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We aimed to study the correlation between leukocyte counts in semen and bacterial pathogens in seminal samples of infertile men, and to establish the minimum leukocyte count associated with significant bacteriospermia. A total of 116 patients who underwent evaluation of fertility were investigated using routine semen analysis according to the guidelines of the WHO and bacterial pathogens analysis by culture and in-house PCR assay. The overall prevalence of bacteriospermia in semen samples was 56.9% independent of the presence of leukocytes. The most common bacterial species detected were Chlamydia trachomatis (41.4%), Ureaplasma urealyticum (15.5%) and Mycoplasma hominis (10.3%). The receiver operating characteristic curve analysis demonstrated that the sensitivity/specificity for detecting bacteria at a cut off level of >or=1 x 10(6) leukocytes per ml (which is the WHO defined level for leukocytospermia) was 20.3%/81.5%. The highest sensitivity/specificity ratio was found in semen samples with a cut-off level of >or=0.275 x 10(6) leukocytes per ml, which is best shown with the odds ratio of 2.47. A significant correlation was found between bacteriospermia and leukocytospermia at the cut-off level of >or=0.275 x 10(6) leukocytes per ml of semen samples (P = 0.032). We proposed that this is a possible new cut-off level to predict the presence of bacteria in semen of infertile men.

Many studies have examined the impact of genital tract infections on male fertility; however, the effect of bacteriospermia on sperm quality is still controversial. Bacterial infections are more frequently found in semen samples from asymptomatic infertile patients than in those from fertile men. Bacteriospermia is also a common problem of male partners from couples undergoing IVF. Therefore, the effects of microorganisms on human sperm acrosome reaction of oocytes have been studied in vitro and in vivo. Incubation of spermatozoa with Escherichia coli or Mycoplasma hominis in vitro resulted in reduced sperm motility and inducibility of acrosome reaction (delta AR) after exposure to calcium ionophore A23187. To show possible effects of E. coli and mycoplasma species on sperm functions in vivo, data from 488 patients were evaluated, in whose ejaculates microbiological examinations and determinations of acrosome reaction after exposure to low temperature had been performed. U. urealyticum and E. coli were found in semen samples from 52 and 31 men, respectively. M. hominis was only present in a minor number of samples and was not included in this study. Semen concentrations of E. coli and U. urealyticum ranged between 500-100,000 cfu x ml-1 and 100-80,000 cfu x ml-1. No correlation was found between delta AR and concentration of bacteria (Spearman rank correlation coefficient, E. coli: r-0.081, P = 0.6644; U. urealyticum: r = -0.081, P = 0.5698). In 69% of cases with U. urealyticum infection and reduced inducibility of acrosome reaction, this sperm function was normal after antibiotic therapy. However, improvement of acrosomal function may only be due to intra-individual variations of acrosome reaction. While E. coli and mycoplasma species affect sperm functions in vitro, the present data and a review of the literature fail to demonstrate similar effects in vivo.