Microbacterium resistens Peritoneal Dialysis-Associated Peritonitis: A Case Report.

Peritoneal dialysis (PD)-associated peritonitis is most commonly caused by Gram-positive organisms; however, infections due to unusual pathogens can present important diagnostic and management challenges. Microbacterium resistens is an environmental Gram-positive bacillus rarely implicated in human infections, and PD-associated peritonitis due to this organism has been reported only once previously, to our knowledge. We report a case of persistent PD-associated peritonitis caused by M resistens in a 65-year-old man receiving automated PD combined with once-weekly hemodialysis. The initial episode was treated by prioritizing the already identified Enterococcus casseliflavus; an initially unidentified Gram-positive bacillus was subsequently identified as M resistens. The patient experienced multiple subsequent episodes despite sequential systemic and intraperitoneal antimicrobial therapies. Although effluent leukocyte counts repeatedly normalized with treatment, M resistens was repeatedly isolated with unchanged antimicrobial susceptibility profiles, suggesting persistent catheter colonization rather than acquired antimicrobial resistance. A definitive cure was achieved only after PD catheter removal. This case highlights that apparent clinical response with effluent leukocyte normalization does not necessarily indicate microbiological eradication in rare device-associated infections and that early catheter removal should be considered when the same unusual organism is repeatedly isolated despite appropriate antimicrobial therapy.