Sphingomonas mucosissima Bacteremia in Patient with Sickle Cell Disease

To the Editor: The genus Sphingomonas was proposed by Yabuuchi et al. in 1990 (1) and amended by Takeuchi et al. in 1993 (2). It now has been subdivided into 4 separate genera: Sphingomonas sensu stricto, Sphingobium, Novosphingobium, and Sphingopyxis. The bacteria of the genus Sphingomonas are yellow-pigmented, nonfermenting, gram-negative bacilli with a single polar flagellum; they are widely distributed in the natural environment, especially in water and soil (3). These bacteria are characterized by the presence of a unique sphingoglycolipid with the long-chain base—dihydrosphingosin, ubiquinone 10 (Q-10), and 2-hydroxymyristic acid (2-OH C14:0)—and the absence of 3-hydroxy fatty acids (4). S. mucosissima was isolated and identified in 2007 by Reddy and Garcia-Pichel from biologic soil crust samples collected from sandy arid soil in the US Colorado Plateau (5). Sphingomonas spp. are opportunistic pathogens and have recently been implicated in a variety of community-acquired and nosocomial infections, considered to originate from contaminated hospital equipment or manipulation of some medical devices (3). The survival of Sphingomonas spp. in indoor dust particles as aerosols and their resistance to many disinfecting and toxic chemicals may explain their ability to colonize medical devices such as mechanical ventilators, catheters, and bronchofiberoscopes (6). In the past few years, these organisms, in particular S. paucimobilis, have been implicated in a variety of community-acquired and nosocomial infections. 
 
We report a case of S. mucosissima bacteremia in a patient with sickle cell disease. In February 2008, a 17-year-old woman with homozygous sickle cell anemia was hospitalized when her condition suddenly became worse. The patient had undergone a splenectomy in 1992 and a cholecystectomy in February 2007. Four days after admission, she had a fever of 38.7°C. Two aerobic blood specimens, drawn on the fifth day of her hospitalization, yielded gram-negative bacilli after a 24-hour incubation. The gram-negative bacilli were positive for catalase and oxidase but remained unidentified by API 20NE strip (bioMerieux, Marcy l’Etoile, France). MICs of antimicrobial drugs were determined for the gram-negative bacilli by using an Etest assay (AB BIODISK, Solna, Sweden) on Mueller-Hinton medium. MICs were 1 μg/mL for cefotaxime, 1 μg/mL for amoxicillin–clavulanic acid, 2–3 μg/mL for vancomycin, 0.064 μg/mL for imipenem, 4–5 μg/mL for ceftazidime, 1 μg/mL for amikacin, 3 μg/mL for ciprofloxacin, and 0.047 μg/mL for trimethoprim-sulfamethoxazole. 
 
DNA was extracted from 1 colony by using a QIAamp Tissue kit (QIAGEN, Hilden, Germany) as described by the manufacturer. A 16S rDNA sequence was obtained (1,410 bp) by using the fD1 (5′-AGAGTTTGATCCTGGCTCAG-3′) and rP2 (5′-ACGGCTACCTTGTTACGACTT-3′) primer pair (7,8). Using BLAST version 2.2.9 software (www.ncbi.nlm.nig.gov/BLAST), we determined that this sequence showed 98% similarity with the 16S rDNA sequence of S. mucosissima (GenBank accession no. {"type":"entrez-nucleotide","attrs":{"text":"AM229669","term_id":"87080454","term_text":"AM229669"}}AM229669). A phylogenetic neighbor-joining tree resulting from comparison of sequences of the 16S rDNA genes of Sphingomonas spp. was made with the MEGA 3.1 software (www.megasoftware.net). This analysis confirmed that the isolate belonged to S. mucosissima. 
 
Initial treatment of intravenous administration of ceftriaxone was begun. The fever resolved after 1 day and the patient’s condition improved. Treatment was stopped after 5 days, and the patient remained apyretic. Two S. mucosissima isolates were recovered from 2 different blood-culture samples drawn 24 hours apart, which suggests that S. mucosissima was not just a transient organism but indeed was responsible for the patient’s septicemia. Phenotypic identification of the gram-negative bacilli failed because the definite bacterial species S. mucosissima was not included in the API database (http://industry.biomerieux-usa.com/industry/food/api/apiweb.htm) used for the phenotypic identification. However, the isolates’ biochemical characteristics were consistent with those previously reported for S. mucosissima (5) (Table). Final identification was achieved by comparing the almost complete 16S rDNA sequence with homologous sequences deposited in GenBank. 
 
 
 
Table 
 
Biochemical characteristics of the previously reported Sphingomonas mucosissima isolate ({"type":"entrez-nucleotide","attrs":{"text":"AM229669","term_id":"87080454","term_text":"AM229669"}}AM229669) and the isolate from this study 
 
 
 
We believe that the patient’s intravenous catheter was the source of the infection because she did not have wound infections and cultures of her urine were negative for infectious agents. Antimicrobial drug treatment, selected on the basis of an in vitro S. mucosissima susceptibility profile, facilitated the patient’s recovery. This case report illustrates that the pathogenic potential of S. mucosissima should be considered in diagnosis in such cases because the organism can cause bacteremia in patients, primarily in those with underlying debilitating conditions and those who have undergone medical interventions.

To the Editor: The genus Sphingomonas was proposed by Yabuuchi et al. in 1990 (1) and amended by Takeuchi et al. in 1993 (2). It now has been subdivided into 4 separate genera: Sphingomonas sensu stricto, Sphingobium, Novosphingobium, and Sphingopyxis. The bacteria of the genus Sphingomonas are yellow-pigmented, nonfermenting, gramnegative bacilli with a single polar fl agellum; they are widely distributed in the natural environment, especially in water and soil (3). These bacteria are characterized by the presence of a unique sphingoglycolipid with the long-chain base-dihydrosphingosin, ubiquinone 10 (Q-10), and 2-hydroxymyristic acid (2-OH C14:0)-and the absence of 3-hydroxy fatty acids (4). S. mucosissima was isolated and identifi ed in 2007 by Reddy and Garcia-Pichel from biologic soil crust samples collected from sandy arid soil in the US Colorado Plateau (5). Sphingomonas spp. are opportunistic pathogens and have recently been implicated in a variety of communityacquired and nosocomial infections, considered to originate from contaminated hospital equipment or manipulation of some medical devices (3). The survival of Sphingomonas spp. in indoor dust particles as aerosols and their resistance to many disinfecting and toxic chemicals may explain their ability to colonize medical devices such as mechanical ventilators, catheters, and bronchofi beroscopes (6). In the past few years, these organisms, in particular S. paucimobilis, have been implicated in a variety of communityacquired and nosocomial infections.
We report a case of S. mucosissima bacteremia in a patient with sickle cell disease. In February 2008, a 17-year-old woman with homozygous sickle cell anemia was hospitalized when her condition suddenly became worse. The patient had undergone a splenectomy in 1992 and a cholecystectomy in February 2007. Four days after admission, she had a fever of 38.7°C. Two aerobic blood specimens, drawn on the fi fth day of her hospitalization, yielded gram-negative bacilli after a 24-hour incubation. The gram-negative bacilli were positive for catalase and oxidase but remained unidentifi ed by API 20NE strip (bioMérieux, Marcy l'Etoile, France). MICs of antimicrobial drugs were determined for the gram-negative bacilli by using an Etest assay (AB BIODISK, Solna, Sweden) on Mueller-Hinton medium. MICs were 1 μg/mL for cefotaxime, 1 μg/mL for amoxicillin-clavulanic acid, 2-3 μg/mL for vancomycin, 0.064 μg/mL for imipenem, 4-5 μg/mL for ceftazidime, 1 μg/mL for amikacin, 3 μg/mL for ciprofl oxacin, and 0.047 μg/mL for trimethoprim-sulfamethoxazole.
Initial treatment of intravenous administration of ceftriaxone was begun. The fever resolved after 1 day and the patient's condition improved. Treatment was stopped after 5 days, and the patient remained apyretic. Two S. mucosissima isolates were recovered from 2 different blood-culture samples drawn 24 hours apart, which suggests that S. mucosissima was not just a transient organism but indeed was responsible for the patient's septicemia. Phenotypic identifi cation of the gram-negative bacilli failed because the definite bacterial species S. mucosissima was not included in the API database (http://industry.biomerieux-usa.com/ industry/food/api/apiweb.htm) used for the phenotypic identifi cation. However, the isolates' biochemical characteristics were consistent with those previously reported for S. mucosissima (5) ( We believe that the patient's intravenous catheter was the source of the infection because she did not have wound infections, and cultures of her urine were negative for infectious agents. Antimicrobial drug treatment, selected on the basis of an in vitro S. mucosissima susceptibility profi le, facilitated the patient's recovery. This case report illustrates that the pathogenic potential of S. mucosissima should be considered in diagnosis in such cases because the organism can cause bacteremia in patients, primarily in those with underlying debilitating conditions and those who have undergone medical interventions.

WU Polyomavirus in Fecal Specimens of Children with Acute Gastroenteritis, China
To the Editor: WU polyomavirus (WUPyV) is a recently described PyV found in patients with acute respiratory tract infections (1). The role of the virus in disease pathogenesis remains unclear. The ability to detect it in clinical specimens would help in the determination of its replication sites and its routes of transmission and dissemination. WUPyV has been found in specimens from the respiratory tract only (1).
Previous studies of other PyVs, including BK virus, JC virus, and the newly identifi ed KIPyV, demonstrated their presence in fecal specimens (2,3), which suggests their potential for transmission through the gastrointestinal (GI) tract (2). Because some children (6.8%-27.7%) who had WUPyV results in previous studies (1,4,5) displayed respiratory and GI clinical signs, we speculated that WUPyV might also be transmitted through the GI tract.
In this study, we tested for the presence of WUPyV in children with acute gastroenteritis. A total of 377 fecal specimens were collected from children with acute nonbacterial gastroenteritis at the Outpatient Clinic Department of the Beijing Children's Hospital from March 2006 through November 2007. Patients with nonbacterial gastroenteritis were defi ned as 1) those who had acute, watery, but not bloody, diarrhea, accompanied by other clinical signs and symptoms such as fever, abdominal cramps, nausea, vomiting, and headache; and 2) those who had negative test results for any known bacteria that might cause gastroenteritis, such as Salmonella spp., Shigella spp., Staphylococcus spp., Campylobacter jejuni, Clostridium spp., Escherichia coli, and Yersinia spp.
All patients, whose ages ranged from 1 month to 13 years (mean age 11.7 months, median age 9 months), did not exhibit apparent clinical respiratory signs. Fecal specimens from patients were diluted in phosphate-buffered saline (pH 7.2) by using a 10% wt/vol ratio and were cleared of cell debris by centrifugation (2,500 × g, 5 min). Virus nucleic acids were extracted by using the NucliSens miniMAG and isolation reagents according to the manufacturer's instructions (bioMérieux, Marcy l'Etoile, France). Samples were subsequently screened for group A rotavirus (RVA) by using the rotavirus ELISA diagnostic kit (Lanzhou Institute for