Skip to main content

Rhodococcus induced false-positive galactomannan (GM), a biomarker of fungal presentation, in patients with peritoneal dialysis: case reports

Abstract

Background

Galactomannan index (GMI) at a level higher than 0.5 provides high sensitivity and specificity for the diagnosis of fungal peritonitis. Here, we report the false-positive of GMI in peritoneal dialysis (PD) effluent (PDE) due to Rhodococcus peritonitis in PD patients.

Case presentation

GMI in PDE of case #1 and case #2 were 1.53 and 0.76, respectively, while serum GMI of both cases was less than 0.5. In addition, GMI from the specimens obtained directly from the stationary phase of Rhodococcus colonies were 1.27 and 1.56, which were isolated from case #1 and #2, accordingly.

Conclusion

High GMI in PDE of PD patients is not specific just for fungal infections but may also be secondary to other infections, such as Rhodococcus spp., especially in endemic areas.

Peer Review reports

Background

Fungal peritonitis is a relatively uncommon but serious complication of peritoneal dialysis (PD) and is associated with a high risk of technique failure and mortality, especially in cases of delayed diagnosis. The galactomannan (GM) test is an easier technique for the detection of fungal cell wall components shedding out of the fungi during fungal growth and death [1]. Indeed, GM index (GMI), analyzed by a sandwich-ELISA (Bio-Rad Platelia™, USA), has been widely used for the diagnosis of systemic fungal infection [2] and has been recently proposed as an alternative marker of fungal peritonitis [3]. Despite the high sensitivity and specificity of GMI in PD effluent (PDE) for the diagnosis of fungal peritonitis [3] and fungal colonization inside a PD catheter [4], we reported a false-positive GMI in PDE from patients infected with Rhodococcus spp. There were 2 patients with rhodococcal infection who had orange stains inside their PD catheters. Both cases were mistakenly diagnosed as fungal peritonitis and resulting in initial treatment failure.

Case presentation

Case #1 was a 71 year-old man with diabetic end-stage renal disease (ESRD) who was performing continuous ambulatory PD (CAPD) at Sunpasitthiprasong Hospital since 2013. On 30 July 2017 (day 0), he presented with acute abdominal pain and cloudy dialysate associated with a normal exit-site. The diagnosis of peritonitis was confirmed with a PDE leukocyte count of 2900 cells/μL of which 91% were neutrophils. The empirical therapy for bacterial peritonitis with intraperitoneal (IP) cefazolin 1 g together with ceftazidime 1 g IP once daily was commenced. Although the dialysate leukocyte gradually decreased, the leukocyte persisted at more than 100/μL with neutrophil predominance. The dialysate from day 0 failed to culture any organism. However, many orange spots were noticed inside the PD catheter on day + 8. GMI in the PDE and the sera were 1.53 (normal< 0.5) and 0.39 (normal< 0.5), respectively. The provisional diagnosis of fungal peritonitis was made. Intravenous amphotericin B, 0.5 mg/kg/day was promptly started on the following day (day + 9), and the PD catheter was subsequently removed on day + 11. The PD catheter, serum, and drained PDE were submitted to the central microbiology lab for microorganism identification. The patient was transferred to hemodialysis (HD) following PD catheter removal. The patient continued to improve while having intravenous (IV) amphotericin and ceftazidime that were prescribed for a total of 2 weeks.

Case #2, a 59 year-old man with a past medical history of diabetes and hypertension, was diagnosed with ESRD from diabetes. He commenced CAPD (4 exchanges/day) in January 2017 at Nakhon Pathom Hospital. While performing CAPD, he was able to maintain adequate dialysis small solute clearance and had never experienced peritonitis. On 16 January 2018 (day 0) the patient presented with cloudy dialysate, abdominal pain, poor appetite, and ultrafiltration failure, associated with a normal exit-site. The PDE cell count was 497 cells/μL with a neutrophil predominance (63%). He was initially diagnosed with CAPD-related peritonitis and received a combination of IP cefazolin and ceftazidime on the same day resulting in partial resolution of the abdominal pain. However, the PDE leukocyte count that was repeated on day + 3 indicated an increased count of 2080 cells/μL (85% neutrophils), while the dialysate culture from day 0 later yielded Corynebacterium spp. The primary physician swapped the antibiotics to IV vancomycin, 1 g every 3 days, and IP amikacin, 25 mg loading dose followed by 12 mg once daily for a total duration of 2 weeks. During the follow-up period, salmon-pink colonies were observed inside the PD catheter and GMI in PDE from day + 10 was later reported positive at a level of 0.76 (< 0.5). Superimposed fungal peritonitis was suspected, although IP amphotericin B was added on day + 13, and the PD catheter was removed on day + 16. Amphotericin was later withdrawn after a return of culture report from the central microbiology lab on day + 19 demonstrated Rhodococcus equi. Temporary HD was performed during day + 17 to day + 56. The PD catheter was reinserted on day + 58, and the patient has remained well on CAPD without any subsequent peritonitis.

At the central microbiology lab, the removed catheters and the PDE were submitted for culture in several media. Interestingly, the orange colonies on tryptic soy agar (TSA) and chocolate agar were observed at 72 h, but no colony growth on SDA (Fig. 1). Rhodococcus spp. and Rhodococcus equi was identified by modified AFB and the biochemistry assay from case #1 and #2, respectively. The GMI in the specimens obtained directly from colonies of Rhodococcus were 1.27 (Case #1) and 1.58 (case #2), which were above the cut-off value (≥ 0.5) using a GM test kit (Bio-Rad Platelia™, USA).

Fig. 1
figure1

The orange stains on (a) PD catheter. b Modified acid-fast stain of TS catheter specimen depicts numerous microorganisms. The orange colony was grown on (c) Blood agar, and (d) chocolate agar after 72 h. Fungal co-infection was excluded by various fungal primers, including ITS (E1), 28S (E2), and 18S (E3) primers. Abbreviations: NC, negative control; PC, positive control

Discussion and conclusion

Rhodococcus, a gram-positive filamentous bacteria which belongs to phylum Actinobacteria, causes disease only in immune-compromised hosts [5]. This organism can survive in various habitats such as terrestrial (soil) and aquatic environments (fresh and saltwater) [6, 7]. Fungal co-infection was excluded from the presented cases using both fungal culture and PCR with universal fungal primers (16S, 28S, and ITS) (Fig. 1e). Although Rhodococcus is sensitive to several antibiotics [6], early catheter removal was performed in both cases because of the misdiagnosis of fungal peritonitis by the primary physicians. The ISPD Guideline 2016 recommends an immediate PD catheter removal when fungi are identified [8]. Thailand has a high incidence of culture-negative peritonitis, particularly in provincial hospitals. The false-positive GMI caused by this infection has never been mentioned despite the reported lower sensitivity and specificity for the GM test (77 and 58% respectively) [3].

The cell envelop of the Rhodococcus does not express GM, it contains a substantial amount of arabinogalactan [AG: a linear galactan of galactofuranose (Galf) residues + discrete arabinan side branches which contain arabinofuranoses) and lipoarabinomannan (LAM: lipoglycan core + mannan side chains) of which both are bound to branched long-chain lipids termed mycolic acids. The galactan of R. equi contains a mixture of (1 → 3), (1 → 5), and (1 → 6) linkages [7]. On the other hand, GM found in pathologic filamentous fungi is a hetero-polysaccharide consisting of a linear-mannan core with a repeating tetramannose unit (2 M–6 M-2 M-2 M) and its side chains (4–5 residues of β-(1 → 5)-Galf attached to mannose) [9, 10]. Both organisms contain β-(1 → 5)-Galf which is a target for the immune system and monoclonal antibody using in the commercial GM test kits (Bio-Rad Platelia™, USA and Pastorex Aspergillus™, Diagnostic Pasteur, France) [9, 10]. However, the Galf is located in a different strand of carbohydrate heteropolymer where filamentous mold is on the side chain of GM while the Rhodococcus is on the backbone of AG [9].

Since there are very few case reports of rhodococcal peritonitis, experiences of the preferred treatment are limited. A combination of antibiotics is the mainstay of treatment, especially antibiotics with intracellular activity against the organism. Although Rhodococcus is initially sensitive to cephalosporins, it is not recommended in clinical practice because of the potential development of late resistance [11]. The duration of treatment in immunocompetent patients may range from 2 to 8 weeks or even longer depending upon the severity of the disease [12]. Removal of the PD catheter should be considered in Rhodococcus peritonitis due to the unpredictable response of this organism to treatment [13]. Our 2 cases demonstrated the success of management of Rhodococcus peritonitis with 2 weeks of antibiotics combined with the PD catheter removal. Case #2 was treated with IP vancomycin plus amikacin. Meanwhile, case #1 was successfully treated by IP ceftazidime. The Rhodococcus infections in both of these cases either responded to the empirical treatment or PD catheter removal.

In conclusion, false-positive GMI results may occur with Rhodococcus infection. Thus, various culture media and polymerase chain reaction should be used to confirm the results of high GMI in PDE, especially in endemic areas of rhodococcal infection.

Availability of data and materials

The data that support the findings of this study are available from the corresponding author upon reasonable request.

Abbreviations

AFB:

Acid-fast stain

AG:

Arabinogalactan

CAPD:

Continuous ambulatory peritoneal dialysis

ESRD:

End-stage renal disease

GM:

Galactomannan

GMI:

Galactomannan index

HD:

Hemodialysis

IP:

Intraperitoneal

ISPD:

International Society for Peritoneal Dialysis

IV:

Intravenous

LAM:

Lipoarabinomannan

PCR:

Polymerase chain reaction

PD:

Peritoneal dialysis

PDE:

Peritoneal dialysis effluent

SDA:

Sabouraud dextrose agar

TSA:

Tryptic soy agar

References

  1. 1.

    Wingard JR. Have novel serum markers supplanted tissue diagnosis for invasive fungal infections in acute leukemia and transplantation? Best Pract Res Clin Haematol. 2012;25(4):487–91.

    CAS  Article  Google Scholar 

  2. 2.

    Hachem RY, Kontoyiannis DP, Chemaly RF, Jiang Y, Reitzel R, Raad I. Utility of galactomannan enzyme immunoassay and (1,3) β-D-Glucan in diagnosis of invasive fungal infections: low sensitivity for aspergillus fumigatus infection in hematologic malignancy patients. J Clin Microbiol. 2009;47(1):129–33.

    CAS  Article  Google Scholar 

  3. 3.

    Worasilchai N, Leelahavanichkul A, Kanjanabuch T, Thongbor N, Lorvinitnun P, Sukhontasing K, et al. (1→3)-β-D-glucan and galactomannan testing for the diagnosis of fungal peritonitis in peritoneal dialysis patients, a pilot study. Med Mycol. 2015;53(4):338–46.

    CAS  Article  Google Scholar 

  4. 4.

    Leelahavanichkul A, Pongpirul K, Thongbor N, Worasilchai N, Petphuak K, Thongsawang B, et al. (1→3)-β-D-Glucan and Galactomannan for a differentiation of chemical “black particles” and fungal particles inside peritoneal Dialysis tubing. Perit Dial Int. 2015;36:402–9.

    Article  Google Scholar 

  5. 5.

    Navarro-Llorens JM, Patrauchan MA, Stewart GR, Davies JE, Eltis LD, Mohn WW. Phenylacetate catabolism in Rhodococcus sp. strain RHA1: a central pathway for degradation of aromatic compounds. J. Bacteriol. 2005;187(13):4497–504.

    CAS  Article  Google Scholar 

  6. 6.

    Riesenberg A, Feßler AT, Erol E, Prenger-Berninghoff E, Stamm I, Böse R, et al. MICs of 32 antimicrobial agents for Rhodococcus equi isolates of animal origin. J Antimicrob Chemother. 2014;69(4):1045–9.

    CAS  Article  Google Scholar 

  7. 7.

    Daffe M, McNeil M, Brennan PJ. Major structural features of the cell wall arabinogalactans of Mycobacterium, Rhodococcus, and Nocardia spp. Carbohydr Res. 1993;249(2):383–98.

    CAS  Article  Google Scholar 

  8. 8.

    Li PK, Szeto CC, Piraino B, de Arteaga J, Fan S, Figueiredo AE, et al. ISPD peritonitis recommendations: 2016 update on prevention and treatment. Perit Dial Int. 2016;36(5):481–508.

    Article  Google Scholar 

  9. 9.

    Stynen D, Sarfati J, Goris A, Prevost MC, Lesourd M, Kamphuis H, et al. Rat monoclonal antibodies against Aspergillus galactomannan. Infect Immun. 1992;60(6):2237–45.

    CAS  PubMed  PubMed Central  Google Scholar 

  10. 10.

    Van Cutsem J, Meulemans L, Van Gerven F, Stynen D. Detection of circulating galactomannan by Pastorex Aspergillus in experimental invasive aspergillosis. Mycoses. 1990;33(2):61–9.

    Article  Google Scholar 

  11. 11.

    Giguere S, Lee EA, Guldbech KM, Berghaus LJ. In vitro synergy, pharmacodynamics, and postantibiotic effect of 11 antimicrobial agents against Rhodococcus equi. Vet Microbiol. 2012;160(1–2):207–13.

    CAS  Article  Google Scholar 

  12. 12.

    Kedlaya I, Ing MB, Wong SS. Rhodococcus equi infections in immunocompetent hosts: case report and review. Clin Infect Dis. 2001;32(3):E39–46.

    CAS  Article  Google Scholar 

  13. 13.

    Tang S, Lo CY, Lo WK, Ho M, Cheng IK. Rhodococcus peritonitis in continuous ambulatory peritoneal dialysis. Nephrol Dial Transplant. 1996;11(1):201–2.

    CAS  Article  Google Scholar 

Download references

Acknowledgments

We are special thanks to Ms. Margaret Clarke for her language guidance and Neil Boudville, M.D., Medical School, University of Western Australia, Perth, Australia for full language support.

Funding

This study is supported by the Ratchadaphiseksomphot Endorsement Fund (CU-GRS_60_12_30_05), Chulalongkorn University, Thailand, The National Research Council of Thailand (156/2560), and Thailand Research Foundation (TRF), Thailand (IRG5780017).

Author information

Affiliations

Authors

Contributions

TC and TK contributed to the study design. WM, NT, and BJ collected data during the study. TC, WM, AL, KT, and TK developed the first draft of the manuscript which was then reviewed and intensively revised by the other authors. TK and AL revised accordingly and responded to the reviewers. All authors read and approved the final manuscript.

Corresponding author

Correspondence to Talerngsak Kanjanabuch.

Ethics declarations

Ethics approval and consent to participate

Not applicable.

Consent for publication

The patient provided written informed consent to this case’s publication.

Competing interests

The authors declare that they have no competing interests.

Additional information

Publisher’s Note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Rights and permissions

Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Chamroensakchai, T., Manuprasert, W., Leelahavanichkul, A. et al. Rhodococcus induced false-positive galactomannan (GM), a biomarker of fungal presentation, in patients with peritoneal dialysis: case reports. BMC Nephrol 20, 445 (2019). https://doi.org/10.1186/s12882-019-1642-1

Download citation