Spermagglutinating Escherichia coli and its role in infertility: In vivo study

An insight into the vaginal microbiome of infertile women in Bangladesh using metagenomic approach

Introduction

The dysbiosis of vaginal microbiota is recognized as a potential underlying factor contributing to infertility in women. This study aimed to compare the vaginal microbiomes of infertile and fertile women to investigate their relationship with infertility.

Methods

Metagenomic analysis was conducted on samples from 5 infertile and 5 fertile individuals using both amplicon 16S and metagenomics shotgun sequencing methods.

Results and discussion

In the infertile group, the bacterial community was primarily represented by three major bacterial genera: Lactobacillus (79.42%), Gardnerella (12.56%) and Prevotella (3.33%), whereas, the fertile group exhibited a more diverse composition with over 8 major bacterial genera, accompanied by significantly reduced abundance of Lactobacillus (48.79%) and Gardnerella (6.98%). At the species level, higher abundances of L. iners, L. gasseri and G. vaginalis were observed in the infertile group. Regarding the microbiome composition, only one fertile and two infertile subjects exhibited the healthiest Community State Types, CST-1, while CST-3 was observed among two infertile and one fertile subject, and CST-4 in three other fertile and one infertile subject. Overall, alpha diversity metrics indicated greater diversity and lower species richness in the control (fertile) group, while the infertile group displayed the opposite trend. However, beta-diversity analysis did not show distinct clustering of samples associated with any specific group; instead, it demonstrated CST-type specific clustering. Shotgun metagenomics further confirmed the dominance of Firmicutes, with a greater abundance of Lactobacillus species in the infertile group. Specifically, L. iners and G. vaginalis were identified as the most dominant and highly abundant in the infertile group. Fungi were only identified in the control group, dominated by Penicillium citrinum (62.5%). Metagenome-assembled genomes (MAGs) corroborated read-based taxonomic profiling, with the taxon L. johnsonii identified exclusively in disease samples. MAG identities shared by both groups include Shamonda orthobunyavirus, L. crispatus, Human endogenous retrovirus K113, L. iners, and G. vaginalis. Interestingly, the healthy microbiomes sequenced in this study contained two clusters, Penicillium and Staphylococcus haemolyticus, not found in the public dataset. In conclusion, this study suggests that lower species diversity with a higher abundance of L. iners, L. gasseri and G. vaginalis, may contribute to female infertility in our study datasets. However, larger sample sizes are necessary to further evaluate such association.

Leukocytospermia and/or Bacteriospermia: Impact on Male Infertility

Infertility is a globally underestimated public health concern affecting almost 190 million people, i.e., about 17.5% of people during their lifetime, while the prevalence of male factor infertility is about 7%. Among numerous other causes, the prevalence of male genital tract infections reportedly ranges between 10% and 35%. Leukocytospermia is found in 30% of infertile men and up to 20% in fertile men. Bacterial infections cause an inflammatory response attracting leukocytes, which produce reactive oxygen species (ROS) and release cytokines, both of which can cause damage to sperm, rendering them dysfunctional. Although leukocytospermia and bacteriospermia are both clinical conditions that can negatively affect male fertility, there is still debate about their impact on assisted reproduction outcomes and management. According to World Health Organization (WHO) guidelines, leukocytes should be determined by means of the Endtz test or with monoclonal antibodies against CD15, CD68 or CD22. The cut-off value proposed by the WHO is 1 × 106 peroxidase-positive cells/mL. For bacteria, Gram staining and semen culture are regarded as the "gold standard", while modern techniques such as PCR and next-generation sequencing (NGS) are allowing clinicians to detect a wider range of pathogens. Whereas the WHO manual does not specify a specific value as a cut-off for bacterial contamination, several studies consider semen samples with more than 103 colony-forming units (cfu)/mL as bacteriospermic. The pathogenic mechanisms leading to sperm dysfunction include direct interaction of bacteria with the male germ cells, bacterial release of spermatotoxic substances, induction of pro-inflammatory cytokines and ROS, all of which lead to oxidative stress. Clinically, bacterial infections, including "silent" infections, are treatable, with antibiotics being the treatment of choice. Yet, non-steroidal antiphlogistics or antioxidants should also be considered to alleviate inflammatory lesions and improve semen quality. In an assisted reproduction set up, sperm separation techniques significantly reduce the bacterial load in the semen. Nonetheless, contamination of the semen sample with skin commensals should be prevented by applying relevant hygiene techniques. In patients where leukocytospermia is detected, the causes (e.g. infection, inflammation, varicocele, smoking, etc.) of the leukocyte infiltration have to be identified and addressed with antibiotics, anti-inflammatories or antioxidants in cases where high oxidative stress levels are detected. However, no specific strategy is available for the management of leukocytospermia. Therefore, the relationship between bacteriospermia and leukocytospermia as well as their specific impact on functional sperm parameters and reproductive outcome variables such as fertilization or clinical pregnancy must be further investigated. The aim of this narrative review is to provide an update on the current knowledge on leukocytospermia and bacteriospermia and their impact on male fertility.

Review of the evidence of the effects of human papillomavirus infection and Gardnerella vaginalis, and their co-infection on infertility

A prevalent sexually transmitted infection, the human papillomavirus (HPV) is typically obtained just after the first sexual activity. The majority of HPV infections are asymptomatic and temporary. Cervical, anal, penile, vaginal, vulvar, and oropharyngeal cancers can occur due to recurrent infections with high-risk (hr)-HPV strains, generally decades later. Infections with HPV are significantly associated with reproductive function abnormalities. Per recent research, HPV infections may result in male infertility by reducing sperm motility. The hr-HPV infection was a risk factor for miscarriage, and the indiscriminate HPV genotype increased the probability of premature labor unexpectedly. Women's endometrial trophoblastic cell implantation is decreased by HPV. Gardnerella vaginalis (GV), an anaerobic bacterium that is a component of the natural vaginal flora, can be associated with bacterial vaginosis (BV) when it starts to overgrow and emerge as the dominant species. Reduced Lactobacillus species abundance and GV are linked to female infertility. Data from in vitro studies suggests that sialidase produced by GV may facilitate the entry and growth of papilloma and other sexually transmitted viruses. Also, based on some studies conducted in the past, it can be said that GV and BV are associated with the development of uterine cancer. However, there is still not enough information about the exact mechanism of GV and HPV in causing infertility, which requires more research.

Using the PCR and Blood Agar in Diagnosis of Semen Bacterial Contamination of Fertile and Infertile Men

BACKGROUND

One of the causes of male infertility is Genital tract infections (GTI). Considering the importance of GTI, widespread recognition of them seems necessary. we aimed to characterize and compare semen microbial populations in fertile and infertile men who referred to an infertility clinic in Yazd, Iran.

METHODS

Semen samples were collected from two groups of fertile (268) and infertile (210) men. Sperm analysis (concentration, morphology, viability and motility parameters) were performed according to the World Health Organization (WHO) 2010 guidelines laboratory manual. Bacterial isolation was performed in Sheep Blood Agar and Eosin Methylene Blue (EMB) agar plates. For PCR, samples were analyzed with genus specific primers.

RESULTS

All semen characteristics were poor in the infertile group compared to those in the fertile men (p-value< 0.05). Enterococcus spp. (18.7%, 17.1%; p= 0.814), E. coli (7.9%, 11.4%; p= 0.486), Staphylococcus aureus (6.4%, 2.9%; p= 0.398) and Proteus mirabilis (0%, 2.9%; p= 0.002) were the most common agents, respectively. Also, the results obtained from PCR were confirmed using culture-base method.

CONCLUSION

Proteus mirabilis contamination was identified in the infertile group. While no significant association was observed between male infertility and semen microbial populations, p. mirabilis may be the leading cause of reproduction impairment in men.

Staphylococcus saprophyticus and Escherichia coli: Tracking from sperm fertility potential to assisted reproductive outcomes

Objective

Bacteriospermia and urogenital infections are common problems in male infertility. This study aimed to evaluate the effects of bacteriospermia on sperm parameters and clinical outcomes in semen samples infected with two common bacteria (Staphylococcus saprophyticus and Escherichia coli) in northern Iran.

Methods

Microbiological tests were performed to isolate and identify organisms from 435 semen samples from infertile couples. Semen samples were assessed according to the World Health Organization criteria. The protamine status, chromatin structure, chromatin condensation, and acrosome reaction of sperm and assisted reproductive outcomes were determined in couples with different male infertility factors.

Results

Among the total cases, the two most prevalent pathogens were considered: S. saprophyticus (38.2%) and E. coli (52.9%). In the semen samples infected with E. coli, the spontaneous acrosome reaction and abnormal chromatin condensation were more common (p<0.05). Significant increases in abnormal chromatin condensation and deprotamination were seen in the presence of S. saprophyticus. In washed semen, tight adhesion between the sperm midpiece and S. saprophyticus was observed. There was also a significant decrease in the fertilization rate using semen samples infected with S. saprophyticus and E. coli during in vitro fertilization cycles (p<0.001). In addition, the presence of S. saprophyticus and E. coli in semen samples was associated with a lower likelihood of clinical pregnancy in couples with various factors of male infertility.

Conclusion

Poor results of assisted reproductive techniques may be correlated with semen samples infected with two common bacteria in northern Iran.

Uropathogenic Escherichia coli in the high vaginal swab samples of fertile and infertile women: virulence factors, O-serogroups, and phenotyping and genotyping characterization of antibiotic resistance

Transmission of urinary tract infections into the reproductive system is unavoidable. The present research was performed to assess the distribution of virulence genes, O-serogroups and antibiotic resistance properties of uropathogenic Escherichia coli (UPEC) strains isolated from the high vaginal swab samples of fertile and infertile women. A total of 460 high vaginal swab samples were taken from fertile and infertile women. Distribution of virulence factors and serogroups and antibiotic resistance properties of the E. coli isolates were assessed. Sixty-five out of 460 (14.13%) swab samples were positive for E. coli. Prevalences of E. coli in samples taken from fertile and infertile women were 13.63% and 14.58%, respectively. O1 (7.69%), O2 (6.15%) and O6 (6.15%) were the most frequently detected serogroups. The most frequently detected virulence genes were sfa (72.72%), afa (72.72%), cnf1 (72.72%) and fim (72.72%). The most commonly detected antibiotic-resistance genes were tetA (95.45%), CITM (88.63%), aac(3)-IV (86.36%) and sul1 (72.72%). UPEC strains harboured the highest prevalence of resistance against tetracycline (88.63%), ampicillin (79.54%), gentamicin (77.27%) and enrofloxacin (52.27%). Seventeen out of 26 (65.38%) UPEC strains isolated from infertile women were resistant toward more than ten antibiotic agents. Infertile women with a history of urinary tract infections had the higher prevalence of UPEC strains and also the other characters. High prevalence of the virulent and resistant UPEC strains in the high vaginal part of the infertile women with a history of urinary tract infections may show an important role of these pathogens as causes of female infertility. However, further research is required to confirm this hypothesis.

The role of infections and leukocytes in male infertility

Declining birth rates are one of the problems facing society today. Male counterparts are responsible for about half of the infertility cases, and genitourinary tract infections may play a contributing role in approximately 15% of male infertility cases. Leukocytospermia is an established indicator of infection in the male urogenital tract, although other microorganisms such as bacteria and virus may also be contributors to the etiology of male infertility. The pathophysiology of these infectious agents may be initiated by a local inflammatory reaction resulting in an increase in reactive oxygen species (ROS). This results in testicular injury, thereby affecting sperm morphology, sperm motility, sperm viability and elevation of the seminal leukocyte as a result of the genital tract infection. The infectious and inflammatory changes can result in male infertility. It is proposed that high concentrations of seminal leukocyte and infectious agents may affect sperm function resulting in clumping of motile spermatozoa, decreasing acrosomal functionality and also causing alterations in sperm morphology. However, the literature has poorly clarified the role of infection in male infertility, provoking further debate and research on this topic.

Potential Pathogenic Bacteria in Seminal Microbiota of Patients with Different Types of Dysspermatism

Human microbiota play an important role in the health of their human hosts. Recent studies have demonstrated that microbiota exist in seminal plasma. The current study aims to elucidate whether seminal microbiota exist in patients with different types of dysspermatism and whether bacterial biomarkers can be identified for them. A total of 159 study participants were recruited, including 22 patients with oligoasthenospermia, 58 patients with asthenospermia, 8 patients with azoospermia, 13 patients with oligospermia, and 58 matched healthy controls. Seminal microbiota composition was analyzed using 16S rRNA gene-based sequencing. The results showed that the composition of seminal microbiota of patients with dysspermatism differed from those of healthy controls. Comparison of the microbiota composition in semen samples from patients with different types of dysspermatism showed that microbiota in patients with asthenospermia and oligoasthenospermia were distinct from healthy controls in beta diversity (P < 0.05). Characteristic biomarkers, including Ureaplasma, Bacteroides, Anaerococcus, Finegoldia, Lactobacillus and Acinetobacter lwoffii, were identified based on LEfSe analysis. Inferred functional analysis based on seminal microbiome data further indicated the presence of potential pathogenic biomarkers in patients with asthenospermia and oligoasthenospermia. These results provided profiles of seminal microbiota exhibited in different types of dysspermatism, thus providing new insights into their pathogenesis.

Colonization of mouse vagina with Pseudomonas aeruginosa: A plausible explanation for infertility

Little attention has been paid to the influence of asymptomatic colonizers of genital tract on female infertility. Albeit, a variety of uropathogens have been known to negatively alter sperm parameters in vitro, but their impact on female fertility outcome under in vivo conditions is not clearly established. Therefore, the present study was intended to investigate the effect of Pseudomonas aeruginosa on sperm parameters and to identify its role in female infertility. The strain of P. aeruginosa was found to reduce sperm motility, viability and sperm Mg⁺⁺ATPase activity. It could also lead to premature acrosomal loss and induce morphological defect in spermatozoa. For fertility studies, female mice administered intravaginally with 10⁴, 10⁶, 10⁸ cfu of P. aeruginosa for 10 consecutive days, were allowed to mate with proven breeder male on day 12. The results showed that group of mice receiving P. aeruginosa were rendered infertile whereas group receiving PBS showed abdominal distension, string of pearls and finally delivered pups at the end of gestation period. Further, no other clinical manifestation could be observed apparently, histologically or immunologically. Thus, it can be concluded that infertility in mice might be attributed to asymptomatic colonization of genital tract with sperm immobilizing P. aeruginosa.

Immunological Tolerance, Pregnancy, and Preeclampsia: The Roles of Semen Microbes and the Father

Although it is widely considered, in many cases, to involve two separable stages (poor placentation followed by oxidative stress/inflammation), the precise originating causes of preeclampsia (PE) remain elusive. We have previously brought together some of the considerable evidence that a (dormant) microbial component is commonly a significant part of its etiology. However, apart from recognizing, consistent with this view, that the many inflammatory markers of PE are also increased in infection, we had little to say about immunity, whether innate or adaptive. In addition, we focused on the gut, oral and female urinary tract microbiomes as the main sources of the infection. We here marshall further evidence for an infectious component in PE, focusing on the immunological tolerance characteristic of pregnancy, and the well-established fact that increased exposure to the father's semen assists this immunological tolerance. As well as these benefits, however, semen is not sterile, microbial tolerance mechanisms may exist, and we also review the evidence that semen may be responsible for inoculating the developing conceptus (and maybe the placenta) with microbes, not all of which are benign. It is suggested that when they are not, this may be a significant cause of PE. A variety of epidemiological and other evidence is entirely consistent with this, not least correlations between semen infection, infertility and PE. Our view also leads to a series of other, testable predictions. Overall, we argue for a significant paternal role in the development of PE through microbial infection of the mother via insemination.

A new enrichment diagnostic platform for semen culture

Urogenital bacterial infections have been described in literature as a potential cause of infertility. For the consequences that a failure in diagnosis could have on the evolution of male urogenital infectious disease, an accurate microbiological procedure to investigate the bacterial species composition of seminal fluid plays a crucial role to better understand the eventual correlation with infertility. In order to improve the quality of semen culture investigations, we have developed a new enrichment diagnostic platform. Semen samples of 540 infertile men were simultaneously analyzed using the standard microbiological semen culture method and an alternative new experimental technique (Brain Heart Infusion broth, BHI, enrichment). Our results established the possibility to apply BHI enrichment to detect bacteria from semen samples with higher sensitivity (100%) and negative predictive value (100%) than the standard technique.

The role of Escherichia coli in reproductive health: state of the art

Escherichia coli is a well-known commensal of the normal intestinal microbiome that can also colonize the vaginal microbiome, usually without symptoms. However, E. coli can also be a highly virulent and frequently deadly pathogen. In this review, I will discuss the role E. coli has in reproductive health and disease.

Is there a role for Serratia marcescens in male infertility: An experimental study?

OBJECTIVE

Establishment of a male BALB/c mouse model to study the role of sperm impairing S. marcescens on mouse reproductive potential. The current study can add to use of reliable animal models to provide a noteworthy evidence for the microbial cause of infertility.

METHODS

The mice in the test groups II, III, IV were intraperitoneally administered with different doses (10⁴, 10⁶ or 10⁸ cfu) of S. marcescens whereas, group I serving as control, received PBS, for 10 consecutive days. The groups were evaluated for any change in body weight, tissue somatic index (%), seminal parameters and histology. Confirmation of S. marcescens from reproductive organs was done by reisolating the same by cultural characteristics and biochemical tests.

RESULTS

The results showed that weight gain was evident only in mice receiving PBS (group I), whereas a decrease was recorded in the test groups (group II, III and IV). Only testes of test groups showed significant changes in TSI values whereas, no change in TSI was observed in any reproductive organ of any test group. Seminal parameters viz. sperm count, motility and viability were found to decrease in test groups II, III and IV as compared to control group I. Interestingly, the number of pus cells and percent decapitation was more prominent in test groups which received higher doses (i.e. group III and group IV). The histopathological examination revealed mild to dense inflammation in vas deferens and caudal epididymis in all test groups except hypospermatogenesis which was observed only in test group III and IV. However, in group I, neither adverse changes nor any sign of inflammation were observed.

CONCLUSION

Intraperitoneal inoculation of S. marcescens could lead to alteration of semen parameters, induction of decapitation in spermatozoa and histopathological changes, thereby decreasing the reproductive potential of male mice.

Abnormal vaginal colonization by gram-negative bacteria is significantly higher in pregnancy conceived through infertility treatment compared to natural pregnancy

OBJECTIVE

To compare abnormal vaginal colonization between natural pregnancy and pregnancy by infertility treatment in high-risk parturient women and to examine the association between abnormal vaginal colonization and early-onset neonatal sepsis (EONS).

METHODS

The clinical characteristics, vaginal culture result, and delivery outcome of patients who admitted to our high-risk unit between 2005 and 2014 were retrospectively reviewed and compared. We investigated the prevalence of EONS according to maternal vaginal colonization and examined the concordance between maternal vaginal bacteria and etiologic microorganism causing EONS.

RESULTS

Among 1096 pregnancies, the rate of vaginal colonization by gram-negative bacteria, especially Escherichia coli was significantly higher in pregnancies by infertility treatment after adjustment of confounding variables (E. coli, OR [95% CI]: 2.47 [1.33-4.57], p = 0.004). The rate of EONS was significantly higher in neonates with maternal abnormal vaginal bacteria colonization (OR [95% CI]: 3.38 [1.44-7.93], p = 0.005) after adjusting for confounding variables. Notably, among microorganisms isolated from maternal vagina, E. coli and Staphylococcus aureus were consistent with the results from neonatal blood culture in EONS.

CONCLUSIONS

Our data implicate a possible association between gram-negative bacteria colonization and infertility treatment and suggest that maternal vaginal colonization may be associated with EONS of neonates in high-risk pregnancy.