” strategy that uses the transition metal gallium to disrupt bacterial Fe metabolism and exploit the Fe stress of in vivo environments. Due to its chemical similarity to Fe, Ga can substitute for Fe in many biologic systems and inhibit Fe-dependent processes. We found that Ga inhibits Pseudomonas aeruginosa growth and biofilm formation and kills planktonic and biofilm bacteria in vitro. Ga works in part by decreasing bacterial Fe uptake and by interfering with Fe signaling by the transcriptional regulator pvdS. We also show that Ga is effective in 2 murine lung infection models. These data, along with the fact that Ga is FDA approved (for i.v. administration) and there is the dearth of new antibiotics in development, make Ga a potentially promising new therapeutic for P. aeruginosa infections.

Authors

Yukihiro Kaneko, Matthew Thoendel, Oyebode Olakanmi, Bradley E. Britigan, Pradeep K. Singh

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Figure 4

Ga kills established biofilms.

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Ga kills established biofilms. (A) Biofilms were grown using GFP-labeled...
(A) Biofilms were grown using GFP-labeled P. aeruginosa for 3 days in the absence of Ga; treated with 100 μM Ga(NO3)3 for the indicated time periods; and stained with 30 μM propidium iodide, which labels dead cells red. Top images are top-down views (x-y plane); bottom images are side views (x-z plane); the dotted line represents the biofilm growth surface; scale bars: 50 μm. Results are representative of 4 separate experiments. (B) High-magnification image of the biofilm killing pattern of Ga and tobramycin. Three-day-old P. aeruginosa biofilms (grown without Ga) were treated with Ga(NO3)3 (100 μM) or tobramycin (1 μg/ml) for 48 hours and stained as described in A. Ga preferentially killed bacteria in the central regions, whereas tobramycin preferentially killed bacteria located in the biofilm periphery. Images are top-down views (x-y plane); scale bar: 50 μm. Results are representative of 3 separate experiments. (C) Fe addition eliminates the central biofilm killing pattern of Ga. GFP-labeled P. aeruginosa biofilms were grown in flow cells for 3 days with or without FeCl3 (50 μM), treated with 100 μM Ga(NO3)3 for 48 hours, and then stained as described in A. Fe addition eliminated the central killing pattern of Ga. Top images are top-down views (x-y plane); bottom images are side views (x-z plane); the dotted line represents the biofilm growth surface; scale bar: 50 μm. Results are representative of 3 separate experiments. (D) Evidence for Fe starvation in the central biofilm regions. P. aeruginosa constitutively expressing red florescent protein and containing the pvdA-gfp(S) reporter (which fluoresces green during Fe limitation; see Supplemental Figure 4) were grown in biofilms for 3 days. In the absence of added Fe, the central biofilm regions appeared green, indicating Fe limitation. Fe addition reduced the size of the central Fe-starved (green) region within 2 hours. Images are top-down views (x-y plane); scale bar: 50 μm. All images in D were taken with identical confocal microscope settings, and results are representative of 3 separate experiments.