E. tarda is a Gram-negative facultative anaerobe belonging to Enterobacteriales and is isolated from turtles, fish, snakes, and lizards associated with fresh and saltwater [5,6,7]. E. tarda is a known pathogen of fish and reptiles and is uncommonly reported in humans. However, E. tarda can be transmitted to humans through contact with reptiles, amphibians, and other carriers of the disease as well as through ingestion of raw fish [8]. E. tarda infection in humans is rare, with a human retention rate of 0.001% [1]. A search of PubMed using “Edwardsiella tarda” and “acute cholecystitis” as search terms yielded several cases. Among them, only 12 cases of acute cholecystitis and Edwardsiella tarda-induced bacteremia have been reported [9,10,11,12]. Our case and its 12 cases are summarized in Table 3. The study population was relatively older, with a mean age of 74.6 years, and comprised 7 males and 6 females. In addition to antimicrobial therapy, we performed invasive gallbladder procedures such as PTGBD in 3 patients and surgery in 5 patients. Furthermore, there are no reports of E. tarda being detected in both blood and bile cultures in cases of acute cholecystitis, similar to the present case.

Intestinal infections account for approximately 80% of all E. tarda infections [13]. E. tarda is biochemically similar to Salmonella; it causes low-grade fever and intermittent watery diarrhea, similar to Salmonella enteritis [8, 9]. Generally, enteritis caused by E. tarda often resolves spontaneously with symptomatic treatment and is rarely clinically severe. However, intra-abdominal abscess, cholecystitis, cholangitis, cellulitis, necrotizing fasciitis, meningitis, and osteomyelitis have been reported as extraintestinal infections, although the number of reports is small [9,10,11, 14,15,16,17,18]. Meanwhile, bacteremia is rare, occurring in less than 5% of all cases of E. tarda infections [8]. However, the mortality from bacteremia caused by E. tarda is 44.6% [3]. Risk factors for severe E. tarda infection include age (≥ 65 years) and a history of underlying diseases such as malignancy, autoimmune disease, liver disease, and diabetes mellitus [3, 9, 11]. In these patients, mortality rates were reportedly more than four times higher especially in patients with cirrhosis [3, 19]. Additionally, deaths have been reported in cases of sepsis associated with soft tissue infections such as necrotizing fasciitis, which may be due to the difficulty in completely removing the infected lesion [3].

Regarding treatment, extraintestinal infections generally require antibiotic therapy. E. tarda is sensitive to several antibiotic agents, including β-lactams, aminoglycosides, quinolones, and tetracyclines [20]. However, in cases of bacteremia, which can be severe, it is necessary to continue antibiotic therapy even after symptoms improve. Therefore, it is important to administer antibiotics after culture testing to determine the appropriate antibiotic therapy. In our case, blood cultures were obtained before antibiotics were administered, and intraoperative bile cultures were also obtained. Results confirmed E. tarda infection, allowing treatment with the appropriate antibiotic agents. Additionally, due to the importance of complete removal of the infected lesion, surgical intervention would be appropriate.

Regarding the route of infection in this case, the patient had no history of keeping fish or reptiles as pets, and the possibility of contact infection was considered low. However, because of her habit of eating raw seafood on a daily basis, the possibility of infection by oral ingestion was considered possible. After the diagnosis of E. tarda infection, fecal culture was performed to reveal intestinal commensal bacterial; however, E. tarda was not detected because culture was performed after antibiotic therapy was started. Although the reported human retention rate is 0.001% [1], the possible presence of E. tarda cannot be ruled out due to the patient’s history of recurrent diarrhea, which was caused by irritable bowel syndrome. In our case, there were no gallbladder stones that could have caused cholecystitis. Gallbladder stones are the most common cause of acute cholecystitis development. Cholecystitis develops due to gallbladder duct obstruction and bile congestion caused by the fitting of a stone, which damages the mucosa of the gallbladder. Conversely, acute acalculous cholecystitis can occur in 3.7–14% patients with acute cholecystitis [21, 22]. Risk factors of cholecystitis include surgery, trauma, infection, burns, and transvenous nutrition [23, 24]. However, these risk factors were not relevant in our case. As diarrhea was previously observed in this case, the patient developed a retrograde biliary infection due to enteritis-induced increased intestinal pressure, which occurred due to irritable bowel syndrome; this could have further led to cholecystitis and then to bacteremia. There have been many reports of patients with a poor prognosis caused by E. tarda sepsis; however, in our case, she had a favorable prognosis. This may be attributed to the patient’s age, early and appropriate surgical intervention to completely remove the infected lesion, and continued systematic administration of antimicrobials based on the culture results, all of which prevented recurrence.