Are seminal fluid microorganisms of significance or merely contaminants?

Objective: To determine the contribution of urethral and skin flora to seminal fluid cultures and the relation between bacteriospermia and seminal leukocytes. Design: Prospective study. Setting: IVF-ET unit at a university teaching hospital. Patient(s): Sixty men starting an IVF-ET program. Intervention(s): Culture of sequential first-catch urine, midstream urine, and semen samples with evaluation of seminal leukocytes. Main Outcome Measure(s): A comparison of microbes from first-catch urine, midstream urine, and semen samples and the correlations of seminal microbes, elevated leukocyte concentrations, and pregnancy. Result(s): Microoganisms were detected in 37% of first-catch urine samples, 27% of midstream urine samples, and 51% of semen samples. Most microorganisms were gram-positive microbes and were common to both urine and semen samples. Mean and median leukocyte concentrations were 0.98 x 10(6)/mL and 0.10 x 10(6)/mL, respectively. There was no correlation between seminal microbes and raised leukocytes or between leukocytospermia and/or bacteriospermia and pregnancy. Conclusion(s): Microoganisms are commonly found in insignificant quantities in the semen of asymptomatic men. The frequent isolation of gram-positive microbes common to both urine and semen and the absence of a correlation with raised leukocyte concentrations suggest that bacteriospermia most commonly represents contamination. (Fertil Steril(R) 2000;74:465-70. (C) 2000 by American Society for Reproductive Medicine.).