Pulmonary hemodynamic and ultrastructural changes associated with Group B streptococcal toxemia in adult sheep and newborn lambs.

A toxin isolated from Group B beta-hemolytic streptococci, Type III was infused into adult sheep and newborn lambs. A two-phased reaction was observed. There was an initial phase of pulmonary hypertension and high flow of protein-poor lymph. This was followed by a second phase when pressures returned to baseline but lymph flow remained twice the baseline values and protein concentration in lymph increased. During the second phase there was a significant increase in lymph protein clearance, suggestive of increased microvascular permeability to protein. The absolute granulocyte count decreased to 10% of baseline values by 60 min after the infusion, and was followed by a variable return to baseline. The sheep with the largest changes in protein clearance were those who had the slowest return to baseline values. Pathologic examination of lung tissue revealed there was capillary dilation, interstitial edema, and large numbers of granulocytes in the lungs. The basement membranes of both capillaries and arterioles showed disruption and widening, along with fragmentation of the internal elastic membrane. This study provides morphologic and physiologic evidence of increased pulmonary vascular permeability after injection of streptococcal toxin associated with granulocyte trapping in the lung. We postulate that granulocytes may be involved as mediators of the pulmonary vascular injury.