Study findings could lead to new clinical laboratory testing biomarkers designed to assess for male infertility
Clinical laboratories are increasingly performing tests that have as their biomarkers the DNA and enzymes found in human microbiota. And microbiologists and epidemiologists know that like other environments within the human body, semen has its own microbiome. Now, a study conducted at the University of California, Los Angeles (UCLA) has found that the health of semen microbiome may be linked to male infertility.
The UCLA researchers discovered a small group of microorganisms within semen that may impair the sperm’s motility (its ability to swim) and affect fertility.
A total of 73 individuals were included in the study. About half of the subjects were fertile and already had children, while the remaining men were under consultation for fertility issues.
“These are people who have been trying to get pregnant with their partner, and they’ve been unsuccessful,” Sriram Eleswarapu, MD, PhD, a urologist at UCLA and co-author of the study, told Scientific American. “This latter group’s semen samples had a lower sperm count or motility, both of which can contribute to infertility.”
“There is much more to explore regarding the microbiome and its connection to male infertility,” said Vadim Osadchiy, MD (above), a resident in the Department of Urology at UCLA and lead author of the study, in a UCLA news release. “However, these findings provide valuable insights that can lead us in the right direction for a deeper understanding of this correlation.” Might it also lead to new biomarkers for clinical laboratory testing for male infertility? (Photo copyright: UCLA.)
Genetic Sequencing Used to Identify Bacteria in Semen Microbiome
Most of the microbes present in the semen microbiome originate in the glands of the male upper reproductive tract, including the testes, seminal vesicles and prostate, and contribute various components to semen. “Drifter” bacteria that comes from urine and the urethra can also accumulate in the fluid during ejaculation. Microbes from an individual’s blood, or his partner’s, may also aggregate in semen. It is unknown how these bacteria might affect health.
“I would assume that there are bacteria that are net beneficial, that maybe secrete certain kinds of cytokines or chemicals that improve the fertility milieu for a person, and then there are likely many that have negative side effects,” Eleswarapu told Scientific American.
The scientists used genetic sequencing to identify different bacteria species present within the semen microbiome. They found five species that were common among all the study participants. But men with more of the microbe Lactobacillus iners (L. iners) were likelier to have impaired sperm motility and experience fertility issues.
This discovery was of special interest to the team because L. iners is commonly found in the vaginal microbiome. In females, high levels of L. iners are associated with bacterial vaginosis and have been linked to infertility in women. This is the first study that found a negative association between L. iners and male fertility.
The researchers plan to investigate specific molecules and proteins contained in the bacteria to find out whether they slow down sperm in a clinical laboratory situation.
“If we can identify how they exert that influence, then we have some drug targets,” Eleswarapu noted.
Targeting Bacteria That Cause Infertility
The team also discovered that three types of bacteria found in the Pseudomonas genus were present in patients who had both normal and abnormal sperm concentrations. Patients with abnormal sperm concentrations had more Pseudomonas fluorescens and Pseudomonas stutzeri and less Pseudomonas putida in their samples.
According to the federal National Institute of Child Health and Human Development (NICHD), “one-third of infertility cases are caused by male reproductive issues, one-third by female reproductive issues, and the remaining one-third by both male and female reproductive issues or unknown factors.” Thus, learning more about how the semen microbiome may be involved in infertility could aid in the development of drugs that target specific bacteria.
“Our research aligns with evidence from smaller studies and will pave the way for future, more comprehensive investigations to unravel the complex relationship between the semen microbiome and fertility,” said urologist Vadim Osadchiy, MD, a resident in the Department of Urology at UCLA and lead author of the study, in a UCLA news release.
More research is needed. For example, it’s unclear if there are any links between the health of semen microbiome and other microbiomes that exist in the body, such as the gut microbiome, that cause infertility. Nevertheless, this research could lead to new biomarkers for clinical laboratory testing to help couples who are experiencing fertility issues.
The UE study sheds light on the types of bacteria in
wastewater that goes down hospital pipes to sewage treatment plants. The study
also revealed that not all infectious agents are killed after passing through
waste treatment plants. Some bacteria with antimicrobial (or antibiotic)
resistance survive to enter local food sources.
The scientists concluded that the amount of AMR genes found
in hospital wastewater was linked to patients’ length-of-stays and consumption
of antimicrobial resistant bacteria while in the hospital.
In a paper the University of Edinburgh published on medRxiv, the researchers wrote: “There was a higher abundance of antimicrobial-resistance genes in the hospital wastewater samples when compared to Seafield community sewage works … Sewage treatment does not completely eradicate antimicrobial-resistance genes and thus antimicrobial-resistance genes can enter the food chain through water and the use of [processed] sewage sludge in agriculture. As hospital wastewater contains inpatient bodily waste, we hypothesized that it could be used as a representation of inpatient community carriage of antimicrobial resistance and as such may be a useful surveillance tool.”
Additionally, they wrote, “Using metagenomics to identify
the full range of AMR genes in hospital wastewater could represent a useful
surveillance tool to monitor hospital AMR gene outflow and guide environmental
policy on AMR.”
Antimicrobial stewardship programs are becoming increasingly critical to preventing the spread of AMR bacteria. “By having those programs, [there are] documented cases of decreased antibiotic resistance within organisms causing these infections,” Paul Fey, PhD, of the University of Nebraska Medical Center, told MedPage Today. “This is another indicator of how all hospitals need to implement stewardship programs to have a good handle on decreasing antibiotic use.” [Photo copyright: University of Nebraska.]
Don’t Waste the Wastewater
Antibiotic resistance occurs when bacteria change in response to medications to prevent and treat bacterial infections, according to a World Health Organization (WHO) fact sheet. The CDC estimates that more than 23,000 people die annually from two million antibiotic-resistance infections.
Wastewater, the UE scientists suggest, should not go to
waste. It could be leveraged to improve hospitals’ detection of patients with antimicrobial
resistance, as well as to boost environment antimicrobial-resistance polices.
They used metagenomics (the study of genetic material
relative to environmental samples) to compare the antimicrobial-resistance
genes in hospital wastewater against wastewater from community sewage
points.
The UE researchers:
First collected samples over a 24-hour period from various areas in a tertiary hospital;
They then obtained community sewage samples from various locations around Seafield, Scotland;
Antimicrobial-resistance genes increased with longer length of patient stays, which “likely reflects transmission amongst hospital inpatients,” researchers noted.
Fey suggests that further research into using sequencing
technology to monitor patients is warranted.
“I think that monitoring each patient and sequencing their
bowel flora is more likely where we’ll be able to see if there’s a significant
carriage of antibiotic-resistant organisms,” Fey told MedPage Today. “In
five years or so, sequencing could become so cheap that we could monitor every
patient like that.”
Fey was not involved in the University of Edinburgh
research.
Given the rate at which AMR bacteria spreads, finding antibiotic-resistance
genes in hospital wastewater may not be all that surprising. Still, the University
of Edinburgh study could lead to cost-effective ways to test the genes of
bacteria, which then could enable researchers to explore different sources of
infection and determine how bacteria move through the environment.
And, perhaps most important, the study suggests clinical
laboratories have many opportunities to help eliminate infections and slow
antibiotic resistance. Microbiologists can help move their organizations forward
too, along with infection control colleagues.
