The use of organ cultures and animal models in the study of Mycoplasma pneumoniae infections.

Organ cultures of ciliated tracheal epithelium derived from various animal species have been used to study several different mycoplasma infections. Human and hamster tracheal cultures have been used in particular to study Mycoplasma pneumoniae which, of all the human mycoplasmas, is the only one which damages the cultures. One reason for this is the capacity of the virulent organisms to attach to the cells; strains which are prevented from attaching or have lost this capacity do not damage the cultures. The organ culture system is therefore valuable in looking at the organisms-cell relationship but it is necessary to use animal models to study immunological processes. Hamsters, and more recently guinea pigs, have been used in this respect. The hamster model has been used to study the pathogenesis of M. pneumoniae pneumonia and also recovery from and resistance to infection. Humoral immune mechanisms seem more important than cell-mediated mechanisms in resistance, and the probable importance of local immunity is discussed. It is pointed out that it should be possible to establish the mechanisms underlying the development of M. pneumoniae sequelae where conditions, similar to those seen in man, occur in animals. Finally, the way in which the hamster model has been used to study the effect of tetracycline and erythromycin on the course of disease is discussed. As in man, therapy often improves the pneumonia but does not eradicate the organisms. This is probably due, at least in part, to the fact that the antibiotics are only mycoplasmastatic. Drugs with mycoplasmacidal properties are needed and the animal model would obviously prove helpful in evaluating these.