Treatment of Actinomyces europaeus and Clostridium innocuum necrotizing fasciitis: Case report and literature review.

PURPOSE: Actinomyces europaeus and Clostridium innocuum are rare causes of necrotizing fasciitis. For both organisms, it is necessary to know the specific species because variations in antibiotic sensitivity exist, making treatment challenging.

SUMMARY: An 86-year-old white female presented to the emergency department with severe pain in her right thigh. A computed tomography scan showed pockets of gas and edema in the subcutaneous tissue extending from the right lateral hemipelvis to the right inguinal area and proximal thigh. Her LRINEC (Laboratory Risk Indicator for Necrotizing Fasciitis) score was 7. The patient was started on intravenous vancomycin, piperacillin/tazobactam, and clindamycin and brought to the operating room for debridement. Anaerobic cultures grew Bacteroides fragilis, Bacteroides uniformis, and C. innocuum. Aerobic cultures were positive for Actinomyces. The laboratory was called to determine the species of Actinomyces and reported A. europaeus. The patient's antibiotics were tailored to meropenem 2 g intravenously every 8 hours and linezolid 600 mg intravenously every 12 hours. The organisms were sent to a reference laboratory for sensitivity testing. Interpretation of sensitivity data and treatment recommendations including duration of therapy are discussed.

CONCLUSION

It is important to rapidly identify the species for both Actinomyces and Clostridium infections and obtain sensitivity values to help ensure proper therapy is given. Interpretation of minimum inhibitory concentrations is difficult without established breakpoints. Piperacillin/tazobactam resistance has been reported for A. europaeus, while vancomycin resistance has been reported for C. innocuum. For Actinomyces infections, duration of therapy should be individualized and can range from 14 days to 1 year based on patient response and the species.