Recovery of microorganisms in semen and relationship to semen evaluation

Semen samples from 120 consecutive unselected men attending our fertility clinic were studied to determine the bacterial isolation rate of semen and its influence on semen quality. Each sample was cultured aerobically, anaerobically, and for Ureaplasma urealyticum and Mycoplasma hominis. The following were analyzed for each semen specimen: motility, morphologic features, and number of sperm cells and viscosity of the ejaculate. Four of the 120 samples had negative results; 101 cultures yielded one or more aerobic organisms (the majority with less than 20,000 microorganisms/ml); 26 yielded anaerobic organisms; and 40 yielded U. urealyticum. No single aerobic or anaerobic organism could be related to abnormal semen samples. Only the presence of U. urealyticum correlated significantly with abnormal semen samples (P less than 0.005). The most affected parameters were the number of spermatozoa (P less than 0.005) and motility (P less than 0.05). We conclude that routine aerobic and anaerobic bacterial cultures of semen are not useful in the clinical evaluation of male infertility. The usefulness of routine screenings for U. urealyticum must be investigated further.