1 Introduction

Brucellosis, a prevalent zoonotic disease globally. Most commonly, people become infected by consuming raw or unpasteurized dairy products. Sometimes the bacteria that cause brucellosis can be spread through the air or through direct contact with infected animals. Brucella bacteria in the milk of infected animals can be transmitted to humans through untempered milk, ice cream, butter and cheese. The bacteria can also be spread through raw or undercooked meat from infected animals. Brucella is easily spread through the air. Farmers, hunters, lab technicians and slaughterhouse workers can inhale the bacteria [1, 2].

The incubation period for brucellosis ranges from 5 days to several months, with an average of 2 weeks. The onset of the disease can be sudden, typically with chills, fever, severe headache, joint and back pain, malaise, and occasionally diarrhea. Or the onset may be insidious, characterized by mild prodromal discomfort, myalgia, headache, and neck and back pain, followed by nocturnal fever and fluctuating fever. Some patients have only transient fever, but others may have recurrent fluctuating fever and remissions extending over months or years, presenting as unexplained fever. After the initial febrile period, nausea, weight loss, abdominal pain, arthralgia, headache, backache, malaise, irritability, insomnia, depression, and emotional instability may occur. Constipation usually develops. Splenomegaly and lymph nodes are mildly or moderately enlarged; hepatomegaly may be present in nearly 50% of patients. Brucellosis has a mortality rate of < 5%, usually from endocarditis or severe central nervous system (CNS) complications [3, 4].

Spontaneous bacterial peritonitis (SBP) is very common in ascites due to cirrhosis. It typically presents with persistent mild to moderate discomfort throughout the abdomen. This infection can cause serious consequences or death. The most common bacteria causing SBP are Gram-stain-negative Escherichia coli and Klebsiella pneumoniae and Gram-stain-positive Streptococcus pneumoniae, usually involving a single group of organisms. Signs of SBP include fever, malaise, encephalopathy, exacerbation of hepatic failure, and worsening of unexplained clinical condition. Peritoneal signs (e.g., abdominal tenderness and rebound pain) may be present, but these signs may be somewhat diminished by the presence of ascites [5, 6]. Brucella peritonitis(BP), though rare, primarily affects patients with cirrhosis and those undergoing peritoneal dialysis. Symptoms range from poor appetite, fatigue, and bloating to fever and joint pain [7,8,9,10]. This study analyzes the general data, epidemiological history, clinical features, laboratory tests, and medical records of four patients with BP, offering valuable insights for clinical diagnosis and treatment.

2 Medical History Section

2.1 General Data and Epidemiologic History

Diagnosis of brucellosis adhered to the 2017 China’s Expert Consensus on Brucellosis Management. Between January 2022 and November 2023, four male patients with BP (ages 42 to 75) were admitted to the Department of Infection at the First People’s Hospital of Kashi Region. All patients were engaged in animal husbandry. All patients presented with a decompensated stage of cirrhosis (refer to Table 1).

The ethics committee of the First People’s Hospital of Kashi approved this study with the code [2023] Expedited Review Study No. (82).

Table 1 Basic data and clinical characteristics of 4 patients
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2.2 Clinical Manifestations

Patients primarily exhibited poor appetite, fatigue, and bloating, with two developing moderate to high fever. Positive mobile turbidities, splenomegaly, and signs of peritoneal irritation were consistent findings during examination (see Table 1).

2.3 Laboratory Tests

All patients tested positive for IgG antibodies to Brucella. One patient had a positive Rose Bengal Plate Agglutination Test (RBPT) and Serum Agglutination Test (SAT, 1:800). Brucella was cultured from blood(2), ascites(1), and pleural fluid(1). Elevated C-reactive protein (CRP) was observed in all patients, while erythrocyte sedimentation rate(ESR) increased in three. Mild liver function abnormalities were noted in three patients. Renal and coagulation functions remained normal. Peritoneal fluid analysis revealed elevated leukocytes, predominantly mononuclear cells. (refer to Table 2).

Table 2 Laboratory tests of 4 patients
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2.4 Radiographic Examination

Abdominal ultrasound or Computed Tomography (CT) examinations for all four patients indicated (1) cirrhosis; (2) splenomegaly; (3) ascites.

2.5 Treatment History

Patients received tailored anti-infection treatments, including levofloxacin 500 mg po daily for 6 weeks and doxycycline 100 mg po twice daily for 6 weeks, or gentamicin 320 mg ivdrip daily for 7 days and doxycycline 100 mg po twice daily for 6 weeks. Three patients with hepatitis C liver cirrhosis were given antiviral treatment with Epclusa(sofosbuvir 400 mg + velpatasvir 100 mg) 1 tablet daily for 6 months; one case of hepatitis B liver cirrhosis was treated with entecavir(ETV,0.5 mg) antiviral therapy. All patients received albumin supplementation, ascites drainage, and diuresis during hospitalization.

2.6 Therapeutic Effects

Following effective anti-infection and symptomatic treatment, clinical symptoms improved in all patients. Blood leukocytes, CRP, and other inflammation indicators returned to normal. Ascites ultrasound before discharge revealed no significant ascites in three patients.

3 Discussion

Brucella transmission occurs through contact with skin, mucous membranes, the digestive tract, and the respiratory tract [1, 2]. While differentsystem damage is common, peritonitis is a rare manifestation. Our study, spanning the past two years, identified four cases of BP among brucellosis admissions, all originating from farmers engaged in animal husbandry. Direct contact with diseased animals was the common mode of transmission.

Brucella-associated peritonitis predominantly occurs in two conditions: cirrhosis and peritoneal dialysis [7,8,9,10].When combined with cirrhosis, atypical symptoms may manifest, such as bloating, poor appetite, and fatigue [10]. Our patients, aligning with existing literature, displayed symptoms consistent with BP. Notably, only 2 out of 4 patients (50%) developed fever, a lower occurrence than reported in other brucellosis cases. This may be related to the fact that all patients had a combination of decompensated cirrhosis and hypersplenism. On the one hand, patients with decompensated cirrhosis are more immunocompromised [11]. On the other hand, patients with chronic liver disease may have had repeated visits to the doctor and a history of antibiotic therapy.

Patients with decompensated cirrhosis are susceptible to SBP, characterized by exudative ascites with elevated polymorphonuclear cells [5, 6]. Common major pathogens are enteric gram-negative bacteria [5, 12]. In combination with BP, it also shows exudative ascites, but elevated mononuclear cells predominate. Usually no high leukocytes in blood count, PCT < 0.25ng/ml [5, 6, 12]. All four patients in our study exhibited elevated mononuclear cells in peritoneal fluid, confirming Brucella as the causative agent.

The Kashi region’s high incidence of tuberculosis necessitates differentiation between BP and tuberculous peritonitis [13]. Our cases, showing low total protein in ascites, ADA < 20, no acid-fast bacilli on ascites smear, and negative DNA for Mycobacterium tuberculosis complex, ruled out tuberculous peritonitis.

Serological diagnostics for Brucella involve RBPT and SAT, with pathogenetic evidence considered the gold standard for diagnosis [3]. Blood counts may reveal leukopenia, thrombocytopenia, decreased hemoglobin, and elevated ESR, CRP, and liver impairment. In our study, all patients exhibited pathogenetic evidence, with elevated CRP and symptomatic improvement following targeted antimicrobial therapy.

Given the specific nature of Brucella infection, SBP caused by Brucella requires tailored anti-infectives. For acute-phase brucellosis, the World Health Organization recommends doxycycline and rifampicin or doxycycline and aminoglycoside antibiotics for 6 weeks. In our cases, rifampicin was excluded due to concerns related to decompensated cirrhosis, potential liver injury [14], and drug-drug interactions with sofosbuvir/velpatasvir [15].

The study’s limitation is primarily the small sample size. Future collaboration with multicenter brucellosis clinics will allow statistical analysis of more medical records.

4 Conclusion

Brucella peritonitis is most commonly seen in people with underlying cirrhosis. Ascites show exudative changes with predominantly mononucleated cells. Positive blood or body fluid cultures for Brucella or SAT help in diagnosis. Antimicrobial drugs may be chosen as doxycycline based therapy in combination with quinolone antibiotics or aminoglycoside antibiotics.