Uncommon Bacteremia: Enterococcus Avium Bloodstream Infection in the Setting of Cholecystitis: A Case Report

Abstract Enterococcus avium , a rare Gram-positive pathogen typically found in birds, is an uncommon cause of human infections compared with E. faecalis and E. faecium . It has been implicated in bacteremia, brain abscesses, urinary tract infections, osteomyelitis, endocarditis, and splenic abscesses, often as part of polymicrobial infections. Due to its rarity, its clinical features and antibiotic susceptibility patterns remain poorly characterized. A 70-year-old man with type 2 diabetes mellitus, hypertension, and dyslipidemia presented with right upper quadrant pain, nausea, and chills lasting one day. Ultrasonography confirmed acute calculous cholecystitis, prompting laparoscopic cholecystectomy and empirical piperacillin/tazobactam therapy. Blood cultures revealed polymicrobial growth: Escherichia coli (Gram-negative bacilli) and Enterococcus avium (Gram-positive cocci), identified via Vitek2. The E. avium isolate was susceptible to vancomycin, linezolid, and high-level gentamicin, but resistant to penicillin and ampicillin, whereas E. coli was sensitive to fluoroquinolones, cephalosporins, and carbapenems. The patient improved clinically and was discharged on oral linezolid (600 mg twice daily) and ciprofloxacin (500 mg twice daily) for 10 days, achieving full recovery at two-week follow-up. This case underscores the rarity of E. avium bacteremia and its association with cholecystitis in a polymicrobial context. Awareness of this pathogen and its susceptibility profile is essential for effective management. Further research is needed to define its role in polymicrobial infections and to optimize treatment strategies.