Background

Brucellosis is a zoonotic disease, which causes serious health risks and economic burdens to many countries and regions in the world [1]. Studies have shown that approximately 500,000 people are suffering from brucellosis each year in the world, with the majority of cases emerging from pastoral areas and rural areas [2], and it has been an increasing trend in recent years [3]. Most people infected with brucellosis have an apparent history of exposure, such as exposure to infected animals, ingestion of brucella contaminated animal products, and inhalation of brucella containing aerosols. Brucellosis is able to cause various symptoms involving multiple systems [4] and easy to be misdiagnosed due to lack of specificity. Here, we report a male 5-year-and-11-month old Chinese child, who was diagnosed brucellosis with meningoencephalitis, coronary aneurysm and keratitis, which has not been reported before.

Case presentation

A 5-year-and-11-month old, previously healthy Chinese child, was developed fever without obvious inducement 20 days ago. The maximum body temperature recorded was 39.4 °C, and sweating was intensified than normal condition. The child was enervated, and developed drowsiness 1 week ago, red eye phenomenon appeared 2 days ago. Physical examination showed nervous system involvement, and drowsiness and irritability occurring alternately, eye conjunctival congestion accompanied with photophobia. Nervous system examination showed hyperreflexia of the neck and positive babinski sign on the left. CT showed a slight widening of the sulcus of the brain. Upon admission, the child was preliminarily diagnosed central nervous system infection. Due to the possibility of central nervous system infection when admitted to hospital, meropenem was applied for anti-infection treatment and mannitol for reducing intracranial pressure. And the lumbar puncture examination after 2 days onwards resulted in normal physical characteristics (colorless and transparent) and normal biochemistry. Total number of white blood cells, the glucose concentration, chloride concentration and protein concentration of cerebrospinal fluids were 2.00 × 106/L (normal range 0 ~ 10 × 106 /L), 2.99 mmol/L(normal range 2.8 ~ 4.5 mmol/L), 125.7 mmol/L(normal range117 ~ 127 mmol /L), and 213.4 mg/L (normal range 200 ~ 400 mg /L) , respectively. CSF-Gram staining, ink staining, acid-fast staining and culture results were all negative. Other laboratory tests are shown in Table 1.

Table 1 Laboratory data and infection work-up
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After 2 days onwards, doppler echocardiographic suggested left anterior descending coronary artery tumor, accompanied with inner diameter dilation of double coronary artery and apparent roughness of endometrium. Taking repeated fever, conjunctival congestion in both eyes, and poor metal condition into consideration, the possibility of incomplete Kawasaki disease with coronary aneurysm and aseptic meningoencephalitis was significant for diagnosis. Intravenous immunoglobulin was given for shock treatment with dosage 2 g/kg, while aspirin and dipyridamole were added for anti-inflammation and anti-platelet aggregation.

After 3 days onwards, brucella rose bengal precipitation test result was positive, and brucella tube agglutination test results were 1:25 (++++), 1:50 (++++), 1: 100 (++++), 1: 200 (++++), 1: 400 (+++) respectively. The result of mNGS of cerebrospinal fluid indicated br.melitensis on the same day (according to Fig. 1). Having asked again about previous medical history of the child, information of goat milk ingestion (drinking) was then learned. Through contacting the sheep owner, we have confirmed that the source individual of goat milk ingested by the child was a sick sheep. Therefore, we revised the diagnosis of brucellosis with meningoencephalitis and coronary aneurysms. After 4 days onwards, we received a report of blood culture form laboratory, in which B.melitensis was prompted. After the diagnosis of brucellosis was confirmed, the adjustment therapy was rifampicin, compound sulfamethoxazole and ceftriaxone triple anti-infection standard treatment, and aspirin and dipyridamole anticoagulant treatment. And aspirin and dipyridamole anticoagulant treatment. After treatment, body temperature of the child gradually returned to normal level and the neurological symptoms disappeared.

Fig. 1
figure 1

The mNGS of cerebrospinal fluid indicated br.melitensis

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Another damaged organ of the child was the eyes. The conjunctiva of both eyes was obviously hyperemic and accompanied by photophobia. Ophthalmological examination revealed mild swelling of both eyelids, conjunctival congestion and edema in both eyes, altogether with corneal edema in both eyes, scattered infiltration of peripheral cornea, and positive corneal fluorescence staining. Fundus examination revealed reddish and round-shaped papillae of both eyes with unclear borders, ambiguous peripheral omentum, with no bleeding observed on the retina. IOP was normal. The ultrasonography of binocular and accessory apparatus indicated that the optic nerves of both eyes were slightly thickened. The CT of both eyes showed no obvious abnormality. With above information, diagnosis was made: 1. Keratitis in both eyes; 2. Papillary edema in both eyes.

After discharge, the child continued to be treated with rifampicin and compound sulfamethoxazole against brucellosis for 2 months, and continued to be treated with warfarin, aspirin and dipyridamole. Review of the doppler echocardiographic after 21 days onwards revealed the presence of multiple coronary aneurysms, warfarin anticoagulation was added. Re-examination of the doppler echocardiographic showed apparent mitigation of the child’s condition (according to Fig. 2). The result of coronary arteries with doppler echocardiographic are shown in Table 2.

Fig. 2
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The doppler echocardiographic after 60 days onwards

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Table 2 Inner diameter of coronary arteries by color doppler ultrasound
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Discussion and conclusions

Brucella is one kind of intracellular parasitic bacteria, which is gram-negative bacteria. The common types of brucella that infects people are B.melitensis, B.abortus and B.suis, and each type causes diseases with different severity. The B.melitensis and B.suis would be more serious. Eating unpasteurized dairy products is a major cause of infection. The main pathogenic mechanism is that a variety of virulence factors released by the bacteria invade the host cells and evade the immune clearance of the host body, so that brucella can survive in the host cells, replicate and reproduce, and then enter the organs and tissues through macrophages to form infectious foci or migratory foci [5]. This child was infected after drinking diseased goat’s milk, and suffered from multiple system damage. The clinical symptoms were severe.

The most common symptoms of brucellosis in adults are joint pain, fever, fatigue, sweating, weight loss, myalgia, and tremor, while fever, fatigue, bacteremia, abnormal level of liver enzyme, and hepatosplenomegaly are the main clinical manifestations of brucellosis in children [6]. In this case, fever, keratitis, nervous system involvement and coronary aneurysm were the main clinical manifestations.

The incidence of neurobrucellosis is 0.5–25%, clinical presentation includes meningitis, meningoencephalitis, meningovascular involvement, parenchymatous dysfunction, peripheral neuropathy, radiculopathy, and various degrees of behavioral abnormalities [7, 8]. Neurobrucellosis is one type of inflammation caused by direct bacterial action and the effects of cytokines and endotoxins on peripheral nerves, spinal cord, meninges, brain or vascular structures [9,10,11,12,13]. Common signs include meningeal irritation, hyporeflexia or hyperreflexia, signs of cranial nerve involvement, positive pathological reflexes, abnormalities in sensory and motor systems to varying degrees, signs of cerebellar dysfunction, and disturbance of consciousness. The diagnosis of neurobrucellosis is based on a positive cerebrospinal fluid culture or any titration of brucella antibodies and abnormal cerebrospinal fluid measurements in the cerebrospinal fluid (cerebrospinal fluid cell count>10 × 106/L, glucose decrease, protein increase) [14,15,16]. Although culture is the gold standard for the diagnosis of neurobrucellosis, the positive rate of culture is quite low (< 15%) [17] and takes long time. In this case, brucella was not cultured in cerebrospinal fluid, but detected by mNGS with test results available within 3 days. Therefore, it is speculated that this test can be used as an effective test for diagnosing neurobrucellosis. Neurobrucellosis has a good prognosis, with mortality reduced to 0–5.5% after appropriate antibiotic treatment. The results showed that the combined application of doxycycline, rifampicin and ceftriaxone was the best for the treatment of neurobrucellosis patients [18].

Cardiovascular involvement is the leading cause of death from brucellosis, and the most common manifestations of which are endocarditis, peripheral and cerebrovascular aneurysms or arteriovenous thrombosis [19]. The diagnosis of brucellosis with coronary aneurysms has not been reported. The patient of this case was admitted due to fever, red eyes and coronary artery aneurysm, which had been suspected to be incomplete kawasaki disease. But the child was still febrile after treatment according to Kawasaki disease. After the diagnosis of brucellosis was confirmed, the coronary aneurysm was considered to be vasculitis caused by brucellosis. Therefore, aspirin, warfarin, and dipyridamole were added to the anti-brucellosis treatment, and the symptoms of coronary artery injury gradually reduced. Therefore, we speculated that if brucellosis is combined with vasculitis in other parts, anticoagulant drugs can be added according to the degree of vascular involvement to relieve local vascular symptoms and reduce cardiovascular adverse events.

In this case, the eyes were obviously affected, indicated by keratitis and papillary edema. The ultrasound showed a slight thickening of the optic nerve in both eyes. We speculated that such phenomenon was caused by (1) neurobrucellosis caused optic neuritis, and (2) vasculitis caused by brucellosis. At present, the possible pathogenesis of neurobrucellosis induced optic neuritis are (1) Brucella-induced optic nerve and retinal nourishing vascular inflammation, and (2) Brucella infection induces an autoimmune response in the body.

According to the experience of this case, the clinical manifestations of brucellosis are diverse, which is easily confused with nervous system infection, incomplete kawasaki disease and other diseases. Therefore, when the children with fever of unknown causes have a history of suspicious exposure, relevant examination of brucellosis must be improved. Children suspected to be diagnosed with brucellosis can be tested by mNGS of brucellosis in relevant body fluids (blood and cerebrospinal fluid) as soon as possible. In particular, as a new method for pathogen detection, mNGS can produce fast results with high reliability (Additional file 1).