Experimental aerobic-anaerobic thoracic empyema in the guinea pig

The clinical and pathological features of experimental aerobic-anaerobic thoracic empyema in the Duncan-Harley guinea pig are described. Thoracic empyema development and early death (less than 14 days after bacterial inoculation) were noted after various concentrations and species were inoculated into the pleural space with a piece of umbilical tape, which was used as a cofactor. The effect of concomitant hemothorax was also tested. Gram-negative infection was found to have a more virulent course than Gram-positive infection in the thoracic cavity. Moreover, these findings support the thesis that intrathoracic inoculation of anaerobic bacteria, even in combination with other anaerobic species, fails to produce clinical empyemas. However, anaerobic bacteria appear to enhance synergistically the virulence of sublethal and subempyema-forming concentrations of aerobic bacteria such as Staphylococcus aureus and Escherichia coli.