Bacterial imbalance of the vaginal flora: a cytological and biomolecular concept of Gardnerella vaginalis

Abstract

Since 1996 all women aged 30 to 60 years are invited for a cervical smear on a 5 year interval. KOPAC, the Dutch national coding system for cervical smears, introduced for determination of cervical abnormalities also evaluates the inflammatory status of the vaginal flora. In this system dysbacteriosis and Gardnerella infection comprise two different cytological entities reflecting cytological bacterial imbalance, the former representing a mild disturbance, the latter an extreme shift towards Gardnerella vaginalis. Bacterial imbalance has significantly decreased over the past decade in all age cohorts. From 2001-2005 prevalence of dysbacteriosis and Gardnerella infection accounted for respectively 27.4 and 1.2 per thousand smears, while prevalences in the first screening period were 34.8 and 3.0. Over the last decade women might have become more aware of the importance of a healthy vaginal flora. Bacterial imbalance of the vaginal flora is associated with a significant higher prevalence of HSIL/carcinoma, the effect being far more pronounced in pure Gardnerella infections. This data might result in treating asymptomatic bacterial imbalance as dysbacteriosis and Gardnerella infection can be clearly differentiated based on cytological criteria. Although cytology is accurate in diagnosing bacterial imbalance, modern technologies gain more and more terrain. This thesis indicates that DNA-PCR might become a potential tool in diagnosis of bacterial imbalance. In this context, it was possible to determine the morphotype of the adherent bacteria in liquid-based cytology (LBC) in smears with healthy and disturbed vaginal flora and to use PCR technology on the same fixed cell sample to establish DNA patterns of the 16S RNA genes of the bacteria in the sample. Thirty samples were randomly selected from a large group of cervical cell samples. This study reveals a strong inverse relationship between Gardnerella vaginalis and Lactobacillus crispatus in dysbacteriosis and Gardnerella infection. A baseline study of colonization of these bacteria in asymptomatic women showed that Gardnerella vaginalis was present in 58.7% of the women, whereas 38.9% of the samples showed Lactobacillus crispatus. Colonization of Lactobacillus crispatus in postmenopausal women decreases from 40.5 to 19.5%. Cessation of production of female sex hormones significantly decreases the colonization pattern of Lactobacillus crispatus. Furthermore, the purpose of this thesis was to examine the concentrations of Lactobacillus crispatus and Gardnerella vaginalis in bacterial imbalanced vaginal microflora in order to develop new and less subjective methods of diagnosis. All samples with concentrations of Gardnerella vaginalis over 2.0x10-2ng/μl displayed bacterial imbalance, however the differentiation between dysbacteriosis and Gardnerella infection could not be made. Finally, the relation between bacterial imbalance (with a shift towards Gardnerella vaginalis and a shortage of lactobacilli) and the presence of high-risk HPV infection is studied. Prevalence of hr-HPV infection was 44.6% (58/130) among smears showing bacterial imbalance of the vaginal flora versus 25.8% (850/3293) in healthy flora. This thesis demonstrates that high-risk HPV infection prefers the bacterial imbalanced milieu, leaving important questions as does the bacterial imbalanced vaginal flora by Gardnerella vaginalis provides a susceptibility to acquiring hr-HPV or is clearance of hr-HPV compromised by such a flora