BERNALILLO, N.M. – It’s necessary to use metronidazole in addition to doxycycline and a cephalosporin to cover all the bacteria species associated with pelvic inflammatory disease, according to an analysis of 198 endometrial biopsy isolates from 170 women with the condition.
"The coadministration of a cephalosporin with doxycycline for women with PID provides coverage for all anaerobic pathogens except Prevotella species. The addition of metronidazole is necessary to provide coverage for these anaerobic gram-negative rods," investigators from the University of Pittsburgh concluded.
Twelve percent of the women had Prevotella species in their endometrium that were resistant to both ceftriaxone and doxycycline, but not metronidazole.
Dr. Sharon Hillier
The Centers for Disease Control and Prevention currently recommends an injectable cephalosporin and oral doxycycline for outpatient PID, but lets clinicians decide whether to include metronidazole.
"If you are going to cover the spectrum of organisms that are there, you really have to add the metronidazole," said senior investigator Sharon L. Hillier, Ph.D., professor of obstetrics, gynecology, and reproductive sciences in the division of infectious diseases at the university.
But "there’s reticence to prescribe it in addition to doxycycline because of the GI upset and lack of tolerance. The concern is that people might not finish their antimicrobials and get worse. It’s truly a conundrum; we don’t have a good alternative to metronidazole," Dr. Hillier said at the annual meeting of the Infectious Diseases Society of Obstetrics and Gynecology.
Also, "there aren’t longitudinal data yet that show that women with untreated Prevotella have worse outcomes. There haven’t been data suggesting that failure to cover those has long-term infertility sequelae. My own view is that we probably should use metronidazole. The bottom line is that no two antibiotics cover everything," she said.
Biopsies from 65 women – all outpatients 15-40 years old with clinical PID diagnoses – grew out one or more organisms. In all, 17 types or species of bacteria were isolated.
Gardnerella vaginalis, Atopobium vaginae, and Prevotella and Lactobacillus species made up 81% of the isolates.
Ceftriaxone was effective for all of them except the Prevotella, while metronidazole was effective against only the Prevotella. Doxycycline susceptibilities ranged from 47% for A. vaginae to 82% for G. vaginalis.
With the exception of Prevotella, ceftriaxone and doxycycline "are effective against many of the anaerobic and facultative bacteria associated with" PID, the researchers concluded.