Vol 8, No 2 (2023)
Original article
Published online: 2023-06-21

open access

Page views 1296
Article views/downloads 327
Get Citation

Connect on Social Media

Connect on Social Media

The state of the microbiota of the genital tract in women who smoke

Inna Georgiivna Ponomarova1, Tamara Oleksandrivna Lisyana1, Olga Ivanivna Matyashova1, Svitlana Urijivna Krishchuk1
Medical Research Journal 2023;8(2):147-151.

Abstract

Introduction: Tobacco use has a negative effect on the immune system and contributes to a decrease in the protective properties of a woman’s body, which leads to dysbiotic changes in the microbiota of the genital tract.
Materials and methods: To assess the species and quantity composition of the microflora of the vagina in women, bacteriological studies were conducted. The research group consisted of women with inflammatory diseases of the genital tract who smoke (40 women) and 40 women who do not smoke. The control group consisted of 30 healthy women who did not smoke.
Results: The obtained results indicate that the state of the microbiota of the genital organs in women who smoke is characterized by an increase in the spectrum of isolated microflora of enterobacteria and Gram-positive cocci, anaerobic bacteria, an increase in the level of viral infection and a significant decrease in the concentration of protective microflora. The microbiota of the genital tract of women who smoke is characterized by the formation of 2–3 component associations (in 45% of women) of infectious agents in various combinations. In non-smoking women, bacterial associations were found in 17.5% of cases.
Conclusions: In women who smoke, there is a significant imbalance of protective and potentially pathogenic flora with active contamination of the genital tract with conditionally pathogenic microorganisms that form multicomponent associations of infectious agents. The obtained data indicate the need for constant monitoring of the causative agents of vaginal dysbiosis in women who smoke, as well as the need for further research to identify the impact of smoking cessation on the vaginal microbiome.

ORIGINAL ARTICLE

Medical Research Journal 2023;

Volume 8, Number 2, 147–151

10.5603/MRJ.a2023.0027

Copyright © 2023 Via Medica

ISSN 2451-2591

e-ISSN 2451-4101

The state of the microbiota of the genital tract in women who smoke

Inna Georgiivna PonomarovaTamara Oleksandrivna LisyanaOlga Ivanivna MatyashovaSvitlana Urijivna Krishchuk
State University „Institute of Pediatrics, Obstetrics and Gynecology named after academician OM Lukyanova, National Academy of Medical Sciences of Ukraine”, Kyiv, Ukraine

Corresponding author:

Inna Georgiivna Ponomarova, State University „Institute of Pediatrics, Obstetrics and Gynecology named after academician OM Lukyanova, National Academy of Medical Sciences of Ukraine”, 8 Platona Maiborody St., 04050, Kyiv, Ukraine; e-mail: microbiki@gmail.com

ABSTRACT

Introduction: Tobacco use has a negative effect on the immune system and contributes to a decrease in the protective properties of a woman’s body, which leads to dysbiotic changes in the microbiota of the genital tract.

Materials and methods: To assess the species and quantity composition of the microflora of the vagina in women, bacteriological studies were conducted. The research group consisted of women with inflammatory diseases of the genital tract who smoke (40 women) and 40 women who do not smoke. The control group consisted of 30 healthy women who did not smoke.

Results: The obtained results indicate that the state of the microbiota of the genital organs in women who smoke is characterized by an increase in the spectrum of isolated microflora of enterobacteria and Gram-positive cocci, anaerobic bacteria, an increase in the level of viral infection and a significant decrease in the concentration of protective microflora. The microbiota of the genital tract of women who smoke is characterized by the formation of 2–3 component associations (in 45% of women) of infectious agents in various combinations. In non-smoking women, bacterial associations were found in 17.5% of cases.

Conclusions: In women who smoke, there is a significant imbalance of protective and potentially pathogenic flora with active contamination of the genital tract with conditionally pathogenic microorganisms that form multicomponent associations of infectious agents. The obtained data indicate the need for constant monitoring of the causative agents of vaginal dysbiosis in women who smoke, as well as the need for further research to identify the impact of smoking cessation on the vaginal microbiome.

Key words: smoking, vaginal microbiota, associations of microorganisms

Med Res J 2023; 8 (2): 147–151

Introduction

In the conditions of modern society with its urbanization, social and economic problems, there is an increase in smoking, especially among the female population. Active and passive smoking leads to a violation of the general and reproductive health of women [1–3].

Cigarette smoke contains many toxic chemical substances, the main component of which is nicotine. Nicotine changes the state of brain structures, worsens the production of sexual hormones and reduces body resistance against infectious viruses, bacteria and fungi [4, 5]. Tobacco use contributes to a decrease in the protective properties of the macroorganism and disruption of systemic and local immunity, which can lead to dysbiotic changes in the microbiome of the genital tract [6, 7].

Scientific studies have proven that nicotine is found not only in the blood of women who smoke but also in other body fluids, namely in cervical mucus. Nicotine has a very strong effect on the microflora of the genital tract, which leads to disruption of the regulation of the microbiome cervical canal and vagina and promotes the uncontrolled growth of pathogenic and conditionally pathogenic microorganisms [8]. Thus, in the work of scientists, it is shown that nicotine can increase the ability of biofilm formation Staphylococcus aureus, which is a defensive reaction from the side of S. aureus to adverse conditions such as exposure to nicotine [9].

The components of tobacco smoke are also able to activate the processes of proteolysis by increasing the permeability of the epithelium of the female genital tract. This is accompanied by an increase in the influx of neutrophilic enzymes that destroy the proteins of the connective tissue matrix and leads to the emergence of an inflammatory process in this biotope [10–12].

Due to the inhibition of the growth and vital activity of the protective microflora of the genital organs in women who smoke, the destruction of the protective layer of mucus and the attachment of conditionally pathogenic bacteria to the epithelial cells of the mucous membrane is observed, which is one of the causes of the development of dysbiosis of the genital organs [13, 14].

Active proliferation of conditionally pathogenic microflora is accompanied by changes in the system of homeostasis and microcirculation, which contributes to chronic inflammation [15–17].

A modern feature of inflammatory diseases of the pelvic organs is the polymicrobial nature of the lesion with the formation of multicomponent associations of conditionally pathogenic microorganisms and other infectious agents on the mucous membrane of the genital tract, which are more resistant to such protective factors as phagocytosis and lysozyme [18–20].

Lactic acid bacteria (Lactobacillus spp.). They act as antagonists to many opportunistic bacteria, stimulate the synthesis of secretory IgA and lysozyme, suppress the toxicity of some microorganisms, and produce substances of an antibiotic nature [21, 22].

But under the influence of various negative endogenous and exogenous factors, the amount of Lactobacillus decreases spp. and the number of conditionally pathogenic microorganisms increases [23, 24].

A change in the protective properties of the endogenous microflora of the vagina in women who smoke poses a threat of ascending infection, which can be realized by the development of chronic endometritis, inflammatory diseases of the pelvic organs, and subsequently by infertility, pregnancy losses, and adverse perinatal consequences [25, 26].

Therefore, this work aimed to study the state of the vaginal microbiota in women with pelvic inflammatory disease who smoke.

Material and methods

Bacteriological studies were carried out in order to evaluate the species and quantitative composition of the microflora of the vagina in 80 women of childbearing age with chronic inflammatory diseases of the lower genital organs (chronic vaginitis, chronic endocervicitis) depending on the use of tobacco. Diagnosis of chronic vaginitis and chronic endocervicitis verified according to the data of clinical and laboratory research methods. When establishing a gynaecological diagnosis, women used the International Classification of Diseases: 10, created by the recommendations of WHO experts and adopted in Ukraine, according to which there are the following forms of inflammatory diseases of the genital organs of the lower part: chronic vulvitis, chronic vaginitis, chronic endocervicitis, chronic cervicitis.

The age of the study participants ranged from 24 to 27 years, the BMI was 18.524.9, and at the time of the examination, the women were not pregnant and did not take medication.

According to the gynaecological history, 45% of women were previously treated for colpitis of various aetiologies, 12.5% of women had a history of cervical erosion, and 22.5% of patients suffered from menstrual cycle disorders.

There was a somatic history weighted in 37.5% of women: 12.5% had disease gastrointestinal tract, 15% were diagnosed with endocrine pathology and 10% suffered from chronic tonsillitis.

The examined patients were divided into groups: Group I women who smoke and have inflammatory diseases of the genital organs (40 women), and Group II women who do not smoke and have inflammatory diseases of the genital organs (40 women).

The data obtained during the examination of 30 healthy women who do not smoke were used as a control.

Conducting microbiological analyses and recording the results was carried out by Order No. 234 of the Ministry of Health of Ukraine dated May 10, 2007, and other regulatory documents.

The following differential diagnostic media were used for vaginal mucus culture: blood agar, yolk-salt agar, Endo media, Saburo media and MRS media for Lactobacillus spp.

Sowing was carried out by the method of sectoral sowing on dense nutrient media, which allows for determining the degree of microbial insemination and revealing the maximum possible spectrum of aerobic and facultatively anaerobic microflora.

The identification of the selected microorganisms was carried out according to their cultural, morphological, tincture and biochemical properties on the automatic microbiological analyser Vitek 2 Compact (France).

Gardnerella vaginalis was diagnosed by the bacterioscopy method by staining smears according to Romanovsky with subsequent counting of „key” cells, performing an amine test and determining p N.

Diagnosis of Chlamydia trachomatis Ureaplasma urealyticum and HSV ½ were performed by the luminescent method using the „Chlamy-Scan”, „Urea-Scan” and „Herpes-Scan” kits.

Statistical processing of the obtained research results was carried out with the help of the standard computer package „Data Analysis” of Microsoft Excel for Windows 2007. The value of the arithmetic mean was calculated the value (M), the average error of the mean value (m) and the probability value (p). The reliability of the obtained data was assessed by the generally accepted method using the Student’s criterion. Reliability was considered established if its probability was at least 95% (0.05).

Table 1. Indicators of microbiocenosis of the vagina of women who smoke and have inflammatory diseases of the genital organs (%, lg CFU/mL)

Microorganisms

Women with inflammatory diseases of the genital organs

Healthy women who do not smoke

(CONTROL)

n = 30

who smoke

(I group)

n = 40

who do not smoke

(II group)

n = 40

%

lg CFU/mL

%

lg CFU/mL

%

lg CFU/mL

S. epidermidis

20

4.5 ± 0.04

22.5

3.8 ± 0.02

20.0

2.2 ± 0.02

S. epidermidis (hem +)

22.5

4.8 ± 0.03

17.5

4.0 ± 0.4

6.6

2.5 ± 0.02

S. aureus

12.5

4.5 ± 0.02*

7.5

3.6 ± 0.06

3.3

2.0 ± 0.03

S. agalactiae

10

4.4 ± 0.04*

5

3.2 ± 0.03

6.7

2.5 ± 0.03

S. pyogenes

15

4.3 ± 0.02

2.5

3.8 ± 0.02

Enterococcus spp.

15

4.2 ± 0.03

10

4.0 ± 0.03

10

3.3 ± 0.02

E. coli

25

4.3 ± 0.04

12.5

3.8 ± 0.07

13.3

3.5 ± 0.02

E. coli (hem+)

20

4.8 ± 0.05

10

3.6 ± 0.01

Klebsiella spp.

15

4.3 ± 0.03

7.5

3.8 ± 0.06

6.6

3.0 ± 0.02

Proteus spp.

5

5.9 ± 0.02*

2.5

3.6 ± 0.01

Candida fungi

2 5

4, 5 ± 0.02

7.5

4.1 ± 0.04

10

3, 1 ± 0.03

Lactobacillus spp.

6 5

3.6 ± 0.04*

82.5

4.6 ± 0.03

100

6.8 ± 0.04

Gardnerella vaginalis

30*

10

10

Chlamydia trachomatis

1 5*

7.5

6,7

Ureaplasma urealyticum

20

1 5

10

HSV 1/2

15

10

6.7

Results

Bacteriological studies conducted on women who smoke with inflammatory diseases (group I) testify to the substantial insemination of the vagina by opportunistic pathogens.

When examined women of the I group Staphylococcus spp. with haemolytic properties were recorded with a moderate frequency: Staphylococcus epidermidis (hem) 22.5%, Staphylococcus aureus 12.5%, various types of Streptococcus spp. were sown in 515% of examined women. Among Enterobacteriaceae were found: Escherichia coli (25%), E.coli with haemolytic properties (20%) and Klebsiella spp. (10%), Proteus spp. (5%). Candida fungi contaminated the vagina of women of this group in 25% of cases. Representatives of normal microflora are Lactobacillus spp. found in 65% of the examined. Decreased Lactobacillus seeding rate spp. registered in 45% of women, and their absence in 35% of patients.

Lactobacillus concentration spp. was lg 3.6 CFU/mL and was lower than in women, who do not smoke but have inflammatory diseases of the genital organs (Tab. 1), from which it can be concluded that smoking has a significant effect on the number of Lactobacillus spp. as part of the microbiota urogenital tract. Smoking has negative effects on immune reactivity and may indirectly reduce the competitive ability of Lactobacillus spp. in the vaginal biotope.

The analysis of quantitative indicators of the microflora of the vagina in patients of the 1st group shows that the concentrations of Gram-positive Staphylococcus spp. and Streptococcus spp. were registered in the range of lg4.0lg4.5 CFU/mL. Intestinal microflora was cultured in concentrations of lg4.3lg5.9 CFU/mL. The level of sowing Candida fungi exceeded the diagnostic level –lg4.5 CFU/mL.

By the method of bacterioscopy, taking into account “key cells” and auxiliary tests of Gardnerella vaginalis was diagnosed in 30% of the examined. Chlamydia registration frequency trachomatis was 15%, Ureaplasma urealyticum 20%. HSV ½ was found in ١٥٪ of patients.

In 45% of sick women who smoke and have inflammatory diseases of the genital organs, the presence of opportunistic microflora in 23 species associations was recorded. The associations included Staphylococcus spp., Enterobacteriaceae and Gardnerella vaginalis or Chlamydia trachomatis.

When comparing the results of the examination of women who smoke and have inflammatory diseases of the genital organs (group I) with the data of women who do not smoke but have inflammatory diseases of the genital organs (group II), a lower frequency of detection of Gram-positive cocci was established in patients of group II. Thus, S. epidermidis (heme) was detected in 17.5% of the examined, at a concentration of lg 4.0 CFU/mL, S. aureus 7.5% in an amount of lg 3.6 CFU/mL, Streptococcus agalactiae was cultured in 5% (lg 3.2 CFU/mL), and Streptococcus pyogenes in 2.5% of examined women in the amount of lg 3.8 CFU/mL. Enterococcus spp. was detected in 10% of women in this group and its level was lg 4.0 CFU/mL.

The frequency of cultivation of Enterobacteriaceae in women of the II group was 2.512.5%, and their quantitative indicators were –lg 3.6 to –lg 3.8 CFU/mL, which did not exceed the diagnostic level. Mushrooms r. Candida was cultured in women of the II group in 7.5% of cases. The concentration of Candida fungi was lg 4.1 CFU/ml. In patients of the II group, a decrease in the level of lactoflora seeding was also established. Lactobacillus spp. was detected in 82.5% of women, and their absence was registered in 17.5%.

Chlamydia diagnosis frequency trachomatis in non-smoking women was 7.5%, Ureaplasma urealyticum 15%. Gardnerella vaginalis and HSV ½ were registered in 10% of patients.

In 17.5% of women of the II group, the isolated microflora was found in associations that included Enterobacteriaceae, Candida fungi, Gardnerella vaginalis and HSV ½ in various combinations.

Discussion

The obtained results showed that the state of the microecology of the genital organs in women who smoke and have inflammatory diseases of the genital organs is characterized by an increase in the level of viral infection, an increase in the specific weight in the general spectrum of isolated microflora of anaerobic bacteria, enterobacteria and a significant decrease in the concentration of protective microflora [27, 28]. Inflammatory diseases of the genital organs are a very urgent problem in modern gynaecology, as they occupy the first place in its structure (up to 70%), and also lead to serious long-term complications, such as infertility, chronic pelvic pain syndrome and ectopic pregnancy.

The conducted research revealed pathological changes in the vaginal microbiota of various degrees in women who smoke. These negative factors cause shifts in the composition of the microbiota at the level of bacterial communities and can increase the pathogenic potential of microbial populations [29, 30]. The obtained results indicate the formation of complex associations of microorganisms, which lead to dysbiotic disturbances of the microflora of the urogenital tract of women.

This indicates the need for constant monitoring of causative agents of vaginal dysbiosis in women in order to select optimal therapy schemes taking into account the biological properties of individual strains that cause imbalances.

It was found that smoking is associated with a vaginal microbiota that contains low proportions of Lactobacillus spp., however, future research is needed to establish whether smoking cessation can positively affect the vaginal microbiome.

The current research has several limitations. The research was designed as a pilot; therefore the size of samples and funds were limited. Wide testing for infections that are transmitted sexually could not be held. In addition, the size sample size was reduced due to the exclusion of women who used hormonal contraception, because the use of hormonal contraception was associated with a reduced risk of bacterial vaginosis in most epidemiological studies [31].

A larger smoking cessation study is needed to establish a causal relationship that smoking directly affects the vaginal microbiome.

Conclusions

The negative influence of smoking on the state of micro biocenosis of the genital tract was established. Women who smoke have a significant imbalance of protective and potentially pathogenic bacterial flora and active contamination of the genital tract with conditionally pathogenic microorganisms.

In women who smoke with inflammatory diseases of the genital organs, there is a significant violation of the microbiota of the vagina, which is characterized by the formation of bacterial associations. With a greater frequency of association of infectious agents in various combinations, it was found in examined smokers (45%). In women who do not smoke, but have inflammatory diseases of the genital organs, bacterial associations were found in only 17.5% of cases.

Studies have shown the need for constant monitoring of causative agents of vaginal dysbiosis in women, as well as their associations for choosing optimal therapy schemes.

Further research is needed to determine whether smoking cessation can have a positive effect on the vaginal microbiome.

Conflict of interest: None.
Funding: None.

References

  1. de Angelis C, Nardone A, Garifalos F, et al. Smoke, alcohol and drug addiction and female fertility. Reprod Biol Endocrinol. 2020; 18(1): 21, doi: 10.1186/s12958-020-0567-7, indexed in Pubmed: 32164734.
  2. Szumilas K, Szumilas P, Grzywacz A, et al. The Effects of E-Cigarette Vapor Components on the Morphology and Function of the Male and Female Reproductive Systems: A Systematic Review. Int J Environ Res Public Health. 2020; 17(17), doi: 10.3390/ijerph17176152, indexed in Pubmed: 32847119.
  3. , et alPractice Committee of the American Society for Reproductive Medicine. Optimizing natural fertility. Fertil Steril. 2008; 90(5 Suppl): S1S6, doi: 10.1016/j.fertnstert.2008.08.122, indexed in Pubmed: 19007604.
  4. Nelson TM, Borgogna JC, Michalek RD, et al. Cigarette smoking is associated with an altered vaginal tract metabolomic profile. Sci Rep. 2018; 8(1): 852, doi: 10.1038/s41598-017-14943-3, indexed in Pubmed: 29339821.
  5. Țarcă V, Țarcă E, Luca FA. The Impact of the Main Negative Socio-Economic Factors on Female Fertility. Healthcare (Basel). 2022; 10(4), doi: 10.3390/healthcare10040734, indexed in Pubmed: 35455911.
  6. Harris CC. Tobacco smoking, E-cigarettes, and nicotine harm. Proc Natl Acad Sci U S A. 2018; 115(7): 14061407, doi: 10.1073/pnas.1722636115, indexed in Pubmed: 29386385.
  7. Wesselink AK, Hatch EE, Rothman KJ, et al. Prospective study of cigarette smoking and fecundability. Hum Reprod. 2019; 34(3): 558567, doi: 10.1093/humrep/dey372, indexed in Pubmed: 30576495.
  8. McCann MF, Irwin DE, Walton LA, et al. Nicotine and cotinine in the cervical mucus of smokers, passive smokers, and nonsmokers. Cancer Epidemiol Biomarkers Prev. 1992; 1(2): 125129, indexed in Pubmed: 1306094.
  9. Shi Le, Wu Y, Yang C, et al. Effect of nicotine on Staphylococcus aureus biofilm formation and virulence factors. Sci Rep. 2019; 9(1): 20243, doi: 10.1038/s41598-019-56627-0, indexed in Pubmed: 31882881.
  10. Siokos ApG, Siokou-Siova O, Tzafetas I. Correlation between cervical carcinogenesis and tobacco use by sexual partners. Hell J Nucl Med. 2019; 22 Suppl 2: 184190, indexed in Pubmed: 31802062.
  11. Haghighi F, Andriasian L, Tran NC, et al. Effect of cigarette and e-cigarette smoke condensates on biofilm formation and gene expression. Int J Environ Res Public Health. 2022; 19(8), doi: 10.3390/ijerph19084626, indexed in Pubmed: 35457494.
  12. Semlali A, Killer K, Alanazi H, et al. Cigarette smoke condensate increases C. albicans adhesion, growth, biofilm formation, and EAP1, HWP1 and SAP2 gene expression. BMC Microbiol. 2014; 14: 61, doi: 10.1186/1471-2180-14-61, indexed in Pubmed: 24618025.
  13. Holdcroft AM, Ireland DJ, Payne MS. The vaginal microbiome in health and disease what role do common intimate hygiene practices play? Microorganisms. 2023; 11(2), doi: 10.3390/microorganisms11020298, indexed in Pubmed: 36838262.
  14. Saraf VS, Sheikh SA, Ahmad A, et al. Vaginal microbiome: normalcy vs dysbiosis. Arch Microbiol. 2021; 203(7): 37933802, doi: 10.1007/s00203-021-02414-3, indexed in Pubmed: 34120200.
  15. Kroon SJ, Ravel J, Huston WM. Cervicovaginal microbiota, women’s health, and reproductive outcomes. Fertil Steril. 2018; 110(3): 327336, doi: 10.1016/j.fertnstert.2018.06.036, indexed in Pubmed: 30098679.
  16. Peric A, Weiss J, Vulliemoz N, et al. Bacterial colonization of the female upper genital tract. Int J Mol Sci. 2019; 20(14), doi: 10.3390/ijms20143405, indexed in Pubmed: 31373310.
  17. Khudoyarova DR, Shopulotova ZA. The role of staphylococcal infection in the structure of inflammatory diseases. Web of Scientist: International Scientific Research Journal. 2022; 3(6): 11801183, doi: 10.17605/OSF.IO/YPH2C.
  18. Severgnini M, Morselli S, Camboni T, et al. Gardnerella vaginalis clades in pregnancy: New insights into the interactions with the vaginal microbiome. PLoS One. 2022; 17(6): e0269590, doi: 10.1371/journal.pone.0269590, indexed in Pubmed: 35700195.
  19. Rodríguez PBV, Reyes RH, Vázquez NJC, et al. Mycoplasma hominis and Ureaplasma spp. in women attending infertility consultations. Rev Cuba Endoc. 2019; 30(3): 234.
  20. Sprong KE, Mabenge M, Wright CA, et al. Ureaplasma species and preterm birth: current perspectives. Crit Rev Microbiol. 2020; 46(2): 169181, doi: 10.1080/1040841X.2020.1736986, indexed in Pubmed: 32141797.
  21. Fuochi V, Cardile V, Petronio Petronio G, et al. Biological properties and production of bacteriocins-like-inhibitory substances by Lactobacillus sp. strains from human vagina. J Appl Microbiol. 2019; 126(5): 15411550, doi: 10.1111/jam.14164, indexed in Pubmed: 30499608.
  22. Valenti P, Rosa L, Capobianco D, et al. Role of lactobacilli and lactoferrin in the mucosal cervicovaginal defense. Front Immunol. 2018; 9: 376, doi: 10.3389/fimmu.2018.00376, indexed in Pubmed: 29545798.
  23. Chen X, Lu Y, Chen T, et al. The female vaginal microbiome in health and bacterial vaginosis. Front Cell Infect Microbiol. 2021; 11: 631972, doi: 10.3389/fcimb.2021.631972, indexed in Pubmed: 33898328.
  24. Schoenmakers S, Steegers-Theunissen R, Faas M. The matter of the reproductive microbiome. Obstet Med. 2019; 12(3): 107115, doi: 10.1177/1753495X18775899, indexed in Pubmed: 31523266.
  25. Jennings LK, Krywko DM. Pelvic Inflammatory Disease. StatPearls [Internet], Treasure Island 2023.
  26. Han Y, Liu Z, Chen T. Role of vaginal microbiota dysbiosis in gynecological diseases and the potential interventions. Front Microbiol. 2021; 12: 643422, doi: 10.3389/fmicb.2021.643422, indexed in Pubmed: 34220737.
  27. Yıldırım R, Vural G, Koçoğlu E. Effect of vaginal douching on vaginal flora and genital infection. J Turk Ger Gynecol Assoc. 2020; 21(1): 2934, doi: 10.4274/jtgga.galenos.2019.2018.0133, indexed in Pubmed: 30821136.
  28. Auriemma RS, Scairati R, Del Vecchio G, et al. The vaginal microbiome: a long urogenital colonization throughout woman life. Front Cell Infect Microbiol. 2021; 11: 686167, doi: 10.3389/fcimb.2021.686167, indexed in Pubmed: 34295836.
  29. Wójkowska-Mach J, Pomorska-Wesołowska M, Romanik M, et al. Prevalence and antimicrobial susceptibility profiles of microorganisms associated with lower reproductive tract infections in women from southern poland-retrospective laboratory-based study. Int J Environ Res Public Health. 2021; 18(1), doi: 10.3390/ijerph18010335, indexed in Pubmed: 33466345.
  30. Han Y, Liu Z, Chen T. Role of vaginal microbiota dysbiosis in gynecological diseases and the potential interventions. Front Microbiol. 2021; 12: 643422, doi: 10.3389/fmicb.2021.643422, indexed in Pubmed: 34220737.
  31. Vodstrcil LA, Hocking JS, Law M, et al. Hormonal contraception is associated with a reduced risk of bacterial vaginosis: a systematic review and meta-analysis. PLoS One. 2013; 8(9): e73055, doi: 10.1371/journal.pone.0073055, indexed in Pubmed: 24023807.