Detection of Gardnerella vaginalis on vaginal smears by immunofluorescence

An indirect fluorescence antibody (IFA) test was developed for the detection of Gardnerella vaginalis. Antisera were prepared in rabbits by using five strains of G. vaginalis. A pool of the antisera was tested for specificity with a variety of isolates known to colonize the human vagina and (or) morphologically resemble G. vaginalis. Six heterologous bacterial isolates reacted with the pooled antiserum at dilutions of 1:10, but none reacted at the working dilution of 1:200. Vaginal swab specimens were collected from symptomatic and asymptomatic patients in order to further evaluate the IFA procedure. The presence of G. vaginalis in the specimens was determined both by culture and by the IFA procedure. Absorbed antisera reacted with all isolates of G. vaginalis tested. In a clinical trial the IFA procedure detected the presence of G. vaginalis in smears from 23 (24.2%) of the patients with nonspecific vaginitis (NSV), from 22 (29.8%) of the asymptomatic individuals tested, and from 3 patients with vaginitis other than NSV. The presence of G. vaginalis in smears as detected by the IFA procedure was confirmed by cultures in all cases using Vaginalis agar supplemented with colistin and nalidixic acid (V-CNA). It is suggested that the IFA procedure may be of use in conjunction with V-CNA in epidemiological studies of the carriage and transmission of G. vaginalis in human populations. It appears that the IFA procedure, at least in our hands, is a useful test for the rapid detection of G. vaginalis even when this microorganism is not the predominant colonizer of the human vagina.