A case of Actinomyces hongkongensis pelvic actinomycosis in an adult woman is described. Conventional phenotypic tests failed to identify the Gram-positive bacillus isolated from a fluid aspirate of a pelvic abscess. The bacterium was identified by 16S rRNA gene sequencing and analysis using the SmartGene Integrated Database Network System software.A 47-year-old, gravida 2, para 2, immunocompetent woman presented to the hospital with pelvic pain and fever 13 days after a total abdominal hysterectomy and salpingectomy for menorrhagia and hydrosalpinx. Her medical profile included smoking, perforated gastric ulcer, appendectomy, tubal ligation reversal, and two diagnostic laparoscopies. She had no history of intrauterine contraceptive device (IUCD) use. One gram of intravenous (i.v.) prophylactic cefazolin had been administered before the procedure. The surgery had proceeded without complication (200-ml estimated blood loss), and the patient was discharged on postoperative day 3. On presentation, the patient's white blood cell count was 21.7 ϫ 10 9 cells/liter (18.6 ϫ 10 9 neutrophils/liter), the hemoglobin level was 117 g/liter, and the platelet count was 570 ϫ 10 9 platelets/liter. Electrolyte and creatinine levels were normal. A mass was palpated at the vaginal apex, and computed tomography (CT) showed a bilocular abscess immediately above the vaginal vault (the larger lobule measuring 8.8 by 5.8 cm), with regional inflammation (Fig. 1). The patient received empirical cefazolin and metronidazole, followed by clindamycin and gentamicin. She was then taken to the operating room for incision and drainage via a vaginal approach, but the mass was no longer palpable, and the procedure was aborted. Her antibiotic regimen was changed to ampicillin, gentamicin, and metronidazole, and fluid was drained from the residual mass under CT guidance the following day. Final CT imaging demonstrated a marked decrease in the size of the abscess. The patient improved clinically and was discharged home after 4 days in the hospital. As she had been afebrile for 2 days, no oral antibiotics were prescribed upon discharge. The patient remains free of symptoms 6 years after discharge from the hospital. The conjoint ethics board at the University of Calgary approved this study.The fluid aspirate was subcultured on Columbia sheep blood agar (BA), chocolate agar (CHOC), MacConkey agar, and Brucella blood agar (BBA) (PML Microbiologicals, Wilsonville, OR) plates and incubated anaerobically at 35°C for 48 h before examination using an Anoxomat Mark II system (Mark Microbiology, Drachten, Netherlands). Growth occurred on BBA plates as nonhemolytic, pinpoint colonies. Gram staining showed the isolate to be a straight Gram-positive bacillus. Biochemical analysis using the Vitek 2 ANC card (bioMérieux, Laval, Quebec, Canada) provided a low-discrimination organism split between Actinomyces meyeri and Propionibacterium acnes. The isolate was biochemically inert, except for positive arginine dihydrolase, alkaline phosphatase, tyrosine arylamidase, l...

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