Oxidative metabolism in experimental Bacteriodies fragilis bactermia

Abstract

Bacteriodes fragilis has received recent attention as a pathogen in surgical patients. In an effort to assess its pathogenicity, 28 male Sprague-Dawley rats underwent carotid cannulation. With the cannula in the root of the aorta, 14 animals had 1 × 10 10 B. fragilis infused over 30 min with a control receiving only saline. This results in an LD 0 despite the number of bacteria being five times the LD 100 for Escherichia coli. Rats had heart rate, mean arterial pressure, pO 2, pCO 2, pH, hematocrit, glucose, and lactate measured very 2 hr. At 6 hr, the hepatic tissue pO 2 was measured with a surface polyelectrode. Paired experimental and control animals were sacrificed at 6 hr, livers were excised and homogenized. Mitochondria were isolated and studied polarographically by measurement of state 3 (ADP-dependent) and state 4 (ADP-independent) respiratory rates. The Respiratory Control Index (RCI) was calculated (state 3/state 4) as a sensitive indicator of mitochondrial oxygen utilization. No hypotension developed in bacteremic rats. Arterial pO 2, pCO 2, and pH were essentially unchanged. Blood glucose was unchanged while lactate rose moderately. RCIs of experimental and control mitochondria were similar ( P > 0.05). B. fragilis bacteremia does not produce the changes of mitochondrial respiratory control of E. coli bacteremia or septic peritonitis.