Female-to-Female Sexual Transmission of Genital Candida
Female-to-Female Sexual Transmission of Genital Candida
This mixed methods study found no evidence (epidemiological or laboratory-based) supporting sexual transmission of genital Candida spp. between women. This is in contrast to findings from a previous study that found increasing odds of VVC (either asymptomatic or symptomatic) among WSW with greater numbers of female partners during the previous year. Bisexual identity, sex with women and men during the past 12 months and numbers of male partners during the past 12 months were the only significant predictors of genital Candida spp. in this study. We found no associations between numbers of female partners (both lifetime and past 12 months) nor sexual practices with female partners (ie, vaginal penetration by female partners, shared use of vaginally inserted sex toys with female partners, inconsistent condom use on sex toys with female partners, etc.) and the presence of genital Candida spp. In addition, RAPD banding patterns were discordant for all yeast isolates among WSW within sexual partnerships in which both partners had a positive yeast culture as well as in a group of controls.
It has been hypothesised that penile-vaginal intercourse might facilitate the movement of Candida spp. into the vagina and result in minor local trauma that creates conditions suitable for tissue invasion. An association between frequency of heterosexual intercourse and symptomatic attacks of VVC has formed the basis of this hypothesis. In addition, epidemiological data suggest that orogenital and anogenital contact may also transmit yeast. Prior studies using molecular techniques to genotype strains of Candida spp. among women with VVC and their male partners have shown genetic similarities, further supporting the hypothesis of sexual transmission. With regards to WSW, it is hypothesised that sexual activities such as orogenital sex and the sharing of sex toys could facilitate cross-infection of Candida spp., leading to vaginal colonisation and subsequent development of infection. Indeed, sexual exchange of infected vaginal fluid has been found to be a possible mechanism for the acquisition of BV among WSW. However, taking into account the results of our study and the fact that genital Candida spp. can gain access to the vaginal lumen from the adjacent perianal area, it may be that the pathogenesis of BV and vaginal yeast infections is different among WSW, that is, WSW may acquire genital Candida spp. endogenously while BV is acquired exogenously from infected female partner(s). Thus, it remains unknown whether Candida spp. are truly sexually transmitted or whether sexual activities only potentiate Candida spp. colonisation while additional factors (ie, use of antibiotics, etc.) influence development of infection.
To our knowledge, this is the first study using RAPD to perform genotypic characterisation of genital Candida spp. among WSW in sexual partnerships in which both partners had a positive yeast culture. We found no evidence of genetic concordance of yeast isolates among WSW in sexual partnerships. In keeping with the hypothesis mentioned above and our results, it may be that female–female sexual practices do not sufficiently facilitate the movement of Candida spp. into the vagina nor induce enough local trauma to create conditions suitable for tissue invasion of yeast. Alternatively, it could also be that repeated sexual exposures to female partner(s), similar to those that predispose WSW to a higher risk of colonisation of Gardnerella vaginalis and other BV-associated bacteria, are necessary to facilitate the transfer of yeast between women. Unfortunately, we did not have data available with regards to the frequency of sexual activities WSW in sexual partnerships participated in with their female partners. It is also important to note that several women in the partnerships were also having sex with men at the time of enrolment; how this influenced their genital yeast isolates is unknown as we did not have their male partners available for testing. Therefore, further research is necessary to confirm the results of our study.
Although not a primary objective, it should be noted that this is the first study detailing the prevalence of genital Candida spp. among a cohort of African-American WSW. Our observed prevalence (53.6%) was much higher than that seen in prior studies of premenopausal women (15–20%) and Caucasian WSW (18.4%). Potential explanations could be that all women in this study were of African-American race (a genetic factor that may predispose to colonisation or vaginitis with yeast), constituted a high-risk STD clinic population frequently diagnosed with BV/STIs and may have recently taken antibiotics or had additional risk factors predisposing them to yeast colonisation/VVC. Unfortunately, we did not collect the latter information and can only speculate that this may have contributed. Interestingly, in a study of 338 predominately African-American women at an STD clinic in Birmingham, Alabama, USA, the prevalence of yeast detected by wet prep/culture was also high at 39.1%.
We also found that multiple species and mixed subspecies of Candida can be isolated from the vaginal vault. The four species associated with VVC in the USA (C albicans, C tropicalis, C glabrata and C parapsilosis) were observed in this population. However, while three of the four species were found in similar rates to those described in the literature,C parapsilosis was present at an unusually higher rate (19.2%). The prevalence of C parapsilosis in the USA is estimated to be 1.7% nationally and 1.8% in the South. Potential reasons for this deviation from the national prevalence of C parapsilosis among women in this study are unknown. Of note, a higher prevalence of C parapsilosis (12%) has been observed in a study of Costa Rican sex workers with or without VVC. In this study, the use of miconazole ≥4 times a year, for treatment or prophylaxis, was significantly associated with drug resistance among the C parapsilosis isolates. Given the recent increase in non-C albicans-associated VVC, perhaps attributed to the overuse/abuse of over-the-counter (OTC) antifungals, one could hypothesise that the increased prevalence of C parapsilosis observed in our study could be related to behavioural factors such as overuse of this type of medication. However, we did not have detailed behavioural information available with regards to frequency of OTC vaginal antifungal use to see whether such a correlation existed.
This study has several limitations. First, the relatively small sample size of African-American WSW presenting to an urban STD clinic in Jackson, MS, limits the generalisability of our results. Second, as this was a pilot study, we were unable to collect data on receptive oral sex with female partners or data on other specific sexual practices with female partners, which could have an association with the presence of genital Candida spp. In addition, although RAPD is a powerful molecular technique that allows for the investigation of genetic information without prior knowledge of the target organism's genome, it has several weaknesses. Template DNA may be contaminated from other sources. In addition, if RAPD conditions are not optimised and consistent from test to test, results may not be reproducible. Resultant banding patterns may be difficult to interpret in number, intensity and position to a standard. Nevertheless, RAPD can be a valuable tool under controlled and well-characterised settings such as those used in our current and prior studies.
In conclusion, in contrast to previous studies of BV, this study found no evidence of sexual transmission of genital Candida spp. between women. More research is needed to better understand the contribution of sexual transmission to genital Candida spp. isolates and VVC among WSW.
Discussion
This mixed methods study found no evidence (epidemiological or laboratory-based) supporting sexual transmission of genital Candida spp. between women. This is in contrast to findings from a previous study that found increasing odds of VVC (either asymptomatic or symptomatic) among WSW with greater numbers of female partners during the previous year. Bisexual identity, sex with women and men during the past 12 months and numbers of male partners during the past 12 months were the only significant predictors of genital Candida spp. in this study. We found no associations between numbers of female partners (both lifetime and past 12 months) nor sexual practices with female partners (ie, vaginal penetration by female partners, shared use of vaginally inserted sex toys with female partners, inconsistent condom use on sex toys with female partners, etc.) and the presence of genital Candida spp. In addition, RAPD banding patterns were discordant for all yeast isolates among WSW within sexual partnerships in which both partners had a positive yeast culture as well as in a group of controls.
It has been hypothesised that penile-vaginal intercourse might facilitate the movement of Candida spp. into the vagina and result in minor local trauma that creates conditions suitable for tissue invasion. An association between frequency of heterosexual intercourse and symptomatic attacks of VVC has formed the basis of this hypothesis. In addition, epidemiological data suggest that orogenital and anogenital contact may also transmit yeast. Prior studies using molecular techniques to genotype strains of Candida spp. among women with VVC and their male partners have shown genetic similarities, further supporting the hypothesis of sexual transmission. With regards to WSW, it is hypothesised that sexual activities such as orogenital sex and the sharing of sex toys could facilitate cross-infection of Candida spp., leading to vaginal colonisation and subsequent development of infection. Indeed, sexual exchange of infected vaginal fluid has been found to be a possible mechanism for the acquisition of BV among WSW. However, taking into account the results of our study and the fact that genital Candida spp. can gain access to the vaginal lumen from the adjacent perianal area, it may be that the pathogenesis of BV and vaginal yeast infections is different among WSW, that is, WSW may acquire genital Candida spp. endogenously while BV is acquired exogenously from infected female partner(s). Thus, it remains unknown whether Candida spp. are truly sexually transmitted or whether sexual activities only potentiate Candida spp. colonisation while additional factors (ie, use of antibiotics, etc.) influence development of infection.
To our knowledge, this is the first study using RAPD to perform genotypic characterisation of genital Candida spp. among WSW in sexual partnerships in which both partners had a positive yeast culture. We found no evidence of genetic concordance of yeast isolates among WSW in sexual partnerships. In keeping with the hypothesis mentioned above and our results, it may be that female–female sexual practices do not sufficiently facilitate the movement of Candida spp. into the vagina nor induce enough local trauma to create conditions suitable for tissue invasion of yeast. Alternatively, it could also be that repeated sexual exposures to female partner(s), similar to those that predispose WSW to a higher risk of colonisation of Gardnerella vaginalis and other BV-associated bacteria, are necessary to facilitate the transfer of yeast between women. Unfortunately, we did not have data available with regards to the frequency of sexual activities WSW in sexual partnerships participated in with their female partners. It is also important to note that several women in the partnerships were also having sex with men at the time of enrolment; how this influenced their genital yeast isolates is unknown as we did not have their male partners available for testing. Therefore, further research is necessary to confirm the results of our study.
Although not a primary objective, it should be noted that this is the first study detailing the prevalence of genital Candida spp. among a cohort of African-American WSW. Our observed prevalence (53.6%) was much higher than that seen in prior studies of premenopausal women (15–20%) and Caucasian WSW (18.4%). Potential explanations could be that all women in this study were of African-American race (a genetic factor that may predispose to colonisation or vaginitis with yeast), constituted a high-risk STD clinic population frequently diagnosed with BV/STIs and may have recently taken antibiotics or had additional risk factors predisposing them to yeast colonisation/VVC. Unfortunately, we did not collect the latter information and can only speculate that this may have contributed. Interestingly, in a study of 338 predominately African-American women at an STD clinic in Birmingham, Alabama, USA, the prevalence of yeast detected by wet prep/culture was also high at 39.1%.
We also found that multiple species and mixed subspecies of Candida can be isolated from the vaginal vault. The four species associated with VVC in the USA (C albicans, C tropicalis, C glabrata and C parapsilosis) were observed in this population. However, while three of the four species were found in similar rates to those described in the literature,C parapsilosis was present at an unusually higher rate (19.2%). The prevalence of C parapsilosis in the USA is estimated to be 1.7% nationally and 1.8% in the South. Potential reasons for this deviation from the national prevalence of C parapsilosis among women in this study are unknown. Of note, a higher prevalence of C parapsilosis (12%) has been observed in a study of Costa Rican sex workers with or without VVC. In this study, the use of miconazole ≥4 times a year, for treatment or prophylaxis, was significantly associated with drug resistance among the C parapsilosis isolates. Given the recent increase in non-C albicans-associated VVC, perhaps attributed to the overuse/abuse of over-the-counter (OTC) antifungals, one could hypothesise that the increased prevalence of C parapsilosis observed in our study could be related to behavioural factors such as overuse of this type of medication. However, we did not have detailed behavioural information available with regards to frequency of OTC vaginal antifungal use to see whether such a correlation existed.
This study has several limitations. First, the relatively small sample size of African-American WSW presenting to an urban STD clinic in Jackson, MS, limits the generalisability of our results. Second, as this was a pilot study, we were unable to collect data on receptive oral sex with female partners or data on other specific sexual practices with female partners, which could have an association with the presence of genital Candida spp. In addition, although RAPD is a powerful molecular technique that allows for the investigation of genetic information without prior knowledge of the target organism's genome, it has several weaknesses. Template DNA may be contaminated from other sources. In addition, if RAPD conditions are not optimised and consistent from test to test, results may not be reproducible. Resultant banding patterns may be difficult to interpret in number, intensity and position to a standard. Nevertheless, RAPD can be a valuable tool under controlled and well-characterised settings such as those used in our current and prior studies.
In conclusion, in contrast to previous studies of BV, this study found no evidence of sexual transmission of genital Candida spp. between women. More research is needed to better understand the contribution of sexual transmission to genital Candida spp. isolates and VVC among WSW.
