Introduction
Brucellosis is a zoonosis transmitted directly or indirectly to humans from infected animals, predominantly domesticated ruminants and swine. Its clinical features are diverse and definite indicators that confirm the diagnosis may be lacking. Thus, bacteriologic and serologic test results must usually back up the clinical diagnosis. Undulant fever with excessive night sweats, arthralgia or arthritis, and hepatosplenomegaly makes up the typical triad[1].
It is a multi-system infection that usually results in musculoskeletal involvement. Osteoarticular involvement including spondylitis, sacroiliitis, osteomyelitis, peripheral arthritis, bursitis, and tenosynovitis represents the most common complication of brucellosis affecting up to 85% of the affected patients[2]. The most common symptom of spondylodiscitis is chronic back pain; however, because it is not a distinct symptom, it often leads to a delay in diagnosis and treatment. Although rare, spinal brucellosis must remain as a differential diagnosis in a patient presenting with the lower back pain and with signs of a chronic infection. Our case report reveals an uncommon case of spinal brucellosis, including its clinical presentation, serological parameters, and management.
Discussion
Brucellae are small, Gram-negative, unencapsulated, non-sporulating rods, or coccobacilli. They grow aerobically on a peptone-based medium incubated at 37°C [1]. Brucella genus has been divided into six species, four of which are known to cause disease in man: B. abortus, Brucella suis, Brucella canis, and B. melitensis, the last being the foremost virulent. Human brucellosis is primarily caused by contact with occupational or domestic exposure to infected animals or their products (most commonly milk or milk products)[3]. The patient in our case worked as a farmer with a history of contact with farm animals such as cattle and pigs, which could have functioned as a vector for his infection. Identifying and eliminating the illness from its animal reservoirs are the most sensible method to regulate human brucellosis.
It is endemic in areas with a higher prevalence of domesticated animals, such as the Mediterranean zone, Eastern Europe, Central Asia, Mexico, and South America [1]. India has one of the largest ruminant populations in the world and brucellosis is endemic in the country in both humans and animals [4]. Human brucellosis is traditionally described as a disease of protean manifestations and the demographic and clinical characteristics are wide with an unexpected spectrum of this disease. The incubation time varies from 1 week to several months, but is typically 2–4 weeks, with fever and other symptoms appearing suddenly or gradually [2]. It often presents in two patterns: (1) Acute brucellosis presenting with undulating fever, weight loss, and fatigue and (2) chronic brucellosis presenting years after initial exposure, characterized by osteomyelitis presenting with persistent back pain, arthralgias, and sweating [5]. Children, adults, and the elderly are more likely to develop monoarthritis (knee/hip), sacroiliitis, and spondylitis, respectively. Spondylodiscitis is said to be responsible for 6–85% of brucellar osteoarticular involvements. In the spinal area, the lumbar (60–69%), thoracic (19%), and cervical segments (6–12%) are known to be involved [6].
Mild anemia may be reported. With relative lymphocytosis, peripheral leukocyte counts are frequently normal or low. Blood culture is the gold standard approach, but sensitivity is low as most patients are treated with antibiotics before the samples are sent for blood culture. Only 53–90% of brucellosis patients have positive blood cultures [7]. Because B. abortus is rarely isolated from blood or tissue, diagnosis of the disease is based primarily on the results of serological tests. Antibody titers for Brucella have been advised for determining the prognosis of the disease. In an acute infection, immunoglobulin M (IgM) antibody appears initially, followed by immunoglobulin G (IgG) and immunoglobulin A. The total number of IgM and IgG antibodies is measured using the standard agglutination test [8].Titer of ≥1:160 for Brucella agglutination test is considered significant as seen in the index case [9]. Tissue biopsy samples may reveal non-caseating granulomas contrasting to caseating granulomas with AFB in tuberculosis as was expected in the patient [10].
The radiological signs of osteoarticular infection appear later and are subtler than those of tuberculosis or other etiologies of septic arthritis, with less bone and joint erosion. The presence of focal erosions of the superior or inferior vertebral body angle is a common radiographic observation in this pathology. This eventually resulted in disc collapse [11]. On MRI, the lesions are seen as a destructive appearance (Pedro Pons’ sign) at the anterosuperior corner of the vertebrae with osteosclerosis, which is a pathognomonic finding. Single-focal, contiguous multifocal, or non-contiguous multifocal involvement can be seen in spondylodiscitis of an infectious etiology. The focused form is limited to the anterior region of an endplate, while the diffuse form can affect the entire vertebral body, as well as the discs, vertebrae, and epidural space[6]. Our patient likely had the non-contiguous multifocal type, involving D10-D11 intervertebral spaceand epidural space and a skip lesion in L4-L5 region.MRI plain narrowed the pathology to infective origin and excluded neoplastic lesions; hence, MRI contrast was not needed in our case. Post recovery MRI was not performed as it was not affordable by the patient. A diagnosis of spinal brucellosis is made if at least two of the following findings are present: (1) Brucella positive blood and/or bone marrow aspirate culture, (2) significantly high titers of Brucella agglutination test, (3) radiographs showing skeletal involvement typical of osteomyelitis or spondylodiscitis, and (4) biopsy suggestive of brucellosis with non-caseating granulomatous tissue[10]. In our case, the patient showed significant B. abortus agglutination titers of 1:320 and MRI findings consistent of D10-D11 infective spondylodiscitis; hence, he was diagnosed with brucellar spondylodiscitis.
The main aim of antimicrobial medications in brucellosis is to treat the disease and its symptoms and signs and to prevent relapses. There is no standard treatment for osteoarticular brucellosis and experts prescribe medications depending on their personal experiences and the severity of the disease. Over the course of 6 months, a triple regimen of Streptomycin (1g daily), Doxycycline (10mg twice day), and Rifampin (15 mg/kg daily) exhibited 100% efficacy against spinal brucellosis [12]. Double therapy with Doxycycline and Rifampin, on the other hand, was linked to relapses. Patients require long-term antibacterial treatment (typically for at least 3 months) to avoid relapses. Spondylodiscitis is the most severe form of musculoskeletal involvement of brucellosis, due to its potential to develop an epidural abscess, and should be treated promptly with decompression to reduce the risk of long-term neurological damage, if nerve compression occurs [8]. In terms of clinical presentation and serological data, there is a significant overlap between brucellosis and tuberculosis [13] Vaccines based on live attenuated Brucella strains, such as B. abortus strain 19BA or 104M, have been used in various countries to protect high-risk populations, despite their short-term efficacy and high reactogenicity [1].