SERRATIA MARCESCENS AS A CAUSE OF CERVICAL MYELOPATHY

ABSTRACT Introduction: The main causative agent of spinal infections is Mycobacterium Tuberculosis, followed by saprophytes of the skin. The most affected segment is the lumbar, followed by the thoracic. Objective: Case report. Results: A previously healthy 40-year-old man with posterior cervical pain and myelopathy was referred to our spine service for vertebral destruction syndrome in C3-C4 and altered carbohydrate metabolism. Microdiscectomy and abscess drainage were performed and a biopsy was taken for definitive diagnosis. Multiresistant Serratia Marcescens was isolated in the culture. Both the myelopathy and carbohydrate intolerance were resolved as the infection was resolved. Conclusion: The significance of this case lies in the infective presentation of the S. Marcescens in an immunocompetent person, since it is mainly an opportunistic microorganism, and in the atypical location. The most commonly isolated pathogen is Mycobacterium Tuberculosis, followed by Staphylococcus aureus. Identification of the causative agent is essential to the initiation of antibiotic therapy. Therefore, microbiological isolation plays a fundamental role in the treatment, recovery and quality of life of the patient. Level of evidence V; Case report.


INTRODUCTION
The incidence of spondylodiscitis has been increasing 1,2 over the last 15 years. There are multiple causes, such as the increase in life expectancy, the increase in the incidence of chronic degenerative diseases, the use of intravenous (IV) drugs and improvement in diagnosis.
In spontaneous spondylodiscitis, hematogenous contamination is the most frequent cause 3,4 and mainly affects the lumbar spine, while the cervical region is more often affected among users of IV drugs. Distant foci have been identified in almost half of the cases, the most frequent being genitourinary (17%), followed by skin and vascular and gastrointestinal accesses. The main risk factor is diabetes mellitus.
The principal causative agent of spinal infections is M. Tuberculosis (9-46% globally), followed by S. Aureus (50% of the non-tuberculous cases), and others such as S. Viridans, Pseudomonas aeruginosa, E. Coli, and Klebsiella. The main segment affected is the lumbar, followed by thoracic and cervical regardless of whether the infection is spontaneous or postsurgical. 5 However, spondylodiscitis from S. Marcescens acquired in the community is quite rare since it is an opportunistic microorganism. 6,7 A rare case of cervical spondylodiscitis due to S. Marcescens was reported in a previously healthy patient, which also caused severe loss of metabolic control and an altered overall condition in the patient and required medical management.

METHODS
We present here a clinical case with prior written patient authorization via an informed consent form and approved by the institutional review board.

Case report
A 40-year-old male was referred to our service for vertebral destruction syndrome. During the previous six months he had experienced multi-treated cervicalgia and two months prior to the consultation he sought medical attention at a local hospital for weakness and paresthesia of the lower limbs, so magnetic resonance (MRI) was performed revealing vertebral destruction of C3-C4, C5-C6-C7. He was also diagnosed with diabetes mellitus and treatment with metformin 850 mg every 12 hours was initiated and he was sent to the HRAEB.
At admission the patient was alert, his temperature was 36.5ºC, his blood pressure was 120/70 mmHg, his heart rate was 87 beats per minute, and his respiratory frequency was 19 breaths per minute. He was diaphoretic with capillary glycaemia of 25 mg/dl and a bolus of 25 cc of dextrose at 50% was administered and a 5% glucose solution was maintained, the oral hypoglycemic agents were suspended and capillary glycaemia monitoring was indicated every 2 hours. He referred to cervical pain, 8/10 on the visual analogue scale (VAS), which increased with movement and decreased when at rest and did not decrease with non-steroidal analgesics. He had lost approximately 10 kilos of weight. In the neurological examination, the patient presented dysesthesias in the lower limbs from L1, strength of 2/5 in the upper limbs and 3/5 in the lower limbs on the Daniels scale with bilateral hyperreflexia of L4 and S1, bilateral Babinski, Asia D, and Frankel D.
Laboratory data showed an increase in the erythrocyte sedimentation rate (ESR) to 40 mm/hr, C-reactive protein (CRP) of 354, and the rest were normal. The MRI had vertebral destruction data and the glycaemia was difficult to normalize.
A protocol for vertebral destruction was initiated with blood culture, urine culture (both negative), serial laboratory tests including complete blood count, ESR (which remained high at a mean of 40 mm/hr), CRP (mean of 348), and blood chemistry (without changes). Both gastrointestinal and respiratory infections were ruled out. In the cervical MRI with contrast, loss of cervical lordosis with an angle of -6º and irregularity in the levels of C3-C4 and C5-C6 were observed. A prevertebral abscess from C2-T1 was observed in the T2 sequence ( Figure 1) and in the ubiquicidin-labelled gammagram (Figure 2).
Surgical management was proposed to the patient and an informed consent form was signed in which he accepted the proposed treatment. An anterior approach cervical microdiscectomy was performed, the abscess was drained (purulent fluid) from the C5-C6 space, and a biopsy was taken and sent to microbiology for culture and pathology to rule out malignancy. Multiresistant Serratia Marcescens was isolated in the culture and the histopathology results were negative for malignancy. Antibiotic treatment with trimethoprim and sulfamethoxazole for 6 weeks was indicated by infectology. The patient progressed towards improvement. The glycaemia normalized until no further treatment was required, so it was concluded that it was due to the metabolic response to the trauma. The myelopathy reversed progressively and at 12 months the patient was neurologically intact. Consolidation of the vertebral bodies causing fusion of the affected segment was observed in imaging studies (Figure 3), in addition to a loss of lordosis and cervical angle of -6º and the spinal cord was without alteration. Instrumentation was proposed to ensure cervical stability, however, the patient did not accept because he was asymptomatic.

DISCUSSION
The importance of this case lies in the presentation in an immunocompetent patient who, in addition to developing an opportunistic infection, had a strong metabolic response to the trauma, characterized by difficult to control glycemic alterations and was initially categorized as a recently diagnosed diabetic. However, once the infection was resolved, his carbohydrate metabolism normalized.

A B
The patient's myelopathy was resolved by the eliminating the effect of volume by draining the abscess. The diagnosis and treatment of spondylodiscites is a challenge because the clinical and radiographical presentation is varied and the etiology can be metabolic, neoplastic or, as in this patient, infectious. Obtaining a sample is vital, since imaging studies only show suggestive data but are not diagnostic of etiology.
There is little specific information in the literature about cervical spondylodiscites since they have the lowest incidence 8,9 at 6%-10%. The most affected segment is C5-C6 at 43%, followed by C6-C7 at 27%, with the least affected segment being C1-C2 at 7%. Lesions extending 3 levels, as in our patient, are the least frequent at 13%, with monosegmental lesions being the most common in 57% of cases. The presence of an epidural abscess is greater in cervical infections; 80% in the 2012 Shousha and Boehm series, however, Heyde el al. 10 reported a low incidence of this phenomenon at 39%.
The main problem lies in the location of these infections, since they can have a much more dramatic outcome than those located in other spinal segments. The most serious cases can present progressive neurological deterioration (40%), sepsis, and life-threatening myelopathy (high levels). However, as in this patient, the literature reports that in most spondylodiscites the main and often only symptom is cervicalgia, which can lead to erroneous diagnoses and treatments, especially in patients without risk factors as in the case presented.
As in other forms of spondylodiscitis, it usually occurs during two age ranges: under twenty and between 50 and 70 years of age. As already mentioned, Serratia Marcescens is not among the usual pathogens. The most common pathogen in pyogenic spinal infections is Staphylococcus aureus (20-84%). S. Marcescens is an opportunistic aerobic gram negative bacillus recognized as a nosocomial pathogen that becomes infectious when the immunity of the host is compromised (with HIV, diabetes mellitus, in chemo/ radiotherapy) and in IV drug users, but non-infectious in immunocompetent patients without associated risk factors (acupuncture or previous surgery), with a predilection for the central nervous system in the postoperative period. 11 Identification of the causal agent is essential to adjust antibiotic therapy because the empirical antibiotic administered may not be adequate and would make the condition chronic. This is the first case of spondylodiscitis from S Marcescens in its infectious form in an immunocompetent patient without a history of cervical spinal surgery. Centeno et al. describe a similar case located in the sacroiliac of a healthy patient, 12 however without the presentation of such an alarming metabolic response to the trauma as in our patient.
In diagnosis, a detailed medical history and a proper physical examination are of vital importance, as well as imaging studies to evaluate bone structures (lysis in vertebral bodies, irregularities in the levels, lordosis or kyphosis angles) and soft tissues, such as a full spinal MRI (reveals the presence of medullary lesions, such as peridural abscesses at one or several locations) and/or gammagraphy. The presence of cervicalgia and neurological symptoms justifies an MRI.
Once the diagnosis is established, surgical cleansing and stabilization of the cervical spine through instrumentation may or may not be performed during the same surgical time. However, the literature reports that, even without instrumentation, stabilization can be achieved once the infection is resolved due to the bone healing process, that allows bone fusion between the affected segments, as was the case in this patient. The con to this is the surgeon's lack of control over the final post-fusion angle of lordosis.

CONCLUSION
Microbiological isolation plays a fundamental role in the recovery and quality of life of the patient. The need for instrumentation once the infection is resolved is evaluated with clinical and radiographical parameters that suggest instability. We have presented here a case report of a microorganism that is rare in spondylodiscitis in a cervical location, which is also uncommon.
All authors declare no potential conflict of interest related to this article.