Validating tyrosinase homologuemelAas a photoacoustic reporter gene for imagingEscherichia coli

Abstract

To understand the pathogenic processes for infectious bacteria, appropriate research tools are required for replicating and characterizing infections. Fluorescence and bioluminescence imaging have primarily been used to image infections in animal models, but optical scattering in tissue significantly limits imaging depth and resolution. Photoacoustic imaging, which has improved depth-to-resolution ratio compared to conventional optical imaging, could be useful for visualizing melA-expressing bacteria since melA is a bacterial tyrosinase homologue which produces melanin. Escherichia coli-expressing melA was visibly dark in liquid culture. When melA-expressing bacteria in tubes were imaged with a VisualSonics Vevo LAZR system, the signal-to-noise ratio of a 9×dilution sample was 55, suggesting that ∼20 bacteria cells could be detected with our system. Multispectral (680, 700, 750, 800, 850, and 900 nm) analysis of the photoacoustic signal allowed unmixing of melA-expressing bacteria from blood. To compare photoacoustic reporter gene melA (using Vevo system) with luminescent and fluorescent reporter gene Nano-lantern (using Bruker Xtreme In-Vivo system), tubes of bacteria expressing melA or Nano-lantern were submerged 10 mm in 1% Intralipid, spaced between <1 and 20 mm apart from each other, and imaged with the appropriate imaging modality. Photoacoustic imaging could resolve the two tubes of melA-expressing bacteria even when the tubes were less than 1 mm from each other, while bioluminescence and fluorescence imaging could not resolve the two tubes of Nano-lantern-expressing bacteria even when the tubes were spaced 10 mm from each other. After injecting 100-μL of melA-expressing bacteria in the back flank of a chicken embryo, photoacoustic imaging allowed visualization of melA-expressing bacteria up to 10-mm deep into the embryo. Photoacoustic signal from melA could also be separated from deoxy- and oxy-hemoglobin signal observed within the embryo and chorioallantoic membrane. Our results suggest that melA is a useful photoacoustic reporter gene for visualizing bacteria, and further work incorporating photoacoustic reporters into infectious bacterial strains is warranted.

Investigating the Antibacterial Effects of Plant Extracts on Pseudomonas aeruginosa and Escherichia coli

“…Escherichia coli is a pathogenic bacteria transmitted by infected food. Worldwide epidemics of this disease have been reported (2). The signs and symptoms of E. coli exposure include diarrhea, nausea, ulcerative colitis, abdominal pain and, in some cases, kidney disorders or death, especially among children (3).…”

Phototrophic purple bacteria as optoacoustic in vivo reporters of macrophage activity

“…In comparison to blood, the raw OA signal at 850 nm of ~2.6 x 10 6 cells in the imaging volume (5 µl) equals that of fully oxygenated sheep’s blood. This is one order of magnitude less cells than would be needed with melanin producing bacteria 12 .…”

“…Major challenges of these genetically encoded labels are the absorbance in the visible part of the spectrum hampering their detection deep in tissues due to strong absorbance of blood at those wavelengths. In contrast, the absorption spectrum of melanin extends to the near-infrared region (NIR) however lacks distinct peaks 12 making it difficult to separate its OA signal from background noise. Moreover, synthesis of melanin in mammalian cell lines for longitudinal studies is often precluded by long-term toxic effects 13 .…”

Antioxidant Activity, Mosquitocidal Activity, Antibacterial Activity of Solvent Extract and Synthesized Nanoparticles of Clausena Excavata (Burm.) F. (Rutaceae) Against Selected Mosquitoes and Pathogenic Bacteria

“…The acquaintance and use of a wide spectrum of medicinal plants have been documented to combat various infectious diseases impeding human life and activity (Pfaller and Diekema, 2012 (Cavallo et al, 2007;Eber et al, 2010;Rao et al, 2011;Kwak et al, 2012;Ko et al, 2013;Dag et al, 2014 andMousavi et al, 2015;Najari and Alimohammadi, 2015;Paproski et al, 2015). Several researchers have been carried out to study the antimicrobial activity of different plant extracts (Rajeshkumar, 2014 and2015;Chandrika and Chellaram.…”