Vancomycin Enhances the Ototoxic Properties of the Aminoglycoside Antibiotic Gentamicin

Transcription

1 Vancomycin Enhances the Ototoxic Properties of the Aminoglycoside Antibiotic Gentamicin Paul Sooby Supervised by Prof. Guy Richardson and Dr. Richard Goodyear

2 Background Sensori-neural hearing loss and tinnitus are well documented side effect of aminoglycosides Selective cochlear hair cell destruction Certain aminoglycosides can be vestibulotoxic Theorised due to the generation of ROS Higher concentrations to cell death Lower Concentrations membrane blebbing and phospholipid externalisation Both processes associated with apoptosis

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4 Vancomycin Ototoxicity Vancomycin is also listed in the BNF as causing sensori-neural hearing loss and tinnitus. Evidence is less substantial, most being case based. 3 in vivo studies done previously, generating contentious results. No in vitro evidence for ototoxicity.

5 Aims of Project To assess the ototoxic properties of vancomycin in comparison to aminoglycoside induced toxicity. Also to examine if vancomycin enhances the ototoxic properties of gentamycin In vivo studies have contentious, and thus this project will examine the direct in vitro effects of the compounds on cochlear hair cells.

6 Methods - Preparation Cochlear Hair cell cultures were produced from 2 day old mouse pups under the appropriate techniques outlined in Richardson and Russel in Cultures treated with varying concentrations either vancomycin, aminoglycoside or control solution (saline solution) for 72hrs.

7 All cultures were analysed qualitatively: Living/Functional cells demonstrate the characteristic V-Shaped stereocilia under fluorescence Damaged tissue demonstrate flattening of the stereocilia or poor fluorescence Dead tissue doesn t fluoresce Methods-Techniques Phalloidin Fluorescence: Naturally occuring poison in death cap mushrooms bound to a fluorophore Stains F-Actin in stereociliary bundles was used to assess hair bundle morphology & living vs dead hair cells

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9 Vancomycin (2 mmol and 5 mmol)

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11 Discussion - Vancomycin A total of 4 phalloidin fluorescence experimental series were performed, with 28 different cochlear cultures examined Cultures treated with 0.5mMol, 1mMol and 2mMol show no significant differences to cultures treated with control solution, with normal morphology and no significant cell death Only 5mMol cultures showed abnormal hair bundle morphology, but this could be due to alterations in ph medium However, this is an extremely high vancomycin level and could not be replicated physiologically Treatment with both aminoglycoside and vancomycin did show significant increases in hair cell loss from cultures treated with a similar concentration of aminoglycoside alone.

12 Conclusions In Vitro evidence that Vancomycin does not itself cause damage to hair cells Limitations: mouse model, external random error, also an assessment of structure rather than functionality Further work: Observational patient study of vancomycin ototoxicity to review concurrent aminoglycoside prescription, Scanning Electron Microscopy data for Vancomycin Also data needs validation via further repetition However, this project generates evidence that vancomycin neither causes hair cell death or apical surface damage There is evidence that vancomycin does enhance aminoglycoside ototoxicity

13 Many Thanks for Listening Any Questions?

14 References Yost WA, Fundamental of Hearing: An Introduction, 5th ed, 2007, San Diego, published by Elsevier, published first in 2000 Various Contributors, edited executively by Mehta DK, British National Formulary 42, 2005, London, published by BMJ publishing group Ltd Mudd PA, Edmunds AL, Glatz F, Campbell KCM, Rybak LP, Inner Ear Ototoxicity, article written for emedicine, updated on Nov 2008, accessed of 17/05/09, overview Clerici WJ, Hensley K, DiMartino D, Allan-Butterfield D, Direct Detection of ototoxicant-induced reactive oxygen species generation in cochlear explants, Hearing Research, September 1996, Volume 98, Issues 1-2, pages Steyger PS, Peters SL, Rehling J, Hordichok A, Dai CF, Uptake of Gentamycin by bullfrog saccular hair cells in vitro, Journal of the association for research in otolaryngology, December 2003, Volume 4, Issue 4, pages Richardson GP, Russel IJ, Cochlear Cultures as a model system for studying aminoglycoside induced ototoxicity, Hearing Research, 1991, Issue 53, pages Richardson G, Goodyear R, Gale J, Ranatunga K, Kros C, Neomycin induces the rapid externalisation of phosphatidylserine on the apical surface of early postnatal mouse cochlear hair cells, Association for Research in Otolaryngology, Abstracts of the 30th annual midwinter meeting, Feb 2007, pages Forouzesh A, Moise PA, Sakalous G, Vancomycin Ototoxicity: A reevaluation in an era of increasing doses, Antimicrobial agents and chemotherapy, Febuary 2009, Volume 53, Number 2, pages Lutz H, Lenarz T, Weidauer H, Federspil P, Hoth S, Ototoxicity of Vancomycin: an experimental study in guinea pigs, Journal for oto-rhino-laryngology and related specialities, 1991, Volume 53, Issue 5, pages Brummet RE, Fox KE, Jacobs F, Kempton B, Stokes Z, Allyson B, Augmented Gentamycin ototoxicity induced by vancomycin in guinea pigs, Archives of Otolaryngology Head and neck surgery, January 1990, Volume 116, Number 1, Pages Nishihara K, Shimizu T, Kotaki H, Sawada Y, Okuno T, Kaga K et al, Lack of effect of vancomycin and gentamycin on auditory function in guinea pigs, Antimicrobial agents and Chemotherapy, May 1996, Volume 40, Issue 5, pages Russell IJ, Richardson GP. The morphology and physiology of hair cells in organotypic cultures of the mouse cochlea. Hear Res Nov;31(1):9 24 Gale JE, Marcotti W, Kennedy HJ, Kros CJ, Richardson GP, FM1-43 dye behaves as a permeant blocker of the Hair-Cell mechanotransducer channel, The Journal of Neuroscience, 2001, Volume 21, Issue 18, Pages