A Rare Case of Spondylodiscitis Due to Actinotignum schaalii in a Patient With Crohn’s Disease

Abstract

We report a case of a 55-year-old male with a history of Crohn’s Disease who presented for acute on chronic worsening back pain. He was found to have spondylodiscitis with adjacent myositis secondary to an uncommon urinary tract infection pathogen, Actinotignum schaalii. He underwent interventional radiology disc biopsy and open surgical biopsy with culture. He was successfully treated with a six-week course of IV daptomycin and ceftriaxone.

1. Background

Spondylodiscitis is an infection of the intervertebral disc, and the adjacent vertebral bodies,1,2 thus causing vertebral osteomyelitis and discitis. It can involve infection to any area of the spinal column. 1,2 Spondylodiscitis can be categorized into pyogenic vs granulomatous based on pathogen.1,2 Pyogenic infections are typically caused by typical bacteria, while granulomatous are typically caused by tuberculosis, brucella, or fungi. The most common pathogen of spondylodiscitis is staphylococcus aureus.1,2 Other bacterial pathogens include pseudomonas aeruginosa, coagulase negative staphylococci, and candida species. Risk factors for spondylodiscitis include intravenous drug use, but immunocompromised patients also have an elevated risk.2

Actinotignum schaalii is a gram positive coccoid rod, which is an uncommon pathogen but reported to cause urinary tract infections and necrotizing soft tissue infections.3–8 Actinotignum schaalii has been reported to cause bacteremia, with elderly patients being at increased risk.4 Spondylodiscitis secondary to Actinotignum schaalii, first reported in 2007,4 is rare and has only been reported twice, with a second case reported in 2011.9 We present the third reported case of spondylodiscitis secondary to Actinotignum schaalii, which occurred in a 55 yearold male with a history of Crohn’s disease (Fig. 1).

Fig. 1.

Bone marrow edema within L2 and L3.

2. Presentation of case

This is a 55-year-old male with a past medical history significant for Crohn’s disease, with most recent infliximab infusion 10 months prior, chronic urinary retention without requiring urine catheterization, and lumbar degenerative disc disease, who presented for worsening back pain. On the day prior to admission, he was treated for a urinary tract infection with ciprofloxacin and prescribed pain medication. On the following day, he presented with worsening right sided back pain and inability to ambulate. He denied fever, chills, dysuria, frequency, urgency, numbness, weakness bilateral lower extremities, or saddle anesthesia. He reported chronic difficulty with urination over the past 15 years. He also reported a one-month history of testicular pain. Due to worsening urinary retention, he was started on an alpha blocker and an indwelling urinary catheter was placed. Patient then regained the ability to ambulate after adequate pain control. A CT abdomen/pelvis was negative for bowel or urinary pathology. Magnetic resonance imaging (MRI) lumbar spine/sacrum revealed bone marrow edema within L2/L3, suspicious for developing discitis and osteomyelitis with adjacent psoas muscle myositis. Abnormal labs included leukocytosis and both erythrocyte sedimentation rate and C reactive protein were elevated (Table 1). Urine and blood cultures remained negative. Patient underwent an interventional radiology-guided L2–3 disc biopsy, which was culture negative. Patient remained off further antibiotics until undergoing an open disc biopsy. Patient was initially started on IV Vancomycin 1.25 gm every 12 hours and Ceftriaxone 2 gm daily. Upon discharge, the vancomycin was transitioned to IV daptomycin 700 mg daily and ceftriaxone continued. The biopsy culture resulted positive for Actinotignum schaalii and staphylococcus epidermidis after discharge from the hospital. The decision was made to complete the prescribed regimen for a total of six weeks. Patient’s pain subsequently resolved. A follow-up colonoscopy revealed only benign polypoid mucosa with rare lymphoid follicles and surface erosions.

Table 1.

Vital signs and labs.

Temperature	36.9°C
Heart Rate	78 bpm
Blood Pressure	106/73
White Blood Cell count (cells x 109/L)	12.9 (4.0–10.8)
Erythrocyte Sedimentation Rate (mm/hour)	35 (0–10)
C-Reactive Protein (mg/L)	36.9 (<5.0)
Blood cultures	Negative x 2 sets

3. Discussion

The incidence of spondylodiscitis increases with age, predominantly impacting patients >50 years old.1,2 Men are slightly more likely to be affected compared to women.1,2 The incidence has been on the rise, increasing from 6.1 to 11.3 per 100,000 from 2010 to 2019.2,10 Increased incidence is likely multifactorial, with increasing iatrogenic bacteremia (intravascular devices, procedural, other health-care related), increasing age of the population, increases in illicit IV drug use, and increasing numbers of immunocompromised patients.2,10 Bacteria may disseminate to the spine via three routes; hematogenous (most common), contiguously, or direct inoculation. A subset of hematogenous spread arises from Batson’s plexus (vertebral venous system).11 It is theorized that a urinary infection could spread via Batson’s plexus from the urinary system to the vertebrae.11 Diagnostic modalities include MRI, disc biopsy, and labs (blood cultures, inflammatory markers).1,2

The differential diagnosis of spondylodiscitis in patients with inflammatory bowel disease (IBD) also includes autoimmune etiologies.12–14 Specifically, HLA B-27 related spondylarthritis has been frequently reported in both ulcerative colitis and Crohn’s disease.12,13 Spondylodiscitis has also been reported as the initial presenting symptom of a patients with Crohn’s disease.14 In patients with IBD and spondylodiscitis, it is essential that infection is ruled out.13 In patients with IBD and spondylodiscitis, the status of the IBD must be ascertained, as fistulas secondary to Crohn’s disease may lead to infectious spondylodiscitis.14 This patient’s CT scan was not suggestive of a fistula.

Inflammatory myositis has been reported as a rare complication of Crohn’s disease.15,16 Although polymyositis has been described,15 cases of focal myositis have also been reported in the gastrocnemius and popliteal muscles.15,16 Infectious myositis, as a complication of spondylodiscitis, has also been rarely reported. Typical bacterial pathogens, including staphylococcus aureus17 and klebsiella pneumoniae, 18 have been reported. Uncommon organisms included zoonotic pathogens streptococcus canis19 and pasteurella multocida,20 which were linked to dog and cat exposure, respectively. Spondylodiscitis with psoas abscess has been more commonly described and usually occurs via hematogenous dissemination.21 Anaerobic infections leading to spondylodiscitis and psoas abscess are very rare.22,23

Actinotignum schaalii is an uncommon pathogen and facultative anaerobe.3–9 Because of its slow anaerobic growth and resemblance to the normal bacterial flora on skin and mucosa, a. schaalii is often overlooked or considered a contaminant.3–5,8 Bacteria are difficult to culture, making hematogenous infection difficult to identify.3–5 As an anaerobe, the bacteria require incubation for at least two to three days in CO2, and specific organism identification may be isolated with either 16rRNA (small subunit ribosomal RNA) sequencing3,5 or MALDI-TOF (Matrix-Assisted Laser Desorption/Ionization-Time-of Flight).3,5,6

The most common infections documented are urogenital infections.3–9 A. schaalii has been primarily identified in elderly patients, with a reported mean age of >60 years.3,5,8 Specific to UTIs, the average age of patients with UTI’s secondary to a. schaalii is older than UTIs due to other pathogens.8 Patients with UTIs due to a. schaalii also are more likely to have underlying anatomic abnormalities,3–5,8 such as urinary stones, strictures, or BPH. However, many laboratories do not conduct direct examination with Gram staining on routine urinalyses and perform only a selective chromogenic agar incubated for 24 hours under aerobic conditions, which does not allow a. schaalii to grow.3,5,8 Sahuquillo-Arce et al. were able to successfully isolate the organism via an automated bacterial culture system, involving liquid enriched culture broth, incubation in vortex agitation, laser analysis of media diffraction, and inoculation in chromogenic media.8 It is unclear whether most labs could develop a similar process.

Bacteremia,3–8 and soft tissue abscesses4–6 have also been reported, with other rare infections including cellulitis,4,5 endocarditis,5 and necrotizing fasciitis.24 A large percentage of skin and soft tissue abscesses have been noted in the inguinal region.6,8 Discitis secondary to actinotignum schaalii has only been reported previously in two patients.5,9 Both patients had bacteremia, but only one of the two had a documented UTI.5,9 Similarly, osteomyelitis has also been reported in several cases, primarily in patients with open wounds or surgical infections.5,6,8 However, myositis due to actinotignum schaalii has not previously been reported. One series did identify several patients with actinotignum schaalii infections secondary to intra-abdominal infections.4 As noted above, our patient had a history of Crohn’s disease. Although his bowel flora may have also been a potential source of infection, this was less likely given that his Crohn’s disease demonstrated only rare mucosal erosions and he had no signs of a fistula.

Crohn’s disease is an immunocompromising condition25 and the patient had previously received anti-TNF therapy. We speculate that immunosuppression may have contributed to his infection. The route of inoculation to the spine is not entirely clear. Although blood cultures remained negative, bacteremia was not entirely excluded due to the difficulty isolating the organism as noted above. In addition, as our lab only uses limited media for urine specimens, it is possible that a urine culture would not have isolated the organism. Given our patient’s pyuria, worsening urinary incontinence, and literature suggesting actintignum schaalii most commonly presents as a UTI,3–9 we speculate that patient may have had a UTI, which may have spread via Batson’s plexus.

In terms of treatment, the guidelines for vertebral osteomyelitis, and thus spondylodiscitis, recommend at least 6 weeks of IV antibiotic therapy.2 Specific to actinotignum schaalii, previously published susceptible antibiotics included beta lactams,3–5,8 tetracyclines, 8 vancomycin,5,6,8,16 linezolid5,6,8,16 rifampin,6,8 moxifloxacin,6,8 and levofloxacin.4,6,8 Significant resistance was observed with ciprofloxacin,3–6,8 clindamycin,5,6,8 erythromycin,6,8 and sulfamethoxazole/ trimethoprim.3–6,8 Unfortunately, susceptibilities were not tested in our patient. A previous patient with discitis was treated successfully with eight weeks of IV amoxicillin/clavulanic acid.8 As our case patient was discharged prior to culture results being available, he was initially treated for culture negative spondylodiscitis. Based on published literature, ceftriaxone monotherapy would likely have been effective. Although the staphylococcus epidermidis was likely a contaminant,26 the decision was made to also continue both the daptomycin and ceftriaxone given patient’s improvement.

4. Conclusion

We report the third documented case of Actinotignum schaalii spondylodiscitis, which also included an adjacent myositis which was successfully treated with long term IV daptomycin and ceftriaxone. This case highlights both potential risks for discitis in Crohn’s patients, considering anatomic risks and immunosuppression, along with considerations of non-infectious causes of spondylodiscitis. The case also highlights challenges in diagnosing actinotignum schaalii infections, particularly in urinary tract infections. Further study should be undertaken to determine cost effective and practical diagnostic modalities.