Scientists will have to rethink their approach to treating bacterial vaginosis due to the presence of a multi-species biofilm that complicates testing.

That’s the conclusion of a review, ’Fighting polymicrobial biofilms in bacterial vaginosis’ by a team from the University of Minho in Portugal that warns that treatment outcome is highly affected by the presence of a multi-species biofilm. The paper has been accepted for publication in Microbial Biotechnology, an Applied Microbiology International publication.

The presence of a polymicrobial biofilm in the vaginal epithelium is a well-established feature of bacterial vaginosis (BV). Some studies have already shown that the presence of a biofilm may be one of the factors that make treatment more difficult and increase cases of recurrence.


In this review, the authors highlighted some of the most important findings that support the evidence that the treatment outcome is highly affected by the presence of a multi-species biofilm.

Threatening complications

“BV is one the most common vaginal infections in women of reproductive age worldwide ,” said principal investigator and corresponding author Dr Nuno Cerca.

“Although the majority of the cases are asymptomatic, the symptoms, including vaginal discharge, fishy smell, and vaginal discomfort, can compromise women’s wellbeing. This condition can have even more threatening complications in pregnant women, such as preterm delivery and miscarriages.

“The high recurrence rates of infection observed after cessation of treatment are one of the most concerning problems that researchers try to understand and overcome. We are currently trying to address what microbial factors contribute to these high recurrence rates.”

Teaming together

One of the team’s most recent discoveries that led them to write this review article was the fact that in BV polymicrobial communities, individual bacterial species that were susceptible to antibiotics on their own demonstrated tolerance when grown in biofilms containing at least one highly resistant bacterial species.

These in vitro results provided the first evidence for the high recurrent rates that have been recorded in clinical studies.

“Standard antimicrobial testing attempts to determine the minimum concentration that is required to kill - or to inhibit growth - of a specific bacterial species or strain ,” Dr Cerca said.

Standard test failings

“However, it is becoming increasingly evident that for polymicrobial infections, these standard tests will not allow us to predict treatment outcomes.

“One thing that is clear to me is that we really can’t perform standard antimicrobial testing when we have multiple species involved.

“A big issue that may not be solvable soon is that in BV many bacterial species are uncultivable, so it’s not possible to assess antimicrobial profile in all of these species.

“However, what could be done with current technology is to consider adjuvant therapies against BV, in order to attempt to target different species and possible synergistic effects.”

Funding for the work of the Cerca Lab is provided by the Portuguese National Foundation for Science and Technology and North-American National Institutes of Health.

’Fighting polymicrobial biofilms in bacterial vaginosis’ is published in Microbial Biotechnology.