Background

Human brucellosis, caused by intracellular gram-negative coccobacilli known as Brucella species, is recognized as one of the most prevalent zoonotic diseases globally. Among all the species, Brucella melitensis is the main pathogenic strain associated with human brucellosis in China.1 According to the latest data released by the China Centers for Disease Control and Prevention (http://www.chinacdc.cn), a total of 69,767 brucellosis cases were reported in China in 2022, incidence rate of 4.69/100,000, an increase in incidence rate (23.29%) compared to the average of the previous three years (2019–2021) (53,683 cases/year). The Xinjiang Uyghur Autonomous Region (XUAR), which borders eight countries, is an epidemic area with a highly prevalence of brucellosis.2 In 2022 Xinjiang reported 6,370 cases, ranking second in China, and in 2023 showed a continued rapid rise, with 8,393 cases reported, up 31.76% compared to 2022. Brucella infection can affect multiple organs and manifest with a wide range of symptoms, varying from asymptomatic to systemic involvement, including hepatic, cardiac, ocular, and central nervous systems (CNS).3 Although CNS cases occur in only 4% to 7%, neurologic involvement is the most serious complication.4 The most common presentation is meningoencephalitis.5 Moreover, in Xinjiang, China, which is a region with a high prevalence of brucellosis and tuberculosis, the diagnosis of neurobrucellosis is an important challenge to differentiate it from neurotuberculosis proper for treatment and outcome.6,7 However, few studies on meningitis attributable to Brucella infection have been conducted in China. In this report, we describe a male patient with meningitis caused by B. melitensis biovar 3 who was treated with a combination of corticosteroids and antibiotics.

Case Presentation

A 46-year-old male patient with an unknown-origin fever reaching 38.4°C (self-measurement), weakness, and generalized body soreness was initially presented to the local hospital (People’s Hospital of Bortala Mongolia Autonomous Region) on April 16, 2021. The patient, responsible for year-round sheep husbandry, had a medical history of atrial fibrillation for the past 3 years, for which he had undergone an ablation procedure. Upon examination, the serum tube agglutination test (SAT) for Brucella was positive, with a titer of 1:400. The patient received doxycycline (100 mg. po.b.i. 24h) and rifampicin (600 mg. ivgtt. q.24h) for anti-infective treatment, but intermittent fever continued.

Six days later, on April 22, 2021, the patient suddenly developed disordered consciousness, speech impairment, and urinary incontinence. Due to the critical condition of the patient, the local hospital recommended his transfer for advanced medical care. He suddenly developed violent limb convulsions lasting for 3 minutes gradually easing. Another convulsion occurred after an interval of 5 minutes during his route to Shihezi at 9 AM on April 23, 2021. Upon arrival, he was admitted to the emergency department of the First Affiliated Hospital of Shihezi University.

We immediately administered anticonvulsant therapy with diazepam injection (20 mg ivp). On admission, a physical examination and laboratory tests were performed. During physical examination, the patient showed a stiff neck and presented with nausea and vomiting. Laboratory tests indicated increases in total protein (8440 mg/dl), total bilirubin (1.60mg/dl), uric acid (10.20 mg/dl), glucose (149.57 mg/dl), creatine kinase (334.6 U/L), lactate dehydrogenase (825.5 U/L), magnesium (2.40 mEq/L), alanine aminotransferase (65.6 U/L), and aspartate aminotransferase (53.1 U/L) levels. An increase in white blood cell (WBC) of 11.3×109/L (8.09 ×109/L neutrophils and 19.7% lymphocytes), and a decrease in eosinophilic granulocytes (0.10%) were also observed. The erythrocyte sedimentation rate and C-reactive protein levels were elevated at 23 mm/h and 1.967mg/dl, respectively. Cerebrospinal fluid examination revealed that the intracranial pressure was > 325 mm H2O (normal range, 80–180 mm H2O), Pandy’s test result was positive, protein level in the abnormal cerebrospinal fluid (CSF) was 155 mg/dl, chloride level had decreased to 386.76mg/dl, and glucose level had decreased to 23.43 mg/dl. In addition, the CT of the head was unremarkable. Baseline electrocardiography showed an ectopic heart rhythm and rapid atrial fibrillation. Mild regurgitation of the mitral valve and incongruous movement of the ventricular wall were observed through TTE. The functions of the liver and thyroid were normal, and indicators of autoimmune diseases were negative. We ruled out Mycobacterium tuberculosis infection by conducting T-cell testing for tuberculosis, blood culture and identification, and sputum smear microscopy. Additionally, we tested for cytomegalovirus DNA, Epstein-Barr virus, and the nucleic acid of SARS-CoV-2, all of which returned negative results. Brucella colonies were isolated from CSF) and identified using standard procedures.8 Phylogenetic analysis revealed that the Brucella isolated in this study closely coincided with those of B. melitensis biovar 3 isolated from sheep in Xinjiang, China (Figure 1). Upon reconfirmation of the patient’s history, we observed that he had been in contact with sick sheep and had not wear protective masks and gloves during feeding and delivery. We postulated that the patient acquired Brucella through direct contact or respiratory transmission. Therefore, we suspected that the patient’s Brucella infection was linked to exposure to the sheep. We detected the strain using PCR with the IS711 gene and confirmed it as B. melitensis (GeneBank: ON09465). The classification of B. melitensis biovar 3 was determined by serotyping, phage typing, fuchsin and thionidine sensitivity, CO2 requirement, H2S production, and metabolic properties (Supplementary Table 1). This process was completed at the Veterinary Station of the Eighth Agricultural Division of the Xinjiang Production and Construction Corps.

Figure 1 The phylogenetic tree of the IS711 gene concatenated sequence of Brucella melitensis (black dot) isolated from cerebrospinal fluid in this study.

The patient was diagnosed with meningitis caused by B. melitensis biovar 3. Cefatriaxone (4 g. ivgtt. q.24h), rifampicin (600 mg. ivgtt. q.24h), moxifloxacin hydrochloride (400 mg. ivgtt.q.24h) and doxycycline (100 mg. po.b.i. 24h) were administered as the initial treatment of infection. The dexamethasone (10 mg ivgtt. q.24h) was used in a gradually decreasing doses regimen and combined with mannitol (125 mL.vgtt.q.8h) to reduce the intracranial pressure. The patient simultaneously received liver-preserving treatment with monoammonium glycyrrhizinate and cysteine and sodium chloride injection (250mL, vgtt.q.24h). After a few days, he demonstrated gradually improvement in consciousness, regained spontaneous respiration, and was able to resume oral feeding by May 6, 2021. His clinical condition gradually improved, and biochemical parameters remained within normal ranges. The patient was discharged with rifampicin (600mg. po. q.24h), moxifloxacin hydrochloride (400 mg. po. q.24h), and doxycycline (100 mg. po.b.i. 24h). The timeline for this case is shown in Figure 2. The oral anti-infective regimen was maintained two months, the pathological symptoms of the patient have basically disappeared, the body temperature was stable, and antibiotics were stopped. The follow-up maintained two years, the patient with no symptomatic recurrences or sequel.

Figure 2 Timeline of the case report.

Discussion and Conclusions

Brucellosis, the most common bacterial zoonosis worldwide, is usually transmitted through contact with infected animals or the ingestion of contaminated food.9 This multi-system disease presents with various clinical manifestations.10,11 Although the incidence of nervous system involvement is only 2% to 5%, it is the most serious complication involving the central and peripheral nervous systems.5 In this case, the patient experienced CNS infection with multiple symptoms. The Xinjiang region of China also has a high incidence of tuberculosis,6 and Mycobacterium tuberculosis infections can also involve the nervous system.7 Therefore, when the patient was transferred to our hospital, we focused on screening for Mycobacterium tuberculosis and Brucella infections through laboratory and clinical examinations, and quickly formulated a symptomatic treatment plan after determining that it was a Brucella infection, thus effectively controlling the progression of the disease. This highlights the importance of differential diagnosis.

Neurobrucellosis presents in a variety of ways, such as meningitis, encephalitis, meningoencephalitis, radiculitis, osteomyelitis, optic neuritis, and behavioral abnormalities, with meningitis being the most common, accounting for 17–74% of cases.3,12 Although CNS involvement is rare, it severely restricts the survival rate of patients without accurate diagnosis and timely treatment. In this case, the patient initially sought treatment at a local hospital for fever, fatigue, and general pain, where they received care for 7 days. Despite receiving anti-infective treatment, the patient’s condition did not improve significantly, leading to the progression of the disease meningitis. This underscores the crucial importance of accurate and timely diagnosis in such cases.

Management of neurobrucellosis requires special attention because the illness occurs suddenly with complications, sequelae, and high mortality. Generally, antibiotic regimens include a combination of two or three antibiotics selected from fluoroquinolones, sulfanilamides, tetracyclines, cephalosporins, rifampicin, and amino glycosides.13 The regimen is often modified several times following developments in symptoms, clinical findings, and the course of the disease. On average, patients with neurobrucellosis are treated for more than three months.1,13,14 Here, given the early identification of Brucella infection, a focused treatment program was promptly devised. The patient received a combination of moxifloxacin hydrochloride, doxycycline, rifampin, cefatriaxone, dexamethasone, and mannitol was administered. Among these, moxifloxacin hydrochloride, doxycycline, rifampin and cefatriaxone have the ability to cross the blood-brain barrier, enabling them to exert an immediately bactericidal effect.15,16 It is worth noting that the dosage of ceftriaxone (4g. q.24h) sodium used in this case was twice than that of the conventional dosage. We used this quadruple antibiotic combined with corticosteroids and mannitol therapy to effectively control disease development and treated the patient in a relatively short period of time.

Among glucocorticoids, which have good anti-inflammatory effects, dexamethasone has a longer half-life and easily crosses the blood-brain barrier.17 In our dexamethasone reduction program, we injected 10, 5, and 2.5 mg intravenously on April 23, April 25, and May 1, 2021. The patient’s physical condition improved gradually, and all medical indicators returned to normal. A combination therapy with dexamethasone can improve many parameters of bacterial meningitis.17 Moreover, early treatment with dexamethasone improves prognosis and survival in adults with acute bacterial meningitis and does not increase the risk of gastrointestinal bleeding.18,19 Among patients with pneumococcal meningitis, 14% of those treated with dexamethasone died and 34% of those treated with placebo died. In addition, patients in the dexamethasone group were significantly less likely to experience impaired consciousness (11% versus 25%), seizures (5% versus 12%), and cardiopulmonary failure (10% versus 20%).18 These findings explain the significant role of dexamethasone in the treatment process. Therefore, we suggest the early administration of dexamethasone following confirmation of meningitis.

The identification of the individual strains of Brucella is important for epidemiology because of the close association between the individual strains of the genus Brucella and their natural hosts.8 Examples include finding the source of zoonotic infections, epidemiologic investigation of outbreaks, monitoring strains that spread in a specific geographic area and their spread over time, and the distinction between wild-type and vaccine strains. Although there have been some reports of meningitis caused by Brucella, few genotypes have been identified.20–22 To the best of our knowledge, there is only one report of human neurobrucellosis caused by B. melitensis biovar 3 in Italy.14 Moreover, no data are available on the characterization of Brucella isolates from humans at the biovar level in China. In previous studies, brucellosis in humans and livestock was mainly caused by B. melitensis biovar 3 in XUAR, and in our study, the genotype of Brucella is consistent here, which is also B. melitensis biovar 3. Current research is limited and we are unable to determine whether B. melitensis biovar 3 is more easily crosses the blood-brain barrier than other biovars and cause nervous system infections.Therefore, we recommend that in the management of patients, all isolated strains identified at the species level to determine their biota, which will help us to make targeted control programs tailored to specific for different regions and effectively control the disease.

This is the first reported case of meningitis caused by B. melitensis biovar 3 isolated from a shepherd in China. Our study indicates that the genetic features identified in B. melitensis biovar 3 will facilitate diagnostic and epidemiological studies on both animal and human brucellosis. However, this case only reports a case of meningitis caused by B. melitensis biovar 3, and its species specificity and associated pathogenic mechanism is still unclear, which is our next research direction. Nonspecific findings of neurobrucellosis often make diagnosis difficult. In regions endemic to brucellosis, it is crucial to consider Brucella as a potential causative agent in individuals with pre-diagnosed meningitis for timely diagnosis and proper treatment. The antibiotic combined with corticosteroids regimen utilized in this case offers guidance for the treatment of early Brucella-induced meningitis. We recommend training in knowledge and skills related to brucellosis prevention in areas with high brucellosis prevalence, as well as routine screening for brucellosis, with a focus on screening high-risk groups such as shepherds, for early detection and treatment.

Data Sharing Statement

All of the data generated or analyzed in this study are included in this published article.

Ethics Approval and Consent to Participate

This study was approved by the Ethics Committee of the First Affiliated Hospital of Shihezi University (KJ2020-034-01) approved the study.

Patient Consent for Publication

Written informed consent was obtained from the patient for publication of this case report and the images. Details of the case can be published without institutional approval.

Acknowledgments

We thank all the subjects who participated in our study.

Author Contributions

Equally contributed to this work as a first author: Shuzhu Cao, Songsong Xie and Shengnan Song. All authors made a significant contribution to the work reported, whether that is in the conception, study design, execution, acquisition of data, analysis and interpretation, or in all these areas; took part in drafting, revising or critically reviewing the article; gave final approval of the version to be published; have agreed on the journal to which the article has been submitted; and agree to be accountable for all aspects of the work.

Funding

This research was supported by the National Natural Science Foundation of China (grant no. 32372973, 32260870), the Scientific and Technological Tackling Plan for Key Fields of the Corps (2024AB034, 2024AB035, 2022DB018), the National Science and Technology Basic Resources Survey Special Project (grant no. 2022xjkk050203), the Corps Five Common One Promotion Project (CZ003802), International Science and Technology Cooperation Promotion Plan (grant nos. 2015DFR31110), and Postdoctoral Fund project of Shihezi University (CZ000901), Chinese Academy of Medical Sciences (CAMS): Special Funding for Basic Research Operating Costs of Centralized Public Welfare Research Institutes (2020-PT330-003), 2021 Shihezi University Young Innovative Cultivation Talent Program Project (CXPY202102), Corps Guiding Science and Technology Program Project (2022ZD026).

Disclosure

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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