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 Table of Contents  
Year : 2022  |  Volume : 24  |  Issue : 2  |  Page : 84-86

Aeromonas veronii biovar sobria causing infected walled-off pancreatic necrosis: A rare infectious complication of chronic pancreatitis

1 Department of Clinical Microbiology and Infection Control, Gleneagles Global Hospitals, Hyderabad, Telangana, India
2 Department of Surgical Gastroenterology, Gleneagles Global Hospitals, Hyderabad, Telangana, India
3 Department of Radiology, Gleneagles Global Hospitals, Hyderabad, Telangana, India

Date of Submission02-Sep-2022
Date of Acceptance10-Oct-2022
Date of Web Publication13-Dec-2022

Correspondence Address:
Rekha Rao Jangam
Department of Clinical Microbiology and Infection Control, Gleneagles Global Hospitals, 6-1-1070/1 to 4, Lakdikapul, Hyderabad - 500 004, Telangana
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/jacm.jacm_13_22

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We report a rare case of infected walled-off pancreatic necrosis in a diabetic patient with chronic pancreatitis caused by Aeromonas veronii biovar sobria. Aeromonads are ubiquitous organisms found mainly in aquatic environments. Infection may occur after the ingestion of contaminated seafood/water, massive aquatic exposure during near-drowning events or by exposure of an abraded wound to the bacteria. The clinical manifestations of Aeromonas infections are mostly gastrointestinal infections, bacteraemia and skin and soft-tissue infections. Intraabdominal infections due to Aeromonas are uncommon with pancreatic infections being even rare.

Keywords: Aeromonads, Aeromonas veronii biovar sobria, pancreatic necrosis

How to cite this article:
Iyer RN, Jangam RR, Nara BK, Karri U. Aeromonas veronii biovar sobria causing infected walled-off pancreatic necrosis: A rare infectious complication of chronic pancreatitis. J Acad Clin Microbiol 2022;24:84-6

How to cite this URL:
Iyer RN, Jangam RR, Nara BK, Karri U. Aeromonas veronii biovar sobria causing infected walled-off pancreatic necrosis: A rare infectious complication of chronic pancreatitis. J Acad Clin Microbiol [serial online] 2022 [cited 2023 Nov 30];24:84-6. Available from: https://www.jacmjournal.org/text.asp?2022/24/2/84/363472

  Introduction Top

Aeromonads are essentially ubiquitous and can be isolated from virtually every environmental niche where bacterial ecosystems exist including aquatic habitats, fish, foods, domesticated pets, invertebrate species, birds and natural soils. This results in constant exposure and interactions between the genus Aeromonas and humans. Three recognised Aeromonas species (A. hydrophila, A. caviae and A. veronii biovar sobria) produce the vast majority (85%) of systemic infections in humans, with a good number of clinical infections being gastrointestinal tract syndromes, followed by wound and soft-tissue infections, septicaemia and miscellaneous infections (intra-abdominal infections, ocular infections, infections of bone and joints and respiratory and urogenital tracts). Intra-abdominal infections due to Aeromonads are less commonly encountered and include peritonitis and infections of hepatobiliary and pancreatic system.[1]

We report a rare case of infected walled-off pancreatic necrosis in a 75-year-old male, diabetic patient with chronic pancreatitis caused by A. veronii biovar sobria.

  Case Report Top

A 75-year-old male patient from Siliguri, West Bengal, with a past history of two episodes of acute pancreatitis was admitted to our hospital with chief complaints of loss of weight, anorexia, early satiety and occasional upper abdominal pain (not radiating to the back) for five months. There was no history of fever, nausea, vomiting, haematemesis, malena, abdominal distension, jaundice or pruritus. The patient had undergone cholecystectomy 20 years ago. He is a known diabetic and hypertensive controlled with medication for seven years. The patient gave a history of regular consumption of seafood (mostly cooked fish) but denied history of smoking or alcohol consumption.

On physical examination, he was afebrile and anicteric. The vital parameters were stable. On abdominal examination, a vague mass was palpable in the epigastrium with mild tenderness. Other system's examination was unremarkable. The initial laboratory investigations on admission showed normal white cell count-5580 cells/μl with an elevated serum lipase of 221 IU/L. Carbohydrate antigen 19-9 (CA 19-9) level was within the normal limits. His liver and renal function tests were unremarkable. Blood cultures drawn on the day of admission were sterile. Contrast-enhanced spiral CT scan of the abdomen done on the day of admission showed acute on chronic pancreatitis with a large walled off necrotic collection of size 7.2 × 6.8 × 6.1 cm in the head of the pancreas with distal pancreatic duct dilatation in the body and tail region [Figure 1]. The patient was started on intravenous (IV) fluids, IV cefoperazone sulbactam and IV pantoprazole. Endoscopic ultrasound (EUS) done the following day showed a walled off pancreatic collection with necrotic debris. EUS guided pancreatic walled off necrosis drainage was done with placement of lumen apposing metal stent (LAMS). The necrotic debris received in the microbiology department were processed using standard procedures.[2] Gram stain of necrotic debris revealed few degenerated polymorphs with Gram-negative bacilli against a necrotic background. ZN stained smears for acid fast bacilli and potassium hydroxide mounts for fungal elements were negative. After overnight incubation, 3–4 mm size, large, raised, opaque, β-haemolytic colonies were observed on 5% sheep blood agar and non-lactose fermenting colonies on MacConkey agar [Figure 2]a and [Figure 2]b which were Gram-negative bacilli, catalase positive, oxidase positive, motile and glucose fermenter. The organism was identified as Aeromonas veronii on Vitek 2 Compact system (BioMérieux, France). Based on the negative ornithine decarboxylase reaction, it was identified as Aeromonas veronii biovar sobria and was found to be susceptible to ceftazidime, cefepime, aztreonam, ciprofloxacin, levofloxacin and trimethoprim-sulfamethoxazole by disc-diffusion method interpreted as per the EUCAST guidelines.[3] The antibiotic treatment was changed to IV ceftazidime which was given for seven days. Following clinical response, the patient was discharged on oral levofloxacin for an additional seven days. As the follow-up EUS done after six weeks did not show any pancreatic collection, the LAMS stent was removed.
Figure 1: Contrast enhanced spiral CT scan of the abdomen showing a large walled off necrotic collection in the head of the pancreas. CT: Computed tomography. Arrow points to the lesion

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Figure 2: Growth of A. veronii biovar sobria on 5% sheep blood agar (a) and MacConkey agar (b) after 24 h incubation at 35°C in ambient air. A. veronii: Aeromonas veronii

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  Discussion Top

Aeromonas species are oxidase-positive, facultatively anaerobic, flagellated gram-negative rods whose natural habitat is freshwater or brackish water. Infection may occur after ingestion of contaminated seafood/water, massive aquatic exposure during near-drowning events, or by exposure of an abraded wound to the bacteria. Clinical manifestations of Aeromonas infections are mostly gastro-intestinal infections, bacteraemia and skin and soft-tissue infections.[1],[4]

Intraabdominal infections due to Aeromonas although uncommon are important medical problems in South-east Asia. Aeromonas spp. is not commonly found among the normal human gastrointestinal flora. However, in persons from the tropical and subtropical climates, asymptomatic Aeromonas colonization rates may reach 30% and is associated with increased human participation in water-related occupations and activities and frequent contamination of seafood with Aeromonas spp.[1] Most intra-abdominal infections are found in middle-aged males with one or more underlying diseases such as cirrhosis, cancer (hepatocellular carcinoma, cholangiocarcinoma and pancreatic cancer), diabetes mellitus, biliary obstruction (malignant/nonmalignant causes), in patients receiving immunosuppressive medications (chemotherapeutic agents and corticosteroids) and following recent surgical procedures on the gastrointestinal tract.[1],[5] Aeromonas-associated peritonitis is an important medical problem in South-east Asia as compared to the United States or Europe.[5] Fifty patients with Aeromonas peritonitis were identified at a regional hospital in Southern Taiwan over a period of seven years. Of these, 9 cases were classified as spontaneous bacterial peritonitis, and 41 cases were classified as secondary peritonitis (most common cause-acute appendicitis).[6] Spontaneous bacterial peritonitis due to Aeromonas hydrophila has been reported previously from Southern India in a patient with underlying chronic liver disease and diabetes mellitus.[7] In a nation-wide study conducted in Korea, of the 336 Aeromonas bacteraemias reported over a 14-year period, a majority were secondary to hepatobiliary infection (50.6%) and peritonitis (18.5%). The infections usually occurred in patients with malignancy, hepatic cirrhosis or diabetes mellitus.[8]

Pancreatic infections due to aeromonads are rare and occur in patients with pancreatic cancer, chronic pancreatitis and necrotising pancreatitis following pancreatic duct obstruction.[5],[9] Pancreatic abscess due to A. hydrophila has been reported previously in a 50-year-old male with alcohol-related liver disease and chronic pancreatitis.[9]

Our patient was a known diabetic and probably developed walled-off pancreatic necrosis due to ascending infection following transient colonisation of the human gastrointestinal tract by A. veronii biovar sobria-most likely an indirect result of the consumption of seafoods/water containing Aeromonas.[1],[10] However, our patient did not develop septicaemia and responded well to treatment as he was relatively immunocompetent as against immunocompromised patients who develop severe sepsis and bacteraemia following Aeromonas infections. The vast majority of the cases of Aeromonas septicaemia are seen in persons who are severely immunocompromised, especially in those with myeloproliferative disorders or chronic liver disease.[11],[12],[13]

In conclusion, Aeromonas species can occasionally cause pancreatic necrosis. Prognosis and response to treatment may vary depending on the immune status of the patient.

Declaration of patient consent

The authors certify that they have obtained all appropriate consent forms. In the form, the patient has given his consent for his image and other clinical information to be reported in the journal. The patient understands that his name and initials will not be published and due efforts will be made to conceal his identity, but anonymity cannot be guaranteed.

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Conflicts of interest

There are no conflicts of interest.

  References Top

Janda JM, Abbott SL. The genus Aeromonas: Taxonomy, pathogenicity, and infection. Clin Microbiol Rev 2010;23:35-73.  Back to cited text no. 1
Procop GW, Church DL, Hall GS, Janda WM, Koneman EW, Schreckenberger PC, et al. Koneman's Color Atlas and Textbook of Diagnostic Microbiology. 6th ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2006.  Back to cited text no. 2
European Committee on Antimicrobial Susceptibility Testing. Breakpoint Tables for Interpretation of MICs and Zone Diameters. Ver. 12.0 1. 2022. Available from: http://www.eucast.org. [Last accessed on 2022 Jul 14].  Back to cited text no. 3
Nolla-Salas J, Codina-Calero J, Vallés-Angulo S, Sitges-Serra A, Zapatero-Ferrándiz A, Climent MC, et al. Clinical significance and outcome of Aeromonas spp. Infections among 204 adult patients. Eur J Clin Microbiol Infect Dis 2017;36:1393-403.  Back to cited text no. 4
Clark NM, Chenoweth CE. Aeromonas infection of the hepatobiliary system: Report of 15 cases and review of the literature. Clin Infect Dis 2003;37:506-13.  Back to cited text no. 5
Lin WT, Su SY, Lai CC, Tsai TC, Gau SJ, Chao CM. Peritonitis caused by Aeromonas species at a hospital in southern Taiwan. Intern Med 2013;52:2517-21.  Back to cited text no. 6
Mukhopadhyay C, Chawla K, Sharma Y, Bairy I. Emerging extra-intestinal infections with Aeromonas hydrophila in coastal region of southern Karnataka. J Postgrad Med 2008;54:199-202.  Back to cited text no. 7
[PUBMED]  [Full text]  
Rhee JY, Jung DS, Peck KR. Clinical and therapeutic implications of aeromonas bacteremia: 14 years nation-wide experiences in Korea. Infect Chemother 2016;48:274-84.  Back to cited text no. 8
De Gascun CF, Rajan L, O'Neill E, Downey P, Smyth EG. Pancreatic abscess due to Aeromonas hydrophila. J Infect 2007;54:e59-60.  Back to cited text no. 9
Isonhood JH, Drake M. Aeromonas species in foods. J Food Prot 2002;65:575-82.  Back to cited text no. 10
Ko WC, Lee HC, Chuang YC, Liu CC, Wu JJ. Clinical features and therapeutic implications of 104 episodes of monomicrobial Aeromonas bacteraemia. J Infect 2000;40:267-73.  Back to cited text no. 11
Llopis F, Grau I, Tubau F, Cisnal M, Pallares R. Epidemiological and clinical characteristics of bacteraemia caused by Aeromonas spp. as compared with Escherichia coli and Pseudomonas aeruginosa. Scand J Infect Dis 2004;36:335-41.  Back to cited text no. 12
Tsai MS, Kuo CY, Wang MC, Wu HC, Chien CC, Liu JW. Clinical features and risk factors for mortality in Aeromonas bacteremic adults with hematologic malignancies. J Microbiol Immunol Infect 2006;39:150-4.  Back to cited text no. 13


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