Bacteriology The surface of the perineum is covered with normal flora, predominantly Staphylococcus epidermidis, followed by its more virulent cousin, Staphylococcus aureus, and bacteria found in deeper structures, including Propionibacterium and Peptococcus species. Normally, urine remains sterile while in the bladder and throughout the majority of the urinary tract. Once urine passes through the urethra, it picks up organisms, including S epidermidis, nonhemolytic Streptococcus and Staphylococcus saprophyticus (found around genitourinary tract skin), among others. Escherichia coli, coliforms (E coli, Klebsiella, Enterobacter, Citrobacter, Serratia) and Enterococcus species are among the most common UTI-causing organisms and are found in high numbers on and around the perineum.2
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