The Use of Blood Culture Bottles to Identify Causative Agents of Endophthalmitis

Abstract

Abstract: : Purpose: To investigate the usefulness of blood culture bottles in isolating causative organisms of endophthalmitis, and to investigate the impact of inoculum size, blood culture bottle volume, and blood culture media on the rate and amount of microbial growth using endophthalmitis isolates. Methods: Staphylococcus epidermidis, Staphylococcus aureus, Streptococcus viridans, Propionibacterium acnes, Pseudomonas aeruginosa, Bacillus cereus, and Candida albicans isolated from the vitreous of patients with endophthalmitis were individually inoculated into each of three different blood culture bottles. The blood culture bottles contained either 1) 70 ml of trypticase soy broth; 2) 70 ml of enriched media (Columbia broth with SPS and CO₂); or 3) 20 ml of brain heart infusion with SPS and CO₂. For each organism, 1.0 ml and 0.1 ml of 100 colony forming units/ml were inoculated into each of the three types of blood culture bottles. Two sterility controls of each blood culture bottle type were prepared. Results: For the six bacterial organisms, the 1.0 ml inocula demonstrated growth at 0-12 hours compared to at 13-24 hours for the 0.1 ml inocula; at 24 hours, there was visible growth of these six organisms in all bottles, although the growth was light for the 0.1 ml inocula and moderate for the 1.0 ml inocula. The 1.0 ml inocula of Candida albicans demonstrated growth in the bottle containing Columbia broth and in the bottle containing brain heart infusion with SPS and CO₂ at 5 days. For all organisms, growth was greater in the 70 ml bottles containing Columbia broth than in the other 2 types of bottles. There was no growth in the sterility control bottles after 14 days. Conclusion: In the management of patients with endophthalmitis, when prompt access to a microbiology laboratory is unavailable, blood culture bottles represent a useful alternative to direct plating of organisms. When only a small sample of intraocular fluid can be obtained, it is recommended that the specimen be placed in a more enriched media; in this study, the media composition was more important than the volume of fluid contained in the blood culture bottle.

Keywords: 398 endophthalmitis