Susceptibility of endometrial isolates recovered from women with clinical pelvic inflammatory disease or histological endometritis to antimicrobial agents.

The CDC recommended outpatient treatment of pelvic inflammatory disease (PID) is an intramuscular dose of ceftriaxone plus 14 days of doxycycline, with or without metronidazole. European guidelines (2017) include moxifloxacin plus ceftriaxone as a first line regimen, particularly for women with Mycoplasma genitalium-associated PID. However, the susceptibility of bacteria recovered from the endometrium of women with PID to moxifloxacin is unknown. The in vitro antibiotic susceptibility of facultative and anaerobic bacteria recovered from endometrial biopsy samples were evaluated from 105 women having symptomatic PID and/or histologically confirmed endometritis. A total of 342 endometrial isolates from enrollment visits were identified using a combination of biochemical tests and sequencing. Isolates were tested for antimicrobial susceptibility using agar dilution against ceftriaxone, clindamycin, doxycycline, metronidazole and moxifloxacin according to the Clinical and Laboratory Standards Institute (CLSI) guidelines. Neisseria gonorrhoeae was susceptible to ceftriaxone with all isolates having an MIC of 0.03 μg/mL. All the other endometrial isolates were susceptible to ceftriaxone, except for Prevotella species, only half of which were susceptible. The in vitro susceptibility profile for BV-associated bacteria (Gardnerella vaginalis, Atopobium vaginae, Prevotella species, Porphyromonas species and anaerobic gram-positive cocci) revealed greater susceptibility to moxifloxacin compared to doxycycline. Moxifloxacin was superior to metronidazole for G. vaginalis and A. vaginae, and either metronidazole or moxifloxacin was needed to cover Prevotella species. Based on in vitro susceptibility testing, the combination of ceftriaxone plus moxifloxacin provides similar coverage of facultative and anaerobic pathogens compared to the combination of ceftriaxone, metronidazole and doxycycline. Head to head clinical studies of these treatment regimens are needed to evaluate clinical efficacy and eradication of endometrial pathogens following treatment.