Invasive Salmonella Saintpaul Infection in an Immunocompromised Adult: Unusual Presentation Following a Suspected Snake Bite.munocompromised Patient: A Case of Salmonella Saintpaul bacteraemia

Abstract

Introduction

Non-typhoidal Salmonella (NTS) infections are typically foodborne and cause self-limiting gastroenteritis. However, in immunocompromised individuals, these infections can become invasive and life-threatening. We describe a case of Salmonella Saintpaul bacteremia in an immunocompromised patient who developed septic shock following a suspected snake bite. Salmonella Saintpaul is a serotype of Salmonella enterica subsp. enterica, and while it is most often linked to contaminated food, reptiles are recognized as potential reservoirs.  of the disease (1, 2)

Although a clear causal relationship between the snake bite and subsequent infection cannot be firmly established, the temporal sequence raises the possibility of reptile-associated transmission. However, given the epidemiology of NTS, a foodborne source remains equally plausible. This case highlights the diagnostic uncertainty that can arise in complex presentations and emphasizes the importance of considering both common and uncommon transmission routes in immunocompromised patients presenting with sepsis.

Case Report

A 53-year-old male who was diagnosed with type 2 diabetes mellitus, hypertension, and autoimmune hepatitis and was on mycophenolate mofetil and prednisolone (>20 mg/day for 3 weeks) presented to Colombo North Teaching Hospital (CNTH) with a history of loose stools (5 episodes), vomiting, abdominal pain, and drowsiness. He was treated at a local hospital five days before for an unknown snake bite on the dorsum of his right thumb and discharged with analgesics and oral co-amoxiclav. He neither had a history of outdoor food consumption nor contact with diarrhoeal disease.

On admission, the GCS was 14/15, the pulse rate was greater than 100 bpm, blood pressure was 84/52 mmHg, respiratory rate was 20 breaths per minute, and saturation on air was 97%. He was afebrile, and Figure 01 displays the patient's fever chart during hospitalization.

 There were bilateral coarse crepitations on auscultation. Initial laboratory findings revealed leucocytosis and elevated inflammatory markers, while blood culture confirmed the presence of an invasive Salmonella Saintpaul. The isolate was identified through biochemical and agglutination testing at CNTH, followed by serotyping at the National Reference Laboratory.

In the ward, he was initially managed for hepatic encephalopathy and lower respiratory tract infection with intravenous ceftriaxone. As he did not improve, ICU care was given for a duration of 5 days (Figure 1 and Figure 2). Due to clinical deterioration, antibiotics were escalated to IV meropenem and azithromycin. Despite early administration of appropriate antibiotic therapy and supportive care, the patient succumbed to death on the 8^th day of hospital admission. Table 01 depicts the patient's investigation summary, as shown below.

Day 1

WBC-11.7x10³/µL                                       

Total bilirubin-94.6µmol/L

Neutrophil- 9.27 x10³/µL                             

Direct bilirubin- 62.5 µmol/L

C-reactive protein- 202mg/L

Serum creatinine- 120 µmol/L

Urine full report-Normal

Chest X-ray - Figure 02 illustrates the chest X-ray with bilateral acute inflammatory changes and probable bronchopneumonia.

Day 3

ESR-49mm/1^st hour

C-reactive protein- 178.7mg/L

Serum amylase 591 U /L

Blood culture – Isolate was identified as Salmonella spp. at the CNTH by biochemicals and agglutination test and confirmed as Salmonella Saintpaul by serotyping at the National Reference Laboratory.

Stool culture- Salmonella not isolated

Ultrasound scan KUB – unremarkable

Day 6

WBC-10.42x10³/µL                                       

INR- 2.44

Neutrophil- 7.19 x10³/µL

Platelets- 54 x10³/µL

Sputum Xpert MTB/RIF- Negative

Day08

C-reactive protein- 110mg/L

Serum creatinine- 116µmol/L

Table 01: Investigation summary of the patient.

Figure :01 Fever chart during the hospital admission                Figure:02 Chest X-ray

Discussion

Salmonella Saintpaul typically causes gastroenteritis and is commonly associated with foodborne outbreaks, but in rare cases, it can lead to invasive infections, including bacteremia and sepsis.

Salmonella Saintpaul sepsis is an uncommon but serious manifestation of infection. It primarily affects elderly and immunocompromised individuals. Invasive forms of Salmonella infection could be associated with high morbidity and require prompt intervention.

Symptoms of Salmonella Saintpaul sepsis is non-specific, often resembling other bacterial infections; hence, blood culture remains the gold standard for diagnosing bacteraemia, though isolation of Salmonella from other sterile sites or stool can also confirm the infection.

Salmonella is recognized as a part of the normal reptile gut microbiota, and the majority of Salmonella strains identified in reptiles belong to Salmonella enterica subspecies 1, followed by subspecies 111b and subspecies 11 (1,3).

Even though the definitive causal relationship between reptile exposure and the infection could not be conclusively established, the temporal association and the known zoonotic potential of reptiles as reservoirs for Salmonella species strongly suggest a plausible link. Reptile-associated salmonellosis (RAS) has been well-documented, particularly in children and immunocompromised adults. Salmonella Saintpaul has been reported as one of the serotypes isolated from reptiles, including geckos, lizards, and other exotic pets (1, 4). However, in Sri Lanka, no literature is found related to RAS.

Most often, supportive therapy is the main treatment for salmonella infections. However, severe or immunocompromised cases may need antibiotics. Recommended antibiotics include third-generation cephalosporins (e.g., ceftriaxone), quinolones (e.g., ciprofloxacin, levofloxacin), and macrolides. Unfortunately, rising bacterial resistance, especially for the quinolone group, has rendered treatment more challenging (2, 5).

Conclusion

This case highlights the importance of considering Salmonella species as potential causes of sepsis, especially in high-risk patients with recent exposure to reptiles.

RAS cases can resemble other forms of salmonellosis, making the link to reptiles go unperceived. Therefore, it is important to inquire about any contact with reptiles in Salmonellosis.

Management of Salmonella Saintpaul sepsis involves prompt administration of appropriate antibiotics, as guided by antibiotic susceptibility testing. Common first-line antibiotics for invasive Salmonella infections in our setting include ceftriaxone and azithromycin.