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Journal of Clinical Microbiology, July 2003, p. 3192-3197, Vol. 41, No. 7
0095-1137/03/$08.00+0     DOI: 10.1128/JCM.41.7.3192-3197.2003
Copyright © 2003, American Society for Microbiology. All Rights Reserved.

Simplifying Collection of Corneal Specimens in Cases of Suspected Bacterial Keratitis

Stephen B. Kaye,^1* Prasad G. Rao,¹ Godfrey Smith,² John A. Scott,¹ Sharon Hoyles,² Clare E. Morton,¹ Colin Willoughby,¹ Mark Batterbury,¹ and Graham Harvey²

St. Paul's Eye Unit,¹ Department of Medical Microbiology, Royal Liverpool University Hospital, Liverpool, L7 8XP, United Kingdom²

Received 25 October 2002/ Returned for modification 4 January 2003/ Accepted 29 April 2003

Identification of the causative organisms in suspected bacterial keratitis traditionally involves collecting multiple corneal scrapes, which are plated directly onto different solid agar culture media. Difficulties have been reported with this practice, so the development of a simpler diagnostic method in suspected bacterial keratitis would be useful. It is unclear whether a single corneal scrape sent to the microbiology laboratory in a liquid transport culture medium (indirect method) is as reliable for the diagnosis of bacterial keratitis as inoculation of multiple scrapes directly onto agar plates (direct method). To investigate this, bacterial recovery was assessed following transfer and transport of different concentrations and types of bacteria from an artificially contaminated surgical blade into brain heart infusion (BHI). Bacterial recovery rates between the proposed (indirect) and standard (direct) method were then compared after the in vitro inoculation of pig corneas and following specimen collection in patients with presumed bacterial ulcerative keratitis. Recovery of bacteria from contaminated surgical blades was found to be the same from both solid and liquid culture media. There was no significant difference in the numbers of positive cultures from solid (direct) and liquid (indirect) culture media, both in the experimental pig cornea inoculation study (P = 0.34) and in experiments with patients with clinical infections (P = 0.4), with an 85.2% agreement between methods (kappa = 0.61, P < 0.0001). In conclusion, therefore, the collection of two corneal scrapes, one used for Gram staining and the other transported in BHI followed by plating and subculturing in an enrichment medium, provides a simple method for the investigation of presumed bacterial keratitis.

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* Corresponding author. Mailing address: St. Paul's Eye Unit, 8Z Link, Royal Liverpool University Hospital, Prescot St., Liverpool L7 8XP, United Kingdom. Phone: 44 (151) 706 2134. Fax: 44 (151) 706 5861. E-mail: stephen.kaye{at}rlbuh-tr.nwest.nhs.uk.

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Journal of Clinical Microbiology, July 2003, p. 3192-3197, Vol. 41, No. 7
0095-1137/03/$08.00+0     DOI: 10.1128/JCM.41.7.3192-3197.2003
Copyright © 2003, American Society for Microbiology. All Rights Reserved.

This article has been cited by other articles:

• Nicola, F., Kaye*, S. B., Smith, G. (2004). Investigating Infectious Keratitis. J. Clin. Microbiol. 42: 2355-2356 [Full Text]