Relapsing Peritoneal Dialysis-Associated Peritonitis due to Kocuria rhizophila: A Case Report Open Access

Peritoneal dialysis (PD)-associated peritonitis is associated with decreased peritoneal function, catheter removal, increased risk of conversion to hemodialysis (HD), progression to encapsulating peritoneal sclerosis, and death [1‒5]. Therefore, selecting the optimal treatment of PD-associated peritonitis is important. Of all the PD-associated peritonitis cases in Japan, 42.7% are caused by gram-positive bacteria, with 21.5% specifically caused by staphylococcus species [4]. Kocuria rhizophila is a soil dwelling gram-positive bacterium that belongs to the family Micrococcaceae in the order Actinomycetales. The first case report of infection in human by Kocuria rhizophila was published in 2008 [6]. There have been some reports of PD-related peritonitis caused by Kocuria species, and antibiotic susceptibility in Kocuria [7‒9]. However, the duration of treatment for PD-associated peritonitis and the phenomenon of biofilm formation in Kocuria remain unclear.

Herein, we present the first case of relapsing PD-associated peritonitis caused by Kocuria rhizophila. The CARE Checklist has been completed by the authors for this case report, attached as online supplementary material (for all online suppl. material, see https://doi.org/10.1159/000534765).

A 78-year-old male patient had been undergoing PD for 3 years and 8 months because of end-stage kidney disease due to diabetic nephropathy. He had a history of PD-associated peritonitis caused by Streptococcus Gordonii and methicillin-resistant Staphylococcus aureus, resulting in the removal and reinsertion of his PD catheter. Subsequently, his treatment regimen was changed to six sessions of continuous ambulatory PDs and one session of HD per week owing to fluid overload. The patient presented to the hospital with complaints of diarrhea and turbid effluent. Upon examination, he had a temperature of 36.7°C, heart rate of 68 beats/min, blood pressure of 147/61 mm Hg, body weight of 61.7 kg, and body mass index of 22.8 kg/m². The patient’s abdomen was tender; however, bowel sounds were normal and no guarding or rebound tenderness was present. No obvious redness or exudate at the exit site was observed. Laboratory data showed a peripheral white blood cell count of 8,100 cells/μL and C-reactive protein of 1.13 mg/dL. The white blood cell count in the peritoneal fluid was 253 cells/μL (neutrophils 59%).

The clinical course is shown in Figure 1. The patient was diagnosed with PD-associated peritonitis, and we initiated treatment with intraperitoneal administration of ceftazidime and vancomycin as our initial treatment protocol. The culture of the PD fluid revealed the presence of Kocuria rhizophila, and antibiotic therapy was changed to penicillin G for 2 weeks; the patient was discharged after the treatment for a total of 3 weeks. However, 1 week after discharge, the patient’s effluent again became turbid, and the culture of the PD fluid again revealed the presence of Kocuria rhizophila.

Once the bacteria grew on agar media, we used the matrix-assisted laser desorption time of flight mass spectrometry (MALDI-TOD MS) to identify the bacteria. This method allows us to quantify how accurately we can evaluate the bacteria. If the accuracy is low or the name of the bacteria cannot be determined with MALDI, 16S rRNA is used to identify the bacteria. In this case, Kocuria rhizophila was detected using MALDI-TOF MS.

We attributed the short-period recurrence of peritonitis to the formation of biofilm in the catheter. Therefore, we ultimately elected to remove the patient’s PD catheter and transition from PD to HD.

We report a case of PD-associated peritonitis caused by Kocuria rhizophila that recurred in a short period of time despite 3 weeks course of sensitive antibiotic therapy. To the best of our knowledge, this represents the first reported case of relapsing peritonitis caused by Kocuria rhizophila.

The patient had a history of two prior episodes of PD-associated peritonitis, both of which were considered to be due to touch contamination of connection devices, with no signs of tunnel infection or exit infection. His PD technique was compromised and was performed with the support of his wife. The catheter replaced the second time was a swan-neck, double-cuff catheter. Preoperative antimicrobials were also administered. The patient was not obese and had no pets. His mental status was stable. Therefore, his age and diabetes were considered risk factors for peritonitis.

Kocuria is a genus of gram-positive bacteria that colonizes the human skin and oral cavity. These organisms can be cultivated on sheep blood agar and other basic culture media. The identification of Kocuria rhizophila and other bacteria can be accomplished through 16S rRNA gene sequencing analysis. Presently, there are 19 recognized species within Kocuria genus [7‒9].

The management of PD-associated peritonitis often revolves around cephalosporins, usually administered in combination with vancomycin. Notably, the guideline for peritonitis established by the International Society for Peritoneal Dialysis peritonitis guideline in 2022 does not specifically mention Kocuria species [10]. Generally, Kocuria species tend to exhibit resistance to cephalosporins while displaying sensitivity to penicillin, gentamicin, amikacin, tobramycin, tetracycline, vancomycin, and teicoplanin [11]. Consequently, the results of bacterial culture play a vital role in guiding the selection of appropriate antibiotics for peritonitis caused by Kocuria. The optimal duration of treatment remains uncertain due to the rarity of this organism, but we treated the patient for a period of 3-week. Although the presence of biofilm formation could not be confirmed in our case, it is plausible that early recurrence after 3 weeks of treatments may have been influenced by biofilm formation.

The genus Kocuria, comprising recently discovered gram-positive bacteria, has been infrequently associated with infections in humans. In particular, Kocuria kristinae has been reported in cases of catheter-associated infection in patients with ovarian cancer [12] and acute cholecystitis [13]. Additionally, a case of catheter-related bacteremia caused by Kocuria rosea has been reported in a patient undergoing peripheral blood stem cell transplantation for relapsed Hodgkin disease [14]. Furthermore, Kocuria marina has caused several cases of PD-associated peritonitis [15, 16] and Kocuria varians 1 case of brain abscesses [17]. Additionally, Kocuria rhizophila has caused 4 cases of recurrent catheter-related infection in patients with methylmalonic aciduria [6], a 3-year-old boy with Hirschsprung’s disease [12], a 28-year-old woman with hypothyroidism and short bowel syndrome who has been dependent on total parenteral nutrition for over 20 years [18]. These mean they had the possibilities to have tube biofilms by Kocuria rhizophila. In addition, Kocuria rhizophila caused peritonitis in a 3-year-old Japanese girl [19].

Regarding the biofilm formation of Kocuria, Kocuria varians is present in the flora of endotracheal tube biofilms [20]. A case report of catheter-related bacteremia caused by Kocuria rosea describes treatment with intravenous vancomycin for 5 days being ineffective, ultimately requiring catheter removal and 14 days of intravenous vancomycin for resolution [14].

Moreover, Kocuria rhizophila caused repeated recurrent central venous catheter infections in 7 cases, suggesting the possibility of biofilm formation in the catheter by Kocuria species. [11]. Additionally, Kocuria marina and Kocuria varians have caused cases of peritonitis that required removal of the PD catheter because of a poor response to antibiotics.

We report a case of recurrent PD-related peritonitis caused by Kocuria rhizophila. Given the rapid recurrence of peritonitis despite antibiotic therapy for 21 days, PD-associated peritonitis due to Kocuria species may be considered a potential risk for recurrence.

The authors would like to thank Yoshihito Otsuka for his technical assistance.

Written informed consent was obtained from the patient for publication of the details of their medical case and accompanying images. This study protocol was reviewed and the need for approval was waived by the Ethics Committee of Kameda Medical Center.

The authors have no conflicts of interest to declare.

No funding was received.

M.N. wrote the first draft. M.N., H.K., T.T., T.I., A.K., M.M., J.F., M.O., and T.S. took care and advice for the patient in our conference. T.S. revised the manuscript. All authors have read and approved the final manuscript.

Data of the patient were extracted from medical records in Kameda Medical Center, Japan and so are not publicly available. Further inquiries can be directed to the corresponding author.