Bacterial flora of the normal conjunctiva. II. Methods of obtaining cultures

The methods used for obtaining bacterial cultures from the normal conjunctiva were reviewed. A comparison was made between four methods: a) platinum loop, b) calcium alginate swab c) dry, and d) wet cotton wool swab, using agar (all methods) and serum-bouillon (methods b, c, d) as culture media. The comparisons were based on the isolation rate of Staphylococcus albus and corynebacteria. At the same time, four topical anaesthetics (benoxinate, tetracaine, proparacaine, cocaine) and one vital stain (tetrazolium - alcian blue mixture) instilled into the conjunctiva immediately before taking samples, were studied for their effects on the isolation rate of Staphylococcus albus and corynebacteria. For isolating Staphylococcus albus, method d was found to be superior to the others when the methods were used in the above mentioned order, and when agar was the only culture medium used. On the other hand, after instillation of the above mentioned eyedrops, causing the so-called “washing-out” effect (Fahmy et al. 1974), method a was found better than the others, providing the methods were used in the a-b-c-d order and when agar only was used. When considering the growth of Staphylococcus albus in serum boullion as well, methods b, c, and d were found equal in effect, but somewhat superior to a. Corynebacteria showed nearly the same isolation rate with all the methods before as well as after the instillation of eye drops.