Single-dose prophylaxis best way to prevent postop infection, expert says. (Ensure Normal Vaginal Microflora).

ST. LOUIS -- Stick to a single dose of antibiotic for prophylaxis against postoperative infection, Dr. Sebastian Faro urged at the 12th Pelvic Reconstructive and Vaginal Surgery Conference.

"Please don't go to 2- and 3-day dosing. You're weakening the effectiveness of that drug and encouraging resistance in your setting," explained Dr. Faro, professor of ob.gyn. at the University of Texas, Houston.

The single dose is to be given within an hour of the start of the procedure. If the operation lasts at least 3 hours, however, or there is at least 1,500 mL of blood loss, give a second dose to keep serum antibiotic concentrations sufficiently high to kill or suppress significant numbers of pathogenic bacteria, he said.

The drugs that American gynecologic surgeons most commonly turn to for prophylaxis are cefazolin, cefotetan, and cefoxitin. All adequately address the pathogens commonly found in the vaginal microflora. Levofloxacin is a good choice for patients who are allergic to cephalosporins; it has a very long half-life and good activity against a broad spectrum of gram-positive and gram-negative organisms, said Dr. Faro, an infectious disease subspecialist.

But he added that the real key to preventing postoperative infections isn't the choice of antibiotic for prophylaxis, it's making sure a normal vaginal microflora is present at surgery.

An altered vaginal microflora as indicated by a vaginal fluid pH greater than 4.5 encourages dominance by gram-negative and other virulent bacteria. It also promotes increased bacterial concentrations. Instead of the [10.sup.3] organisms/mL or fewer that prevail in a normal vaginal microflora, the bacterial concentration burgeons to 106 or more.