Which organisms cause spontaneous bacterial peritonitis (SBP)?

Updated: Nov 26, 2018
  • Author: Thomas E Green, DO, MPH, MMM, CPE, FACEP, FACOEP; Chief Editor: Jeter (Jay) Pritchard Taylor, III, MD  more...
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Answer

Traditionally, three fourths of spontaneous bacterial peritonitis infections have been caused by aerobic gram-negative organisms (50% of these being Escherichia coli). The remainder has been due to aerobic gram-positive organisms (19% streptococcal species). E coli is displayed in the image below.

Gram-negative Escherichia coli. Gram-negative Escherichia coli.

However, some data suggest that the percentage of gram-positive infections may be increasing. [2, 3] One study cites a 34.2% incidence of streptococci, ranking in second position after Enterobacteriaceae. [3] Viridans group streptococci (VBS) accounted for 73.8% of these streptococcal isolates.

Anaerobic organisms are rare because of the high oxygen tension of ascitic fluid.

A single organism is noted in 92% of cases, and 8% of cases are polymicrobial.


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