Effects of common Gram-negative pathogens causing male genitourinary-tract infections on human sperm functions

Area of Science:

• Microbiology
• Reproductive Biology
• Urology

Background:

• Male genitourinary tract (MGT) bacterial infections contribute to 15% of male infertility cases.
• Mechanisms linking MGT infections to decreased semen quality remain poorly understood.

Purpose of the Study:

• To investigate the in vitro effects of common Gram-negative uropathogenic bacteria on human sperm parameters.
• To identify bacterial factors responsible for reduced sperm quality.

Main Methods:

• In vitro evaluation of human spermatozoa exposed to E. coli, K. pneumoniae, P. aeruginosa, and E. cloacae strains.
• Assessment of sperm motility, viability, mitochondrial oxidative status, DNA fragmentation, and caspase activity.
• Genetic analysis (RecX gene sequencing) to identify factors like Sperm Immobilizing Factor (SIF).

Main Results:

• Most tested Gram-negative bacteria, except P. aeruginosa, significantly reduced sperm motility.
• Sperm Immobilizing Factor (SIF), encoded by the recX gene in E. coli, was a key factor in motility reduction.
• Homologous sequences to E. coli's recX gene were found in K. pneumoniae and E. cloacae, suggesting a shared mechanism.
• One E. coli strain also induced sperm viability loss, caspase activity, oxidative stress, and DNA fragmentation.

Conclusions:

• Gram-negative uropathogenic bacteria, beyond E. coli, can impair sperm motility via RecX products.
• Interspecies variability exists in the production of spermatotoxic factors.
• Semen infection evaluation is crucial in diagnosing male infertility.