Diagnosis of pelvic actinomycosis by 16S ribosomal RNA gene sequencing and its clinical significance.

Traditional ways of identification of anaerobic Gram-positive non-sporulating bacilli by isolation of the organism and studying it phenotypically by elucidation of its morphologic and biochemical characteristics and metabolic end products are associated with a need for special equipment and expertise, and strains that are "unidentified" because of ambiguous biochemical profiles. In this study, an anaerobic Gram-positive non-sporulating bacterium was isolated from the intrauterine contraceptive device of a 36-year old woman with pyosalpinx. The Vitek system (ANI) showed that it was 99% Propionibacterium granulosum; whereas the API system (20A) showed that it was 78% Actinomyces meyeri/odontolyticus. The 16S ribosomal RNA gene of the strain was amplified and sequenced. There was 0 base difference between the isolate and A. odontolyticus (GenBank Accession no. AJ234047), indicating the isolate most closely resembled a strain of A. odontolyticus. Identification of the organism in this study was important because the duration of antibiotic therapy would be entirely different. In the present case, identification of the bacterium as A. odontolyticus inferred that the patient suffered from an intermediate form of pelvic actinomycosis. A prolonged course of antibiotics would be more desirable, as the relapse rate of actinomycosis after a short course of antibiotics is high.