Letter to the Editor: Shewanella algae : An Emerging Pathogen Implicated in Acute Cholangitis

To the Editor:

S hewanella algae is a rare gram-negative facultative anaerobic motile bacillus found in tropical marine environments [1,2]. Shewanella algae are commonly associated with systemic sepsis, skin and soft tissue infections, and hepatobiliary sepsis. However, there are only two reports describing Shewenalla algae causing acute cholangitis [2,3]. We present here an elderly immunocompetent male patient with moderate acute cholangitis on a previously inserted internal biliary plastic stent background.

A 72-year-old male patient was admitted with a three-day history of upper abdominal pain radiating to the back. His past medical history included treatment for pyelonephritis and endoscopicbiliary stent placement for acute cholangitis. Abdominal examination was unremarkable and he was febrile. Serum biochemistry revealed elevated total white cell count, elevated bilirubin, normal renal function, and normal coagulation screen. A computed tomography scan of the abdomen and pelvis showed a distal common bile duct calculi with mild biliary tree dilatation. He was managed with empirical intravenous amoxicillin/clavulanic acid and gentamicin for established diagnosis of moderate acute cholangitis based on the Tokyo Guidelines 2018 (TG18) classification system [4]. Blood cultures revealed extended-spectrum β-lactamase (ESBL) producing and non-ESBL producing Escherichia coli as well as pan-sensitive Shewanella algae. The antibiotic regimen was revised to intravenous meropenem. For source control, urgent endoscopic biliary decompression was performed. At endoscopy, sphincterotomy was performed to facilitate extraction of biliary calculi, and the previous biliary stent was removed. Index admission laparoscopic cholecystectomy was performed, and the patient was discharged well with a two-week course of oral co-trimoxazole.

Shewanella algae infections are an uncommon cause of systemic sepsis. Hepatobiliary infections, including cholecystitis, cholangitis, and pyogenic liver abscess, are anecdotally reported to be caused by Shewanella algae. Shewanella algae bacteremia can run a fulminant course in patients with hepatobiliary diseases [2]. Our patient was moderate severity based on TG18 classification. Marine exposure or seafood consumption are reported as risk factors for Shewanella algae infections [1,2]. Our patient did not have these risk factors but did have a history of an endoscopic biliary stent. A foreign body along with obstructed biliary system would have facilitated Shewanella algae bacteremia caused by cholangio-venous reflux [1]. For optimal clinical outcomes in acute cholangitis, culture-directed antibiotic agnets along with prompt biliary decompression are essential [4]. Urgent biliary decompression and source control was achieved in our patient by endoscopic retrograde cholangiography.

Shewanella algae infections are polymicrobial in up to 50% of cases, as in our patient [1]. A plastic biliary stent should not be left in situ for prolonged periods or it forms a nidus for encrustation and stone formation, including a reservoir of pathogens, including Shewanella algae. Long-term stent placement or percutaneous transhepatic biliary drainage catheters are not only associated with risks of sepsis, but stent migration or catheter fracture are also reported [5]. Because of the rarity and paucity of Shewanella algae, we are reporting here to raise awareness of this emerging pathogen that is increasingly implicated in hepatobiliary sepsis.