The Role of Microbial Factors in the Pathogenesis of Male Infertility: A Literature Review

The influence of infectious diseases on the development of infertility continues to be an area of active research. This review explores how the microbial environment within the male reproductive system may contribute to infertility. It examines how certain pathogenic characteristics of microorganisms can lead to reproductive issues when inflammation occurs in the male urogenital tract, focusing on how such infections impact sperm quality - such as reducing sperm count, impairing motility, altering morphology, and diminishing fertilization potential. Additionally, the review addresses how the body’s immune response and its resistance mechanisms may play a role in sustaining chronic inflammation in male reproductive organs. Purpose: To delineate how specific microbial communities and pathogen-linked virulence traits contribute to male infertility by disrupting spermatogenesis, sperm function and local immune homeostasis in the urogenital tract. Material and Methods: Narrative literature review based on a systematic search of microbiology, andrology and urology studies that compared semen microbiota, immune markers and clinical outcomes between proven-fertile and infertile men; key in-vitro and animal mechanistic papers were also appraised to integrate pathophysiological insights. Findings: Infertile semen shows a reproducible shift from protective Gram-positive Lactobacillus/Corynebacterium spp. to opportunistic Escherichia coli, Gardnerella, anaerobic Bacteroides and coagulase-negative staphylococci. Uropathogenic E. coli fimbriae, toxins and stress proteins, high anti-lysozyme staphylococci and Chlamydia/Ureaplasma lipopolysaccharides induce sperm agglutination, oxidative DNA damage and apoptosis. Declines in seminal lysozyme, lactoferrin and zinc - particularly in chronic prostatitis or hyper-viscous semen - halve bactericidal capacity, allowing chronic inflammation to persist.