Eye / conjunctiva / lid swabs

by JimHutchinson

Eye / conjunctival / lid swabs are collected for the diagnosis of conjunctivitis.

It is preferable that both eyes be swabbed, even if the infection is unilateral. Swabs should be collected prior to the instillation of topical anaesthetics or antibiotics, and sent in transport medium.

Viral isolation requires special universal transport media (UTM).

Occasionally, specimens collected by an ophthalmologist will be inoculated directly onto culture plates at the bedside. The ophthalmologist will inoculate the plates in a short spiral line. If lid swabs are also collected, these will be inoculated onto the same culture plates next to the conjunctival inoculation. Lid swabs will be inoculated in the shape of an “L” or “R” indicating left or right, respectively. These plates should be kept in the incubator (35°C) until processed.

Setup If pre-inoculated culture plates are received, these should be incubated as listed below. No Gram stain will be performed.

Direct Examination

Not indicated

Culture

Media Incubation
Blood Agar (BA) CO2, 35°C x 48 hours
Chocolate Agar (CHOC) CO2, 35°C x 48 hours

If Neisseria gonorrhoea requested, add:

Vancomycin-Colistin-Nystatin Agar (VCN) CO2, 35°C x 72 hours

Interpretation Examine the BA and CHOC and VCN (if indicated) plates after 24, 48 and 72 (VCN) hours incubation.

Any growth of S. aureus, H. influenzae, M. catarrhalis, N. gonorrheae, Gp.A Strep, S. pneumoniae, Moraxella spp., and P. aeruginosa is significant. Susceptibility tests are not performed except if S. aureus is identified and only to screen for MRSA.

Reporting

Culture

Negative Report
“Normal flora” or “No growth”. If GC culture was set up, report “No N. gonorrhoeae isolated”

Positive Report
Quantitate all significant isolates. If normal flora is also present, report with quantitation.

If S. aureus was isolated screen for MRSA only and report as either “MRSA isolated” or “S. aureus isolated”. Do not report susceptibility on any isolate. Add comment “Susceptibility testing of topical antibiotics is not standardized and not routinely performed on superficial eye specimens.”

References H.D. Isenberg. 2004. Specimen Collection, Transport and Acceptability p. 2.1.1 – 2.1.28. In Clinical Microbiology Procedures handbook, 2nd Edition, Vol 1 ASM Press, Washington, D.C

H.D. Isenberg, 2004. Wound Cultures – Wound and Soft Tissue Cultures, p. 3.13.1.1 – 3.13.1.16. In Clinical Microbiology Procedures Handbook, 2nd Edition, Vol 1 ASM Press, Washington, D.C.

H.D. Isenberg. 2004. Ocular Cultures p. 3.10.1. – 3.10.8. In Clinical Microbiology Procedures Handbook, 2nd Edition, Vol 1 ASM Press, Washington, D.C.