The agents most often implicated in acute PID—infection that ascends from the cervix or vagina to the endometrium and/or fallopian tubes—include the primary causes of endocervicitis (e.g., N. gonorrhoeae and C. trachomatis); other organisms (e.g., M. genitalium, Prevotella spp., peptostreptococci, E. coli, Haemophilus influenzae, and group B streptococci) account for 25-33% of cases.