Diverse inside and out: vaginal microbes differ with ethnicity?

Every time I read about a study on the microbiota composition whether it is from the gut, skin, or vagina, I wonder with which bacteria am I sharing my body. As a Peruvian researcher living in Belgium and now being involved in the Isala project, I also wonder about my vaginal microbiota composition and the ones from women like me: women with non-Belgian ethnicity but living in Belgium for several years. Perhaps our vaginal microbiota has changed over time and became similar to women with Belgian ethnicity? Or our ethnic background is “resisting” the possible Belgian environmental influence?

Now, probably you are asking yourself, what is ethnicity? Are ethnicity and race the same? Well the answers are complex. While ethnicity refers to cultural characteristics (e.g. language, accent, religion, social customs, food and dietary preferences or restrictions), race refers to physical characteristics that define a person as being a member of a specific group (e.g. skin/hair/eye color, physical build) (Sociologist Julie Maes, personal communication). From a scientific point of view, classifying individuals by their physical appearance lacks of validity, as demonstrated by genetic studies where the genetic differences within individuals of a certain “racial group” is higher than between “racial groups”1. From a social point of view, race is a category forged historically through oppression, slavery, and conquest2. Even though ethnicity and race have different meanings, they are usually used interchangeably.

Initial studies that gave the first insights on vaginal microbiota composition included only Caucasian women. These studies showed that the vaginal microbiota often was dominated by lactobacilli. Further studies conducted mainly in the United States included women from different ethnic groups showed that women from different ethnic background display a different healthy vaginal bacterial composition, with lactobacilli not playing the most prominent role3. Thus, it was found that the healthy vaginal microbiome of women from European ancestry are less diverse (dominated by Lactobacillus species) than those of African ancestry (non-Lactobacillus dominated)4. To the question ‘does a healthy vagina always needs to be dominated by Lactobacillus?’, more research is needed including different ethnic groups to understand what a “healthy vaginal microbiome” really means. However, apparently, we always need Lactobacillus species during pregnancy5. Interestingly, research has indicated that the presence of Lactobacillus species plays a positive role during pregnancy. Even more, the vaginal microbiome composition of pregnant women tends to be dominated by Lactobacillus species however it becomes less lactobacillus dominant during the post-partum irrespective of community structure during pregnancy and independent of ethnicity6. This makes the question on the relevance of the presence of lactobacilli even more interesting.

Why is there a difference? For the moment, the answers are unclear. Host genetics and environmental factors might contribute to the difference, however these factors don’t explain all of the variation seen in the vaginal microbiota of different ethnic backgrounds.

In the context of the Isala project, we aimed to include women from different ethnic groups, but because it is a Citizen Science project, we were unsure whether we could reach them. These uncertainties are common in research and several factors play a role for citizen participation7. Interestingly, based on the questionnaires, almost 11% of the participants, identify themselves with one or more culture(s) different from the Belgian one. Moreover, in terms of nationality, our project includes women from 99 different countries!  In this way, Isala’s volunteers are contributing to disentangle the effects of sociodemographic, behavioral, environmental, and genetic factors on vaginal microbiota composition.

We look forward to study the vaginal microbiome in other countries in collaboration with partner institutions, hopefully we will start a new Isala-like project in a multiethnic country like Peru, so fingers crossed!

Special thanks to Lore van Praag and Julie Maes for their help to verify the concepts of ethnicity and race.


  1. Rosenberg NA, Pritchard JK, Weber JL, et al. Genetic structure of human populations. Science 2002;298:2381-5
  2. https://genderedinnovations.stanford.edu/terms/race.html
  3. Ravel, J., P. Gajer, Z. Abdo, G. M. Schneider, S. S. K. Koenig, S. L. McCulle, S. Karlebach, R. Gorle, J. Russell, C. O. Tacket, R. M. Brotman, C. C. Davis, K. Ault, L. Peralta and L. J. Forney (2011). “Vaginal microbiome of reproductive-age women.” Proceedings of the National Academy of Sciences 108(Supplement 1): 4680-4687
  4. Serrano MG, Parikh HI, Brooks JP, et al. Racioethnic diversity in the dynamics of the vaginal microbiome during pregnancy. Nat Med. 2019;25(6):1001-1011.
  5. Romero, R., Hassan, S.S., Gajer, P. et al. The composition and stability of the vaginal microbiota of normal pregnant women is different from that of non-pregnant women. Microbiome 2, 4 (2014). https://doi.org/10.1186/2049-2618-2-4
  6. MacIntyre, D., Chandiramani, M., Lee, Y. et al.  The vaginal microbiome during pregnancy and the postpartum period in a European population.  Sci Rep 5, 8988 (2015).
  7. Redwood, S., & Gill, P. S. (2013). Under-representation of minority ethnic groups in research–call for action. The British journal of general practice: the journal of the Royal College of General Practitioners, 63(612), 342–343.

Face masks: always a healthy choice during this COVID-19 pandemic?

Due to the corona pandemic, Belgium went into lockdown starting from the 18th of March 2020. Multiple changes in our day-to-day life had to be made as more and more regulations came into place. Physical distancing and wearing face masks are the ‘new normal’ in our country at the moment. Moreover, face masks are increasingly obliged in the community, outside hospitals and care facilities, mainly based on the precautionary principle, since conclusive evidence is not (yet) available. Face masks are a medical device and placebo-controlled conclusive well-controlled clinical trials that prove the benefit of wearing a face mask in community settings are lacking (Martin, 2020). Such studies are important to double check safety and efficacy of medical devices and drugs. While well-designed face masks show high efficacy in specific settings, such as in hospitals with a high chance of COVID-19 patients, they could also have some unexpected side effects. Due to a shortage of the surgical face masks at the beginning of the crisis, self-made cotton face masks are promoted, but their safety and efficacy is not well documented. Wearing them for longer periods of time, like in schools and restaurants, could result in a concentration of microbes on the masks that should be carefully monitored.

What we as bioscience engineers learn in our first microbiology lesson is that bacteria and fungi need a surface or substrate, moisture, a little bit of food, nice temperature, and an absent immune system to grow exponentially. This environment seems to be exactly what is created when wearing a face masks for multiple hours. When these masks are then not washed or disinfected properly, these bacteria might resume on the face mask even before using it.

For a scientist, “measuring is knowing” is the most important life motto and so we started experiments in the lab to determine how many bacteria could concentrate on different mask types after wearing them for four hours and how to clean them in the best way. In the figure below you can see the set-up of our experiments.

First of all, we could see that cotton masks concentrate 10 to 20 times more bacteria than the surgical-type masks tested. This might be due to the higher amount of moisture in the cotton masks and less antimicrobial and more growth supporting properties of the material used. Surgical face masks always contain a filter and consist of more absorbing material.

Furthermore, we isolated bacteria from the mouth masks and tested their resistance to the antibiotics erythromycin and ampicillin. In the figure below, you can see that almost 50% of the isolates tested were resistant to at least one antibiotic and some isolates were even resistant to both antibiotics. It has been stated by the WHO that by 2050 more people will die from an infection caused by antibiotic resistant bacteria than cancer (WHO, 2019). An important concern is that the increased use of face masks in the community should not negatively contribute to this trend. Antibiotic stewardship is still crucial, also during the COVID-19 crisis (Hsu, 2020).

Lastly, we tested different washing and disinfection methods for the self-made cotton masks, to determine the best way to get rid of these bacterial cells on the masks. We tested: washing at 100°C, washing at 60°C with soap, ironing with a steam iron, putting it in the freezer overnight and leaving it on a counter top for 72h. As can be seen in the figure below, we can recommend to either wash your mask at 100°C or 60°C with soap or use a steam iron. These methods resulted in 25 times, 60 times, and 95 times less bacteria, respectively.

Based on these results, we are no advocates for the obligation of face masks in the community at places where physical distancing is possible. A high number of bacteria is present on these masks, especially on the cotton masks, and not handling or washing them properly might be harmful. By touching the mask, bacteria and viruses present on the face mask could spread easily, especially when the masks have become humid, because liquid is known to promote microbial transfer. In addition, people that wear a face mask often touch their face more frequently, increasing the chances to spread unwanted microbes. The good news is, that the bacteria we could identify on the masks are unlikely to make you instantly sick. However, they could cause acne and other skin infections, especially in combination with the friction of the face mask on the skin. Furthermore, food infections might occur due to touching the mask with your hands. In the worst-case scenarios, lung and systemic infections can be caused since bacteria could grow exponentially out of the control of our immune system and microbiota. Especially when bacteria show antibiotic resistance, safety measures must be taken when using these masks.

As bacteriologists, we recommend to ensure social distancing and wash your hands as much as needed. These actions are very effective and should always be taken as first safety measures in the community during a pandemic. When physical distancing is not possible for longer than a few minutes (15 minutes is often used as a general rule to determine high-risk contacts) and when the SARS-CoV-2 infection rate in the community is still high, face masks are advised. But they must be used properly and stored in a breathable container to transport home or when not used for a certain period (anyway, wearing masks longer than 4 hours seems not advisable based on our results☺). If available, surgical-like masks are preferred, as they hold less bacteria, and can be easily disposed of after wearing.

Starting a PhD during lockdown

When you start a new job, you always have the first-day or even first-week jitters. For me, this was not any different. My first workweek was quite unusual as it coincided with the lab retreat. This week was full of meetings, workshops and the ongoing and upcoming research projects were discussed. This retreat was a great opportunity to get to know my colleagues and their research topics. If you are interested be sure to read our blogpost about the lab retreat. 

After this interesting and fun week, I was looking forward to my first ‘normal’ week on the job. Unfortunately, this was not a standard week either. It was cut short as SARS-CoV2 started taking over Belgium. Due to the corona crisis, telework became the norm. After cleaning out a messy room at home, I created a private office where I could work undisturbed. As for everyone, adapting was not always so easy, but it was the perfect opportunity to read literature, write a review and freshen up my bioinformatic skills. I learned the basics of the R programming language, improved my Linux skills, and made my first python scripts. Additionally, I investigated what bioinformatic tools could replace our current tools to identify and elucidate novel nonribosomal peptide synthetase clusters. These new skills and tools will be very useful during my PhD. 

As the regular contact with colleagues has diminished, our lab has organized weekly meetings in smaller groups per research topic. The PostDocs take lead of one the groups. During these weekly meetings, we discuss what we are working on, and what we hope to finish by the next meeting. It is not only a great way of motivating yourself and keeping track of your own work progress, but it also helps to combat the loneliness and lack of social contact that comes with telework. Currently, the corona lockdown measures are gradually being relaxed. Hopefully, we can all start working in the lab again soon!