Scrotal Abscess in a Japanese Patient Caused by Prevotella bivia and Streptococcus agalactiae, Successfully Treated with Cefazolin and Amoxicillin: A Case Report

BACKGROUND: Infections caused by Prevotella bivia, a gram-negative anaerobic bacillus, are rare, with no reported cases in Japan. We present a novel case of scrotal abscess in a Japanese patient co-infected with Prevotella bivia and Streptococcus agalactiae. CASE PRESENTATION: A 41-year-old uncontrolled diabetic man complained of swelling and pain in the scrotum. On examination, computed tomography revealed an abscess of 5-cm diameter in the scrotum. Then, the abscess was incised and drained. He was treated with cefazolin empirically. Prevotella bivia and Streptococcus agalactiae were identified in the pus cultures obtained from the abscess. However, the susceptibility tests for Prevotella bivia could not be submitted. Seven days following admission, the pain reduced, and the drainage slowed. The patient was discharged on day 14 when cefazolin was discontinued and oral amoxicillin (750 mg/day) was started. Amoxicillin was continued until day 42; improvement was confirmed. CONCLUSION: To the best of our knowledge, this case is the first report of Prevotella bivia in Japan. We suggest that cephem antibiotics such as cefazolin may be effective against Prevotella bivia in Japan.