June 2017
Volume 58, Issue 8
Open Access
ARVO Annual Meeting Abstract  |   June 2017
Characterization of ocular clinical isolates and non-ocular multi-drug resistant strains of Pseudomonas aeruginosa and their susceptibility to killing by glycyrrhizin
Author Affiliations & Notes
  • Xudong Peng
    Anatomy and Cell Biology, Wayne State University, Detroit, Michigan, United States
  • Sandamali Amarasingha Ekanayaka
    Anatomy and Cell Biology, Wayne State University, Detroit, Michigan, United States
  • Sharon A McClellan
    Anatomy and Cell Biology, Wayne State University, Detroit, Michigan, United States
  • Alicia Eby
    Kresge Eye Institute, Detroit, Michigan, United States
  • Linda Hazlett
    Anatomy and Cell Biology, Wayne State University, Detroit, Michigan, United States
  • Footnotes
    Commercial Relationships   Xudong Peng, None; Sandamali Amarasingha Ekanayaka, None; Sharon McClellan, None; Alicia Eby, None; Linda Hazlett, Wayne State University (P)
  • Footnotes
    Support  This work was supported by grants R01EY016058, and P30EY004068 from the National Eye Institute, National Institutes of Health and by a Research to Prevent Blindness unrestricted grant to the Department of Ophthalmology, Kresge Eye Institute. Dr. Hazlett is the recipient of a 2012 Alcon Research award.
Investigative Ophthalmology & Visual Science June 2017, Vol.58, 5762. doi:
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      Xudong Peng, Sandamali Amarasingha Ekanayaka, Sharon A McClellan, Alicia Eby, Linda Hazlett; Characterization of ocular clinical isolates and non-ocular multi-drug resistant strains of Pseudomonas aeruginosa and their susceptibility to killing by glycyrrhizin. Invest. Ophthalmol. Vis. Sci. 2017;58(8):5762.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Purpose : To characterize ocular clinical isolates and non-ocular multi-drug resistant (MDR) strains of Pseudomonas aeruginosa for expression of type III-secreted effector molecules (ExoS, ExoT and ExoU) critical for virulence and the susceptibility of these strains to killing by glycyrrhizin (GLY), a small triterpenoid molecule.

Methods : Bacterial cultures (from the Kresge Eye institute, Alicia Eby, MD and Mark McDermott, MD) were prepared and bacterial growth examined as described before (Ekanayaka et al. IOVS 2016) with the following modifications. Serial dilutions (0, 5, 10, 20 and 40 mg/ml) of GLY were prepared in PTSB in sterile tubes and 10 μL of each bacterial culture (washed and reconstituted in saline) was added. The minimum inhibitory concentration (MIC) of GLY was determined by spectrophotometric reading at 540 nm following incubation at 37°C for 18 hours. Values of MIC50 and MIC90 were defined as the lowest concentrations that resulted in a 50% and 90% decrease in absorbance compared with the growth control. A polymerase chain reaction (PCR) was used to characterize cytotoxic (expressing ExoU) vs non-cytotoxic (ExoS, T expressing) strains.

Results : All clinical isolates were non-cytotoxic and expressed ExoS and ExoT. None expressed ExoU. For clinical isolates R59733 and 070490, absorbance values were significantly reduced at 20 and 40 mg/ml GLY. For G81007 absorbance values were reduced significantly at all concentrations tested. For all 3 isolates MIC50 values were >20 but <40 mg/ml. For MDR isolates [#2, 3, 6, 10 (Detroit Medical Center)], #3, 6, and 10 expressed ExoU and T, while #2 expressed ExoS and T. Absorbance values for MDR strains (#2, 3, 10) were reduced significantly at 10, 20 and 40 mg/ml GLY. However, for MDR strain #6, absorbance values were reduced only at 20 and 40 mg/ml GLY. For MDR strain #2, 6, and 10 the MIC90=40mg/ml GLY.

Conclusions : These data provide evidence that GLY kills all clinical isolates (G81007, R59733 and 070490) tested, none of which were cytotoxic. It also effectively kills cytotoxic (#3, 6 and 10) and invasive (#2) MDR strains without antibiotics.

This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.

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