What are the types of spontaneous bacterial peritonitis described in Harrison's textbook?

Types of Spontaneous Bacterial Peritonitis

Spontaneous bacterial peritonitis is classified into three distinct variants based on ascitic fluid analysis: classic SBP (neutrophils ≥250/mm³ with positive culture), culture-negative neutrocytic ascites (CNNA; neutrophils ≥250/mm³ with negative culture), and monomicrobial non-neutrocytic bacterascites (MNB; positive culture with neutrophils <250/mm³). 1

Classic Spontaneous Bacterial Peritonitis

• Classic SBP is defined by ascitic fluid polymorphonuclear (PMN) count ≥250 cells/mm³ with positive bacterial culture showing a single organism. 1
• The most common pathogens are Gram-negative enteric bacteria (particularly Escherichia coli and other Enterobacteriaceae), accounting for approximately 70% of cases, though Gram-positive cocci (Streptococcus species and Enterococcus) are increasingly isolated. 2, 3
• This variant requires immediate empirical antibiotic therapy without waiting for culture results, as each hour of delay increases in-hospital mortality by 3.3%. 4

Culture-Negative Neutrocytic Ascites (CNNA)

• CNNA is characterized by ascitic fluid neutrophil count ≥250 cells/mm³ but negative bacterial culture despite appropriate culture techniques in blood culture bottles. 1
• This variant accounts for approximately 40% of patients meeting neutrophil criteria for SBP. 1
• Patients with CNNA demonstrate an identical clinical course and outcomes to culture-positive SBP and must be treated identically with empirical antibiotics. 1
• The negative culture likely reflects prior antibiotic exposure, low bacterial inoculum, or technical limitations rather than absence of infection. 4

Monomicrobial Non-Neutrocytic Bacterascites (MNB)

• MNB is defined by positive ascitic fluid culture showing a single bacterial organism but neutrophil count <250 cells/mm³. 1
• This variant represents either transient bacterial colonization of ascites or the early stage of developing SBP. 1
• Management depends on clinical presentation: asymptomatic patients often resolve spontaneously without antibiotics and should undergo repeat paracentesis to confirm clearance, while symptomatic patients (fever, abdominal pain, systemic inflammatory signs) require immediate empirical antibiotics. 1, 5
• If repeat ascitic fluid culture remains positive regardless of neutrophil count, antibiotic treatment is mandatory. 5, 1

Important Differential: Secondary Bacterial Peritonitis

• Secondary bacterial peritonitis must be differentiated from SBP as it requires surgical intervention rather than antibiotics alone. 1
• Suspect secondary peritonitis when multiple organisms are present on Gram stain or culture, ascitic neutrophil count is >1,000/mm³, or there is inadequate response to appropriate antibiotic therapy. 5, 1
• Additional clues include localized abdominal symptoms or signs, very high ascitic protein concentration, and elevated ascitic CEA (>5 ng/mL) or alkaline phosphatase (>240 U/L) suggesting intestinal perforation. 5, 1
• Patients with suspected secondary bacterial peritonitis should undergo prompt CT scanning and early surgical consultation. 5

Related Entity: Spontaneous Bacterial Empyema

• Spontaneous bacterial empyema represents infection of pre-existing hepatic hydrothorax in cirrhotic patients. 1
• Diagnostic criteria include pleural fluid neutrophils >250/mm³ with positive culture OR neutrophils >500/mm³ with negative culture, in the absence of pneumonia. 5, 1
• This complication occurs in approximately 16% of cirrhotic patients with pre-existing hydrothorax and carries a mortality of approximately 38%. 5, 1
• Pleural fluid culture in blood culture bottles yields positive results in approximately 75% of cases. 1