Microbiologic aerobic studies on normal male urethra

To carefully collect samples from the external urethral orifice, navicular fossa, and penile urethra and perform a semiquantitative evaluation and identification of gram-positive and gram-negative bacteria present in the normal male urethra.

Thirty uncircumcised male patients 18 to 40 years old without any inflammatory and/or infectious urethral processes were enrolled in this study. Samples were collected from the external urethral orifice, navicular fossa, and penile urethra with sterile alginate swabs that were immediately transferred to tubes containing buffered phosphate solution. Inoculation was done by spreading 0.01 mL of the buffered solutions on sheep blood agar plates and MacConkey agar plates; the plates were then incubated at 36.5 degrees C for 24 hours. After this period, the quantification and identification of each type of colony was performed.

Among the 30 patients studied, 12 (40%) had bacteria isolated from the three segments, 10 (33.3%) had bacterial colonization in two segments, and 8 (26.7%) had colonization in only one segment (external urethral orifice). Staphylococcus coagulase-negative species, group viridans alpha-hemolytic streptococci, Corynebacterium species, and Enterococcus species were the bacteria more frequently isolated from these three segments.

From the findings in this study, it was clear that the bacterial urethral flora was abundant, not evenly distributed, concentrated in the external urethral orifice and navicular fossa, and basically consisted of gram-positive aerobic bacteria.