EFFECTS OF PROPHYLACTIC ANTIBIOTICS ON ENDOMETRIAL FLORA IN WOMEN WITH POSTCESAREAN ENDOMETRITIS

Objective: To determine the effect of prophylactic antibiotics on endo metrial and endocervical microflora upon diagnosis of postcesarean end ometritis. Methods: The medical records of patients enrolled in open-l abel comparative trials of therapeutic antibiotics for postpartum endo metritis between 1989 and 1994 were reviewed (n = 682). Endometritis w as diagnosed by a standard definition that included fever and localizi ng signs. Endometrial cultures were obtained by a sheathed injection/a spiration technique. Aerobes and anaerobes were isolated by standard m icrobiologic techniques. The primary outcome, endometrial and endocerv ical microflora, was compared in women who received intravenous ampici llin (2 g every 6 hours for 1-3 doses), cephalosporin (2 g every 6 hou rs for 1-3 doses), or no prophylaxis. Secondary outcomes included the cure of endometritis and the prevalence of wound infection in the thre e groups. Results: Four hundred sixty-five of 682 patients (67%) had a cesarean delivery. One hundred fifty-one patients received ampicillin prophylaxis, 100 patients received cefazolin prophylaxis, 18 patients received extended-spectrum antibiotics, and 196 patients received no prophylaxis. Patients who received cefazolin prophylaxis had a signifi cant increase in enterococcus (P < .05) and a significant decrease in Proteus species (P < .05) from endometrial samples. Patients who recei ved ampicillin prophylaxis had a significant increase of Mycoplasma sp ecies (P < .05), Klebsiella pneumoniae (P < .0001), Escherichia coli ( P = .04), and any aerobic gramnegative rod (P = .003) from endometrial samples. Ampicillin prophylaxis was associated with a decrease in Pre votella bivia (P < .05) and any anaerobe (P < .01). Endometritis cure rates were similar between prophylaxis groups and between prophylaxis and treatment groups. However, the cefazolin prophylaxis followed by c ephalosporin treatment was associated with more wound infections (19%) than other prophylaxis and treatment groups, (6%, P < .01). Conclusio n: Ampicillin and cefazolin prophylaxis alters endometrial and endocer vical microflora of women who develop endometritis. Whereas these chan ges had no effect on endometritis cure rate (power > 80%), the associa tion between cefazolin prophylaxis followed by an extended-spectrum ce phalosporin and wound infection may warrant caution against the use of the combination. (Obstet Gynecol 1998;92:262-8. (C) 1998 by The Ameri can College of Obstetricians and Gynecologists.).