Abstract
Male genitourinary tract (MGT) bacterial infections are considered responsible for 15% of male infertility, but the mechanisms underlying decreased semen quality are poorly known. We evaluated in vitro the effect of strains of Gram-negative uropathogenic species (two E.coli strains, three K. pneumoniae strains, P. aeruginosa and E. cloacae) on motility, viability, mitochondrial oxidative status, DNA fragmentation and caspase activity of human spermatozoa. All strains, except P. aeruginosa, reduced significantly sperm motility, with variable effects. Sperm Immobilizing Factor (SIF) was largely responsible for deteriorating effects on sperm motility of E. coli strains since they were completely reverted by knockout of SIF coding recX gene. Sequence alignment for RecX showed the presence of high homologous sequences in K. pneumoniae and E. cloacae but not in P. aeruginosa. These results suggest that, in addition to E.coli, other common uropathogenic Gram-negative bacteria affect sperm motility through RecX products. In addition to sperm motility, the E. coli strain ATCC 35218 also affected sperm viability, and induced caspase activity, oxidative stress and DNA fragmentation suggesting an interspecies variability in the amount and/or type of the produced spermatotoxic factors. In general, our results highlight the need for a careful evaluation of semen infections in the diagnostic process of the infertile man.
Highlights
Male genitourinary tract (MGT) bacterial infections are considered responsible for 15% of male infertility, but the mechanisms underlying decreased semen quality are poorly known
Whole semen samples were incubated with live bacterial cells from E. coli (ATCC 29522 and ATCC 35218), K. pneumoniae, P. aeruginosa, E. cloacae and K. aerogenes strains at sperm/bacteria ratio of 1:1023 and progressive and total motility was recorded after 1 (n = 13) and 3 h (n = 16)
A direct adhesion of bacterial cells to the sperm tails as well as sperm agglutination was observed in cultures with E. cloacae ATCC 13047 (Supplemental Figure S1 and video S1), whereas such effects were not observed with the other bacterial strains
Summary
Male genitourinary tract (MGT) bacterial infections are considered responsible for 15% of male infertility, but the mechanisms underlying decreased semen quality are poorly known. We evaluated in vitro the effect of strains of Gram-negative uropathogenic species (two E.coli strains, three K. pneumoniae strains, P. aeruginosa and E. cloacae) on motility, viability, mitochondrial oxidative status, DNA fragmentation and caspase activity of human spermatozoa. Sequence alignment for RecX showed the presence of high homologous sequences in K. pneumoniae and E. cloacae but not in P. aeruginosa These results suggest that, in addition to E.coli, other common uropathogenic Gram-negative bacteria affect sperm motility through RecX products. Whether other bacterial species as K. pneumoniae, K. aerogenes, Enterobacter cloacae, P. aeruginosa, commonly causing genitourinary tract infections (GUTI), affect human sperm motility or other sperm functions is not yet known. Inhibitory effect of E. coli on sperm motility have been attributed to release of SIF2,8, whether SIF is involved in the inhibitory effect of other bacterial species is presently less clear, nor it is known the role of this factor in other sperm alterations due to bacterial infections
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