Peritonitis is well recognized as the Achilles tendon of peritoneal dialysis (PD). Reoccurrence of peritonitis due to the same organism, defined as either repeat or relapsing peritonitis under the 2005 guidelines by the International Society for Peritoneal Dialysis, often results in PD technique failure. Rothia dentocariosa, a low-virulent human oropharynx commensal, is a rarely reported pathogen in human infection, particularly infective endocarditis. R. dentocariosa PD-related peritonitis is exceedingly uncommon yet potentially results in repeat or relapsing peritonitis which requires catheter removal. We report a case of R. dentocariosa repeat and relapsing peritonitis in a PD patient who was treated successfully with antimicrobial therapy.
Rhodococcus equi, a recognized pathogen in horses, is emerging as a human opportunistic pathogen, especially in immunocompromized hosts. We describe four immunocompromized patients who had serious R. equi infections with an overall mortality of 75%. The natural habitat of R. equi is soil, particularly soil contaminated with animal manure. Necrotizing pneumonia is the commonest form of infection but extrapulmonary infections, such as wound infections and subcutaneous abscess, have also been described in humans. R. equi is cultured easily in ordinary non-selective media. Large, smooth, irregular colonies appear within 48 hours. It is a facultative, intracellular, nonmotile, non-spore forming, gram-positive coccobacillus, which is weakly acid-fast staining and bears a similarity to diphtheroids. It forms a salmon-colored pigment usually after 48 hours incubation. A particular characteristic of this organism is that it undergoes synergistic hemolysis with some bacteria on sheep blood agar. R. equi may be misidentified as diphtheroids, Mycobacterium species, or Nocardia. In vitro R. equi is usually susceptible to erythromycin, ciprofloxacin, vancomycin, aminoglycosides, rifampin, imipenem and meropenem. The organism can be difficult to eradicate, making treatment challenging. Increased awareness of the infection may help with early diagnosis and timely treatment.
Tsukamurella spp. are a rare but important cause of intravascular catheter-related bacteremia in immunocompromised patients. The organism is an aerobic, Gram-positive, weakly acid-fast bacillus that is difficult to differentiate using standard laboratory methods from other aerobic actinomycetales such as Nocardia spp., Rhododoccus spp., Gordonia spp., and the rapid growing Mycobacterium spp. We report a case of Tsukamurella tyrosinosolvens catheter-related bacteremia in a 51-year-old haematology patient who responded to treatment with imipenem and subsequent line removal. 16srRNA sequencing allowed for the prompt identification of this organism.