A healthy human vagina is primarily colonized by the genus
The hormonal changes occur during the reproductive stages with the resulting fluctuating levels of hormones that regulate the menstrual cycle. This is an important influence on the vaginal microbiota during human reproductive years (Farage et al. 2010). Women of different racial groups may exhibit different composition of microbial communities and, correspondingly, different susceptibility to vaginal infections. Women are more prone to urinary tract infections (UTI) than men due to the position of the urethra. The reduction in protective vaginal flora may increase the risk of these infections (Gupta et al. 2017).
Lactic acid bacteria (LAB) have been shown to inhibit the
The antimicrobial activity of the vaginal fluids correlates with an increased lactic acid content, low pH and competitive exclusion. The increased susceptibility to disease may be also related to vaginal microbiota fluctuations (Gajer et al. 2012). Ayeni and Adeniyi (2013) and Agboola et al. (2014) had reported the presence of organisms in healthy and menstruating women with their antimicrobial properties in Nigeria. However, there is no information to establish changes in vaginal microbiota at different stages of the menstrual cycle and the antimicrobial effects of the isolated LAB. Therefore, this study aimed at determining the prevalence of LAB at different stages of the menstrual cycle in Nigerian women with their potential antimicrobial properties.
In the first experiment, an overnight culture of
The three organisms used exhibited high resistance (i.e. 0 mm zones of inhibition) towards most of the antibiotics used. The
Ten volunteers were assessed for a level of LAB in their vagina at different stages of the menstrual cycle. It was observed that in seven (70%) out of the ten volunteers, there was a significant shift of the LAB level from low to high (8 × 105 to 7.6 × 109) CFU/ml over the course of the menstrual cycle. In the remaining three (30%) volunteers, the presence of LAB was not observed throughout the menstrual cycle (Table I).
Evaluation of the LAB counts at different stages of the menstrual cycle.
Week | Menstruation Period | Safe Period | Ovulation Period | |||
---|---|---|---|---|---|---|
Total CFU/ml | LAB CFU/ml | Total CFU/ml | LAB CFU/ml | Total CFU/ml | LAB CFU/ml | |
1 | 1.02 × 108 | 4.2 × 107 | 1.81 × 1010 | 9.3 × 109 | 2.22 × 1010 | 1.51 × 1010 |
2 | 5.6 × 107 | 1.0 × 106 | 1.91 × 1010 | 5.2 × 109 | 1.90 × 1010 | 1.14 × 1010 |
3 | 7.8 × 107 | 1.2 × 106 | 1.89 × 1010 | 7.4 × 109 | 2.53 × 1010 | 1.51 × 1010 |
4 | 7.0 × 107 | 2.2 × 106 | 1.87 × 1010 | 1.89 × 1010 | 9.8 × 109 | − |
5 | 9.2 × 107 | 1.4 × 106 | 1.52 × 1010 | 4.2 × 109 | 1.87 × 1010 | 1.02 × 1010 |
6 | 6.1 × 107 | 8 × 105 | 8.3 × 109 | 3.0 × 109 | 1.12 × 1010 | 7.6 × 109 |
7 | 1.13 × 108 | 2.5 × 106 | 2.11 × 1010 | 5.4 × 109 | 3.26 × 1010 | 1.02 × 1010 |
8 | 2.0 × 103 | Nil | 1.05 × 104 | − | 1.05 × 104 | Nil |
9 | 3.8 × 103 | Nil | 8.5 × 103 | − | 5.8 × 103 | Nil |
10 | 4.2 × 103 | Nil | 1.12 × 104 | − | 8.5 × 103 | Nil |
Note – Nil means no count of bacteria
A total of twenty-seven (27) bacterial species were identified from the three different stages of menstrual cycle as five species (
The cell-free supernatants and viable cells showed a clear inhibitory antimicrobial activity against
Determination of the antimicrobial activity of the cell-free supernatant and viable cells.
Cell-free supernatant | Viable Cell* | |||||
---|---|---|---|---|---|---|
16 | 12 | 20 | 20 | 15 | 20 | |
20 | 13 | 0 | 20 | 18 | 12 | |
15 | 14 | 0 | 18 | 20 | 0 | |
15 | 14 | 12 | 18 | 20 | 15 | |
20 | 10 | 15 | 20 | 15 | 18 | |
15 | 15 | 15 | 20 | 18 | 18 | |
10 | 12 | 13 | 19 | 20 | 15 | |
20 | 12 | 10 | 15 | 20 | 20 | |
22 | 13 | 17 | 20 | 16 | 20 | |
19 | 14 | 0 | 20 | 20 | 18 | |
22 | 12 | 0 | 13 | 18 | 20 | |
18 | 10 | 0 | 20 | 15 | 20 | |
19 | 12 | 0 | 20 | 20 | 20 | |
19 | 20 | 20 | 20 | 20 | 15 | |
18 | 20 | 16 | 20 | 15 | 20 | |
19 | 20 | 15 | 20 | 20 | 20 | |
8 | 10 | 0 | 0 | 20 | 15 | |
10 | 0 | 0 | 12 | 15 | 0 | |
14 | 13 | 15 | 12 | 15 | 15 | |
10 | 15 | 0 | 10 | 18 | 0 | |
0 | 18 | 0 | 0 | 18 | 0 | |
0 | 0 | 0 | 0 | 0 | 0 | |
0 | 0 | 0 | 10 | 0 | 0 | |
0 | 13 | 0 | 10 | 15 | 0 | |
0 | 10 | 0 | 0 | 10 | 0 | |
0 | 18 | 18 | 10 | 18 | 18 | |
0 | 10 | 0 | 0 | 12 | 0 |
Antimicrobial activity is expressed as diameters of inhibition zones in mm
The capability of the LAB strains to inhibit the
Inhibition of
Inhibition of
The resistance to broad-spectrum antibiotics is a persistent challenge in the management of infections (Ayeni et al. 2011). In this study,
The species of beneficial bacteria identified from the vaginal samples in this study were
Many researchers have reported the prevalence of different LAB species isolated from the vagina of women from different geographical area (Gajer et al. 2012; Chaban et al. 2014; Shiraishi et al. 2011), but few have been able to report the type of LAB present or absent during the different stages of a woman’s menstrual cycle in different countries and specific ethnic aspects; this could influence the structure of the microbiota in specific niches. It was observed that during the menstruating period, the LAB count was low while at the safe/follicular period, the presence of the LAB was greater, but a large amount of LAB was found at the latter part of the cycle. Thereby, there was a significant shift in the LAB level from low to high over the course of the menstrual cycle. Menstruation may enhance a distortion of the bacterial microbiota around the vulva (Shiraishi et al. 2011) and influence
The absence or low the LAB count during menses may suggest the growth of yeast which can outgrow the bacteria in immunocompromised patients causing yeast and other urogenital infections. However, during safe and ovulation periods when the LAB count is increasing there is a decrease in the yeast count probably due to the antagonistic effect of these LAB on yeast or the hormonal changes taking place during these periods (Relloso et al. 2012). Women may be more susceptible to urogenital tract infections during the menstruation period compared to the ovulation period due to the high prevalence of the LAB during the ovulation period. The dynamic nature of the vaginal environment leads to changes in the microbiota of the vagina as a result of exposure to pathogens and physiologic fluctuations of the menstrual cycle (Farage et al. 2010). In the course of this study,
Lactobacilli isolated from the vagina have a prominent role as a prophylactic aimed at improving the vaginal microbiota defense against bacterial infections. The cell-free supernatant and the viable LAB cells exhibited capabilities to inhibit the growth of the uropathogens, albeit to a different extent. The vaginal strains of
The resistance of
The high LAB counts were found during the ovulation period while during menstruation, there was a decrease in the LAB counts. The highest occurrence in the vagina of Nigerian women was shown for