“My pap test diagnosis reads ‘bacteria consistent with Actinomyces species’ — what should I do?”

At PathAdvantage, we are often asked the above question; we receive swabs for cultures of the vagina or an IUD (with request to identify Actinomyces), or a request for sensitive, amplified molecular testing for this organism. In all cases, we are unfortunately obligated to deny such tests, saying that they are either unavailable, not recommended or simply not possible.

Actinomyces are fastidious, obligate anaerobic, gram-positive, slow-growing bacilli. These features make Actinomyces difficult to identify using routine specimen handling and culture techniques. If these organisms are to be cultured, an anaerobic swab is required as exposure to oxygen, even briefly, is often enough to kill anaerobic organisms. (For example; an IUD received in a sterile container is surrounded by oxygen, and consequently anaerobic culture cannot be performed.) Additionally, even if an appropriately anaerobic specimen (such as a blue top anaerobic gel swab) is used in attempt to culture Actinomyces vaginally, the other resident anaerobic flora will compete with the slow-growing Actinomyces, which therefore will not be detected.

Actinomyces are present as commensal organisms in healthy humans and are best thought of as opportunistic pathogens. Therefore, the mere presence of Actinomyces is not diagnostic of disease. (This is also why no molecular test exists for Actinomyces.)  

Actinomyces may colonize the female genital tract and be present in polymicrobial pelvic abscesses—and while IUD-associated actinomycosis has been reported, case reporting is poor and therefore there are no clear statistics regarding the total number of cases. It is therefore impossible to give an accurate risk of occurrence; however, these abscesses are generally regarded as exceedingly rare.

Actinomyces-like organisms are seen on an average of 7% of Pap tests, which is clearly far greater than the prevalence of these (rare) abscesses. Therefore, the Pap test has a high false-positive rate and an extremely low positive predictive value for Actinomyces related disease. Sensitivity of the Pap test for Actinomyces is also poor; even among women with actinomycotic abscesses, only half of these had a Pap test that was positive for Actinomyces. 

In conclusion, according to ACOG committee opinion, in the absence of symptoms, women with Actinomyces-like organisms on a Pap test do not need antimicrobial treatment or IUD removal. If PID is suspected or the clinician believes antibiotic therapy is necessary, the patient can initially be treated without IUD removal. The antibiotic of choice is penicillin VK 500mg orally 4 times daily for 1 month. One month after completion of treatment, the Pap test should be repeated. If Actinomyces is still present or recurs or the woman shows signs and symptoms of PID, the IUD may need to be removed.