Mycobacterium Smegmatis Infection of a Lumbar Spine Instrumented Fusion

Problem statement: To demonstrate the presentation of atypical mycoba terial postsurgical infections and their management. Approach: Single patient case report. Results: Successful management of atypical mycobacterial post operative inf ction with preservation of instrumented hardware posterior pedicle screw fixation and inter body cages. Conclusion: This report suggests that these atypical mycobacterial infections can be erad icated with successful outcomes with preservation of spinal instrumentation.

The case is presented below: 56 y/o WF admitted for elective L5/S1 fusion and discectomy on 10-18-2004. Her prophylactic, pre-operative antibiotic coverage was Ancef 1 gm IV. The patient was discharged to home on post-operative day #4 with a dry, intact suture line. On post-operative day #11, she underwent staple removal. She called on post-operative day #21 for increased drainage from a re-opened incision. She was started on a trial of oral Keflex 500 mg orally QID. Her C-reactive protein level and CBC were normal. Follow-up evaluation after 10 days of oral Keflex, revealed a persistent draining wound. A 'suture granuloma' at the draining site was suspected. Exploration under local anesthetic was performed on 12/2/2004. No granuloma was found. Instead a large subcutaneous purulent cavity was packed and a re-exploration was planned to r/o deep fascial infection. A serendipitous acid-fast stain of the purulent material revealed acid fast bacteria. On 12/3/2004, she underwent formal exploration and packing, under general anesthesia. The thoracolumbar fascia was intact. Wound packing was initiated with saline soaked gauze dressing changes. She was discharged on a ten day antibiotic course (Keflex 500 mg QID) with a stable wound. Wound bacterial culture results reported on 12/8/2004 revealed Staphylococcus Epidermidis (2 species) one sensitive to Cephalothin; one resistant. A routine office visit on 12/15/2004 revealed the wound to be healing nicely off antibiotics. The patient was discharged home on the above antibiotic regimen on 3/9/2005.
A repeat surveillance lumbar CT on 3/22/2005, unexpectedly, revealed the accumulation of a large psoas and lateral paraspinal of purulence. A CT guided abscess drainage procedure was undertaken with placement of a 10 Fr self-retaining catheter with 50 cc of purulence drained! She was seen in my office on 3/30/2005, with a nearly completely healed surgical wound and the draining "pig-tail" catheter. Clinically, she had an improving C-reactive protein and ESR.
A third surveillance CT of the lumbar spine on 4/11/2005 was obtained and revealed no residual fluid filled cavities. Her 'pig-tail' catheter was removed the next day.
An office visit on 5/5/2005 revealed a healed wound and drain site. Her C-reactive protein level was now normal. On her office visit of 6/15/2005, she noted slow steady weight gain. At the 1st annual office visit s/p lumbar fusion, she had solid x-ray evidence of healed L5/S1 fusion with intact instrumentation. On her 2nd annual office visit 10/17/2006, she had no recurrence of infection.

DISCUSSION
This case demonstrates the insidious onset of the infection despite the initial healing post-surgical wound (Pruitt et al., 1993;Hand and Sanford, 1970;Chada et al., 1998;Cobbett, 1918), the lack of response to surgical drainage alone (Widgerow et al., 1995;Smith, 1976;Plaus and Hermann, 1991), the importance of expanding the extent of anatomic imaging studies, the role of interventional CT guided biopsy and drainage (Pruitt et al., 1993;Brown et al., 1999) and the role of antibiotic therapy with multiple antibiotics (Prosser, 1986;Hasegawa et al., 1992). This study suggests that these atypical mycobacterial infections-like their TB counterparts-can be resolved in the face of retained hardware with aggressive medical treatment of these infections (Jain et al., 2007;Chen et al., 2011;Fukuta et al., 2003;Kim et al., 2004;Rappaport et al., 1990;Guven et al., 1994;Swanson et al., 2006)-although other opinions exist (Plaus and Hermann, 1991;Hasegawa et al., 1992).

CONCLUSION
I would like to thank the numerous collaborators that assisted me with caring for this patient and writing this report: Dr. Joseph Alexander, MD, Dr. Jon Thomas, PhD and our WCA Librarians, Ms. Bonnie Engberg and Ms. Mary Franklin.