To the Editor—Marrazzo’s interesting editorial commentary [1] about the “enigmatic ecological mystery” of bacterial vaginosis (BV) fails to take into account the recent findings of several investigations [2–5] that call into question some long-held assumptions about this disorder. Her essay begins with the pronouncement that we have known for decades that the normal vagina is dominated by hydrogen peroxide–producing lactobacilli and then follows this with the declaration that decreases in the numbers of lactobacilli have been associated with a host of problems, including BV, gonorrhea, HIV infection, and cervicitis. However, several investigations conducted using cultivation-independent methods have shown that a significant proportion (∼30%) of healthy women lack appreciable numbers of Lactobacillus species

A critical problem in studies of the etiology of BV is the diagnostic criteria used. Although numerous studies have shown that women with high numbers of Lactobacillus species do not have BV, it is a logical fallacy to conclude that women whose vaginal communities have few or no Lactobacillus species have BV. Formally, this is termed a “fallacy of propositional logic” (it is also known as “denial of the antecedent”). Unfortunately, this fallacy is the premise of the Nugent criteria [6] and is a component of the Amsel criteria [7], which are widely used for the diagnosis of BV—for these criteria, the degree of “healthiness” is assessed by scoring the abundance of Lactobacillus species by microscopic analysis of a Gram-stained smear or wet mount prepared from a vaginal sample

We postulate that, because of this logical fallacy, BV is often misdiagnosed. This could partly account for the reported high incidence of so-called asymptomatic BV in reproductive-age women [8] and could also explain a proportion of BV treatment failures and apparent recurrences of BV in women. Acknowledgment that not all vaginal communities of healthy women are dominated by Lactobacillus species would also be in accordance with the observation that the vaginal communities of postmenopausal women (not receiving hormone-replacement therapy) often lack Lactobacillus species, yet these individuals do not exhibit other untoward symptoms

We suspect that the causes of and cures for BV will continue to be enigmatic until it is recognized that, although “normal and healthy” can be equated with high numbers of lactobacilli, the converse—“unhealthy” being equated with low numbers of or no lactobacilli—is not necessarily true. We must be vigilant and recognize that, for a significant proportion of women, normal and healthy can also occur in the absence of appreciable numbers of Lactobacillus species

References

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JM
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G
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Potential conflicts of interest: none reported