Superficial corneal foreign body: laboratory and epidemiologic aspects

To determine by bacterioscopy and culture the microorganisms carried by corneal foreign body and their sensitivity to antibiotics by antibiotic sensitivity test.

A prospective study was carried out and information was collected on 101 patients who presented with corneal foreign body at the São Paulo Hospital Eye Emergency Service. Prior to any treatment, a sample of the ipsilateral inferior conjunctival fornix and the foreign body were collected and immersed in thioglycolate broth. Samples were sown on solid culture media including blood, chocolate and Sabouraud agar. Bacterioscopic examination using Gram and Giemsa staining and sensitivity test were performed. Positive foreign body culture results were compared to ipsilateral conjunctival fornix culture to exclude possible normal flora growth.

Approximately 92% of patients were males with a mean age of 35 years and in 62.4% (95% confidence interval: 52.2-71.8%) had the right eye was affected. Foreign body positive cultures were achieved in 32.7% (95% confidence interval: 23.7-42.7%) of the cases. The microorganisms isolated from the foreign body culture were identified as: Streptococcus, alpha-hemolytic (n=4), Staphylococcus aureus (n=4), Staphylococcus, coagulase-negative (n=4), Corynebacterium xerosis (n=3), unidentified Gram-positive bacillus (n=2), Moraxella sp (n=1), Serratia sp (n=1), Acynetobacter sp (n=1). The microbial sensitivity test showed that 95% of the cases were sensitive to chloramphenicol and 90% were sensitive to ciprofloxacin, these being antibiotics used in our routine service.

Superficial corneal foreign body acts as important contaminant vector and the great majority of isolated bacteria were sensitive to the antibiotic prophylaxis used in the treatment.