Appendicitis in non-typhoidal salmonella bacteraemia

Abstract Salmonella typhi and paratyphi infections can manifest as acute abdomen due to intestinal perforations, salpingitis and rarely appendicitis. Non-typhoidal salmonella infection that usually only causes self-limiting gastroenteritis, is rarely associated with appendicitis. We present the case of a 78-year-old gentleman with Salmonella bacteraemia complicated by acute appendicitis. He was treated conservatively due to multiple comorbidities. His condition improved after completion of 2 weeks of antibiotics guided by the blood and stool culture results. Appendicitis is a rare but important complication to consider in Salmonella bacteraemia. More research needs to be done with regards to the clinical course of Salmonella related appendicitis.


INTRODUCTION
Bacteraemia is a serious extra-intestinal complication of Salmonella infection that is more common in elderly patients with chronic or immunosuppressing conditions [1]. Based on two studies, the incidence of non-typhoidal salmonella bacteraemia is only~5-10% [2]. An association between Salmonella bacteraemia and acute appendicitis has previously been reported but is poorly understood, and difficult to differentiate from other conditions mimicking appendicitis such as mesenteric adenitis [3]. While management of acute appendicitis is primarily surgical and appendicitis can potentially be a surgical emergency, accurate diagnosis of appendicitis and prompt surgical management can be influenced especially in such cases where the patient is septic and appendicitis presents in an atypical manner [3]. This case highlights the need for more widespread recognition of this rare complication of Salmonella bacteraemia and more research into the clinical course of this condition.

CASE REPORT
The patient was a 78-year-old Chinese gentleman who presented with fever, cough, diarrhoea and vomiting, of 1 day duration.
Other than bilateral crepitations in the lung, the physical examination was otherwise unremarkable. Initial investigations were significant for a mild leucocytosis, acute kidney injury and mild hypokalaemia (Table 1). Chest and abdominal radiographs were unremarkable. Treatment was initiated for an infective exacerbation of bronchiectasis. Blood cultures and stool microbiology studies were sent off, and intravenous Co-amoxiclav and hydration were started.
Blood culture initially was reported as positive of gram negative rod. An ultrasound of abdomen was done. It showed no intra-abdominal abscess. Over the next few days, stool and blood cultures came back positive for non-typhoidal Salmonella species sensitive to ampicillin, ceftriaxone and cotrimoxazole. Salmonella serovar was not specified due to the hospital laboratory protocol. A computed tomography (CT) aortogram ( Fig. 1) was done to look for aortitis as our patient has significant atherosclerosis. It did not show aortitis; however, an enlarged (11-12 mm in diameter), fluid filled appendix with hyperenhancement of the wall, minimal adjacent fat stranding and small mesenteric nodes in the right iliac fossa, was found.
This was consistent with acute inflammation of the appendix and likely reactive lymphadenopathy. There was no evidence of abscess or perforation. A surgical and radiological consult was obtained, both agreed that the findings were in keeping with acute appendicitis. The decision was made to proceed with conservative management in view of poor premorbid status and multiple comorbid conditions.
The patient completed 2 weeks of intravenous ceftriaxone. Repeat blood culture did not show persistent salmonella bacteraemia. Acute kidney injury resolved and the patient was discharged well.

DISCUSSION
Salmonella infections can be broadly classified into typhoidal and non-typhoidal salmonelloses [4]. Invasive systemic disease such as bacteraemia is a known clinical manifestation in typhoidal salmonella infections but uncommon in non-typhoidal salmonella infections which typically manifests as self-limiting gastroenteritis [4]. Appendicitis is a rare form of presentation of acute abdomen in Salmonella infections [5]. Van Noyen et al. [6] showed that only an estimated 8% of culture-proven bacterial enteritis had histologically proven appendicitis due to Salmonella. Two mechanisms on how Salmonella causes appendicitis have been described; either by direct invasion or via blood or lymphatics resulting in inflammation [3,5].
This case report highlights the importance of recognizing appendicitis as a complication of enteric non-typhoidal Salmonella infection. Early recognition allows clinicians to facilitate appropriate management. Availability of microbiology result that confirms enteric bacterial infection would not or should not change the decision to treat appendicitis surgically [3]. In our case, the identification of appendicitis in our patient was an incidental finding on CT aortogram initially performed to rule out aortitis after detection of Salmonella bacteraemia. Although our patient was a poor candidate for surgical intervention, the positive cultures obtained from his stool and blood samples played an important role in his recovery by prompt use of culture-guided antibiotics. Steward-Parker et al. [5] described how timely microbiological analysis of stool and intraoperative pus samples were important for selection of the most appropriate antibiotics for eventual effective treatment. Some clinicians believe that intraoperative bacteriology in appendicitis is of minimal benefit [7], but several studies believe otherwise especially in the context of atypical presentations [7,8]. Presentations such as diarrhoea associated with appendicitis, unresolved abdominal pain after appendicectomy
There is very little evidence on antibiotic responsiveness of Salmonella associated appendicitis [3]. Little is also known about their complication rates or clinical trajectory compared to other cases of appendicitis [3].
This is a rare case of acute appendicitis associated with culture-proven non-typhoidal salmonella infection. While less common as an infective source, it can be important to consider acute appendicitis in patients with Salmonella bacteraemia. More research needs to be done with regards to the clinical course of Salmonella related appendicitis.