Acute hypoxia does not increase bacterial translocation in newborn rabbits

We have previously demonstrated that spontaneous bacterial translocation (BT) occurs in newborn rabbits and correlates strongly with small bowel colonization (BC). Birth stress, specifically hypoxia, is believed to increase this pathologic process and thus lead to sepsis. This study investigated the relationship between BT and acute hypoxia in newborn rabbits.

Four hundred seventeen rabbit pups (aged 0, 2 to 4, 6, and 28 days) were divided into four groups according to the type of hypoxic stress: 9% O(2) for 1 hour, 9% O(2) + 12% CO(2) for 1 or 4 hours, and 21% O(2) (control animals). The animals were killed 1.5 or 20 hours after the stress. Sterile specimens of mesenteric lymph nodes (MIN), spleen, liver, small bowel, and large bowel were incubated aerobically at 37 degrees C for 24 hours in thioglycolate broth, and subsequently plated on both MacConkey and Colistin Naladixic Acid media. After 24 hours, the growth on both plates was recorded. X(2) analysis was used, and P values of less than .05 were considered significant.

BC of the small bowel and BT to the MLN were low in the first 4 days of life in the hypoxic groups (range, 0% to 21% BC, 0% to 6% BT) and the control group (range, 4% to 30% BC, 3% to 12% BT). After an increase in BC at 6 days of age, the rate of BT increased to 25% to 29% in control animals. The rate of BT in the hypoxic groups (25%) did not differ significantly from that of the controls (P > .05). Additionally, killing at 20 hours (v 1.5 hours) was not associated with an increase in the incidence of BT. None of the stress groups had a significant increase in BT compared with the controls. Importantly, although 4 hours of 9% O(2) + 12% CO(2) resulted in a 30% mortality rate, the incidence of BT was no higher than that of the control animals (13% v 29%; P > .05).

Severe hypoxic stress in newborn rabbits does not increase the incidence of BT. Because the incidence of BT correlates with that of BC, and because BC is the same in the control and hypoxic animals, the sepsis observed in hypoxic newborns probably is not related to an increased incidence of BT.