Cellulosmicrobium cellulans isolated from a patient with acute renal failure

Received 11 December 2013 Accepted 21 May 2014 Department of Pathology, Schulich School of Medicine and Dentistry, Western University, London, Ontario, Canada Department of Microbiology and Immunology, Schulich School of Medicine and Dentistry, Western University, London, Ontario Division of General Surgery, Schulich School of Medicine and Dentistry, Western University, London, Ontario, Canada Laboratory Services, London Health Sciences Centre, London, Ontario, Canada


Case report
A 59-year-old man was admitted to the intensive care unit (ICU) with intractable seizures.His past medical history was significant for ischaemic heart disease with two previous myocardial infarctions, peripheral vascular disease requiring a left femoral-femoral bypass and a right femoral-popliteal bypass surgery, chronic obstructive pulmonary disease, dyslipidemia, and a prior admission to the ICU for pneumonia and septicemia.Four months earlier, he had suffered a stroke in the left middle cerebral artery region, leaving him with word-finding difficulties and confusion.
On physical examination, the patient was confused, tachycardic (heart rate 120) and tachypneic (respiratory rate of 40).He had decreased air entry and crackles on auscultation of both lungs, and the rest of his physical examination was unremarkable.Laboratory tests showed a normal blood cell count, electrolytes, urea and creatinine.The patient's venous blood gas analysis pH was 7.04, with a partial CO 2 pressure of 96 and an elevated anion gap of 16.He He was intubated and underwent a computed tomography scan of his head, which showed old cerebral infarcts in both hemispheres, generalized atrophy of the brain, and no abscess or haemorrhage.A chest X-ray demonstrated diffuse pulmonary oedema with possible underlying pneumonia.Electroencephalogram recordings revealed moderate metabolic encephalopathy without a clear seizure focus.A lumbar puncture yielded normal results.
Empirical treatment with intravenous piperacillin-tazobactam (4.5 g every 6 h) and acyclovir (1500 mg initial dose and then 200 mg every 12 h) was started.One day after admission, Gram-positive and Gram-negative cocci grew in respiratory cultures and were subsequently identified as Moraxella catarrhalis and Staphylococcus aureus.Identification was initially made by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS; Bruker Daltonics), and was .2.0 on several repeats, including the formic acid extraction method, which yielded a score of .2.3.The S. aureus isolate was susceptible to vancomycin (MIC 1 mg ml 21 ), cloxacillin (MIC 0.5 mg ml 21 ), clindamycin (MIC ,0.25 mg ml 21 ), erythromycin (MIC ,0.25 mg ml 21 ) and sulfamethoxazole-trimethoprim (MIC ,10 mg ml 21 ).At this time, the patient's creatinine rose significantly to 160 mmol l 21 (normal 62-120 mmol l 21 ).Acyclovir was discontinued and the dosage of piperacillin-tazobactam [2.25 g intravenously (IV) every 12 h] was reduced because of the patient's poor creatinine clearance.Vancomycin (1 g IV every 24 h) was also added based on the lack of response to treatment and suspicion of methicillin-resistant Staphylococcus aureus as a cause of the infection.
Seven days later, the patient developed fever, hypotension and tachycardia, and an increased frequency of seizures despite IV anti-epileptic treatment with phenytoin (100 mg every 6 h).Repeat lumbar puncture and respiratory cultures were negative.However, two sets of blood cultures drawn 6 h apart from a peripheral vein and the left internal jugular central venous catheter grew Gram-positive rods, which were identified as Cellulosimicrobium cellulans by MALDI-TOF MS.The catheter was replaced, and the patient remained on antimicrobial therapy with piperacillin-tazobactam and vancomycin.The patient did not recover his renal function and required daily haemodialysis.He could not be weaned off mechanical ventilation, and began requiring inotropic support to maintain his blood pressure.After 16 days in the ICU, the family elected to withdraw care, and the patient died.
Cell morphology obtained from both sets of blood culture bottles showed Gram-positive rods.After overnight incubation at 37 u C in aerobic conditions on BBL Trypticase Soy Agar II plus 5 % sheep blood plates (Becton Dickinson and Co.), colonies were 1 mm in size, non-haemolytic, grey, smooth and convex (Fig. 1).A culture grown in aerobic tryptic soy broth (TSB; Becton Dickinson and Co.) demonstrated easily decolorized Gram-positive coccobacillary morphology during the stationary phase as seen in Fig. 2(a), and slender, long, Gram-positive rods in the exponential phase as demonstrated in Fig. 2(b).PCR of the 16S rRNA gene was performed on DNA isolated from cultures grown in TSB (forward primer: 59-AGAGTTTGATCCTGGCTCAG-39; reverse primer: 59-AAGGAGGTGATCCAGCCGCA-39; Invitrogen).Sequencing of the purified PCR product (Robarts Research Institute Sequencing Facility, London, Ontario, Canada) and a BLAST search of related sequences in GenBank showed that the sequence matched the type strains of C. cellulans at 100 % nucleotide identity, Cellulosimicrobium funkei at 100 % nucleotide identity and Cellulomonas sp. at 100 % nucleotide identity.
Similar to a previous study (Magro-Checa et al., 2011), our sequencing results demonstrated that 16S rRNA sequencing alone may not be able to distinguish between the three closely related species, although the differentiation may not necessarily affect treatment (Brown et al., 2006).C. cellulans has been reported as being resistant to erythromycin and other macrolides but is considered susceptible to vancomycin, which was the therapy of choice in most of the reported cases.Other treatment options such as linezolid or rifampin may be associated with a higher rate of cure (Magro-Checa et al., 2011;Tucker et al., 2008).
To our knowledge, this case represents the first documented case of C. cellulans infection following acute renal failure.While C. cellulans can cause infections in healthy patients (Casanova-Roman et al., 2010;Tucker al., 2008), our case demonstrates its role as an opportunistic pathogen in the context of a patient who sustained renal injury and had a prolonged stay in the ICU.

Fig. 2 .
Fig. 2. Gram stain of C. cellulans from colony isolated on sheep blood agar demonstrated easily decolorized Gram-positive coccobacillary morphology during the stationary phase (a), and slender, long, Gram-positive rods in the exponential phase (b).