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Journal of Clinical Microbiology, March 2001, p. 1202-1203, Vol. 39, No. 3
0095-1137/01/$04.00+0   DOI: 10.1128/JCM.39.3.1202-1203.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.

Case of Synovitis Potentially Caused by Dolosigranulum pigrum

Departments of Clinical Pathology¹ and Infectious Diseases,² Cleveland Clinic Foundation, Cleveland, Ohio 44195-5140

Received 21 August 2000/Returned for modification 23 October 2000/Accepted 8 December 2000

	ABSTRACT

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We report a case of synovitis in a 64-year-old man who developed the infection while on steroid therapy for rheumatoid arthritis. Dolosigranulum pigrum, a gram-positive catalase-negative coccus, was isolated from two sets of blood cultures prior to antibiotic therapy. The patient was treated with 4 weeks of appropriate antibiotics, and the synovial inflammation resolved. Although synovial aspirates were never positive for any bacteria or fungi, the timing of positive blood cultures and absence of other pathogens suggest the possible etiology as D. pigrum.

	CASE REPORT

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A 64-year-old male with rheumatoid arthritis requiring weekly methotrexate (7.5 mg once a day) and daily prednisone (5 mg/week) to control synovitis presented to the outpatient clinic with a 4-day history of pain and swelling in both wrists, metacarpal joints, and the left ankle. He also reported some nausea, fevers, and night sweats. Examination was remarkable for an oral temperature of 37.7°C and a warm, tender left ankle. Attempt of ankle aspiration was unsuccessful in obtaining synovial fluid. Laboratory studies revealed a white blood cell count of 7,180 cells/µl, a hemoglobin level of 12.3 mg/dl, a Westergren sedimentation rate of 91 mm/h, and C-reactive protein level of 15 mg/dl. Two sets of blood cultures drawn from two different peripheral sites were positive for gram-positive cocci in clusters. The Streptococcus Lab at the Centers for Disease Control and Prevention (CDC), Atlanta, Ga., eventually identified these organisms as Dolosigranulum pigrum. The patient was admitted to the hospital for presumed septic arthritis and started on cefazolin (1 g every 8 h). Synovial fluid was obtained from the left ankle and right wrist on hospital day 2. The fluid was yellow and turbid with 86,625 white blood cells, 83% of which were neutrophils; the fluid was negative for crystals, and cultures remained negative for bacteria and fungi. A transthoracic echocardiogram, performed to rule out infective endocarditis, did not reveal vegetations or regurgitation. The patient received a total of 4 weeks of antibiotics (2 weeks of parenteral cefazolin and 2 weeks of oral dicloxacillin), with resolution of the synovial inflammation.

Organism. The two blood cultures (Organon Teknika BacT/Alert aerobic and anaerobic FAN bottles) were positive within the first 24 h of incubation. Gram staining of the fluid demonstrated gram-positive cocci in tight clusters, resembling staphylococci. Isolation on blood agar produced small greyish-white alpha-hemolytic colonies. The organism was catalase negative, L-pyrrolidonyl--naphthylamide (PYR) positive, leucine aminopeptidase (LAP) positive, and hippurate weakly positive. No growth occurred on bile esculin medium, but the organism did grow in 6.5% NaCl. Serologic tests for Streptococcus groups A, B, C, D, F, and G were negative. Biochemical testing gave negative results for production of urease, esculin hydrolysis, and motility. There was no activity in a wide variety of Andrade's sugars. There was a large zone of inhibition around penicillin and vancomycin disks. The isolate was submitted to the Streptococcus Lab of the CDC for further identification. In addition to the tests performed in our lab, the CDC obtained weakly positive results for tellurite and a positive esculin hydrolysis, bacitracin resistance, production of neither levans nor dextrans on 5% sucrose agar, and an arginine dihydrolase negative reaction. They identified the organism as Dolosigranulum pigrum.

A MIC tray containing Mueller-Hinton broth supplemented with lysed horse blood was inoculated to determine susceptibility of the isolate, with the following results: penicillin, 0.06 µg/ml; clindamycin, 0.03 µg/ml; ceftriaxone, 0.25 µg/ml; cefuroxime, 0.12 µg/ml; amoxicillin, 1.0 µg/ml; trimethoprim-sulfamethoxazole, 0.5/10 µg/ml; erythromycin, 0.5 µg/ml; and tetracycline, 1.0 µg/ml. Using the NCCLS breakpoints for these agents versus Streptococcus spp. or S. pneumoniae specifically, all of these results would be interpreted as susceptible except for the result for erythromycin, which would be interpreted as nonsusceptible. The breakpoints for erythromycin are 0.25 µg/ml (susceptible) and 1.0 µg/ml (resistant).

D. pigrum was described in 1993 (1) as a new genus of the lactic acid bacteria with a low G+C content. The phenotypic characteristics of the organism were felt originally to be those of Gemella spp., but no cross-reactivity was observed with specific anti-G. haemolysans or anti-G. morbillorum antibodies. In addition, the cell wall peptidoglycans proved to be different from those of Gemella spp. Sequencing of the 16S rRNA verified the new phylogenetic position. The most consistent characteristics of D. pigrum appear to be PYR positivity, LAP positivity, NaCl positivity, esculin hydrolysis positivity, and clusters of gram-positive cocci that are catalase negative with gamma or alpha hemolysis. Although initially our isolate appeared to be negative for esculin hydrolysis, it was found to be esculin positive by the CDC. Upon repeat testing in our lab, the isolate remained negative, but we only held the esculin tube for 5 days before reporting the results as negative. Approximately 85% of D. pigrum isolates at CDC are esculin positive, some requiring as long as 2 weeks of incubation. These isolates should, however, be identified correctly if they fit the characteristics mentioned above, regardless of the esculin reaction (Richard Facklam, personal communication).

There are rare reports of this organism causing clinical disease in humans. The first isolate was recovered from frozen spinal cord tissue removed at autopsy from a patient with multiple sclerosis; a second isolate was recovered from the contact lens and eye swab cultures of a woman with blurred vision and discomfort. LaClaire and Facklam (2) have recently reported on the clinical sources of 27 isolates of D. pigrum sent to the CDC. In addition to the two cases described above, there have been five cases of sepsis and seven additional blood culture isolates from other patients whose clinical conditions were unknown. There are no reports of the organism causing synovitis. Our report is of the association of Dolosigranulum with synovitis. The organism was not isolated from the synovial fluid, but the patient was treated appropriately 24 h before the aspiration. The isolation of a catalase-negative, alpha-hemolytic gram-positive coccus in clusters that is positive for PYR, LAP, and growth in NaCl should raise suspicion of a variety of genera, including Dolosigranulum, Alloiococcus, Facklamia, and Ignavigranum (1, 2, 3). A positive esculin hydrolysis test may aid in differentiating D. pigrum from the other three genera. It is difficult to further identify such organisms unless conventional biochemical methods are employed, since commercial systems may not include these genera in their databases (4).

	ACKNOWLEDGMENTS

We are thankful to the CDC for their assistance in the identification of this isolate.

	FOOTNOTES

^* Corresponding author. Mailing address: Clinical Microbiology, L-40, Cleveland Clinic Foundation, Department of Clinical Pathology, 9500 Euclid Ave., Cleveland, OH 44195-5140. Phone: (216) 444-5990. Fax: (216) 445-6984. E-mail: hallg{at}ccf.org.

	REFERENCES

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1.	Aguirre, M., D. Morrison, B. D. Cookson, F. W. Gay, and M. D. Collins. 1993. Phenotypic and phylogenetic characterization of some Gemella-like organisms from human infections: description of Dolosigranulum pigrum gen. nov., sp. nov. J. Appl. Bacteriol. 75:606-612.
2.	LaClaire, L., and R. Facklam. 2000. Antimicrobial susceptibility and clinical sources of Dolosigranulum pigrum cultures. Antimicrob. Agents Chemother. 44:2001-2003[Abstract/Free Full Text].
3.	LaClaire, L., and R. Facklam. 2000. Comparison of three commercial rapid identification systems for the unusual gram-positive cocci Dolosigranulum pigrum, Ignavigranum ruoffiae, and Facklamia species. J. Clin. Microbiol. 38:2037-2042[Abstract/Free Full Text].
4.	Miller, P. H., R. R. Facklam, and J. M. Miller. 1996. Atmospheric growth requirements for Alloiococcus species and related gram-positive cocci. J. Clin. Microbiol. 34:1027-1028[Abstract].

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