IDENTIFICATION AND PRELIMINARY CHARACTERIZATION OF A CYTOTOXIN ISOLATED FROM MOBILUNCUS SPP

Mobiluncus curtisii and M. mulieris are anaerobic curved rods commonly isolated, together with other bacteria, from the vagina of women with bacterial vaginosis (BV). We have shown that of 11 strains of M. curt isii and four strains of M. mulieris examined, each produced a cytotox in after growth in three types of liquid media. The toxin present in s upernatant fluids after centrifugation of Mobiluncus cultures was acti ve against Vero cells and four other cell lines tested, producing a ma rked cytopathic effect with destruction within 72 hours. The supernata nt fluids could be diluted no more than 8 to 16-fold before toxic acti vity was lost. In bovine oviduct organ cultures, the supernatant fluid s from cultures of eight M. curtisii and two M. mulieris strains that were tested caused loss of ciliary vigour which was usually complete a fter 60 hours. In addition, there was raggedness of the epithelial cel l border with detachment of cells seen histologically and loss of cili a together with bloating and loss of ciliated cells observed by scanni ng electron microscopy. The toxin was extracellular, relatively thermo stable (surviving heating to 56-degrees-C for 30 min but not boiling f or 20 min) and was inactivated under extremes of pH (pH 9 and pH 3). T he existence of the toxin means that the Mobiluncus spp could have an active role in the development of BV.