Stress modifies the vaginal flora in cyclic female rats*

The understanding of the pathogenesis of vaginitis is directly dependent upon the factors which promote the colonization by bacterial genital microflora. Disruption of the bacterial barrier function afforded by the predominant microflora can lead to colonization by pathogenic or opportunistic pathogenic subdominant species. The present study focused on the effects of stress on the bacteria of the vaginal flora. For this purpose two types of psychological stress were employed: acute and subacute mild unpredictable stress. Estimation of the vaginal flora of 22 Wistar rats was performed according to the distinct phases of the estrous cycle: PE (proestrous), E (estrous), ME (metestrous), and DE (diestrous). Bacteria isolated from the vaginal flora were identified following Bergey’s Manual criteria. Escherichia coli, Clostridium , and Clostridium perfringens (vegetative and spore forms), showed increased numbers at PE-E after acute and subacute stress. Enterococcus was increased after acute stress, in all stages, while S treptococcus was increased after acute stress only at ME-DE. Staphylococcus aureus was detected at ME-DE only after stress. Staphylococcus epidermidis seemed to be predominant, but not influenced by stress at PE-E. However, it was detected in increased numbers at ME-DE after stress. Fusobacterium was detected at low levels in all phases and remained unaffected after exposure to stress. Both types of stress increased the numbers of Bacteroides at PE-E. Finally, the absence of Lactobacillus was noticed at PE-E 24 h after acute and subacute mild unpredictable stress, while Lactobacillus was decreased at ME-DE 72 h after stress. Hormonal fluctuations during the different phases of the estrous cycle may be associated with alterations in the vaginal flora. The data showed that stress acting on the vaginal flora and its immunity potential may contribute to disturbances of the natural balance in the area by altering the numbers of several bacteria that belong to the vaginal microflora. Continuous research on the factors that regulate the vaginal microflora is considered as essential, to prevent complications in infections that may be caused by indigenous microorganisms. Key words: stress, vaginal flora, clostridium, lactobacillus