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Journal of Clinical Microbiology, December 2008, p. 4106-4108, Vol. 46, No. 12
0095-1137/08/$08.00+0 doi:10.1128/JCM.01179-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.
| CASE REPORT |

Division of Infectious Diseases, Department of Medicine,1 Hand and Upper Extremity Service, Department of Orthopaedic Surgery,2 Division of Plastic and Reconstructive Surgery, Department of Surgery,3 Department of Pathology,4 Division of Infectious Diseases and Laboratory of Developmental Immunology, Department of Pediatrics, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts5
Received 21 June 2008/ Returned for modification 28 July 2008/ Accepted 24 September 2008
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On examination, the patient was afebrile and had right middle finger symmetric edema, partial flexion contractures of both the distal and proximal interphalangeal joints, and mild tenderness to palpation along the flexor tendon sheath. There was no crepitus or fluctuance to suggest an abscess, and the patient was hemodynamically stable. His white blood cell count and erythrocyte sedimentation rate were within normal limits. In light of his unremitting symptoms, radiologic studies were obtained. Plain roentgenograms of the right hand did not show bone displacement or foreign bodies. Magnetic resonance imaging of the right hand showed a very small fluid collection within the affected tendon and overlying inflammation of the flexor tendon of the third digit that prompted operative debridement. Using a volar incision from the distal phalanx to the carpal tunnel, the flexor tendon sheath was exposed and resected. There was extensive synovitis that affected not only the tendons and the sheath but also the A1, A3, and A5 pulleys. Fibrinous gelatinous material was debrided from the deep and superficial middle finger flexors with complete excision of the A1 and A3 pulleys and partial excision of the A5 pulley. The A2 and A4 pulleys were preserved to avoid bowstringing of the tendon. A foreign body was removed. The wound and flexor tendons were thoroughly irrigated, and they were closed with absorbable sutures. Deep wound samples obtained in the operating room revealed a moderate number of polymorphonuclear cells but no organisms on Gram staining.
Aerobic and anaerobic cultures from the deep surgical site and tendon sheath grew multiple types of gram-positive rods. Two different colony types of Bacillus species were isolated, which were both susceptible to trimethoprim-sulfamethoxazole (MICs of <0.25 and <4.8 µg/ml, respectively), ciprofloxacin (MIC = 0.12 µg/ml), and vancomycin (MIC = 4 µg/ml) and resistant to penicillin G (MIC > 32 µg/ml), when tested using CLSI guidelines and interpretive breakpoints for Bacillus spp. (1). Interpretive breakpoints for Bacillus and linezolid are not available, but the isolates had MICs of 0.5 µg/ml to linezolid, suggesting susceptibility based on CLSI interpretive breakpoints for either Corynebacterium spp. or Staphylococcus. Another isolate had yellow pigment on blood agar and was found to be catalase positive and motile (9). This second isolate was identified as Cellulosimicrobium cellulans by using the API Coryne strip (bioMérieux, Durham, NC). The identification of this organism was 99.9% according to the manufacturers' database (Table 1). Preliminary identification was a Corynebacterium sp. and initially considered to be a contaminant; therefore, only a limited number of antibiotics were selected for susceptibility testing. When the treating physicians became aware that C. cellulans was the final identification, the organism was no longer available for rifampin susceptibility testing or 16S rRNA gene testing, which would have been instructive. The organism had MICs of <0.25 and <4.8 µg/ml, respectively, to trimethoprim-sulfamethoxazole, an MIC of 1 µg/ml to linezolid, an MIC of 0.5 µg/ml to vancomycin, and an MIC of 8 µg/ml to ciprofloxacin by using CLSI testing method guidelines for Corynebacterium spp. (1). It also appeared to be resistant to cefazolin (no zone around the disk). An acid-fast smear, a mycobacterial culture, and a fungal culture were negative.
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View this table: [in a new window] |
TABLE 1. Comparison of clinical isolate characteristics to Cellulosimicrobium cellulans ATCC 27402 (API Coryne reference strain) and Cellulomonas hominis
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This case of pyogenic tenosynovitis produced all four symptoms and signs classically associated with this clinical entity, as follows: symmetric digital edema, flexed posture of the affected digit, tenderness to palpation along the flexor tendon sheath, and pain with extension of the distal interphalangeal and proximal interphalangeal joints (5). Pyogenic tenosynovitis often results from the introduction of foreign material at the flexor crease where the tendon sheath is most superficial, but it can also be a complication of paronychia in children (4) and hematogenous Neisseria gonorrhoeae spread in adults (6). Bacillus spp. have been described previously as a cause of pyogenic tenosynovitis (4), whereas Cellulosimicrobium cellulans has not previously been causally implicated.
Cellulosimicrobium cellulans, formerly known as Oerskovia xanthineolytica, inhabits soil and is a rare human pathogen that has been associated with indolent foreign-body-associated infections. This bacterium is a gram-positive bacillus in the suborder Micrococcineae that was recently reclassified based on 16S rRNA gene sequences (8). Like Nocardia, this organism is gram-positive, and temporary mycelia break up into rod-shaped forms (3). Microbiologic identification of this organism is difficult, especially since it is rarely encountered in clinical samples. There have been case reports of Oerskovia xanthineolytica causing soft tissue infection in normal hosts (3). Distinguishing invasive gram-positive rods from presumed nonpathogenic commensals that may contaminate culture samples can be difficult, but in our case, the extensive gelatinous necrosis and isolation of two potential pathogens from a surgically obtained specimen strongly supported the diagnosis of pyogenic flexor tenosynovitis. Furthermore, the clinical failure of cephalexin in this case microbiologically correlates to the resistance of the Cellulosimicrobium cellulans isolate to cefazolin. Although 16S rRNA gene data would have provided stronger evidence for a causative pathogenic role of Cellulosimicrobium cellulans, this clinical case meets five of the six criteria that have been cited to establish an association between coryneform bacteria and disease (3).
Optimal therapy for Cellulosimicrobium cellulans infection generally involves removal of the foreign body in addition to antibiotic therapy. In vitro studies have shown that this organism is intrinsically resistant to penicillins, cephalosporins, aminoglycosides, and macrolides (8). A course of vancomycin or vancomycin in combination with rifampin alongside removal of the foreign body has been successful in the small number of reported cases (7, 8, 10).
In conclusion, optimal management of pyogenic wound infections that complicate penetrating hand injuries should include early debridement, removal of foreign bodies, and comprehensive microbiologic evaluation. Prompt invasive surgical debridement is essential in such cases, especially in light of the long-term functional problems associated with pyogenic flexor tenosynovitis. We evaluated a 5-year-old child following a penetrating hand injury and diagnosed an indolent polymicrobial pyogenic flexor tenosynovitis associated with Bacillus spp. and Cellulosimicrobium cellulans, a rare saprophytic pathogen that may have been overlooked if the isolate had not been further identified. This case underlines the importance of final identification of diphtheroids since the C. cellulans was initially misidentified as a diphtheroid. The child's pain and function both improved with surgical debridement and a prolonged course of trimethoprim-sulfamethoxazole and rifampin. This is the first report of a case of flexor sheath tenosynovitis associated with Cellulosimicrobium cellulans, a human pathogen with increasing clinical relevance.
M.F. is on the Scientific Advisory Board for bioMérieux.
Published ahead of print on 1 October 2008. ![]()
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