Spontaneous bacterial peritonitis due to Brucella species versus peritoneal dialysis-related peritonitis: a systematic review

Abstract

Introduction

Brucella-associated primary peritonitis is an exceptionally rare condition that may present as spontaneous bacterial peritonitis (SBP) or peritoneal dialysis-related peritonitis (PDrP). We investigated demographic and clinical characteristics of these two entities caused by Brucella species.

Methods

A systematic review of the literature was undertaken to identify published cases of primary peritonitis caused by Brucella species and perform comparative analysis. Cases were categorized as SBP or PDrP and analyzed for demographics, clinical features, microbiology, treatment regimens and outcomes.

Results

A total of 33 cases were identified: 22 of SBP and 11 of PDrP. Among these, SBP cases occurred predominantly in older cirrhotic males (mean age 55.2 years), with Brucella isolated mainly from blood cultures (72.7%) and an associated mortality rate of 13.6%. In contrast, PDrP cases involved younger, generally healthier individuals on PD (mean age 47.5 years), where Brucella was universally isolated from peritoneal fluid and mortality was 0%. Catheter removal was required in 36.4% of PDrP cases. Epidemiological risk factors were more common in PDrP (81.8% vs. 45.5%). Blood culture positivity was significantly higher in SBP (p=0.016), while peritoneal fluid cultures were more often diagnostic in PDrP (p=0.028). Most patients received combination therapy with doxycycline and rifampicin, while treatment duration tended to be longer in PDrP.

Conclusion

Brucella peritonitis shows differing patterns in SBP and PDrP. Early identification and appropriate intervention are essential for favorable clinical results.

Introduction

The peritoneum is a delicate serous membrane enveloping the abdominal cavity, functioning as a critical immunological barrier that contributes to host defense against microbial invasion. Inflammation of this membrane, termed peritonitis, is broadly classified into primary and secondary forms, based on the presence or absence of an identifiable intra-abdominal source of infection [1]. Primary peritonitis encompasses both spontaneous bacterial peritonitis (SBP) typically affecting patients with liver cirrhosis, and peritoneal dialysis (PD)-related peritonitis (PDrP), which occurs in individuals receiving PD [2]. Despite their inclusion under the same classification, SBP and PDrP involve distinct patient populations, pathogenic mechanisms, microbiological profiles and therapeutic strategies.

Brucellosis, a significant zoonotic disease caused by intracellular Brucella species, remains prevalent in regions including the Mediterranean basin, the Middle East, parts of Asia and Latin America [3]. Humans typically acquire the disease by consuming unpasteurized dairy products or through direct contact with infected animals [4]. Although brucellosis most commonly presents as a systemic illness with diverse organ involvement, peritoneal infection due to Brucella is extremely rare. When it does occur, it may manifest either as PDrP in patients on PD or as SBP in cirrhotic individuals, both representing unusual and diagnostically challenging clinical scenarios [5,6]. In most cases, PDrP is attributed primarily to Gram-positive cocci, with Gram-negative bacilli less frequently involved [7]. Brucella species represents an uncommon and often overlooked pathogen, even in areas where the disease is endemic. In contrast, SBP is most attributed to enteric Gram-negative bacteria such as Escherichia coli and Klebsiella species, as well as to certain Gram-positive organisms like Streptococcus species [8]. Brucella-associated SBP constitutes an infrequent clinical entity and is often underrecognized in clinical practice.

Owing to the differing pathophysiological backgrounds, routes of infection and clinical profiles of Brucella-induced PDrP and SBP, clearly distinguishing these conditions is essential to ensure accurate diagnosis and guide appropriate therapeutic strategies. This comprehensive review synthesizes and compares the available case data on Brucella-related primary peritonitis, aiming to support clinicians in the recognition, management, and prognosis of these rare but important infections.

Methods

Study design and protocol registration

This systematic review was developed and implemented following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) 2020 guidelines, which promote a structured and transparent methodology for synthesizing evidence [9]. The review protocol was prospectively registered in the PROSPERO international database (Registration Number: 2025 CRD420251042629; available at: https://www.crd.york.ac.uk/PROSPERO/view/CRD420251055905), ensuring methodological consistency and minimizing bias.

Eligibility criteria

We included all published case reports, case series and clinical studies reporting infectious complications due to Brucella species manifesting as peritonitis in patients of any age. Both PDrP and SBP cases were eligible for inclusion. Inclusion was based on microbiological confirmation of Brucella infection through culture or molecular diagnostics from peritoneal dialysis effluent, ascitic fluid and/or blood cultures.

Diagnostic definitions

Diagnosis of SBP was established when patients fulfilled criteria (ii) and (iii), with or without the presence of clinical signs (criterion i). Specifically, the required criteria included: i) the presence of clinical signs consistent with peritonitis, such as abdominal pain, tenderness or fever (supportive but not required for diagnosis); ii) an ascitic fluid neutrophil count ≥250 cells/mm³ with predominance of polymorphonuclear cells; and iii) microbiological or serological confirmation of Brucella infection, namely a positive peritoneal fluid culture, and/or a positive blood culture isolating pathogen species, and/or elevated pathogen-specific serologic titers (e.g., SAT ≥1:160). The exclusion of secondary causes of peritonitis was also essential to attribute the infection to pathogen [3].

Diagnosis of PDrP was established when patients fulfilled at least two of the following criteria: i) clinical signs suggestive of peritonitis (such as abdominal pain, fever, or cloudy effluent); ii) dialysate white blood cell count >100 cells/mm³ with >50% polymorphonuclear neutrophils; and iii) a positive culture of peritoneal fluid isolating Brucella species, which was considered mandatory for confirming the diagnosis [7]. The identification of Brucella in the peritoneal dialysis effluent was essential to attribute the infection specifically to this pathogen.

Literature search and data sources

a systematic search was performed in two major electronic databases, PubMed and Google Scholar, encompassing literature available up to May 1, 2025. Search terms included combinations of “Brucella”, “peritonitis”, “spontaneous bacterial peritonitis”, “peritoneal dialysis” and related synonyms. There were no restrictions based on language; studies published in languages other than English were translated with the aid of reliable machine translation software. Additionally, the reference lists of the selected articles were manually reviewed to identify further relevant publications.

Screening and selection process

the initial screening was conducted by two independent reviewers (J.D. and A.P.) assessing titles and abstracts for relevance. Articles deemed potentially eligible proceeded to full-text review by three independent reviewers (J.D., C.A. and A.P.). Disagreements were resolved through consensus discussions among all authors (J.D., C.A., A.P. and N.P.) to ensure reliability and minimize selection bias.

Data extraction

A standardized data collection form was employed to collect detailed information from each report included. Extracted variables encompassed: publication year, geographical origin, patient demographics (age, sex), underlying hepatic or renal disease/indication for peritoneal dialysis, previous history of peritonitis or exit-site infections, clinical presentation and symptomatology, laboratory parameters, inflammatory biomarkers, identification methods for Brucella species and antimicrobial susceptibility profiles, therapeutic regimens (drug choice, dosage, route of administration, treatment duration), catheter management strategies (removal, retention, or replacement), clinical outcomes and mortality.

Ethical considerations

As this review exclusively involved data from previously published studies and retrospective analyses, no new patient data were collected, and institutional ethical approval or informed consent were not applicable. Any retrospective data obtained from medical records was already covered by existing institutional ethics approvals.

Data synthesis and statistical analysis

All extracted data were organized in Microsoft^® Excel (version 5.2.3790.1830, Redmond, WA, USA). Descriptive statistics were used to summarize clinical and demographic characteristics. Continuous variables were expressed as mean ± standard deviation, while categorical variables were presented as frequencies and percentages. Group comparisons (e.g., PDrP vs. SBP) were performed using one-way ANOVA for normally distributed data or Kruskal-Wallis test for non-parametric data. Categorical variables were compared using Chi-square or Fisher’s exact test, as appropriate. Statistical significance was set at a two-tailed p-value < 0.05. All analyses were carried out using GraphPad Instat software (version 3.10, GraphPad Inc., San Diego, CA, USA).

Results

A total of 33 documented cases of primary peritonitis caused by Brucella species were identified following a comprehensive review of 29 published articles. The process of literature selection and inclusion, conducted in accordance with the PRISMA 2020 guidelines, is illustrated in Figure 1. All cases were categorized into two distinct clinical groups based on the underlying condition: 22 cases were classified as SBP [10–28], which are presented in Table 1, while the remaining 11 cases were categorized as PDrP [6, 29–37], detailed in Table 2. The comparative analysis of the two clinical entities including clinical features, microbiology, treatment, and outcomes between the two entities is summarized in Table 3.

Figure 1.

The PRISMA flowchart illustrates the process followed for identifying, screening, and selecting studies included in this review

Table 1.

Summary of published cases of Spontaneous Brucella Peritonitis (SBP) as reported in the international medical literature

No	Reference, year	Age (years)/Gender	Symptoms	Infectious source	Underlying Condition	Blood Culture	Peritoneal fluid culture	STA; titer	Treatment	Outcome
1	Diab et al., 1989 [10]	55/F	N/A	Unknown	Nodular plaques on the peritoneum, intestinal obstruction	Negative	Negative	1/640	Doxycycline-rifampicin	Cured
2	Demirkan et al., 1993 [11]	60/M	Melena	Unknown	Liver cirrhosis	B. mellitensis	Negative	1/640	Ofloxacin	Cured
3	Doganay et al., 1993 [12]	23/F	N/A	Unknown	Liver cirrhosis (chronic HBV and HDV superinfection)	Negative	Negative	1/1,280	Pefloxacin (switched to co-trimoxazole / streptomycin	Cured
4	Bourantas et al., 1997 [13]	54/F	Fever, shivering, night sweats, anorexia, fatigue, and weight loss	Contact with animal	None	B. mellitensis	Negative	Negative	Oxytetracycline (6w) - streptomycin (3w)	Cured
5	Alcala et al., 1999 [14]	42/M	Malaise, abdominal pain, and reduced urine output	Unknown	Chronic carrier of HBV surface antigen	B. mellitensis	B. mellitensis	1/20,480	Ofloxacin-doxycycline	Death (10 d)
6	Ozakyol et al., 1999 [15]	51/M	Rigor, abdominal swelling, abdominal pain, and peripheral edema	Unknown	Alcoholically decompensated liver cirrhosis	B. mellitensis	B. mellitensis	1/640	Doxycycline-streptomycin (6w)	Cured
7	Erbay et al., 2003 [16]	65/F	Fever, night sweats, diarrhoea, abdominal pain and arthralgia	Unpasteurized dairy product consumption	Liver cirrhosis due to chronic HCV	B. mellitensis	B. mellitensis	1/10,240	Doxycycline-Rifampicin switched to co-trimoxazole/Streptomycin (6w)	Cured
8	Gençer et al. 2003 [17]	67/F	Fever, dyspnea, malaise, abdominal distension and night sweats	Unknown	Congestive heart failure	B. mellitensis	B. mellitensis	1/1,280	Doxycycline-streptomycin (6w)	Cured
9	Gürsoy et al., 2003 [18]	63/M	Weakness, backache, abdominal pain and abdominal swelling.	Unknown	DM	B. mellitensis	B. mellitensis	1/1,280	Doxycycline-rifampicin (8w)	Cured
10	Hermida et al., 2005 [19]	59/M	Abdominal distension, edema and purpuric rash	Unknown	smoking and alcohol abuse	B. mellitensis	B. mellitensis	1/320	Doxycycline-levofloxacin-rifampicin (6w)	Cured
11	Kantarçeken, al. 2005 [20]	65/M	Fatigue, arthralabdominal pain and distention	Unknown	Liver cirrhosis due to chronic HBV	B. mellitensis	B. mellitensis	1/1,280	Doxycycline-ofloxacin-ceftriaxone	Death (10 d)
12	Dizbay et al., 2007 [21]	64/M	Abdominal pain, nausea and progressively-developing weakness	Unknown	None	Negative	B. mellitensis	1/10,240	Doxycycline-rifampicin	Death (28d)
13	Güçlü et al., 2007 [22]	60/F	Abdominal pain, weakness, dyspnea, diffuse body pain and abdominal distention.	Unknown	Liver cirrhosis	B. mellitensis	B. mellitensis	1/1,280	Ciprofloxacin-rifampicin (6w)	Cured
14	Ferreira et al, 2013 [23]	47/M	Ascites, jaundice and encephalopathy	Unknown	DM, Liver cirrhosis due to chronic HCV	Brucella spp.	Brucella spp.	Not tested	Doxycycline-rifampicin (8w)	Cured
15	Javeri et al., 2014 [24]	54/M	Dyspnea on exertion, early satiety, new onset abdominal distention, bilateral lower extremity edema	Contact with dog	Liver cirrhosis due to chronic HCV and alcohol	Negative	B. canis	Not tested	Doxycycline (6w)-gentamycin	Cured
16	Makaritsis et al., 2015 [25]	69/M	Low back pain and abdominal distension, abdominal pain	Contact with animal	None	Brucella spp.	Brucella spp.	1/1,260	Doxycycline-rifampicin-streptomycin (18w)	Cured
17 *	Pan et al., 2024 [26]	42/M	Fever, weak sweats, anorexia, bloating	Contact with animal	DM, liver cirrhosis, HCV	Brucella spp.	Negative	1/800	Levofloxacin/doxycycline (6w) or doxycycline (6w)-gentamicin (7d)	Cured
18 *	#	75/M	Weak, anorexia, bloating	Contact with animal	HT liver cirrhosis, HCV	Negative	Brucella spp.	Not tested	Levofloxacin/doxycycline (6w) or doxycycline (6w)-gentamicin (7d)	Cured
19 *	#	49/M	Fever, weak, anorexia, bloating	Contact with animal	Liver cirrhosis, HCV	Brucella spp.	Negative	Not tested	Levofloxacin/doxycycline (6w) or doxycycline (6w)-gentamicin (7d)	Cured
20 *	#	44/M	Weak, anorexia, bloating	Contact with animal	DM, liver cirrhosis, HBV	Negative#	Negative#	Not tested	Levofloxacin/doxycycline (6w) or doxycycline (6w)-gentamicin (7d)	Cured
21	Almasri et al, 2025 [27]	52/M	diffuse abdominal pain, cough, right-side pleuritic chest pain	Contact with camel	DM, cryptogenic liver cirrhosis	Brucella spp.	Brucella spp.	Not tested	Doxycycline-rifampicin	Cured
22	Kıymaz et al, 2025 [28]	30/M	Fever, night sweats, weight loss, migratory joint pain, abdominal pain, and distension	Contact with animal, unpasteurized cheese consumption	Chronic HBV	Brucella spp.	Brucella spp.	1/160	Doxycycline-rifampicin (6w)	Cured

STA, Serum Tube Agglutination; M, Male; F, Female; N/A, not available; HBV, Hepatitis B Virus; HCV, Hepatitis C Virus; HDV, Hepatitis D Virus; DM, Diabetes Mellitus; HT, Hypertension-related.

^*All patients originated from the same reference.

^#A positive culture for Brucella species from pleural effusion, indicating hematogenous or trnsdiaphragmatic spread of infection and confirming the systemic involvement of the pathogen.

Table 2.

Summary of published cases of peritoneal dialysis-associated infections caused by Brucella species

No	Reference,year	Age (years)/Gender	Previous peritonitis	Infectious source	Clinical presentation	Culture	Brucella spp. isolated	Treatment	Outcome
1	Taskapan et al. 2002 [29]	47/M	No	Unpasteurized cheese consumption	Fever and cloudy PD effluent	Blood and peritoneal fluid culture (+)	B. mellitensis	Rifampicin and doxycycline for 18 weeks	PD catheter removed and shift to hemodialysis
2	Ozisik et al. 2006 [30]	39/F	Yes	Contact with animal	Nausea and severe abdominal pain	Peritoneal fluid culture (+)	B. mellitensis	Rifampicin and doxycycline for 12 weeks	PD catheter removed and shift to hemodialysis
3	Alothman et al. 2008 [31]	67/M	NA	Unpasteurized milk consumption	Abdominal pain, cloudy dialysate and edema of lower extremity	Peritoneal fluid culture (+)	B. mellitensis + B. abortus	Rifampicin and doxycycline for 8 weeks	PD catheter removed and shift to hemodialysis
4 *	Unal et al. 2009 [32]	52/M	NA	Unpasteurized cheese consumption	Nausea, vomiting and fever	Peritoneal fluid culture (+)	B. mellitensis	Rifampicin and doxycycline for 6 weeks	Continued PD
5 *	#	38/M	NA	Unpasteurized milk and cheese consumption	Nausea and vomiting	Blood and peritoneal fluid culture (+)	B. mellitensis	Rifampicin and doxycycline for 6 weeks	Continued PD
6	Solak et al. 2012 [33]	46/M	NA	Contact with sheep and cattle	Abdominal pain, abdominal bloating, and constipation	Peritoneal fluid culture (−) (positive results through serum brucella agglutination testing)	Brucella spp.	Rifampicin and ceftriaxone for 6.5 weeks	Continued PD
7	Koz et al. 2014 [34]	49/M	NA	Unknown	Abdominal pain and cloudy PD effluent	Peritoneal fluid culture (+)	Brucella spp.	Rifampicin, doxycycline and ip amikacin for 6 weeks	Continued PD
8	Bukkhari et al, 2018 [35]	45/M	NA	Unpasteurized cheese consumption	Fever, generalized dull abdominal pain, vomiting and diarrhea	Peritoneal fluid culture (+)	B. mellitensis	Minocycline and ciprofloxacin for 12 weeks	PD catheter removed and shift to hemodialysis
9	Niu et al. 2018 [36]	54/F	Yes	Unpasteurized beef consumption	Abdominal pain, cloudy PD effluent and ultrafiltration decrease	Peritoneal fluid culture (+)	Brucella spp.	Rifampicin, minocycline, and levofloxacin for 18 weeks	Continued PD
10	Al Zabali et al. 2021 [37]	14/F	Yes	Unknown	Abdominal pain	Peritoneal fluid culture (+)	Brucella spp.	Rifampicin and doxycycline for 6 week	Continued PD
11	Huang et al, 2024 [6]	56/M	Yes	Unpasteurized mutton consumption	Fever, abdominal pain and cloudy dialysate	Blood and peritoneal fluid culture (+)	B. mellitensis	Rifampicin and doxycycline for 6 weeks	Continued PD

PD, Peritoneal dialysis.

^*All patients originated from the same reference.

Table 3.

Comparative demographic and clinical characteristics of patients with Brucella primary peritonitis: Spontaneous bacterial peritonitis (SBP) versus Peritoneal Dialysis-related Peritonitis (PDrP)

	SBP n (%)	PDrP n (%)	p-value
Age (mean ± sd)	55.2 ± 11.3	47.5 ± 10.2	p=0.045
Male	15 (68.2%)	8 (72.7%)	p=0.999
Underlying liver disease	18 (81.8%)	0 (0%)	p<0.001
Clinical manifestation	Abdominal pain 20/22 (91%) (most common)	Abdominal pain 10/11 (91%) (most common)
Peripheral blood WBC count (cells/μL)	6,772 ± 3,071 (range 3,300 - 12,800)	9,991 ± 575,901 (range 3,090 -19,300)	p=0.18
Infectious source**	10/22 (45.5%)	9/11 (81.8%)	p=0.079
Positive blood culture	16/22 (72.7%)	3/11 (27.3%)	p=0.016
Positive peritoneal fluid culture	15/22 (68.2%)	11/11 (100%)	p=0.028
Peritoneal fluid WBC count (cells/μL)	849 ± 436 (range 280 - 1,900)	1,733 ± 991 (range 820 - 59,658)*	p=0.04
Treatment regimen	Doxycycline + rifampicin 13/22 (59.1%) (most common)	Doxycycline + rifampicin 7/11 (63.6%) (most common)
Treatment duration (mean ± sd)	7.47 ± 3	9.95 ± 4.4	p=0.12
Outcome/Death	3/22 (13.6%)	0/11 (0 %)	p=0.544

PD, Peritoneal Dialysis; WBC. White Blood Cell.

^*Statistical comparison was performed after removing extreme outliers from PDrP group.

^**Unpasteurized dairy product consumption and/or contact with animal.

Data are presented as mean ± standard deviation for continuous variables or as number (n) and percentage (%) for categorical variables. Statistical analyses were performed using one-way analysis of variance (ANOVA) for continuous variables and the Chi-square test or Fisher’s exact test for categorical variables, as appropriate. An independent two-sample t-test was used to compare the mean peripheral blood WBC count, peritoneal fluid WBC count and treatment duration between the SBP and PDrP groups. A A p-value of less than 0.05 was considered indicative of statistical significance.

The 22 SBP cases, documented across multiple decades and reported from diverse Brucella-endemic regions, predominantly involved patients with underlying liver cirrhosis, most commonly secondary to chronic hepatitis B or C infection or alcohol-induced liver disease. Notably, in 72.7% of these cases, Brucella was isolated from blood cultures, reflecting the hematogenous dissemination typical in cirrhotic hosts. The mortality rate in this subgroup was 13.6%, with a mean duration of hospitalization of 16.0 ± 8.49 days, ranging between 10 and 28 days.

This review includes a detailed analysis of 11 reported PDrP cases, emphasizing their main clinical and microbiological characteristics. Most patients were middle-aged individuals on PD without major comorbidities. Brucella was isolated from peritoneal fluid in all cases, while only 27.3% had positive blood cultures, suggesting a predominantly localized infection. Although some cases were severe, no mortality occurred. However, catheter removal was required in 36.4% of patients, necessitating a transition to hemodialysis.

The mean age of patients with SBP was significantly higher than that of the PDrP cohort (55.2 ± 11.3 vs. 47.5 ± 10.2 years, p=0.045), suggesting that spontaneous Brucella peritonitis tends to occur in older individuals, often with multiple comorbidities. Both groups exhibited a male predominance (68.2% in SBP vs. 72.7% in PDrP, p=0.999), reflecting either gender-related exposure patterns or health-seeking behaviors. Underlying liver disease was documented in 81.8% of SBP cases, predominantly cirrhosis related to chronic viral hepatitis (HBV/HCV) or alcohol. In contrast, no cases of liver disease were observed in the PDrP group (p < 0.001). These findings underscore the pathophysiologic vulnerability of cirrhotic patients to hematogenous seeding of Brucella to the peritoneal cavity.

In contrast, the PDrP cohort included relatively younger individuals with preserved hepatic function and no significant comorbidities.

The most frequently reported clinical manifestation in both groups was abdominal pain, occurring in 91% of cases. Other systemic symptoms such as fever, night sweats and gastrointestinal disturbances were variably reported. Epidemiologic risk factors, including ingestion of unpasteurized dairy products and contact with livestock, were reported more frequently in PDrP cases (81.8% vs. 45.5%, p=0.079), probably due to the increased probability of direct environmental or dietary exposure among PD patients. Microbiological confirmation through positive peritoneal fluid cultures was universally achieved in the PDrP group (100%) but only in 68.2% of SBP cases (p=0.028). Conversely, blood cultures were significantly more often positive in SBP (72.7% vs. 27.3%, p=0.016), possibly indicating a more systemic nature of infection in the context of cirrhosis-related immune dysregulation and impaired reticuloendothelial clearance. In addition, peritoneal fluid white blood cell (WBC) counts differed significantly between the groups. Patients with PDrP exhibited a higher mean WBC count compared to those with SBP (1,733±991 cells/μL vs. 849±436 cells/μL, p=0.04), suggesting a more pronounced local inflammatory response in dialysis-related infections.

The most frequently utilized antimicrobial treatment in both groups consisted of a combination of doxycycline and rifampicin, administered in 59.1% of SBP cases and 63.6% of PDrP cases. This indicates that approximately 40% of patients in both groups received alternative regimens. Specifically, doxycycline was used in combination with other antimicrobials in 77.3% of SBP cases, while rifampicin was combined with other agents in 90.9% of PDrP cases, representing the most common therapeutic choices within each group. Fluoroquinolones (ciprofloxacin, levofloxacin, pefloxacin) were also frequently employed, administered in 31.8% of SBP cases and 18.2% of PDrP cases. Treatment durations varied, with a trend toward longer therapy in PDrP (9.95±4.4 vs. 7.47±3 weeks, p = 0.12), although this difference did not reach statistical significance. Notably, all PDrP patients survived, whereas the SBP group exhibited a mortality rate of 13.6% (p=0.544).

Discussion

This systematic review and detailed analysis of 33 reported cases of Brucella-associated primary peritonitis provides important insights into two clinically and epidemiologically distinct entities: PDrP and SBP. These patient groups demonstrate significant differences in demographic profiles, underlying comorbidities, microbiological characteristics, clinical presentation, management approaches and outcomes. These differences reflect distinct pathophysiological mechanisms and routes of infection inherent to each condition, emphasizing the need for tailored diagnostic and therapeutic strategies to optimize patient care.

In the SBP subgroup, most patients suffered from advanced liver disease, primarily cirrhosis related to chronic viral hepatitis (HBV or HCV) or alcohol abuse [5,38]. This predisposition reflects the well-established susceptibility of cirrhotic patients to infections due to immune dysfunction, including impaired reticuloendothelial system clearance and compromised gut barrier integrity, which facilitate bacterial translocation and hematogenous dissemination [5]. These mechanisms have been extensively documented in the literature, highlighting the multifactorial immune alterations in cirrhosis that contribute to increased risk of infection [39]. The high rate of positive blood cultures (72.7%) in SBP cases underscores the systemic nature of Brucella infection in this context, consistent with a bacteremic phase that seeds the peritoneum.

Conversely, the PDrP cohort consisted of relatively younger patients undergoing PD, without evidence of underlying liver disease. The infection in these cases appears to be primarily localized to the peritoneal cavity, as reflected by universal positivity of peritoneal fluid cultures and less frequent blood culture positivity (27.3%). Epidemiologic exposure to Brucella through ingestion of unpasteurized dairy products or direct contact with livestock was more commonly documented in this group, suggesting a direct environmental or dietary source of infection rather than secondary hematogenous spread [6]. The absence of mortality in the PDrP group, despite symptoms severity in most cases, may relate to preserved systemic immunity and prompt targeted treatment, although catheter removal was required in four patients, illustrating the potential for device-related complications [7].

Differences in age and sex distribution, though modest, were clinically meaningful between the two groups. The older age observed in SBP patients likely reflects the cumulative impact of chronic liver disease and associated comorbidities that increase susceptibility to infection [4,38]. The male predominance noted in both cohorts may be attributed to a combination of occupational and sociocultural factors. In endemic regions, men are more frequently engaged in high-risk occupations such as animal husbandry, veterinary practice and meat processing, which heighten the likelihood of Brucella exposure. This epidemiological pattern has been consistently observed across different populations, as a similar gender distribution was reported in a previous study [4].

Clinically, abdominal pain was the hallmark symptom in both groups, confirming its diagnostic importance in peritoneal infections. However, systemic symptoms were more prominent in the SBP cohort, consistent with disseminated infection and systemic inflammation [5]. Clinical features such as fever, night sweats and generalized malaise highlight the systemic inflammatory response typical of SBP in these patients [38]. These differences are also reflected in microbiological findings, where blood culture positivity was significantly higher in SBP cases, indicating more frequent bacteremia, while peritoneal fluid cultures were universally positive in PDrP, confirming a localized peritoneal infection.

Therapeutically, the majority of cases in both cohorts were treated with doxycycline and rifampicin, a regimen consistent with current brucellosis management guidelines [40]. In PDrP, the duration of therapy was generally extended beyond that of standard brucellosis treatment, likely reflecting the ISPD’s recommendation for individualized treatment based on pathogen characteristics, infection severity, and response to therapy [40]. The presence of an indwelling peritoneal catheter may necessitate prolonged antimicrobial exposure to ensure complete eradication of the intracellular pathogen. Notably, catheter removal was required in some PDrP cases, underscoring the ISPD guideline’s emphasis on timely catheter management in cases of relapsing or refractory infection [7]. This phenomenon can be attributed to the propensity of Brucella species to establish robust biofilms on PD catheters. Such biofilm formation confers enhanced resistance to antimicrobial agents and shields the bacteria from host immune defenses, facilitating persistent colonization and complicating eradication. Although data on Brucella biofilm development remain limited, recent experimental studies have demonstrated biofilm formation by Brucella under specific environmental conditions such as hyperosmotic stress, highlighting a potential mechanism of persistence in PDrP [40].

Although similar antimicrobial regimens were employed across both groups, outcomes varied significantly in terms of mortality. Despite occasionally severe clinical presentations, no deaths were reported among patients with PDrP. In contrast, mortality occurred exclusively in the SBP group, highlighting the profound influence of underlying hepatic dysfunction on prognosis. This discrepancy suggests that factors beyond antimicrobial therapy, such as host comorbidities and timing of diagnosis, play a crucial role in determining outcomes [5]. Moreover, delayed recognition in SBP may further contribute to the increased mortality observed in this population [3].

This study is inherently limited by the small number of cases reported in the literature, reflecting the rarity of Brucella-associated primary peritonitis and potential underreporting, especially in non-endemic regions. The retrospective nature of case reports and case series included introduces heterogeneity in diagnostic criteria, microbiological methods and treatment protocols, limiting direct comparability. Incomplete reporting of clinical variables and outcomes in some cases may have biased the analysis. Additionally, publication bias favouring more severe or unusual cases may have influenced the observed mortality rates and complication frequencies. Prospective, multicentre studies are needed to better characterize the epidemiology, optimal diagnostic approach, and treatment strategies for Brucella peritonitis.

Conclusion

In summary, Brucella-associated primary peritonitis comprises two distinct clinical syndromes with different pathogenetic mechanisms, clinical courses and outcomes. In the first form, SBP due to Brucella primarily affects older cirrhotic patients, presenting as a systemic infection with a significant mortality risk, whereas PDrP associated with Brucella occurs in younger patients, typically as a localized infection with more favourable outcomes. Awareness of these distinctions is critical for timely diagnosis and appropriate management, especially in endemic areas, to improve prognosis and reduce the morbidity and mortality associated with this uncommon but serious infection.

Funding

There is no financial support.

Conflicts of interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.