Enterococcus faecalis: An unusual etiology of lumbar spondylodiscitis in a patient with chronic kidney disease (undergoing hemodialysis) and sigmoid diverticulosis
The incidence of spondylodiscitis in developing countries is 2.4:100,000 cases per year. It raises multiple problems regarding the etiological diagnosis, mainly because the usual biological and imaging tests are nonspecific. Staphylococcus aureus and Mycobacterium tuberculosis are the most frequently isolated pathogens; however, several other microorganisms can be implicated.
We report a case of enterococcal spondylodiscitis in a patient with chronic renal disease under hemodialysis, and with associated sigmoid diverticulosis. There are a few cases of enterococcal spondylodiscitis reported till date that have been observed mostly in patients with infective endocarditis.
A 67-year old male patient with end-stage renal disease undergoing hemodialysis was admitted for severe low back pain and fever (37.5°C) for 3 weeks. The intravenous catheter for hemodialysis was replaced 7 days prior to his illness with an arteriovenous fistula because of local inflammatory signs. The patient received non-steroidal anti-inflammatory treatment and a muscle relaxant for 5 days without showing any signs of improvement.
The physical examination showed a low-grade fever (37.3°C), irregular cardiac sounds, systolic murmur in the mitral area, a heart rate of 110/min, and a blood pressure of 150/80 mmHg. The spinous process percussion was painful in the lumbar region, with limitation of body flexion. The pulmonary and spinal radiographs were within normal limits, and the electrocardiogram showed atrial fibrillation.
Biological tests showed moderate anemia and a mild inflammatory syndrome. Lumbar spine MRI indicated L1-L2 osteodiscitis, with increased fluid signal in the intervertebral disc space, and fluid collection in the left iliopsoas muscle with edematous infiltration [Figure 1] and [Figure 2].
The empirical antimicrobial regimen covered both gram-positive cocci and gram-negative bacilli comprising ceftriaxone 2 g/day and vancomycin 1 g/day (after the dialysis session). The bone lesion biopsy performed before the initiation of antibiotics showed a positive culture for Enterococcus faecalis irmed by matrix-assisted laser desorption/ionization [MALDI] time-of-flight (TOF) mass spectrometer, Biomerrieux) [Figure 3] and negative Mycobacterium tuberculosis onfirmed by a negative result on deoxyribonucleic acid polymerase chain reaction [DNA-PCR]). Three blood cultures were also positive for ampicillin-susceptible E. faecalis. After the results of the microbiological tests were obtained, the antimicrobial regimen was changed to ampicillin 2 g/day (according to creatinine clearance) and a clinically favorable outcome was obtained. Considering the enterococcus bacteremia, transthoracic and transesophageal echocardiography were also performed, which excluded the presence of infective endocarditis. The colonoscopy revealed sigmoid diverticulosis, with mild inflammatory signs.
The follow up MRI performed after 4 weeks showed a favorable picture with regression of the bony lesion and resorption of the psoas collection. The patient received intravenous ampicillin for 5 weeks and continued oral ampicillin at home for 3 weeks until the complete regression of the MRI lesions had been ascertained.
In Romania, the most frequent pathogens involved in spondylodiscitis are the pyogenic bacteria (Staphylococcus in almost 70% of the cases) and M. tuberculosis.
The most common routes of spinal infection are the hematogenous spread or iatrogenic inoculation; the lumbar region is the most frequently reported level. Primary infectious foci are often heterogeneous; in 12% of cases, infective endocarditis has also been reported.
Leukocytosis occurs in approximately 50% of the patients and the inflammatory markers are usually increased. Procalcitonin has a low diagnostic and prognostic value in patients with discitis. In our case, the patient had a normal procalcitonin level.
The bone and soft tissue biopsies and blood cultures remain the most useful tests to establish an etiological diagnosis. The rate of positive blood cultures in patients with discitis is 30–78%. A study conducted among 110 patients with enterococcus infections revealed bone or joint involvement in only 4% of the cases. The incidence of Streptococcus and Enterococcus spp. among patients with discitis was 5–20%; some studies showed an incidence of Enterococcus etiology in 2.8% of the cases. Most cases were either associated with infective endocarditis (5 cases), or urinary tract infections with secondary bacteremia (3 cases). There are two previous cases of enterococcal spondylodiscitis reported in patients undergoing hemodyalisis. The primary site of infection seems to be, in both cases, the intravascular catheter used for dialysis.
The investigation of the gastrointestinal tract is clearly recommended in all cases of Enterococcus-positive blood cultures. In our case, the colonoscopy showed colonic diverticulosis. As the same strain of E. faecalis was isolated from blood culture and the culture from bone biopsy, we could clearly differentiate between colonization and bone infection.
There is a controversy prevailing regarding the duration of treatment that ranges from 6 to 12 weeks. In fact, the therapy is stopped only when the MRI lesions totally disappear. Surgical intervention is another treatment option, which should be carried out in conjuction with antimicrobial therapy.
Spondylodiscitis should be considered as a possible lesion in an immunocompromised patient with fever and back pain. Although E. faecalis is not a frequent cause of spondylodiscitis, it must be considered in these cases. If the blood cultures indicate an enterococci bacteremia, an echocardiography and various gastrointestinal tract investigations are strongly indicated.
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[Figure 1], [Figure 2], [Figure 3]