Primary septic peritonitis is an abdominal infection without a primary focus, such as a perforated bowel. The most common cause in cats is feline infectious peritonitis. Little is known about primary bacterial septic peritonitis in cats. The investigators examined the medical records of twelve cats diagnosed with primary bacterial septic peritonitis and identified significant characteristics associated with this condition. The overall mortality rate was 31%, and cats that experienced clinically significant decreased heart rates and hypothermia did not survive. Other clinical findings were similar to cats with septic peritonitis from identifiable causes (e.g., fever, abdominal pain, elevated white blood cell counts, elevated serum bilirubin). All cats had anaerobic bacteria isolated from the infection; these microbes are common in the gastrointestinal tract. This would indicate that in these cases, antibiotic treatment directed against anaerobes should be effective. All but two of the organisms identified in these cases are common oral flora, but gingival disease was not found to be a contributor. For primary bacterial septic peritonitis, a mechanism for inoculation of the bacteria into the abdomen has yet to be determined, but an oral source is suggested. The investigators concluded that cats with primary bacterial septic peritonitis have a fair to good prognosis if they are treated aggressively prior to development of shock. This treatment should include surgical intervention, nutritional support, and appropriate antibiotic therapy. [MK]