Quantitative ocular bacteriology: a method for the enumeration and identification of bacteria from the skin-lash margin and conjunctiva

Abstract

Type 1 Calgiswabs were used to collect bacterial specimens from the skin-lash margins and conjunctivae of normal volunteers. The swabs were held in a nonnutritive balanced salt solution during transportation to the laboratory. Alginate swabs were dissolved in a two-step procedure in TC Eagle's medium and 2.5% sodium hexametaphosphate solution. Aliquots of suspended bacteria from the dissolved swab were plated on blood agar. After incubation, bacterial colonies present were enumerated and identified. Cultures from both the skin-lash margin and conjunctiva show significant variation in the number and types of microorganisms isolated. Quantities of bacteria isolated from the lid margin were usually greater than from the conjunctiva. Staphylococcus epidermidis was the most prevalent bacterium isolated. The adsorption of bacteria onto alginate swabs from bacterial suspensions and the recovery of a red pigment-producing organism from the conjunctivae of rabbit eyes previously inoculated show that the method is sensitive and highly reproducible.