The Interaction of Mycoplasmas and Influenza Viruses in Tracheal Organ Cultures

Organ cultures of porcine and bovine trachea were used as host systems in a study of interactions between influenza viruses and mycoplasmas. While Myco-plasma hyorhinis produced only minimal histopathological changes in the epi-thelium and swine-influenza virus produced moderate damage, there was some evidence that a double infection with both agents increased the destruction of the respiratory epithelium.This effectwas not seen when influenzaA WS was used, or when bovine instead of porcine cultures were used as the host system. Titers of virus in the organ culture fluids were unaltered by the presence of concurrent infection with M. hyorhinis, but growth of this mycoplasma was enhanced in cultures infected with swine-influenza virus as compared with control cultures. An examination of bovine tracheal cultures infected with swine-influenza virus and a bovine T-strain mycoplasma, either singly or in combination, showed no evidence of interaction between these two agents. Since the original observation made by Shope in 1931 [1-3] that a synergistic action between in-fluenza virus and Hemophilus suis was important in the pathogenesis of swine influenza, there have been many studies of combined infection with viruses and bacteria under both natural and ex-perimental conditions. On the other hand, exam-ples of interaction between viruses and mycoplas-mas have been noted less frequently. In tissue cultures, mycoplasmal infection has been found either to diminish [4, 5] or to enhance yields of virus [6]. In animals, there are instances in which concurrent infection with mycoplasmas appears to increase the severity of the viral infection [7-9]. The present report concerns interactions be-tween influenza virus and mycoplasmas, as studied in organ cultures of porcine and bovine tracheas. These model systems are suitable for quantitative studies of the infecting agents and also allow ob-Received for publication July 6, 1970, and in revise