Interactions of actinomyces -like organisms with host cells: light microscopic examination

To determine the interactions of Actinomyces-like organisms (ALOs) with host cells, including vaginal epithelial cells, polymorphonuclear leukocytes (PMNLs) and erythrocytes, using Pap smear microscopy and based on their light microscopic appearances.

Cervicovaginal samples obtained from 200 patients were examined by both Pap smear microscopy and anaerobic culturing. Since the results obtained by these methods were not concordant for diagnosis of genital Actinomyces, the results of Pap smear microscopy were used as a reference, and the smears with ALOs were carefully screened with regard to interactions of ALOs with host cells.

ALOs were detected as attached to vaginal epithelial cells, PMNLs and erythrocytes via their filament-like structures. At some attachment sites, the epithelial cell membrane and filaments of ALOs were almost fused with each other. A group of PMNLs surrounded the ALOs. However, ALOs were observed to form colonies to evade phagocytosis by PMNLs. At the connection points between erythrocytes and ALOs, the findings of interest were the changes in the shapes of the erythrocytes and filament-like structures of the ALOs on the erythrocyte membrane.

The adhesiveness of ALOs can be observed in routine Papanicolaou-stained cervicovaginal smears at light microscopic level.