Antimycoplasmal Activity ofDimethylphenols inaTracheal Explant Culture System

isomers protected tracheal explants fromthesechanges after exposuretovirulent M. pneumoniae strain PI1428. Theeffect was concentration, time, andisomer dependent. Atconcentrations of10-' M orgreater, 2,4-dimethylphenol completely prevented themorphological (loss ofciliated cells) andbiochemical (decreased dehydrogenase activity) changes normally observed after exposure toM.pneumoniae. Apparently, 2,4-dimethylphenol interfered withan early eventinthe infection process.Complete protection required thatitbepresent during thefirst 2hofexposureoftheexplants totheinfecting mycoplasmas. Thesexylenols may provetobeuseful tools forhelping todefine themechanisms ofpathogenesis in certain respiratory infections. Viractin, avolatile agentfoundincrude extracts ofStreptomyces griseus cultures, issuspected ofhaving antiviral activity against commonrespiratory infections. In1964, Leachetal. (17)reported thatviractin waseffective clinically intheprevention ofhumanupperrespiratoryinfections, although otherinvestigators failed toconfirm theseresults (22). Subsequently, Leach(B.E.Leach, manuscript inpreparation) identified a component fromthese crude extracts, 2,4-dimethylphenol (2,4-DMP),