Micrococcus lutus is common gram-positive aerobic cocci present in soil, water, dust, and the skin of humans and animals. A 72-year-old man was admitted to the hospital with a complaint of abdominal pain and a turbid peritoneal dialysate. He was empirically treated with intraperitoneal (IP) cefazolin and ceftazidime. Seven day after admission, Gaffkya species was identified from the peritoneal effluent. He was treated with same organism one month ago and discharged with the dialysis catheter intact. So, we suspected that organism is true pathogen, and identified M. luteus by culture. We changed the antibiotics to cefoxitin, which were given for the total of 14 days. This is the first report of relapsing peritonitis by M. luteus and successful treatment without catheter removal.

Algicidal bacterium was isolated from sea water during the declining period of Cochlodinium polykrikoides blooms and this bacterium had a significant algicidal activity against C. polykrikoides. In this study, algicidal bacterium was identified on the basis of biochemical and chemotaxonomic characteristics, and analysis of 16S rDNA sequences. The algicidal bacterium showed 98.6% homology with Micrococcus luteus ATCC 381T. Therefore, this bacterium was designated Micrococcus luteus SY-13. The optimal culture conditions of the algicidal bacterium was 25℃, initial pH 8.0, and 3.0% NaCl concentration. M. luteus SY-13 is assumed to produce secondary metabolites which have algicidal activity. When 10% culture filtrate of this strain was applied to C. polykrikoides (1.0 × 104 cells/㎖) cultures, over 98% of C. polykrikoides cells were destroyed within 6 hours. The culture filtrate of M. luteus SY-13 exhibited similar algicidal activity after heat-treatment at 121℃ for 15 min. While algicidal activity remained in filtrates with pH adjusted to 8.0, loss of algicidal activity occurred when the pHs of filtrates were adjusted to over 9.0 or heat-treated at 121∼180℃ for 1 hour. M. luteus SY-13 showed significant algicidal activities against C. polykrikoides (98.9%) and a wide algicidal range against various harmful algal bloom (HAB) species. However, there was no algicidal effect on diatom and marine livefood organisms except Isocrysis galbana. These results suggest that M. luteus SY-13 could be a candidate for use in the control of HABs.