Neisseria gonorrhoeae is responsible for about one-third to one-half of cases of acute pelvic inflammatory disease (PID), although there is considerable geographical variation. Chlamydia trachomatis is also an important aetiological agent, and is currently isolated 4 times more commonly from the cervix than the gonococcus. However, it is now clear that acute PID is polymicrobial in aetiology. Even when N. gonorrhoeae and/or C. trachomatis are isolated from the endocervix, anaerobes such as Bacteroides fragilis, Peptococcus and Peptostreptococcus and aerobes, especially the Enterobacteriaceae such as E. coli, are also frequently isolated.

Bacterial synergism, coinfection with the gonococcus and C. trachomatis and the involvement of multiple other micro-organisms including aerobes and anaerobes and antibiotic resistance make the selection of an optimal antibiotic regimen difficult. The Centers for Disease Control (CDC) recommendations first proposed in 1982 and revised in 1985 emphasise broad spectrum antimicrobial therapy including coverage of C. trachomaus. In September 1989, the CDC revised its recommendation for the treatment of acute PID. Current recommendations include the use of newer third generation cephalosporins such as ceftriaxone, ceftizoxime and cefotaxime which give excellent coverage of the gonococcus and the Enterobacteriaceae. It is still important to include doxycycline or a tetracycline to cover C. trachomatis. For patients with advanced disease or a tuboovarian abscess, clindamycin plus gentamicin has been the regimen of choice. Aztreonam, a new monobactam, has several advantages over gentamicin including less toxicity, more dependable blood levels and good coverage of N. gonorrhoeae and the Enterobacteriaceae.