Microbiological Evaluation and Sperm DNA Fragmentation in Semen Samples of Patients Undergoing Fertility Investigation

The elusive male microbiome: revealing the link between the genital microbiota and fertility. Critical review and future perspectives

There is a growing focus on understanding the role of the male microbiome in fertility issues. Although research on the bacterial communities within the male reproductive system is in its initial phases, recent discoveries highlight notable variations in the microbiome's composition and abundance across distinct anatomical regions like the skin, foreskin, urethra, and coronary sulcus. To assess the relationship between male genitourinary microbiome and reproduction, we queried various databases, including MEDLINE (available via PubMed), SCOPUS, and Web of Science to obtain evidence-based data. The literature search was conducted using the following terms "gut/intestines microbiome," "genitourinary system microbiome," "microbiome and female/male infertility," "external genital tract microbiome," "internal genital tract microbiome," and "semen microbiome." Fifty-one relevant papers were analyzed, and eleven were strictly semen quality or male fertility related. The male microbiome, especially in the accessory glands like the prostate, seminal vesicles, and bulbourethral glands, has garnered significant interest because of its potential link to male fertility and reproduction. Studies have also found differences in bacterial diversity present in the testicular tissue of normozoospermic men compared to azoospermic suggesting a possible role of bacterial dysbiosis and reproduction. Correlation between the bacterial taxa in the genital microbiota of sexual partners has also been found, and sexual activity can influence the composition of the urogenital microbiota. Exploring the microbial world within the male reproductive system and its influence on fertility opens doors to developing ways to prevent, diagnose, and treat infertility. The present work emphasizes the importance of using consistent methods, conducting long-term studies, and deepening our understanding of how the reproductive tract microbiome works. This helps make research comparable, pinpoint potential interventions, and smoothly apply microbiome insights to real-world clinical practices.

Unraveling the Intricacies of the Seminal Microbiome and Its Impact on Human Fertility

Although the microbial communities from seminal fluid were an unexplored field some decades ago, their characteristics and potential roles are gradually coming to light. Therefore, a complex and specific microbiome population with commensal niches and fluctuating species has started to be revealed. In fact, certain clusters of bacteria have been associated with fertility and health, while the outgrowth of several species is potentially correlated with infertility indicators. This constitutes a compelling reason for outlining the external elements that may induce changes in the seminal microbiome composition, like lifestyle factors, gut microbiota, pathologies, prebiotics, and probiotics. In this review, we summarize the main findings about seminal microbiome, its origins and composition, its relationship with fertility, health, and influence factors, while reminding readers of the limitations and advantages introduced from technical variabilities during the experimental procedures.

Effect of environmental factors on seminal microbiome and impact on sperm quality

Objective

This review provides a comprehensive overview of the existing research on the seminal microbiome and its association with male infertility, while also highlighting areas that warrant further investigation.

Methods

A narrative review was conducted, encompassing all relevant studies published between 1980-2023 on the male reproductive tract microbiome in humans. This review considered studies utilizing culture-based, polymerase chain reaction (PCR)-based, and next-generation sequencing (NGS)-based methodologies to analyze the microbiome. Data extraction encompassed sample types (semen or testicular tissue), study designs, participant characteristics, employed techniques, and critical findings.

Results

We included 37 studies comprising 9,310 participants. Among these, 16 studies used culture-based methods, 16 utilized NGS, and five employed a combination of methods for microorganism identification. Notably, none of the studies assessed fungi or viruses. All NGS-based studies identified the presence of bacteria in all semen samples. Two notable characteristics of the seminal microbiome were observed: substantial variability in species composition among individuals and the formation of microbial communities with a dominant species. Studies examining the testicular microbiome revealed that the testicular compartment is not sterile. Interestingly, sexually active couples shared 56% of predominant genera, and among couples with positive cultures in both partners, 61% of them shared at least one genital pathogen. In couples with infertility of known causes, there was an overlap in bacterial composition between the seminal and vaginal microbiomes, featuring an increased prevalence of Staphylococcus and Streptococcus genera. Furthermore, the seminal microbiome had discernible effects on reproductive outcomes. However, bacteria in IVF culture media did not seem to impact pregnancy rates.

Conclusion

Existing literature underscores that various genera of bacteria colonize the male reproductive tract. These organisms do not exist independently; instead, they play a pivotal role in regulating functions and maintaining hemostasis. Future research should prioritize longitudinal and prospective studies and investigations into the influence of infertility causes and commonly prescribed medication to enhance our understanding of the seminal microbiota's role in reproductive health.

Controversy and Consensus on Indications for Sperm DNA Fragmentation Testing in Male Infertility: A Global Survey, Current Guidelines, and Expert Recommendations

PURPOSE

Sperm DNA fragmentation (SDF) testing was recently added to the sixth edition of the World Health Organization laboratory manual for the examination and processing of human semen. Many conditions and risk factors have been associated with elevated SDF; therefore, it is important to identify the population of infertile men who might benefit from this test. The purpose of this study was to investigate global practices related to indications for SDF testing, compare the relevant professional society guideline recommendations, and provide expert recommendations.

MATERIALS AND METHODS

Clinicians managing male infertility were invited to take part in a global online survey on SDF clinical practices. This was conducted following the CHERRIES checklist criteria. The responses were compared to professional society guideline recommendations related to SDF and the appropriate available evidence. Expert recommendations on indications for SDF testing were then formulated, and the Delphi method was used to reach consensus.

RESULTS

The survey was completed by 436 experts from 55 countries. Almost 75% of respondents test for SDF in all or some men with unexplained or idiopathic infertility, 39% order it routinely in the work-up of recurrent pregnancy loss (RPL), and 62.2% investigate SDF in smokers. While 47% of reproductive urologists test SDF to support the decision for varicocele repair surgery when conventional semen parameters are normal, significantly fewer general urologists (23%; p=0.008) do the same. Nearly 70% would assess SDF before assisted reproductive technologies (ART), either always or for certain conditions. Recurrent ART failure is a common indication for SDF testing. Very few society recommendations were found regarding SDF testing.

CONCLUSIONS

This article presents the largest global survey on the indications for SDF testing in infertile men, and demonstrates diverse practices. Furthermore, it highlights the paucity of professional society guideline recommendations. Expert recommendations are proposed to help guide clinicians.

Metagenomics Reveals Specific Microbial Features in Males with Semen Alterations

Infertility incidence is rising worldwide, with male infertility accounting for about 50% of cases. To date, several factors have been associated with male infertility; in particular, it has been suggested that semen microbiota may play a role. Here, we report the NGS-based analyses of 20 semen samples collected from men with (Case) and without (Control) semen alterations. Genomic DNA was extracted from each collected sample, and a specific PCR was carried out to amplify the V4-V6 regions of the 16S rRNA. Sequence reactions were carried out on the MiSeq and analyzed by specific bioinformatic tools. We found a reduced richness and evenness in the Case versus the Control group. Moreover, specific genera, the Mannheimia, the Escherichia_Shigella, and the Varibaculum, were significantly increased in the Case compared to the Control group. Finally, we highlighted a correlation between the microbial profile and semen hyperviscosity. Even if further studies are required on larger groups of subjects to confirm these findings and explore mechanistic hypotheses, our results confirm the correlation between semen features and seminal microbiota. These data, in turn, may open the way to the possible use of semen microbiota as an attractive target for developing novel strategies for infertility management.

Decrease of air pollution during lockdown in Tuscany (Italy): An effect on sperm DNA fragmentation?

In March 2020, the Italian government imposed a national lockdown which was almost completely removed in June 2020. Due to the abrupt stop of human activities, emissions of air pollutants decreased. Air pollution is an environmental risk factor for noncommunicable disease and mortality. Emerging evidence also suggests a role in male infertility. In this study, we compared sperm DNA fragmentation (sDF) levels and conventional semen parameters between subjects undergoing sDF determination and routine semen analysis in a single Italian centre, during about 6 months before (N = 119) and after lockdown (N = 105). After lockdown, we found an improvement of sperm progressive motility (48.00[38.50-58.00]% vs. 42.00[33.00-53.00]%) and sDF levels (as total: 24.79[18.33-33.97]% vs. 35.02[25.04-45.73]%, p < .001; brighter: 14.02[10.69-17.93]% vs 18.54[13.58-25.82]%, p < .001 and dimmer sDF: 9.24[5.64-15.78]% vs. 12.24[8.08-19.10]%, p < .01), mirrored by a decrease of leukocyte semen concentration (p < .01). The improvement of sperm motility and DNA quality was maintained after adjusting for leukocyte concentration and several conditions known to affect sperm motility and/or sDF levels. With a significant decrease in air pollution observed in Tuscany during and after lockdown, associated improvement in sperm motility and DNA quality in patients referred to the infertility clinic is suggestive of the potential role of air pollution in male infertility.

Sperm DNA fragmentation testing in clinical management of reproductive medicine

Background

Approximately 8%-12% of couples worldwide face infertility, with infertility of individuals assigned male at birth (AMAB) contributing to at least 50% of cases. Conventional semen analysis commonly used to detect sperm abnormalities is insufficient, as 30% of AMAB patients experiencing infertility show normal results in this test. From a genetic perspective, the assessment of sperm DNA fragmentation (SDF) is important as a parameter of sperm quality.

Methods

In this narrative study, we review and discuss pathophysiological causes, DNA repair mechanisms, and management of high SDF. We then summarize literature exploring the association between SDF and reproductive outcomes.

Main Findings

Recent systematic reviews and meta-analyses have revealed a significant association between high SDF in AMAB individuals and adverse reproductive outcomes including embryo development, natural conception, intrauterine insemination, and in vitro fertilization. However, the association with live birth rates and pregnancy rates following intracytoplasmic injection remains inconclusive. The disparities among quantitative assays, inconsistent reference range values, absent high-quality prospective clinical trials, and clinical heterogeneity in AMAB patients with elevated SDF represent the main limitations affecting SDF testing.

Conclusion

The evaluation and management of SDF plays an important role in a subset of AMAB infertility, but widespread integration into clinical guidelines will require future high-quality clinical trials and assay standardization.

Endometriosis and dysbiosis: State of art

Endometriosis is a complex and heterogeneous disease affecting approximately 10% of reproductive age women. The hypothesis that alterations in the microbiota are involved in the pathogenesis of endometriosis has been postulated. Possible explanations for the implications of dysbiosis in endometriosis include the Bacterial Contamination hypothesis and immune activation, cytokine-impaired gut function, altered estrogen metabolism and signaling. Thus, dysbiosis, disrupt normal immune function, leading to the elevation of proinflammatory cytokines, compromised immunosurveillance and altered immune cell profiles, all of which may contribute to the pathogenesis of endometriosis. The aim of this review is to summarize the available literature data about the relationship between microbiota and endometriosis.

Semen dysbiosis—just a male problem?

Seminal microflora is crucial to male fertility. Dysbiosis—disturbance of quantitative ratios of individual bacteria or appearance of pathogenic species—rarely results in symptomatic disease. Inflammation results in decreased sperm production, lower motility, or morphological changes and, in the long term, can cause ejaculatory duct obstruction, leading to infertility. Moreover, it may cause infection of the partner’s female genital tract. Dysbiosis in both partners results in fertility problems, disorders in embryo implantation, or miscarriages. In addition, chronic inflammation of the male genitourinary system may accelerate the appearance of antisperm antibodies. A comprehensive examination of seminal microflora can clarify the causes of infertility or prevent pathological conditions that affect seminal parameters. Seminal microflora as a direct impact on fertility problems as well as a decrease in the effectiveness of assisted reproduction methods, insemination, or in vitro procedures.

Molecular Epidemiology of Genital Infections in Campania Region: A Retrospective Study

This study provides updated information on the prevalence and co-infections caused by genital microorganisms and pathogens: Mycoplasma genitalium, Mycoplasma hominis, Ureaplasma parvum, Ureaplasma urealyticum, Trichomonas vaginalis, and Gardnerella vaginalis, by retrospectively analyzing a cohort of patients living in the Naples metropolitan area, Campania region, Southern Italy. To investigate the genital infections prevalence in clinical specimens (vaginal/endocervical swabs and urines) collected from infertile asymptomatic women and men from November 2018 to December 2020, we used a multiplex real-time PCR assay. Of the 717 specimens collected, 302 (42.1%) resulted positive for at least one of the targets named above. Statistically significant differences in genital prevalence of selected microorganisms were detected in both women (62.91%) and men (37.08%). G. vaginalis and U. parvum represented the most common findings with an 80.2% and 16.9% prevalence in vaginal/endocervical swabs and first-voided urines, respectively. Prevalence of multiple infections was 18.18% and 8.19% in women and men, respectively. The most frequent association detected was the co-infection of G. vaginalis and U. parvum with 60% prevalence. Our epidemiological analysis suggests different infection patterns between genders, highlighting the need to implement a preventative screening strategy of genital infections to reduce the complications on reproductive organs.

The Impact of Bacteriocenoses on Sperm Vitality, Immunological and Oxidative Characteristics of Ram Ejaculates: Does the Breed Play a Role?

Bacterial contamination of semen is an often overlooked, yet important, factor contributing to decreased sperm vitality. Understanding the impact of bacterial presence on sperm structural integrity and functional activity may assist the development of effective strategies to prevent, or manage, bacteriospermia in the breeding practice. The aim of this study was to describe the bacterial profiles of ram semen (n = 35), and we also focused on the associations between bacteriospermia, sperm structure, and function, as well as oxidative and inflammatory characteristics of semen. For a better insight, the samples were divided into three groups, according to the breeds used in the study: native Wallachian (NW), improved Wallachian (IW), and Slovak dairy (SD) breeds. The results showed a significantly lower motility and membrane integrity in the NW group in comparison to the IW and SD groups, which was accompanied by a significantly higher concentration of leukocytes, increased reactive oxygen species (ROS) generation, and subsequent oxidative insults to the sperm lipids and proteins. Accordingly, the NW group presented with the highest bacterial load, in which Staphylococcus and Escherichia were the predominant representatives. The Pearson correlation analysis uncovered positive relationships amongst the bacterial load and leukocytospermia (r = 0.613), the extent of lipid peroxidation (r = 0.598), protein oxidation (r = 0.514), and DNA fragmentation (r = 0.638). Furthermore, positive correlations were found between the bacterial load and pro-inflammatory molecules, such as the C-reactive protein (r = 0.592), interleukin 1 (r = 0.709), and interleukin 6 (r = 0.474), indicating a possible involvement of the immune response in the process of bacteriospermia. Overall, our data indicate that ram semen quality may be equally affected by the bacterial load and diversity. Furthermore, we can assume that the presence of bacteria in ejaculates triggers inflammatory processes, causes ROS overproduction, and, thereby, contributes to alterations in the sperm structure, while at the same time compromising the fertilization ability of male gametes.

Semen microbiota in normal and leukocytospermic males

Large numbers of microbes can be present in seminal fluid, and there are differences in the semen microbiota between normal and abnormal semen samples. To evaluate the semen microbiota in patients with leukocytospermia, 87 seminal fluid samples, including 33 samples with a normal seminal leukocyte count and 54 samples with leukocytospermia, were obtained for a cross-sectional analysis. Twenty samples with a normal seminal leukocyte count had normal sperm parameters (Control group), and 13 samples with a normal seminal leukocyte count were from asthenozoospermia patients (Ast group). However, 32 samples with leukocytospermia were from asthenozoospermia patients (LA group), and only 22 samples with leukocytospermia had normal sperm parameters (Leu group). The 16S ribosomal RNA (rRNA) gene sequencing method was used to sequence the microbiota in the seminal fluid, and multiple bioinformatics methods were utilized to analyze the data. Finally, the results showed that the worse sperm parameters were observed in the leukocytospermia-related groups. Semen microbiota analysis found that there was increased alpha diversity in the leukocytospermia-related groups. Firmicutes, Proteobacteria, Actinobacteria, and Bacteroidetes were the primary phyla in the seminal fluid. Two microbiota profiles, namely, Lactobacillus-enriched and Streptococcus-enriched groups, were identified in this study. The majority of the samples in the groups with a normal seminal leukocyte count could be categorized as Lactobacillus-enriched, whereas the majority of the leukocytospermia samples could be categorized as Streptococcus-enriched. Our study indicated that males with leukocytospermia have worse sperm parameters and a different semen microbiota composition compared to males with a normal seminal leukocyte count.

Mixed Sexually Transmitted Infections in Infertile Couples: Empirical Treatment and Influence on Semen Quality

BACKGROUND

Trichomonas vaginalis (TV), Mycoplasma genitalium (MG) and Ureaplasma urealyticum (UU) are common sexually transmitted infections (STIs) that are diagnosed in infertile couples (cps). In cases with their simultaneous presence in a patient (mixed STI, MSTIs), treatment is complicated by the different sensitivity of microorganisms to antibacterial drugs. Moreover, in cases of complicated infections, the empirical treatment should be started before obtaining the results of drug susceptibilities.

OBJECTIVE

The objective of the current study is to find the effective and well-tolerated combination of drugs for the empirical antibacterial treatment of mixed STIs presented by TV, MG and UU in infertile couples. We also aimed to establish the influence of mixed STIs on semen quality.

METHODS

Our prospective study included 154 infertile couples (308 patients) with confirmed symptomatic MSTIs in one of the couples caused by the simultaneous presence of TV, MG and UU. All couples were randomized on three groups for empirical treatment: Group 1 (n=49 cps, 98 pts) who were treated by initial prescribing of anti-trichomoniasis drug Secnidazole, 2.0 g po followed by Azythromycin 500 mg on day 1 continuing by 250 mg on days 2-7; Group 2 (n=52 cps, 104 pts: Secnidazole, 2.0 g po followed by Josamycin 1000 mg bid for 12 days); Group 3 (n=53 cps, 106 pts: Secnidazole, 2.0 g po followed by Moxifloxacin 400 mg once daily for 12 days). The endpoints were clinical and microbiological cure rates as well as the frequency of side-effects in analyzed groups. We determined the basic parameters of the spermogram and Deoxyribonucleic acid (DNA) fragmentation levels in 59 patients with MSTIs before and at the 3rd, 6th and 9th month after pathogens eradication comparing them with results in 63 healthy sperm donors.

RESULTS

After the treatment, clinical cure rates in analyzed groups were 82.6% (Group 1) vs. 96.1% (Group 2) vs. 92.3% (Group 3). Microbiological cure rates (UU+MG) were 73.9% vs. 97.1% vs. 84.5% correspondingly (p<0.05). TV microbiological cure rates were 97.8% vs. 98.0% vs. 96.1% (p>0.05). Side-effects were registered in 28.6% vs. 12.5% vs. 18.9% cases correspondingly (p<0.05). In MSTIs patients, we registered the increasing DNA fragmentation rates, leucocytes count and decreasing semen volume, motility, vitality, sperm concentration, total spermatozoa number and number of spermatozoa with normal morphology. At the 6th month after complete pathogens eradication, these parameters approached normal values.

CONCLUSION

At the present time, the combination of Secnidazole+Josamycin can be considered the most effective and well-tolerated for the empirical treatment in patients with MSTIs presented by TV, MG and UU. Complete eradication of these MSTIs in males improves their semen parameters.

Identification of Bacterial Profiles and Their Interactions with Selected Quality, Oxidative, and Immunological Parameters of Turkey Semen

Simple Summary

Overbreeding—and its associated increase in the chest areas of turkeys—has led to the loss of their natural ability to reproduce. Therefore, commercial production of turkey meat relies on artificial insemination. However, along with the physiology of the genital tract of turkeys, there is high potential for bacterial contamination of ejaculates. These bacteria may affect crucial semen quality parameters required for successful fertilization. As such, it is important to pay close attention to the bacteria present in turkey ejaculates and possible solutions to eliminate their adverse effects on avian spermatozoa.

Abstract

This study focused on the identification of naturally occurring bacteria in the reproductive fluid and impact on the quality of ejaculates obtained from the turkey breed British United Turkeys (BUT) Big 6 (n = 60). We determined possible relationships between the bacterial load and advanced sperm quality parameters that are important for effective artificial insemination and high fertility, as well as the concentration of selected antimicrobial proteins and pro-inflammatory markers of turkey semen. Sperm motility was assessed with computer-assisted sperm analysis (CASA), while the membrane and acrosome integrity were examined with smearing and staining methods. Reactive oxygen species (ROS) generation was quantified via luminometry, sperm DNA fragmentation was evaluated using the TUNEL assay, and the JC-1 assay was applied to evaluate the mitochondrial membrane potential. Cell lysates were prepared to investigate the extent of lipid and protein oxidation. Furthermore, levels of interleukins 1 and 6 (IL-1, IL-6), C-reactive protein, cathelicidin, and β-defensin were quantified in the seminal plasma using the ELISA method. The most dominant species identified by the matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry was Escherichia coli, Proteus mirabilis, Staphylococcus lentus, and Citrobacter braakii. The bacterial load had a negative effect on the sperm motility (p < 0.001), as well as membrane (p < 0.05) and acrosome integrity (p < 0.01). A strong positive relationship between the bacterial load and DNA fragmentation (p < 0.001) was detected as well. Positive associations were recorded between the increasing presence of bacteria, ROS overgeneration (p < 0.001), and a subsequent oxidative damage to the proteins (p < 0.001) and lipids (p < 0.01). It was revealed that the antimicrobial peptides β-defensin (p < 0.001) and cathelicidin (p < 0.001) had a positive relationship with the motility. In contrast, pro-inflammatory markers, such as IL-1 (p < 0.001) and IL-6 (p < 0.001), had a negative impact on the motion behavior of turkey spermatozoa. Our results suggest that the semen quality may be notably affected by the bacterial quantity as well as quality. It seems that bacteriospermia is associated with inflammatory processes, oxidative stress, sperm structural deterioration, and a subsequent risk for a failed artificial insemination in turkey breeding.