What organism typically causes Spontaneous Bacterial Peritonitis (SBP)?

From the Guidelines

Spontaneous bacterial peritonitis (SBP) is most commonly caused by gram-negative enteric bacteria, with Escherichia coli (E. coli) being the predominant organism, as reported in the most recent study by 1. The most frequent causative organisms of SBP include:

• Escherichia coli (E. coli)
• Klebsiella pneumoniae
• Streptococcus species
• Enterococcus species These organisms are responsible for the majority of SBP cases, which typically develop in patients with cirrhosis and ascites due to increased intestinal permeability, bacterial overgrowth, and impaired immune function 1. The diagnosis of SBP is made when the ascitic fluid neutrophil count exceeds 250 cells/mm³, and treatment should be initiated promptly with third-generation cephalosporins such as cefotaxime or ceftriaxone, as recommended by 1 and 1. The most recent study 1 highlights the importance of isolating a microorganism from ascites or blood to guide antibiotic therapy, and bedside inoculation of at least 10 mL of the ascitic sample into blood culture bottles increases the sensitivity of the culture to >90% in the diagnosis of SBP. It is essential to note that there has been a shift toward gram-positive and multidrug-resistant organisms (MDRO) in nosocomial and health care–associated SBP, which has led to a decreased response to the recommended initial empirical antibiotic 1. In patients with a history of SBP, long-term antibiotic prophylaxis may be recommended to prevent recurrence, as the risk of subsequent episodes is high and associated with significant mortality 1. Overall, the management of SBP requires prompt diagnosis, appropriate antibiotic therapy, and consideration of the underlying causes and complications of the disease, as emphasized by the most recent study 1.

From the Research

Organism Causing Spontaneous Bacterial Peritonitis (SBP)

The organism that typically causes Spontaneous Bacterial Peritonitis (SBP) includes:

• Gram-negative bacteria, such as Escherichia coli and Klebsiella species, which are the most common cause of SBP 2, 3
• Gram-positive bacteria, which are increasingly being reported as a cause of SBP 2, 3
• Other less common organisms, such as Streptococcus pneumoniae 4, Streptococcus bovis 5, Salmonella 6, and Brucella 6

Characteristics of SBP-Causing Organisms

Key characteristics of the organisms that cause SBP include:

• Enteric origin, with 70% of cases caused by pathogens from the gastrointestinal tract 4
• Increasing prevalence of quinolone-resistant and multidrug-resistant bacteria 3
• Ability to infect ascitic fluid without an apparent intraabdominal source of infection 4