
==== Front
Intern Med
Intern Med
Internal Medicine
0918-2918
1349-7235
The Japanese Society of Internal Medicine

38220190
10.2169/internalmedicine.2998-23
Case Report
Successfully Treated Roseomonas mucosa-induced Peritonitis Diagnosed by Mass Spectrometry
Nariyama Tomoyuki 12
Ito Yasuko 1
Fujita Koji 3
Ito Takafumi 1
Terawaki Hiroyuki 14
1 Division of Nephrology, Department of Internal Medicine, Teikyo University Chiba Medical Center, Japan
2 Department of Nephrology, Kawanishi City Medical Center, Japan
3 Department of Laboratory, Teikyo University Chiba Medical Center, Japan
4 Clinical Laboratory Department, St. Luke's International Hospital, Japan
Correspondence to Dr.　Hiroyuki Terawaki, terawaki@med.teikyo-u.ac.jp

13 1 2024
15 8 2024
63 16 23112315
1 10 2023
26 11 2023
Copyright © 2024 by The Japanese Society of Internal Medicine
https://creativecommons.org/licenses/by-nc-nd/4.0/ The Internal Medicine is an Open Access journal distributed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License. To view the details of this license, please visit (https://creativecommons.org/licenses/by-nc-nd/4.0/).
Roseomonas mucosa is difficult to identify using routine analytical techniques. We herein report a case of peritoneal dialysis (PD)-related peritonitis caused by R. mucosa identified using matrix-assisted laser desorption/ionization-time-of-flight (MALDI-TOF) mass spectrometry (MS). A 70-year-old woman was admitted to our hospital with PD-related peritonitis. Blood agar medium of dialysate culture derived colony pale pink in color, and the organism was identified as R. mucosa using MALDI-TOF MS. She was successfully treated with ciprofloxacin and meropenem without catheter removal. To our knowledge, this is the first case of R. mucosa peritonitis in which technique failure has been avoided.

peritoneal dialysis
peritonitis
Roseomonas
mass spectrometry
MADLI-TOF
==== Body
pmcIntroduction

Peritonitis is the most common complication of peritoneal dialysis (PD) and the leading cause of withdrawal from PD (1). According to a previous national survey in Japan, Streptococcus spp. and Staphylococcus aureus (including MRSA) are the most common causes of peritonitis among Gram-positive bacteria (GPB), while the frequency of Pseudomonas aeruginosa is the highest among Gram-negative bacteria (GNB) (2). As this situation is similar in our hospital, we offer vancomycin (VCM) for GPB coverage and ceftazidime (CAZ) for GNB coverage as a first-line drug combination for empirical therapy for incident PD peritonitis.

In the case reported in this study, therapeutic resistance to the first-line drug combination was encountered, so matrix-assisted laser desorption/ionization-time-of-flight (MALDI-TOF) mass spectrometry (MS) was performed to identify the bacterial species. Roseomonas mucosa, identified using MALDI-TOF MS in this case, is a non-fermented Gram-negative glucose bacillus that lives in aquatic environments, including healthy skin. Infections caused by Roseomonas are often reported in susceptible hosts with underlying diseases, such as malignant tumors, acquired immunodeficiency syndrome, kidney failure, and diabetes. Most cases of separation of clinical specimens are from blood cultures, but there are some reported cases of wounds, exudates, abscesses, urinary materials, and peritoneal dialysate as causative organisms of PD peritonitis (3-5). Owing to the slow development of Roseomonas, it is difficult for many laboratories to identify Roseomonas at the species level, and there are few reports in which the species has been confirmed as R. mucosa.

We herein report a case of PD peritonitis caused by R. mucosa that was successfully identified with MALDI-TOF MS.

Case Presentation

A 70-year-old woman who had received 13 months of PD therapy was admitted to our hospital with a cloudy peritoneal effluent dialysate. She had started receiving continuous ambulatory PD at 69 years old for end-stage kidney disease secondary to diabetic nephropathy. Since her residual kidney function was sufficiently maintained, 1.5 L of neutral icodextrin solution (Nicoperiq, Terumo, Tokyo, Japan) was administered in 1 bag (9 am to 5 pm) per day. She visited our outpatient clinic complaining of marked cloudiness of effluent dialysate (5 pm) on the same day as admission, although there was no abdominal pain or pyrexia. The effluent dialysate test confirmed an increase in the number of neutrophil-dominant white blood cells; therefore, the patient was hospitalized with a diagnosis of PD-related peritonitis. Until this admission, she had had no history of PD-related peritonitis or catheter-related infection.

On admission, the patient was alert. Her height was 145.9 cm; weight, 57.5 kg, body temperature, 36.8°C; blood pressure, 102/68 mmHg; heart rate, 84 beats/min; and SpO2, 100% (room air). The patient had no abdominal tenderness. The exit site and catheter tunnel did not show any evidence of infection. Regarding her laboratory data at admission, the inflammatory response in peripheral blood tests was within the normal category, with a white blood cell count of 8,500 /μL and a C-reactive protein level of less than 0.3 mg/dL, suggesting that not much time had passed since the appearance of peritonitis. The number of leukocytes in the effluent dialysate was 2,500 /μL with 81.0% neutrophils. Computed tomography did not show an increase in the adipose tissue concentration around the catheter tunnel. No apparent abnormalities were detected on upper or lower gastrointestinal endoscopic examination.

A tentative diagnosis of PD peritonitis was established (6), and the patient was empirically treated with intraperitoneal administration of CAZ (1.0 g/day) and VCM (loading dose 1.75 g/bag, additional administration 1.25 g on day 4 of hospitalization) after inoculation of the last peritoneal effluent in a blood culture bottle for aerobes and anaerobes by a dialysis nurse. However, the cloudiness and high leukocyte count (neutrophil-dominant) persisted in the dialysate.

On day 5 of hospitalization, pink colonies were observed in the blood agar medium for the initial PD dialysate culture (Figure A), consisting of Gram-negative short bacilli (Figure B). Therefore, MALDI-TF MS was performed for rapid species identification, and R. mucosa was identified. Following the identification of the bacterial species, susceptibility tests were performed using the DxM Microscan WalkAway (Beckman Coulter, Tokyo, Japan). Based on the test results (Table 1), the antibiotic was changed from CAZ + VCM to oral ciprofloxacin (500 mg/day) + intravenous administration (3.0 g/day of meropenem. After the change in antibacterial drugs, the number of leukocytes in the dialysate improved to 650 /μL (neutrophil 72.0%) on day 8 and reached the normal range of 98 /μL (neutrophil 46.0%) on day 11 of hospitalization. After rehabilitation and re-education about the PD procedure, the patient was discharged on day 21 of hospitalization.

Figure 1. Roseomonas mucosa obtained from peritoneal dialysate culture in this case. (A) Gross appearance of the colonies in cultured blood agar medium. The colonies derived from the peritoneal dialysate were pale pink in color, fitting the characteristic features of Roseomonas. (B) Displayed Gram-negative coccobacilli were isolated.

Figure 2. Antibiotics treatment and the change in dialysate leukocyte count. CAZ: ceftazidime, VCM: vancomycin, MEPM: meropenem, CPFX: ciprofloxacin

Table 1. Antimicrobial Susceptibility of Cultured Roseomonas Mucosa.

Drug (name)	Minimal inhibitory concentration (μg/mL)	Susceptibility (CLSI category)	
Piperacillin	>64	Resistant	
Ceftazidime	>16	Resistant	
Cefozopran	16	Intermediate	
Cefepime	16	Intermediate	
Imipenem / Cilastatin	≤1	Susceptible	
Meropenem	≤1	Susceptible	
Aztreonam	>16	Resistant	
Cefoperazone / Sulbactam	>32	(No category)	
Piperacillin / Tazobactam	>64	Resistant	
Gentamicin	≤2	Susceptible	
Tobramycin	≤2	Susceptible	
Amikacin	≤8	Susceptible	
Minocycline	≤2	Susceptible	
Levofloxacin	≤0.5	Susceptible	
Ciprofloxacin	≤0.25	Susceptible	
Ceftriaxone	>2	Resistant	
Sulfamethoxazole / Trimethoprim	>2	Resistant	
Fosfomycin	>16	(No category)	
CLSI: Clinical and Laboratory Standards Institute

Discussion

PD-associated peritonitis is a serious complication for patients undergoing PD and is usually caused by bacterial or fungal infection. Common clinical symptoms include abdominal pain and cloudy effluent, with abdominal pain reported in 80%, a fever of ≥37.5°C in 30%, nausea and vomiting in 50%, cloudy effluent in 80%, and hypotension in approximately 20% (7). The diagnostic criteria are 1) abdominal pain and dialysis drainage opacity, which are clinical signs of peritonitis, or any other; 2) ≥100 /μL or ≥0.1×109/L white blood cells in dialysis drainage (after at least 2 h of storage) and neutrophils at ≥50%; and 3) positive culture of effluent dialysate (6).

Most cases of peritonitis are caused by bacterial infections. The causative bacteria of peritonitis are known to vary among regions, and Schaefer et al. reported a higher frequency of GNB in Argentina and Asia, half GNB and half GPB in the United States, and a higher frequency of GPB in Western and Eastern Europe, Turkey, and Mexico (8). In contrast, Prasad et al. reported 303 cases of peritonitis in northern India, and as in Europe, Turkey, and Mexico, GPB is more frequent than GNB (33.7% vs. 29.4%), and the most common bacteria are coagulase-negative Staphylococcus (23.4%) (9). Furthermore, Ghali et al. analyzed peritonitis in Australia based on registered data from the Australian and New Zealand Dialysis and Transplant Registry and found that, among 6,229 total cases of peritonitis, GPB was cultured in 53.4% and GNB in 23.6% (10). In Japan, Mizuno et al. (1) reported 561 cases in the Tokai region; GPB was more frequent than GNB (45.6% vs. 18.6%), and the leading genus was Staphylococcus (21.5%). Furthermore, a questionnaire survey of 466 cases in 114 facilities in Japan by Higuchi et al. (2) found that GPB was more frequent than GNB (57.9% vs. 24.9%). The reason for the high frequency of GNB in Argentina and Asia (except for northern India and Japan) is unclear; however, differences in hygiene conditions for drinking water and meals may be partly affected.

Antimicrobial administration for peritonitis treatment should be initiated as soon as possible after specimen collection to prevent aggravation and preserve the peritoneal function. Before the causative bacteria are identified, physician is recommended to administer antibacterial drugs that cover both GPB and GNB as empirical treatments. The 2022 International Society of Peritoneal Dialysis (ISPD) guidelines encourage the combined use of GPB coverage drugs (first-generation cephalosporin cefazolin or VCM) and GNB coverage drugs (third- and fourth-generation cephalosporins, such as CAZ or aminoglycosides) (6).

The genus Roseomonas is part of the so-called “acetic acid bacteria,” which ferment alcohol to produce acetic acid. Phylogenetically, “acetic acid bacteria” belong to the phylum Pseudomonadota-Order Alphaproteobacteri-Class Rhodospirillales-Family Acetobacteraceae. “Acetic acid bacteria” are divided into two groups: an “acetous group”, which includes the genera Acetobacter and Gluconobacter, and an “acidophilic group”, which includes the genus Roseomonas. The first report on the genus Roseomonas by Gilardi and Faur described it as “a nonfermented glucose Gram-negative bacillus of unknown lineage that produces pink pigments” (11). The formation of characteristic pink colonies on the medium is the reason this genus bears the name “rosé.” The bacteria were given the name of the new genus “Roseomonas” in 1993, at which time, based on biochemical properties and DNA hybridization, they were classified into six species: R. gilardii (genomospecies 1), R. cervicalis (genomospecies 2), R. fauriae (genomospecies 3), and R. genomospecies 4, 5, and 6 (12). Since then, many new species have been reported in the genus Roseomonas, and 37 species are recognized as of September 2023.

The genus Roseomonas is commonly found in both water and soil. R. mucosa, the causative microorganism in this case, is known as a beneficial (rather than harmful) skin-resident bacterium. Indeed, the beneficial effects of R. mucosa were found to include improving the skin barrier function, activating innate immunity, and suppressing Staphylococcus aureus in a study using atopic dermatitis model mice (13). A recent report showed that skin lesions were significantly improved by applying a mixed solution of R. mucosa and sugar water to the skin of patients with atopic dermatitis (14). Considering these situations, our present case report suggests that even beneficial skin-resident bacteria can be pathogenic if they enter the abdominal cavity. Although the path of infection in this case is unknown, considering the finding in animal experiments that bacterial translocation (transfer of bacteria from the intestinal tract to the blood and lymph nodes) is likely to occur in a uremic environment (15), the possibility of bacterial translocation as a route of peritoneal infection cannot be ruled out. Of course, the possibility of touch contamination must be taken into account, as R. mucosa is commonly found in water and soil and on normal skin, as described above.

According to a PubMed search, three cases of PD peritonitis caused by R. mucosa have been reported worldwide (3-5), making the present case the fourth. The outlines of these four cases are summarized in Table 2. Since ciprofloxacin has been administered in three cases, including ours, it is believed to be effective for peritonitis in PD patients caused by R. mucosa as a rule.

Table 2. Summary of Four Cases Reported to have Roseomonas Mucosa> Peritonitis with Outcome.

Reference	Patient age/gender	Patient primary CKD	Study country	Dialysis modality	Method to identify
R. mucosa	Treatment received	Outcome	Modality changed	
3	19/M	HIV-related nephritis	USA	CCPD	16S rRNA gene sequencing	IP ceftazidime and then IP ciprofloxacin	Resolved	Yes, to HD	
4	61/M	Diabetic nephropathy	Japan	CAPD	16S rRNA gene sequencing	IP ceftazidime and then IP ciprofloxacin	Resolved	Yes, to HD	
5	65/F	(no description)	USA	CCPD	MALDI-TOF MS	IP vancomycin plus aztreonm and then IP gentamicin	Resolved	Yes, to HD	
(Our case)	70/F	Diabetic nephropathy	Japan	CAPD	MALDI-TOF MS	IP vancomycin plus IP ceftazidime and then IP meropenem and PO ciprofloxacin	Resolved	No	
M: male, F: female, HIV: human immunodeficiency virus, USA: the United States of America, IV: intravenous, PO: per oral, CAPD: continuous ambulatory peritoneal dialysis, CCPD: continuous cycler peritoneal dialysis, HD: hemodialysis

It should be noted that this is the first case of R. mucosa peritonitis in which technique failure was avoided by rapid detection of R. mucosa using MALDI-TOF MS. MALDI-TOF MS is a method for identifying microorganisms established on the technology “Desorption ionization Method for Mass Spectrometry of Biopolymers” developed by Dr. Koichi Tanaka (Shimadzu, Kyoto, Japan), who won the Nobel Prize in Chemistry in 2002. Using this method, by comparing findings to previously reported bacterial species, it is possible to identify the bacterial strain in only about 5 min. As an example of the improvement in culture results with the introduction of MALDI-TOF MS, Table 3 shows a comparison before and after the introduction of the MALDI Biotyper (Bruker Daltonics Japan, Yokohama, Japan) for MALDI-TOF MS in cadaveric blood culture results at the author's facility (Clinical Laboratory Department, St. Luke's International Hospital, Tokyo, Japan). With the widespread use of MALDI-TOF MS, the diagnosis of R. mucosa infection will be facilitated, and the true frequency and clinical significance of R. mucosa peritonitis will be able to be clarified.

Table 3. Comparison of the Positive Rate and the Number of Idenfified Organisms on Agonal Blood Culture before and after the Introduction of MALDI-TOF MS* (4 Cases/3 Months, Each).

Use of MALDI-TOF MS*	Positive for postmortum blood culture (Any microorganism)	Number of identified organisms	
No	3/4 (75%)	0 in 1 case 1 in 3 cases	
Yes	4/4 (100%)	1 in 2 cases 3 in 2 cases	
*Matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry.

The authors state that they have no Conflict of Interest (COI).
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