dAllelic replacement mutants were constructed within arginine deiminase (arcA1 and arcA2) to assess the function of the arginine deiminase (ADI) pathway in organic acid resistance and biofilm formation of Staphylococcus epidermidis 1457. A growth-dependent acidification assay (pH ϳ5.0 to ϳ5.2) determined that strain 1457 devoid of arginine deiminase activity (1457 ⌬ADI) was significantly less viable than the wild type following depletion of glucose and in the presence of arginine. However, no difference in viability was noted for individual 1457 ⌬arcA1 (native) or ⌬arcA2 (arginine catabolic mobile element [ACME]-derived) mutants, suggesting that the native and ACME-derived ADIs are compensatory in S. epidermidis. Furthermore, flow cytometry and electron paramagnetic resonance spectroscopy results suggested that organic acid stress resulted in oxidative stress that could be partially rescued by the iron chelator dipyridyl. Collectively, these results suggest that formation of hydroxyl radicals is partially responsible for cell death via organic acid stress and that ADI-derived ammonia functions to counteract this acid stress. Finally, static biofilm assays determined that viability, ammonia synthesis, and pH were reduced in strain 1457 ⌬ADI following 120 h of growth in comparison to strain 1457 and the arcA1 and arcA2 single mutants. It is hypothesized that ammonia synthesis via the ADI pathway is important to reduce pH stress in specific microniches that contain high concentrations of organic acids.

Scleral buckle removal is an uncommon procedure performed for various reasons. Microbiological information on explanted scleral buckles remains limited. The authors identified 37 cases of scleral buckle removal during an 18-year period. Bacterial cultures isolated an organism in 4 of 9 patients (44%) with clinical infection. Organisms identified included methicillin-resistant Staphylococcus aureus, Pseudomonas aeruginosa, Mycobacterium abscessus, and coagulase-negative Staphylococcus species. Bacterial cultures isolated an organism in 3 of 11 patients (27%) without clinical infection. Organisms identified included Nocardia species, Alcaligenes xylosoxidans, and Mycobacterium chelonae. Scleral buckles appearing clinically infected may be associated with more virulent organisms and a greater chance of identifying an organism. Bacterial cultures may be of value for scleral buckles upon removal.

Scleral buckle removal is effective in eliminating SB-related pain and infection. Symptomatic diplopia can sometimes improve after SB removal. The rates of RD after SB removal observed in this study (12%) and in others performed in the era of vitrectomy were notably lower than those of previous reports.